Geological, Petrographic, and Structural Investigation of Gada’Ale Volcano and Surrounding Areas, Northern Afar Depression, Ethiopia

Geological, Petrographic, and Structural Investigation of Gada’Ale Volcano and Surrounding Areas, Northern Afar Depression, Ethiopia | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Geological, Petrographic, and Structural Investigation of Gada’Ale Volcano and Surrounding Areas, Northern Afar Depression, Ethiopia Teka Asresie, Professor Miruts (PhD) Hagos This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7947350/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 11 You are reading this latest preprint version Abstract The geology, petrography, and structure of the Gada’Ale area has not yet been explored. This study presents a detailed geological, petrographic, and structural analysis of the Gada’Ale and surrounding areas in the northern Afar Depression, Ethiopia. The research highlights significant geological formations, including basaltic volcanic rocks, recent sediments, hydrothermally altered deposits, and evaporites. Petrographic results of this study indicate that the volcanic rocks exhibit aphanitic and vesicular textures, with average mineralogical proportions of ~ 51.75% plagioclase, ~ 26.5% clinopyroxene, ~ 7.5% olivine, and opaque minerals up to 13.5%). Additionally, this research explains the stratigraphic relationships among the rock units and the interplay between tectonism and magmatism in the study area. Using remote sensing data and field observations, we mapped the lithological units, and volcano-tectonic structures of the study area. Our findings reveal various volcanic and tectonic features, such as shield volcanoes, fractures and faults, a salt dome, a collapsed caldera, lava tubes, and maar volcanoes, emphasizing the interactions between magmatism and tectonism. Notably, the study identifies the prevalence of NNW-SSE trending extensional fractures that align with regional tectonic patterns (The Red Sea Rift Trend). This research enhances our understanding of the geological evolution of the Afar region and highlights the significance of ongoing geological activity in the Gada’Ale area for future studies of the region's geological evolution. Geology shield volcano Gada’Ale petrography volcano-tectonic Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 Figure 14 1 Introduction The Afar Depression, located at a triple plate junction above a hot mantle plume is characterized by active extensional deformation and a range of volcanic activity from basaltic to rhyolitic compositions. This region serves as the source from which the Red Sea, Gulf of Aden, and Main Ethiopian rifts radiate [1, 5; Fig. 1 b]. The floor of the Depression is dominated by a variety of magmatic products and sediments filled in the basin. Volcanism was widespread in the region between ~ 31 and 22 Ma, during which flood basalts, shield basalts, and associated felsic pyroclastic rocks were erupted [ 7 , 20 , 23 ]. The Afar Depression as a whole, and the Danakil Depression in particular, are on the verge of transitioning to oceanic crust or proto-oceanic spreading [ 18 , 21 , 31 ]. The Danakil Depression represents a highly evolved segment of the East African Rift System (EARS) and is one of the most volcanically and tectonically active regions on Earth (38, 39). Although it is a low-lying area with an average elevation of ~ 200 meters, it drops to ~ 124 meters below sea level in the Dallol Depression. Despite this low elevation, the region is home to several prominent shield volcanoes, including Erta’Ale, Tat’Ale, and Alyata (Figs. 1 c and 2 ), characterized by intense seismicity, hydrothermal activity, and basaltic volcanism. The Erta'Ale range is one of the most volcanically and tectonically active segments in the region, consisting of seven volcanic centers aligned in an NNW-SSE direction [ 19 , 35 ]. From north to south, these centers are Gada’Ale, Alu, Dalaffilla, Borale’Ale, Erta’Ale, AleBagu, and Hayli Gubi (Fig. 2 ). The range is characterized by basaltic magmatism, extensional fractures/normal faults, volcanic structures, and fissure-fed lavas that are primarily transitional to tholeiitic in composition, with some interbedded felsic derivatives accompanying the basaltic flows [ 2 , 3 ]. Typically, basaltic fissure eruptions align along NNW-SSE belts (Fig. 2 ), reflecting the regional tectonic trend of the Red Sea rift, and produce the < 1 million years old shield volcanoes of the range [ 9 , 36 ]. We utilized various types of remote sensing imageries and field data for geological and structural mapping in the Gada’Ale and surrounding areas. This paper presents petrological, petrographic, and structural data from the study area. These data are interpreted to understand the geology, petrographic, and structural features of the Gada’Ale and surrounding areas. The Danakil Depression is one of the unique sub-aerial exposures in the globe and allows direct observation of mid-ocean ridge volcano-tectonic processes. It provides an opportunity to investigate the relationship between petrology, volcanism, tectonism, and sedimentation. In comparison to other areas within the Danakil Depression, the Erta’Ale range demonstrates a more pronounced interaction between tectonism and magmatism, making it crucial for understanding the surface manifestations of active magmatism. Additionally, the Danakil Depression is characterized by thick evaporite deposits (~ 1500 m) overlaying thin crustal materials [~ 15 km; 28]. However, due to the hostile environment, poor infrastructure, and extremely high temperatures, geological and structural investigations have primarily been conducted at a regional scale and have mostly relied on remote sensing techniques [ 4 , 18 , 19 , 25 , 26 , 29 ]. Furthermore, detailed field-based geological and structural investigations focused on individual shield volcanoes have yet to be carried out. Specifically, the geology, petrography, and structural features of the northern end of Erta'Ale volcanic range, particularly the Gada'Ale area (Fig. 2 ), remain unexplored. The Gada'Ale is an interesting area that separates the northern non-magmatic, hydrothermally active Dallol Depression from the southern magmatic range (Fig. 2 ). It features a shield volcano with a diameter of ~ 4 km and elevated from the Dallol salt crust by ~ 300 m. Located ~ 4 km southwest of the volcano's summit are a semi-circular crater that has collapsed and a geometrically remarkable salt dome. The main goal of this study is to conduct a comprehensive geological, petrographic, and structural investigation to constrain the field stratigraphic relationships, and volcano-tectonic features of the study area. This study aims to achieve the following objectives: (1) provide a detailed description of the lithologic units, (2) determine the mineralogy and fabric of the volcanic rocks, and (3) describe the volcano-tectonic structures and morphological features of the study area. 2 Regional geological setting The Afar Depression is a highly extended area located at the triple junction of the Red Sea, Gulf of Aden, and East African rifts [ 40 ]. Covering an area of ~ 250,000 km², it is one of the few places on Earth where researchers can study the entire processes of mantle plume dynamics, rift-rift-rift triple junctions, and microplate formation on land [ 16 ]. Magmatic activity in the depression commenced ~ 4 million years after the peak volcanism in the Ethiopian Plateau [ 18 ]. Since the Oligocene, the region has experienced 30 million years of mafic, felsic, and pyroclastic volcanism, with significant eruptions (notably the Stratoid series) linked to the initiation of sea-floor spreading in the Gulf of Aden and Red Sea rifts [ 42 ]. Pleistocene to Quaternary volcanism is mainly confined to the active tectonic and magmatic segments of the embryonic spreading centers [ 13 , 37 , 42 ]. Located in the northern tectonic-magmatic domain of the Afar Depression, the Danakil Depression is a well-defined active rift segment bordered by major faults and dissected escarpments (Fig. 2 ; [ 31 , 34 ]. The attenuated continental crust has a thickness of < 15 km, with shallow magma chambers (2–5 km deep) located beneath its axial zones [ 27 , 28 , 30 , 41 ]. Volcanic activity in the Danakil Depression has been intense since the Pliocene, primarily concentrated in the axial zone, where three prominent volcanic shields-Erta’Ale, Tat’Ali, and Alayta-are found [ 12 , 17 ]. The NNW-SSE trending Erta’Ale volcanic range dominates the southern portion of the depression and is the focus of most Quaternary to Recent basalt activity in the Afar region [Fig. 2 ; 12 ]. A notable fissure eruption at the Alu-Dalafilla volcano in 2008, oriented sub-parallel to the rift axis, represents one of the recent volcanic activities in the Erta'Ale Volcanic Range [ 19 , 30 ]. The shield volcanoes of the Erta’Ale axial range, which are < 1 million years old, are typically formed by basaltic fissure eruptions arranged in NNW-SSE belts that align with the regional tectonic trend of the Red Sea rift [ 9 , 36 ]. The lowest areas of the Danakil Depression are often filled with recent lacustrine sediments and evaporite beds, underlain by fissure-fed basaltic lava flows. Over the past million years, widespread fissure-fed basaltic flows, basaltic shields, scoria cones, and alkaline to peralkaline silicic rocks have erupted along the dynamically expanding axial ranges of the Afar Depression [ 32 , 36 ]. Volcanism across the axial ranges of the northern Afar Depression, such as Erta’Ale, has produced fissure-fed transitional-tholeiitic basalts with elemental and isotopic compositions similar to those of mid-ocean ridge basalts (MORBs) [ 15 ]. These basalts, often referred to as ‘Aden Series’ basalts, and are closely resemble MORBs [ 11 ]. The presence of dyke intrusions in the Erta'Ale ridge, a shallow magma chamber beneath the evaporites in the Dallol area, and the occurrence of intense shallow seismicity [ 29 ] suggest a north-northwestward propagation of the Erta’Ale magmatic and tectonic activity linked rifting. The northern Afar Depression is marked by intense tectonic and hydrothermal activities, alongside basaltic volcanism, primarily focused on several axial volcanic ranges aligned parallel to the Red Sea axis [ 15 ]. Volcanic activity in the depression has been vigorous since the Pliocene and is currently concentrated in the axial zone, forming three prominent volcanic shields: Erta’Ale, Alayta, and Tat’Ali [ 12 , 17 ]. The lavas erupted from these systems show an affinity with mid-ocean ridge basalts (MORB), with slight enrichment possibly attributed to the influence of the Afar plume [ 8 , 12 ]. These axial volcanic ranges are distinguished by their predominantly basaltic nature, their alignment along fissures that follow the dominant N-NW regional trends, and their unique petrological and geochemical characteristics [ 9 ]. The Erta’Ale volcanic range, with an area of ~ 2500 km² [ 8 ], features NNW-SSE trending elevated volcanic centers with a mean elevation of ~ 200 m (Fig.). It is an active area of basaltic magmatism, characterized by fissure-fed lavas with some felsic derivatives interbedded with the basaltic flows [ 3 ]. The felsic derivatives, including trachytes and rhyolites, are believed to have originated from the fractional crystallization of basaltic magmas with little or no crustal contamination [ 6 , 10 ]. 3. Sampling and methods Our sampling was mainly focused on the western part of the Gada’Ale shield volcano with only two rock samples taken from the eastern part, as it is inaccessible. Despite the challenges due to the remote location, we collected sixteen (16) fresh surface rock samples, each weighing < 1 kg. These samples were chosen based on their spatial distribution, mineralogical and lithologic variations, and overall areal coverage. The majority of the samples were taken from the mafic lava flows with only three samples from pyroclastic layers, hydrothermally altered rocks, and evaporites. From the sixteen samples, ten (10) rock samples-six from fine-grained basalts and four from blocky vesicular basalts-were chosen for petrographic analysis. The sampling locations were recorded using GPS, and an outcrop photograph of each sample was taken. Detailed field observations were conducted to identify rock units, noting to their color, texture, mineralogy, morphological and structural features, and weathering. Lithological contacts and geological structures were traced and interpreted on Google Earth and thematic satellite imagery. Thin sections were prepared in the Geological Survey of Ethiopia laboratory center found in Addis Ababa, and mineralogical examinations were performed under a petrological microscope at Mekelle University. The thin sections were analyzed to identify modal proportions, textures, alterations, and microstructural features of the volcanic rocks under both plane-polarized light (PPL) and cross-polarized light (XPL). The modal proportion of minerals was estimated using the simple counting technique of [ 33 ]. 4 Results and discussion 4.1 Geological description The Danakil Depression, characterized by its below-sea-level land surface, presents a unique geological setting in East Africa. The deepest valley is filled with a thick sequence of ~ 1500 m of siliciclastics, carbonates, and evaporites [ 22 ], forming the highly evolved Dallol plain. These plain lacks volcanic materials, while the geological history of its southern part (the Gada’Ale area) is strongly influenced by volcanic activity and extensional tectonics during the late Quaternary/Holocene period. The Gada’Ale and surrounding area is primarily covered by Quaternary fissure basaltic lava flows, thin pyroclastic materials interlayered with halite-dominated evaporites, and recent sediments. Field stratigraphy of this study reveals that the recent sediments represent the youngest lithologic units, while the evaporites are the oldest rocks in the mapped area. These sediments are predominantly deposited in the southwestern parts of the area, confined to small depressions such as calderas and pit craters (Fig. 3 a). Detailed field and petrographic descriptions of each rock unit and/or stratigraphic succession of the study area, from young to old is presented here below. It has to be noted that all units are younger than 10 Ka and age comparison is so local. 4.1.1 Recent sediments: - The alluvial/lagoonal sediments are the youngest units in the study area. They are mainly deposited in the southwestern parts of the Gada’Ale volcano, and within the semi-circular caldera (Fig. 3 a). The sediments are composed of clay, silt, sand, gravel and boulders. The color of the sediments is ranging from white, light gray to dark gray (Fig. 4 a). They are reworked from the hydrothermal altered deposits. In some cases, since there is pyroclastic layering intercalated with the lava flows, a significant amount of the alluvial deposit is also derived from the weathered and eroded products of the western escarpment. At the central part of the semi-collapsed caldera, the lagoonal sediment is flat whereas the eastern and western side is covered by massive and vesicular basaltic volcanic rocks. The sediments are very fine and containing shales of some fossils. The presence of lacustrine sediments and thick evaporites might indicate the presence of ancient lakes in the study area. 4.1.2 Hydrothermal related deposits: - They are exposed in the northeastern parts of the study area, mostly at the summit and southern flanks of the Gada’Ale volcano (Fig. 3 a). Most of the southern flanks of the Gada’Ale volcano (i.e., the western-southern rim), is covered by reworked pyroclastic materials with some sulfur precipitates whereas in the eastern flank of the crater (i.e., ENE rim), the altered materials are covered by young vesicular basalts. The hydrothermally altered rim of the crater exhibits no sign of sliding but the blocky basalts with NE-oriented fractures. The deposits at the summit of the Gada’Ale volcano are deeply altered by an intense hydrothermal activity, and transformed into soft clay-like materials. The young hydrothermally altered rocks are rich in sulfur, clay, volcanic ashes, and other reworked pyroclastic materials. They are highly jointed and/or fractured. The reworked alluvial sediments at the center of the crater, are highly altered as a result of an intense volcanic activities and fluid-rock interaction that might occurred in a long period of time. In most cases, the color of these materials is changed into yellowish, mainly because of the presence of sulfur precipitates. They are also commonly observed on the peripheries of the semi-circular calderas, and small local craters found in the whole flanks of the Gada’Ale volcano. 4.1.3 Pyroclastic materials: - These rocks are very thinly bedded and cover a small portion of the study area. They are unmappable and only traced on profile-section (Fig. 4 b). They are mainly confined to the western parts, and southern flanks of the Gada’Ale volcano. In the western part of the shield volcano at the semi-circular ring, ~ 1–2.5 m thick reworked pyroclastic material is deposited underneath the blocky vesicular basalts (Fig. 4 b). They are mainly felsic pyroclastic materials, like volcanic ashes. The pyroclastic materials are commonly observed interlayered with the lava flows and the layered evaporite (halite). They are characterized by light weight, light gray color, soft nature and intense weathering and alteration. The intense weathering and alteration of these rocks is due to the hydrothermal activities taken place in the past. They look like very soft clay-like materials, thin and also consists of visible feldspars and quartz. They are horizontally layered, and show slight lateral variations in thickness, but are less readily differentiated. 4.1.4 Basaltic lava flows Based on field observations and mineralogical analysis, two types of basaltic lava flows are recognized in the Gada’Ale and surrounding area: relatively older and younger mafic lava flows. Younger lava flows: - Throughout the Erta’Ale volcanic range, the basaltic outcrops are younger than 100 ka [ 24 ], and are part of the Aden series basaltic eruptions. The young basaltic rocks, the most recent flows in the study area, cover a small portion of the mapped area, restricted only to the eastern, northeastern and southern parts of the Gada’Ale area (Fig. 3 a). The younger fissure eruptions that took place on the eastern and southeastern flanks of the Gada’Ale volcano (Fig. 3 a) are related with the extensional tectonic fissures of NNW-direction that affect the southeastern flank of the volcano. They display both fresh, less weathered pahoehoe and a’a lava types. The a’a lava flows are characterized by rough or thorny texture and dark color with mostly unweathered surfaces. Except for the northern part of the shield volcano, these fissure basalts are almost gently dipping, and in most cases, they flow radially away from the volcano. The fissures aligned commonly to NNW and some N-S are characterized by recent tectonic fractures and indicate active lava flowing in the area. Older lava flows: - They are the most dominant basaltic rocks, constitute almost > 70% of the mapped area. They represent relatively older fissure-fed basaltic lava flows of both a’a and pahoehoe types erupted through the NNW-aligned extensional fractures. The a’a lava flows are characterized by rough and dark color with mostly unweathered surfaces. Samples were collected from the southeastern part of the ring structure, located in the southwestern part of the Gada’Ale volcano. These outcrops are relatively fractured, weathered and altered compared to the young basaltic volcanic rocks. Based on field and petrographic observations, these are texturally classified into two; blocky vesicular basalts and aphanitic basalts. Vesicular lava flows: - The vesicular basalts are characterized by a smooth surface, light-dark color and highly vesiculated texture, mostly filled with fresh argilic materials (Figs. 6 a and b). The vesicles are rounded to subrounded in shape and are formed by the expansion of bubbles of gas that was trapped inside the lava. They have relatively low density and hardness compared to the fine-grained basalts, mainly due to the presence of vesicles. The vesicular lava flows are commonly found in the northern, northeastern sides of the summit of the crater, most flanks of the Gada’Ale volcano, and in the southwestern and most flat laying parts of the study area. In the western flanks of the volcano, the blocky vesicular basalts are interlayered with the evaporite and aphanitic basalts on top (e.g., Fig. 5 a). In the western parts within the eastern side of the ring, blocky vesicular basalts of ~ 7 m thick is overlain by ~ 2 m thick fine grained lava flows. Most of the lava flows are collapsed and toppled down towards the semi-circular calderas, in the form of blocks and debris, to form talus deposits (Fig. 4 a and b). The toppling of these lava flows is considered to be mainly because of local uplift and subsidence. They are relatively weathered (e.g., exfoliation weathering), altered and characterized by blocky nature. Joints are common within these outcrops and this together with the highly vesiculated nature of these lavas lead to speedy water circulation and increased rate of weathering. Sometimes, the color and composition of these rocks are changed, due to an intense degree of alteration and weathering, especially near discontinuities. The highly weathered nature of these lava flows is, due to the presence of vesicles and fractures; which in turn leads to speedy water and/or fluids circulation. They are highly fractured, altered, sometimes changed into yellowish color and form small volcanic caves and lava tubes. The lava tubes might indicate flow of lava beneath the hardened lava flow down from the center of the shield volcano. They are highly fractured and faulted. In the southwest part of the Gada’Ale dome, there is one major fracture on the vesicular basalt and upper pahoehoe lava flow, with opening ~ 5 m, oriented NNW with a dip amount of 85 0 , almost vertical. Samples were collected from both sides of the semi-collapsed caldera structure to distinguish the mineralogical makeup, and textural variations of the basalts. Aphanitic lava flows: - Based on field observation, this volcanic rock is characterized by dark-brown color, and fine texture (Figs. 7 a and b). They appear mostly in the form of pahoehoe with some a’a nature. They are fresh, slightly altered and their lower successions are blocky and vesicular in nature. The lava sheets are twisted into rope-like shapes (pahoehoe) lavas. The a’a types are formed when the lava loses its dissolved gases; it becomes thick, brittle, forms rough, jagged blocks of rock. This volcanic rock sequence is also characterized by light yellowish color, slightly fractured, tilted, jointed (Fig. 7 a and c), and varied degree of weathering. They are relatively less weathered with local variations in weathering grades, thinner and massive compared to vesicular lava flows. The fine-grained basalts are highly jointed (e.g., columnar joints) and are characterized by open joints, mostly unfilled with secondary materials. In most flanks of the Gada’Ale volcano, they form lava tube structures. The massive basalts are mostly sitting on top of the blocky vesicular lava flows. They are characterized by highly fragmented rock debris, resulted from rock movement and block rotations that might occurred due to tectonic activities. Once the primary structures (e.g., columnar joints) were developed within the massive basaltic lava flows, tectonics gradually change the rocks into rock debris formed due to block movement. This movement may further result in the formation of many fractures, most of which are oriented NNW, NE to NNE and some N-S direction. Toppling of the basalts from the top to the bottom parts is common phenomenon observed in the field, mainly along the peripheries of the semi-collapsed caldera structures (Fig. 4 a). Especially, along the dome-caldera structure, most of the lava flows which were placed above the evaporite sequence, are presently collapsed and slumped down from the top mainly as a result of uplifting. This rock unit is also found in the flat-lying areas of the study area, alongside vesicular lava flows, creating a talus deposit at the lowest portions. 4.1.5 Evaporite deposits: - Evaporites are the oldest rock units in the Gada’Ale area. The age comparison is basically based on field stratigraphic sequence. They are mainly exposed in the northwestern and southwestern parts of the Gada’Ale area (Fig. 3 a). They are characterized by thick, light gray in color, hard, sub-horizontally bedded and commonly representing the rock salt (halite) (e.g., Fig. 4 ). In the western part of the Gada'Ale volcano, there is ~ 80 m thick halite, where the whole basaltic sequence is flowing on top of it (Figs. 3 a and b) forming ~ 2 km diameter dome-like structure. The formation of this uplifted salt ring structure is related to local uplifting, magmatism and faulting. Two-types of evaporites have been recognized: the first is a flat-lying and thinly bedded, whereas the second is very massive and recrystallized. The flat-lying evaporites, which are found in the northwestern portion of the mapped area are the southern extension of the Dallol evaporites. The recrystallized evaporite is basically exposed on the sides of the collapsed semi-circular caldera (Fig. 3 a). Although they are unmappable, they are also commonly observed at the most flanks of the Gada’Ale volcano interlayered with the lava flows. These evaporites are elevated from the flat-lying once by ~ 70–90 m. This indicates that magma-assisted uplifting placed these rocks in the mountainous areas, within the flanks of the volcano. The presence of such thick evaporites and the underlined young sediments (lacustrine) in the Gada'Ale area might indicate the presence of lakes in the past 100 Ka, because the basis for sodium chloride is considered to be oceans and/or sea water. The origin of halite is entirely associated with evaporation of lake or sea water resulting in the loss of water and increasing the concentrations of Na + and Cl − in the remaining water. 4.2 Petrographic description Ten thin sections were prepared to investigate the mineralogical, textural, and microstructural properties of the basaltic volcanic rocks of the Gada’Ale area. 4.2.1 Vesicular lava flows: - Petrographically, these rocks are represented by vesicular texture. They are fine grained basalts carrying few localized phenocrysts of plagioclase, clinopyroxene and some olivine (Fig. 6 c-f). Olivine and some clinopyroxene phenocrysts mostly show curvi-linear fractures/cleavages and are highly altered. They are pale brown in color and form irregular or anhedral shape (Figs. 6 c and f). They range up to 1 mm in size, and contains needle-like to granular crystals of opaque minerals. The plagioclase phenocrysts are characterized by polysynthetic and albitic twinning and mostly randomly oriented (Fig. 6 c-f). Vesicles are also commonly observed in these samples. Proportion of the minerals in the vesicular basalts is; plagioclase (~ 52%), clinopyroxene (~ 27%), olivine (~ 8.5%), and opaque minerals (~ 12%) (Figs. 4.8c-f). 4.2.2 Aphanitic lava flows: - Minerals cannot be readily observed by necked eye except few plagioclase minerals, because of the fine texture of these volcanic rocks. High magnification lens was used to differentiate the high magnesian basalts. From a petrographic point of view, these rocks exhibit an aphyric texture with very few micro-phenocrysts of plagioclase and few olivine, set on plagioclase dominated groundmass of clinopyroxenes, and opaque minerals (Figs. 7 c, e and g). Olivine phenocrysts are highly fractured and altered. The fabrics of these samples, in general, are inequigranular with finely crystallized plagioclase-lath showing albitic-polysynthetic twinning (Fig. 7 c, f, g and h), and are mostly randomly oriented. Some highly elongated plagioclase micro-phenocrysts (e.g., samples GA-008 and GA-014A) show flow (trachytic) texture (Fig. 7 d and f). Mega-phenocrysts of plagioclase are common (e.g., sample GA-004) but mega-phenocrysts of clinopyroxene and olivine are rare. Euhedral to subhedral plagioclase phenocrysts show albitic twinning (Figs. 7 c, f and h). Plagioclase crystals are elongated to laths shaped (ranging from 0.2–0.3 mm in size). The mineralogical composition of the fine-grained basalts includes ~ 51.5% plagioclase, 26% clinopyroxene, 6.5% olivine, and 15% opaque minerals, and others (Figs. 7 c-h). 4.3 Structural and morphological features The axial zone of the Danakil Depression imprints some important physiographic elements of incipient ocean basin. Intermittent shield volcanoes rising from ~ 300 meters above sea level (e.g., the Gada’Ale shield volcano) to ~ 615 meters above sea level (i.e., the Erta’Ale shield volcano) characterize the axial part of the Danakil Depression. Satellite images and DEMs show that Gada’Ale volcano is slightly elliptical/sub-circular (4.3 × 3.9 km), with a NNW-trending long axis parallel to the axial range extensional fractures (Fig. 2 ). The salt dome at the southwestern base of Gada’Ale volcano is also another morphological feature with a peak elevation of 300 m.a.s.l. or rising ~ 150 m high over the salt crust of the Dallol plain. The two topographic profiles (i.e., profiles a-a’ and b-b’; Fig. 8 ), constructed along the Gada'Ale area, indicate the geomorphological and structural patterns. The geological map along with constructed geological cross sections (x-x’, y-y’; Fig. 3 a-c) provides two clearly distinct and highly elevated morphologies: a flat-topped dome (central) and a well-defined shield volcano. The majority of the extension fractures and faults are oriented parallel to the rim structure (i.e., non-tectonic origin), with some transverse structural trends of NE, NNE and E-W orientations (Fig. 3 a). Normal faults with visible displacement are scarce, the only measurable fault throws are found on the western rims of the Gada’Ale dome. As we can see from the profile sections (Fig. 9 a-c), the summit of the dome is described by subdued horst and graben morphology. The interpretation of remote sensing and DEM data sets, supported with field measurements, showed that the area has two distinct structural trends: the dominant and well clustered NNW - SSE- trending extensional fractures, aligned parallel to the axial rift trend, and the local curvilinear structures which in-turn developed half-graben and horst-type morphology (Fig. 8 ). The outer rim of the dome is characterized by single to imbricate listric normal faulting with reverse drag (Fig. 13 a and c). At the northern and southern sides of the dome, the young pahoehoe lavas are dissected by swarms of parallel-aligned NNW – SSE oriented fractures (i.e., N22°W) (Fig. 8 ). The average orientation of these fractures is similar (i.e., with only 2–3° deviation) with the alignment of the rift axis (N24°W). 4.4 Nature of structures in the axial zone Structural data have been collected along the entire Gada’Ale shield volcano and uplifted salt dome (for an area of ~ 125 km 2 ) of the northern EVR. The study along the salt dome and the axial segment of the Gada’Ale area permit to analogically explore the volcano-tectonics of an incipient oceanic crust. The structures have been measured and mapped at a considerable scale. Within the premises of the well-defined Gada’Ale salt dome, three sets of structures have been recognized: tectonic structures, volcanic structures and/or a combination of these two. 4.4.1 Tectonic structures: - The northern part of the Erta’Ale volcanic range (EVR) exhibits both regional and/ or local tectonics, and fracture trace analysis has been considered mandatory to outline the axial rift structures. In order to evaluate the Quaternary geometry and kinematics of the region, rift axis fracture data have been collected from the fissure basalts of the area. The area includes various tectonic elements, such as extensional fractures, elliptical shield volcanoes and craters, and ring structures. For a better understanding of the kinematics of the Gada’Ale area, only late Holocene to present extensional fractures were analyzed using stereo plots [ 2 ]. All fractures from the salt dome were not involved in this analysis; because, they are more of non-tectonic in origin and formed during the local uplift and subsidence process. A total of ~ 50 fracture orientations and 10 asperities from the fissural basalts of the Gada’Ale area, were measured (e.g., Fig. 10 a-c). All measured open fractures have an opening between 0.03 and 1 m and a length between 5 and 500 m; their depth of penetration, ~ 700 m, is inferred from mechanical considerations [ 2 ]. The asperities along the walls of open fractures were sharp, fresh and unaffected by erosion and other secondary deformation, as for example shown in Fig. 10 a - c. This characteristic, together with the late Holocene–age of the rocks, confirms that the fractures were active features in the study area. The open fractures, which have clear asperities, were analyzed and all found to be consistent with an overall ENE-WSW (059.4°) extension direction of the open fractures orthogonal to the mean trend of the axial structures (i.e., 335°; Fig. 10 f). 4.4.2 Volcanic structures: - Gada’Ale is an area where most of its volcanic structures are young and well exposed. The major volcanic-related structures are shield volcano, lava tubes, volcanic caves, a’a and pahoehoe lavas, collapse structures of various sizes, and maar volcanic rings. Shield volcano: - The Gada’Ale volcano, with a peak elevation of 370 m from the crusted salt surface, is one of the youngest and best-preserved volcanic structures in the EVR. The slopes of the shield along its E-W profile are between 11° and 12° (Fig. 11 a). At the top of the volcano, there is a well-preserved, about 80 m deep and 500 m diameter, circular crater (Fig. 11 c). The southeastern rim of the crater is lower by ~ 20 m, and most of the recent hydrothermal-related deposits (i.e., chimneys of sulfur, salt and reworked ash) are concentrated there and flow southwards up to the base of the volcano (Fig. 11 a & c). The fresh pahoehoe and some a’a lavas are vesiculated on their upper layers. This single volcanic crater is filled with hydrothermally altered sulfur-rich soft clay-like materials. These materials are highly altered as a result of intense fumarolic activity and fluid-rock interaction. There are no recently erupted magmatic products on the shield volcano (i.e., like the Alu-Dallafilla and Erta’Ale shield volcanoes); however, fragile structures (e.g., fumaroles and chimneys of sulfur and salt) are still undisturbed indicating the presence of hydrothermal activities in the past few decades. Small local pit craters and side-wall caldera collapses of various size are also common all over the flanks of the shield volcano (e.g., Fig. 11 b). Lava tubes and Maar volcanoes: - Most of the volcanic rocks of Gada’Ale area are late Quaternary/Holocene in age, and hence meso-volcanic structures associated with the lava are fresh and undisturbed. Lava tubes and/or caves, pahoehoe and maar or ring structures, layered vesicles and other features are present. Most of the lava tubes are few centimeters in diameter, but some as large as 1.5 m in diameter (i.e., long axis; Fig. 12 b). They developed in massive/thick lava flows and form perfectly elliptical tubes extending sub-horizontally for several kilometers. Most such structures are found at the periphery of the shield volcano and are radiating outwards for tens of kilometers. As the lava tubes extend further from the vent, they generally become wider, with a more rounded to elliptical shape and smoother floor, due to the decreasing flow velocity and gradual cooling of the lava as they travel further downhill. In most cases, the size of the tube is inversely proportional from the vent and slope of the volcano; i.e., the smaller the lava tube is the closer to the eruptive center and steeper slope. Maars, tuff rings, and scoria cones are also among the common volcanic structures in the area. The Maar volcano found at the southern part of Gada’Ale shield volcano forms a “negative” landform, characterized by a circular and well-defined crater with a floor below the elevation of the surrounding rift floor and well-preserved rims of accumulated tephra (also called tephra rings). The Maar volcanoes are commonly associated with the basaltic lava flows of the rift floor volcanoes and are entirely mafic in composition. The floor of the maar is filled by fragmented country rock and/or juvenile volcaniclastic material and is still lying ~ 20 m below the normal surface (Fig. 12 ; profile A-A’). It is the youngest (late Holocene; most probably in the last 100 years) volcanic structure erupted at the center of the axial zone and very close to the lake Bikila, and representing the entire Afar maar structures. The position of the lake within 1.5 km distance and a shallow magma chamber underneath [~ 2.4 km deep; 29] most probably enabled for the formation of such phreatomagmatic eruption. The southern rim of the maar is partly collapsed as a result of the very late scoria eruption. Uplift and subsidence related structures: - At about 4 km WSW of the Gada’Ale shield volcano, there is 3.5 km in diameter evaporite deposit (Fig. 4 ) covered by a thin veneer (~ 13-m-thick) of magmatic materials and bounded by arcuate-shaped (plan-view) outward dipping fault. The circular evaporite deposit, uplifted from the normal salt surface of the Dallol plain by about 130 m, is one of the unique geological features where you can observe pronounced dome, steep fault surfaces, well-defined half grabens and subdued horst and graben morphology on its summit (Fig. 4 c and Fig. 13 ). Listric faults and associated structures - At the northern, western and southern peripheries of the dome, steeply dipping (i.e., 80–85°) semi-circular or curvilinear (plan view) faults with a measured throw of ~ 100 m dominate the area. Underneath, the fault surface is covered by alluvium and the hanging wall block. The rolling-over geometry on the hanging-wall block and inverted dip of an originally vertical fractures indicate that the dome-bounding faults are listric in nature (Fig. 13 c). Along the curved surface of the hanging wall block (i.e., rolled-over folded layer), fracture openings are very wide (i.e., up to 3 m) and converge inwards at the interface with the underlying salt layers. Fracture lengths and openings on the hanging wall block increase towards the fault surface. A semi-circular half-graben, partly filled by recent sediments, separates the dome from the normal rift floor. This structure, ~ 450 m wide and ~ 6 km long, forms one of the visible extensional structures in the floor of the northern end of the EVR. The inner wall of the half-graben is a faulted surface cutting the overlying thin volcanic layer and underlying thick deposit of the evaporite sequence (upper halite; Fig. 13 b & c). The outer wall of the half-graben is a rolled-over folded layer of the volcano-sedimentary sequence. Field observations showed that the underlying salt layers are not intensively fractured instead dragged and bended forming open folds. Salt layers have high ductility, meaning they can undergo significant plastic deformation without fracturing. The brittle deformation observed on the overlying volcanic rocks is, therefore, accommodated by crystal stretching in the underlying salt layers. 4.5 Structural comparison The structures of the Gada’Ale area have two major average orientations; NNW and NE to NNE structural trends (Figs. 8 ). However, the NNW- striking extension structures are the dominant structural features in the mapped area; and are used to compare the Gada’Ale structures with regional structural trends around in the Region. Accordingly, the NNW- trending extensional fractures of the study area are oriented parallel to subparallel to the NNW- striking regional extensional fractures and normal faults of the Red Sea and northern Afar rifts [ 18 ]. The orientation of the transverse structures, NE to NNE is, however, not related to any of the trend of the axial structures in the Erta’Ale rift segment. Instead, they are similarly oriented with the NNE- trending active extension fractures and normal faults of the MER structure (e.g., Wonji Fault Belt, WFB) and more similarly oriented with the transverse/transform structures of the northern Red Sea rift. They are aligned orthogonal/oblique to the NNW- trending extensional structures of the Gada’Ale area. In order to evaluate the Pleistocene-Recent rift-axis kinematics and geometry of the Erta’Ale range and TMH rifts, [ 18 ] has collected structural data along the entire western part of the Erta’Ale range and central parts of the Tendaho graben. Because of their location on the axial range of the northern Afar Depression, parallel trend to the Erta’Ale range trend, and Pleistocene-Present age of the open fractures, their extension direction is considered to be resulted from the existing kinematics of the Ethiopian plateau and Danakil Microplate. The average extension direction of the TMH rift is N53 0 E; whereas that of the Erta’Ale and Gada’Ale rifts is N66 0 E and N59.4 0 E, respectively (Fig. 14 ). As compared to the Erta’Ale, the orientations of the Gada’Ale extension fractures are deviated by 002 0 towards the west (Fig. 14 ), that is, the Erta’Ale range is oriented to N23 0 W [ 18 ] and the average strike of the study area is N25 0 W. The geometric difference between the Gada’Ale and Erta’Ale extension fractures is, therefore, almost insignificant. The geometric difference with the TMH rift is, however, wide (i.e., 007 0 ), with the TMH- trending to N32 0 W [ 18 ]. The trend of the Gada’Ale area is, therefore, deviated by 007 0 to the east from the average trend of the Tendaho rift. All measured open fractures of the Erta’Ale range, TMH rift and the Gada’Ale area, are consistent with an overall ENE-WSW (066 0 , 053 0 and 059.4 0 ) extension directions of the open fractures, orthogonal to the mean NNW-SSE (337 0 , 328 0 and 335 0 ) trends, respectively (Fig. 14 ). The strike and extension direction of open fractures/normal faults of the Erta’Ale and TMH axial rift zones vary by 009 0 and 013 0 , respectively. The deviation in the general orientation of the central Tendaho graben by 009 0 to the west from the average trend of the Erta’Ale range shows that the involvement of the Gulf of Aden rift (E-W- oriented ridge) is higher than the MER [ 18 ]. The extension direction of the Gada’Ale area varies by 6.6 0 and 6.4 0 from the opening directions of the Erta’Ale and TMH rifts, respectively (Fig. 14 ). The angle between the trends of the extensional fractures and extension direction in all cases is, however, similarly orthogonal (i.e., 89 0 , 84.4 0 and 85 0 ) for the Erta’Ale, Gada’Ale, and TMH rifts, respectively. 5 Conclusions This study is the first to extensively examine the geological and structural features of the Gada’Ale area through field observations, remote sensing data, and petrographic investigations. The analysis reveals a narrow lithologic spectrum predominantly composed of basaltic lava flows, recent rift sediments, evaporites, and thinly bedded pyroclastic ash flows interbedded with the basaltic rocks. Petrographic results indicate that the volcanic rocks exhibit aphanitic and vesicular textures, primarily dominated by plagioclase, with average mineralogical proportions of ~ 51.75%, clinopyroxene ~ 26.5%, olivine ~ 7.5%, and opaque minerals up to 13.5%). Additionally, this research explains the stratigraphic relationships among the rock units and highlighted the interplay between tectonism and magmatism in the study area. The structural features of the Gada’Ale area can be categorized into two main types: the prominent tectonic structures including columnar joints, fractures, normal faults, listric faults, and associated rollover folds; and volcanic structures such as domes, caldera collapses, lava tubes, maar volcanoes, as well as a’a and pahoehoe flows. The tectonic structures display well-defined patterns, predominantly oriented NNW-SSE, paralleling the main rift axis and the Red Sea rift, and accommodating nearly orthogonal extension. In contrast, NE to NNE-trending transverse fractures which connect the Gada’Ale dome with the shield volcano, aligns parallel to the axial fractures and normal faults of the Wonji Fault Belt in the Main Ethiopian Rift. The structural analysis confirms the predominance of NNW-SSE trending extensional fractures, highlighting the area's tectonic activity. These findings significantly enhance our understanding of the geological mechanisms shaping the northern Erta’Ale volcanic range and provide critical insights into the behavior of active volcanic systems. Continued research is essential to study ongoing geological events and deepen our understanding of the tectonic evolution of this significant region. Declarations Acknowledgments The authors would like to thank to the community of Afar and Tigray Regional states for their friendly support during the fieldwork. They are also thankful for the logistics support received from Aksum University and Mekelle University, Ethiopia. Author contribution statement All authors contributed to the study’s conception and design. Teka Asresie performed the methodology, data curation, investigation, formal analysis, validation, and wrote the original draft of the manuscript. Miruts Hagos contributed to the conceptualization, methodology, data curation, investigation, funding acquisition, resources, project administration, software, supervision, and wrote the review and editing. All authors read and approved the final manuscript. Funding This research was supported by Aksum University and Mekelle University. Data availability The datasets generated and/or analyzed during this study are available based on a reasonable request from the corresponding author. Ethical approval and consent to participate Not applicable. Consent for publication Not applicable. Competing interests The authors declare that they have no known conflicts of interest. References Abbate E, Passerini P, Zan L. Strike-slip faults in a rift area: a transect in the Afar Triangle, East Africa. Tectonophysics. 1995;241(1–2):67–97. Acocella V, Korme T. Holocene extension direction along the main Ethiopian Rift, East Africa. Terra Nova. 2002;14(3):191–7. Acocella V. Regional and local tectonics at Erta Ale caldera, Afar (Ethiopia). J Struct Geol. 2006;28(10):1808–20. Amelung F, Oppenheimer C, Segall P, Zebker H. Ground deformation near Gada ‘Ale Volcano, Afar, observed by radar interferometry. Geophys Res Lett. 2000;27(19):3093–6. Audin L, Quidelleur X, Coulié E, Courtillot V, Gilder S, Manighetti I, Gillot PY, Tapponnier P, Kidane T. Palaeomagnetism and K-Ar and 40Ar/39Ar ages in the Ali Sabieh area (Republic of Djibouti and Ethiopia): constraints on the mechanism of Aden ridge propagation into southeastern Afar during the last 10 Myr. Geophys J Int. 2004;158(1):327–45. Ayalew D, Barbey P, Marty B, Reisberg L, Yirgu G, Pik R. Source, genesis, and timing of giant ignimbrite deposits associated with Ethiopian continental flood basalts. GeochimicaetCosmochimicaActa. 2002;66(8):1429–48. Baker JA, Thirlwall MF, Menzies MA. Sr- Nd- Pb isotopic and trace element evidence for crustal contamination of plume-derived flood basalts: Oligocene flood volcanism in western Yemen. GeochimicaetCosmochimicaActa. 1996;60(14):2559–81. Barberi F, Varet J. The Erta Ale volcanic range (Danakil depression, northern afar, Ethiopia). Bull Volcanologique. 1970;34(4):848–917. Barberi F, Varet J. Volcanism of Afar: Small-scale plate tectonics implications. Geol Soc Am Bull. 1977;88(9):1251–66. Barberi F, Ferrara G, Santacroce R, Varet J. Structural evolution of the Afar triple junction, in Afar depression. Ethiopia. 1975;1:39–54. Barberi F, Tazieff H, Varet J. Volcanism in the Afar depression: its tectonic and magmatic significance. Tectonophysics. 1972;15(1–2):19–29. Barrat JA, Fourcade S, Jahn BM, Cheminee JL, Capdevila R. Isotope (Sr, Nd, Pb, O) and trace-element geochemistry of volcanics from the Erta'Ale range (Ethiopia). J Volcanol Geoth Res. 1998;80(1–2):85–100. Bastow ID, Keir D. The protracted development of the continent–ocean transition in Afar. Nat Geosci. 2011;4(4):248–50. Boccaletti M, Bonini M, Mazzuoli R, Abebe B, Piccardi L, Tortorici L. Quaternary oblique extensional tectonics in the Ethiopian Rift (Horn of Africa). Tectonophysics. 1998;287(1–4):97–116. Bonatti E, Gasperini E, Vigliotti L, Lupi L, Vaselli O, Polonia A, Gasperini L. Lake Afrera, a structural depression in the northern Afar Rift (Red Sea). Heliyon. 2017;3(5):e00301. Eagles G, Gloaguen R, Ebinger C. Kinematics of the Danakil microplate. Earth Planet Sci Lett. 2002;203(2):607–20. Ebinger CJ, Keir D, Ayele A, Calais E, Wright TJ, Belachew M, Hammond JO, Campbell E, Buck WR. Capturing magma intrusion and faulting processes during continental rupture: seismicity of the Dabbahu (Afar) rift. Geophys J Int. 2008;174(3):1138–52. Hagos GM. 2011. Geochemical and petrographic studies of the volcano-tectonic evolution of northern Afar (Doctoral dissertation, uniwien). Hagos M, Koeberl C, de Vries BVW. The Quaternary volcanic rocks of the northern Afar Depression (northern Ethiopia): Perspectives on petrology, geochemistry, and tectonics. J Afr Earth Sc. 2016b;117:29–47. Hofmann C, Courtillot V, Feraud G, Rochette P, Yirgu G, Ketefo E, Pik R. Timing of the Ethiopian flood basalt event and implications for plume birth and global change. Nature. 1997;389(6653):838–41. Hurman GL, Keir D, Bull JM, McNeill LC, Booth AD, Bastow ID. 2023. Quantitative analysis of faulting in the Danakil depression rift of Afar: The importance of faulting in the final stages of magma-rich rifting. Tectonics , 42 (6), p.e2022TC007607. Hutchinson RW, Engels GG. 1970. Tectonic significance of regional geology and evaporite lithofacies in northeastern Ethiopia. Philosophical Trans Royal Soc Lond Ser Math Phys Sci, pp.313–29. Kieffer B, Arndt N, Lapierre H, Bastien F, Bosch D, Pecher A, Yirgu G, Ayalew D, Weis D, Jerram DA, Keller F. Flood and shield basalts from Ethiopia: magmas from the African superswell. J Petrol. 2004;45(4):793–834. Lahitte P, Gillot PY, Kidane T, Courtillot V, Bekele A. 2003. New age constraints on the timing of volcanism in central Afar, in the presence of propagating rifts. J Geophys Research: Solid Earth, 108 (B2). López-García JM, Moreira D, Benzerara K, Grunewald O, López-García P. 2020. Origin and evolution of the halo-volcanic complex of Dallol: proto-volcanism in Northern Afar (Ethiopia). Frontiers in Earth Science , 7 , p.351. Magee C, Bastow ID, van Wyk de Vries B, Jackson CAL, Hetherington R, Hagos M, Hoggett M. Structure and dynamics of surface uplift induced by incremental sill emplacement. Geology. 2017;45(5):431–4. Maguire PKH, Keller GR, Klemperer SL, Mackenzie GD, Keranen K, Harder S, O’reilly B, Thybo H, Asfaw L, Khan MA, Amha M. Crustal structure of the northern Main Ethiopian Rift from the EAGLE controlled-source survey; a snapshot of incipient lithospheric break-up. Geol Soc Lond Special Publications. 2006;259(1):269–92. Makris J, Ginzburg A. The Afar Depression: transition between continental rifting and sea-floor spreading. Tectonophysics. 1987;141(1–3):199–214. Nobile A, Pagli C, Keir D, Wright TJ, Ayele A, Ruch J, Acocella V. 2012. Dike-fault interaction during the 2004 Dallol intrusion at the northern edge of the Erta Ale Ridge (Afar, Ethiopia). Geophysical Research Letters , 39 (19). Pagli C, Wright TJ, Ebinger CJ, Yun SH, Cann JR, Barnie T, Ayele A. Shallow axial magma chamber at the slow-spreading Erta Ale Ridge. Nat Geosci. 2012;5(4):284–8. Rime V, Foubert A, Ruch J, Kidane T. 2023. Tectonostratigraphic evolution and significance of the Afar Depression. Earth-Science Reviews , 244 , p.104519. Tefera M, Chernet T, Haro W. Explanation of the geological map of Ethiopia. Geological Survey of Ethiopia; 1996. Terry RD, Chilingar GV. Summary of Concerning some additional aids in studying sedimentary formations, by MS Shvetsov. J Sediment Res. 1955;25(3):229–34. Tesfaye S, Harding DJ, Kusky TM. Early continental breakup boundary and migration of the Afar triple junction, Ethiopia. GSA Bull. 2003;115(9):1053–67. Thurmond AK, Abdelsalam MG, Thurmond JB. Optical-radar-DEM remote sensing data integration for geological mapping in the Afar Depression, Ethiopia. J Afr Earth Sc. 2006;44(2):119–34. Varet J, Gasse F. Geology of central and southern Afar (Ethiopia and Djibouti Republic): Paris. Editions du Centre National de la RechercheScientifique, Report; 1978. Vidal P, Deniel C, Vellutini PJ, Piguet P, Coulon C, Vincent J, Audin J. Changes of mantle sources in the course of a rift evolution: the Afar case. Geophys Res Lett. 1991;18(10):1913–6. Waltham T. Extension tectonics in the Afar Triangle. Geol Today. 2005;21(3):101–7. Wolfenden E, Ebinger C, Yirgu G, Deino A, Ayalew D. Evolution of the northern Main Ethiopian rift: birth of a triple junction. Earth Planet Sci Lett. 2004;224(1–2):213–28. Wolfenden E, Ebinger C, Yirgu G, Renne PR, Kelley SP. Evolution of a volcanic rifted margin: Southern Red Sea, Ethiopia. Geol Soc Am Bull. 2005;117(7–8):846–64. Wright TJ, Ebinger C, Biggs J, Ayele A, Yirgu G, Keir D, Stork A. Magma-maintained rift segmentation at continental rupture in the 2005 Afardyking episode. Nature. 2006;442(7100):291–4. Yirgu G, Ebinger CJ, Maguire PKH. 2006. The afar volcanic province within the East African Rift System: introduction. Geological Society, London, Special Publications , 259 (1), pp.1–6. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Revision requested 11 Dec, 2025 Reviews received at journal 04 Dec, 2025 Reviews received at journal 30 Nov, 2025 Reviews received at journal 28 Nov, 2025 Reviewers agreed at journal 16 Nov, 2025 Reviewers agreed at journal 14 Nov, 2025 Reviewers invited by journal 11 Nov, 2025 Editor assigned by journal 11 Nov, 2025 Editor invited by journal 06 Nov, 2025 Submission checks completed at journal 06 Nov, 2025 First submitted to journal 06 Nov, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7947350","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":545878237,"identity":"49d4daf3-94d0-4360-a351-1afb4dfe40c9","order_by":0,"name":"Teka Asresie","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA/0lEQVRIie2PMUsDMRTHEwK55WnXC1fsVzjpJJ7cV+lxcC7t7uAQCaRL1bVOfovOJ4G4FJwlH8D1DkSCFmlT1DFxFMxvePwf/H88HkKRyJ+E7udwMBCPtnN7EhDgSwG21BO2dAr5rZK30zwDF0NKmciqf70oALVtPi7eV6NDgnDXTz1XQKtsuG4ACz6pZzfmWBJE2N3Ko6TnPGNSAdmdUbOFwTuFkgOfMnoRH+xTAUXVlThZmDKspFSznisAVBOCrKnCyrppTpFuIE01xdfc1JJg4f0lmevxs70sjsqn2zdkN+bsfi4eut6jOAh8Jyz3k/v7rmJ/4iZYjkQikX/IFpUbTgirlwf2AAAAAElFTkSuQmCC","orcid":"","institution":"Aksum University","correspondingAuthor":true,"prefix":"","firstName":"Teka","middleName":"","lastName":"Asresie","suffix":""},{"id":545878238,"identity":"cd05a09b-d075-41bc-9d59-1ef87267afab","order_by":1,"name":"Professor Miruts (PhD) Hagos","email":"","orcid":"","institution":"Mekelle University","correspondingAuthor":false,"prefix":"","firstName":"Professor","middleName":"Miruts","lastName":"(PhD)","suffix":"PhD"}],"badges":[],"createdAt":"2025-10-27 10:50:36","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7947350/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7947350/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":96603908,"identity":"3d845388-7807-47fb-a4cf-e556ccf5a5f0","added_by":"auto","created_at":"2025-11-24 09:12:01","extension":"docx","order_by":0,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":20621717,"visible":true,"origin":"","legend":"","description":"","filename":"ManuscriptTekaRevised.docx","url":"https://assets-eu.researchsquare.com/files/rs-7947350/v1/f75809d7a2870085d750d681.docx"},{"id":96605408,"identity":"2904f0e1-60e1-471e-86b2-b132091d8764","added_by":"auto","created_at":"2025-11-24 09:22:49","extension":"json","order_by":1,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":5103,"visible":true,"origin":"","legend":"","description":"","filename":"3aa2a39ed9d640bbb809422d891f5a31.json","url":"https://assets-eu.researchsquare.com/files/rs-7947350/v1/a81f15d1a5fd042c9374ca3b.json"},{"id":96536264,"identity":"bb815ce2-ddfe-4a60-9bcb-6925f8f8d4f1","added_by":"auto","created_at":"2025-11-22 18:39:03","extension":"xml","order_by":2,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":135070,"visible":true,"origin":"","legend":"","description":"","filename":"3aa2a39ed9d640bbb809422d891f5a311enriched.xml","url":"https://assets-eu.researchsquare.com/files/rs-7947350/v1/9bbff192d74ff730a67d5dfa.xml"},{"id":96536266,"identity":"7b90546d-6295-4536-adfb-b301a9bc9380","added_by":"auto","created_at":"2025-11-22 18:39:03","extension":"jpeg","order_by":3,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":1823708,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7947350/v1/1aaa2698e963267640cb1812.jpeg"},{"id":96536273,"identity":"8660e1b2-9d53-4341-85de-2508dbbe18d1","added_by":"auto","created_at":"2025-11-22 18:39:03","extension":"jpeg","order_by":4,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":774138,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage10.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7947350/v1/ae32ed26c947bc5134bd5df6.jpeg"},{"id":96604141,"identity":"51c245d1-3403-4317-aeff-1a2ac75c787c","added_by":"auto","created_at":"2025-11-24 09:12:54","extension":"png","order_by":5,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":1118600,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage11.png","url":"https://assets-eu.researchsquare.com/files/rs-7947350/v1/302f142fec8c5d66d295fc9e.png"},{"id":96605450,"identity":"e9ae05b9-e632-458a-a16a-b1558a73c6a6","added_by":"auto","created_at":"2025-11-24 09:23:04","extension":"png","order_by":6,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":2006019,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage12.png","url":"https://assets-eu.researchsquare.com/files/rs-7947350/v1/8f7e8ad26e047d50cc023e65.png"},{"id":96536282,"identity":"cba81227-6519-4edc-ae4b-1ae73e4285bf","added_by":"auto","created_at":"2025-11-22 18:39:04","extension":"png","order_by":7,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":1069394,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage13.png","url":"https://assets-eu.researchsquare.com/files/rs-7947350/v1/cc2f2e2c0c2938c5533d2fcd.png"},{"id":96536279,"identity":"6ff57259-b4d7-4e2a-a027-7af49190fc11","added_by":"auto","created_at":"2025-11-22 18:39:04","extension":"jpeg","order_by":8,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":265934,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage14.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7947350/v1/cf6620d1aa77d037533480cc.jpeg"},{"id":96604105,"identity":"bd787556-ce43-461e-8321-54634ffa1d9d","added_by":"auto","created_at":"2025-11-24 09:12:46","extension":"png","order_by":9,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":919170,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-7947350/v1/e0b195ddce645f15a7a3907c.png"},{"id":96536289,"identity":"33811854-b9f0-4702-9c4e-626a51e3f0e6","added_by":"auto","created_at":"2025-11-22 18:39:04","extension":"jpeg","order_by":10,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":2086754,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage3.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7947350/v1/2ff54675ad1aa907860e5a95.jpeg"},{"id":96536305,"identity":"0fc25903-364e-409d-aacb-2f2738451887","added_by":"auto","created_at":"2025-11-22 18:39:05","extension":"png","order_by":11,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":1739041,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-7947350/v1/aae5ad95fa7ac96000647d6a.png"},{"id":96536270,"identity":"321067af-9f93-46a3-9794-9fe7c7e17478","added_by":"auto","created_at":"2025-11-22 18:39:03","extension":"jpeg","order_by":12,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":327231,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage5.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7947350/v1/c3bfa68aa9b67cc62cf95fc3.jpeg"},{"id":96536309,"identity":"5070440a-08d4-4f48-a556-f6494e61dc9a","added_by":"auto","created_at":"2025-11-22 18:39:05","extension":"jpeg","order_by":13,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":2893756,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage6.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7947350/v1/88c198a0330279db99fd7dd1.jpeg"},{"id":96604830,"identity":"b368d417-e30f-40bf-ad4e-5046f8991050","added_by":"auto","created_at":"2025-11-24 09:15:11","extension":"jpeg","order_by":14,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":3318124,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage7.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7947350/v1/b9310403e2d384efac81d0cc.jpeg"},{"id":96536292,"identity":"5eb44dda-1f3f-4423-b0ac-2a9458aca148","added_by":"auto","created_at":"2025-11-22 18:39:04","extension":"emf","order_by":15,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":5819256,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage8.emf","url":"https://assets-eu.researchsquare.com/files/rs-7947350/v1/2f9e35091583b41b1bac698c.emf"},{"id":96536302,"identity":"0014666d-9174-4ee8-a139-14d84e3ee15a","added_by":"auto","created_at":"2025-11-22 18:39:04","extension":"emf","order_by":16,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":6327100,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage9.emf","url":"https://assets-eu.researchsquare.com/files/rs-7947350/v1/d9bc469973c72ca1b34040b6.emf"},{"id":96604764,"identity":"366ded4e-2224-4454-8b39-df3d79ef2deb","added_by":"auto","created_at":"2025-11-24 09:14:50","extension":"png","order_by":17,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":238297,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-7947350/v1/f824a0d58fc0db7ed86bb96f.png"},{"id":96536303,"identity":"25e54abb-af88-4559-bf87-7e8fe4501ba1","added_by":"auto","created_at":"2025-11-22 18:39:05","extension":"png","order_by":18,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":184743,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage10.png","url":"https://assets-eu.researchsquare.com/files/rs-7947350/v1/a18e00ac290af0e48d577b7e.png"},{"id":96604304,"identity":"76c737a6-56b8-4aa6-942c-e3ae49965c51","added_by":"auto","created_at":"2025-11-24 09:13:32","extension":"png","order_by":19,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":180242,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage11.png","url":"https://assets-eu.researchsquare.com/files/rs-7947350/v1/fae8874b9f66d44cb0338a19.png"},{"id":96536274,"identity":"34f92286-7952-4cdf-9618-4cee6ed5806b","added_by":"auto","created_at":"2025-11-22 18:39:04","extension":"png","order_by":20,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":367358,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage12.png","url":"https://assets-eu.researchsquare.com/files/rs-7947350/v1/bd95eb0e0f662f1dd5a62840.png"},{"id":96536306,"identity":"465da5cd-f746-4fe9-b8d7-1050af646355","added_by":"auto","created_at":"2025-11-22 18:39:05","extension":"png","order_by":21,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":198146,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage13.png","url":"https://assets-eu.researchsquare.com/files/rs-7947350/v1/20e77cc15031bbfe520a4b55.png"},{"id":96536298,"identity":"776105e5-1e3d-4a0c-ab74-d93582613e9f","added_by":"auto","created_at":"2025-11-22 18:39:04","extension":"png","order_by":22,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":28911,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage14.png","url":"https://assets-eu.researchsquare.com/files/rs-7947350/v1/111545588b93b2de0d498b05.png"},{"id":96604349,"identity":"82270717-0a54-4ffc-9df3-befb0f385070","added_by":"auto","created_at":"2025-11-24 09:13:41","extension":"png","order_by":23,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":240425,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-7947350/v1/7e23ee4330db76e481afa68a.png"},{"id":96536295,"identity":"16a6966b-6268-414a-a17d-89b28436bbcc","added_by":"auto","created_at":"2025-11-22 18:39:04","extension":"png","order_by":24,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":322194,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-7947350/v1/c7f6b5c3a7efdd9da2071cba.png"},{"id":96536287,"identity":"610883d2-9e42-4927-82d4-697625c6e446","added_by":"auto","created_at":"2025-11-22 18:39:04","extension":"png","order_by":25,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":256672,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-7947350/v1/7c312a0f904aa8bcdbe3272e.png"},{"id":96536291,"identity":"adac20fe-c6bb-408a-9717-3ab2aee4449c","added_by":"auto","created_at":"2025-11-22 18:39:04","extension":"png","order_by":26,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":217092,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-7947350/v1/50f4b2a13309a6bdd7de2bfc.png"},{"id":96536288,"identity":"f986d683-2190-4116-b280-36ad2fbe1069","added_by":"auto","created_at":"2025-11-22 18:39:04","extension":"png","order_by":27,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":458690,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-7947350/v1/fa4d0206e8f927bc28eddd95.png"},{"id":96604440,"identity":"795de6b1-1480-4727-a7a1-13f024a37d2c","added_by":"auto","created_at":"2025-11-24 09:13:57","extension":"png","order_by":28,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":584993,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-7947350/v1/7e8835cee98cdc4400a37b43.png"},{"id":96536293,"identity":"b12efd89-8fb2-4a2d-8c8e-67dbf812ba6d","added_by":"auto","created_at":"2025-11-22 18:39:04","extension":"png","order_by":29,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":73360,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage8.png","url":"https://assets-eu.researchsquare.com/files/rs-7947350/v1/ea172a3ca51946925b6a8761.png"},{"id":96536290,"identity":"27f7daaf-5a08-4e3d-a375-ff1d05172c1c","added_by":"auto","created_at":"2025-11-22 18:39:04","extension":"png","order_by":30,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":219934,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage9.png","url":"https://assets-eu.researchsquare.com/files/rs-7947350/v1/fe63426d92e3e4b0114b2f3d.png"},{"id":96536285,"identity":"3a54282a-d4d2-41f3-abe2-2b0e4dff5bb3","added_by":"auto","created_at":"2025-11-22 18:39:04","extension":"xml","order_by":31,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":130975,"visible":true,"origin":"","legend":"","description":"","filename":"3aa2a39ed9d640bbb809422d891f5a311structuring.xml","url":"https://assets-eu.researchsquare.com/files/rs-7947350/v1/7785d1c6045024d240eae064.xml"},{"id":96536300,"identity":"59f36518-5f33-497c-adb5-ee187b1461f0","added_by":"auto","created_at":"2025-11-22 18:39:04","extension":"html","order_by":32,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":142448,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-7947350/v1/c8c3abdc495777405c767dc2.html"},{"id":96536265,"identity":"4639aacf-b4f1-4132-9dfc-20254593805c","added_by":"auto","created_at":"2025-11-22 18:39:03","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":1433334,"visible":true,"origin":"","legend":"\u003cp\u003eLocation map of the Gada’Ale area produced from Landsat-5 ETM composite images (Bands 7, 5 and 1) of the Afar, zone two, resized by using ENVI 4.5 software, and the projection of the Satellite image is Adindan, UTM zone 37N (a); tectonic map of the entire Afar Depression (b); geological map of the northern Afar Depression (after 18) (c); rectangular inset indicates study area boundary.\u003c/p\u003e","description":"","filename":"image1.png","url":"https://assets-eu.researchsquare.com/files/rs-7947350/v1/f3240f6eed82ab43ffd87c61.png"},{"id":96604495,"identity":"0ab729d5-3855-4e49-b9bd-7e69bf35982c","added_by":"auto","created_at":"2025-11-24 09:14:03","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":919170,"visible":true,"origin":"","legend":"\u003cp\u003eSimplified geological and structural map of northern Afar Depression: prepared on interpretations of Sentinel and Landsat-5 ETM and reconnaissance fieldwork.\u003c/p\u003e","description":"","filename":"image2.png","url":"https://assets-eu.researchsquare.com/files/rs-7947350/v1/475645fd5e65c8e29a18eae1.png"},{"id":96536263,"identity":"292b41d6-e085-4298-8046-ed21a43b0476","added_by":"auto","created_at":"2025-11-22 18:39:03","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":1315466,"visible":true,"origin":"","legend":"\u003cp\u003eSimplified geological and structural map (a), geological profile sections W-E (b) and SSW-NNE (c) of the Gada’Ale area illustrating the nature of deformations. Vertical exaggeration of the cross sections is 2.5 m. The geology and structures were digitized from Google Earth and Landsat images and further modified using ArcGIS 10.4.1 software and CorelDraw 11 map editor.\u003c/p\u003e","description":"","filename":"image3.png","url":"https://assets-eu.researchsquare.com/files/rs-7947350/v1/fe763fd943336222539b8c46.png"},{"id":96536277,"identity":"2d91b539-cc6b-4c5a-9d28-da074af48533","added_by":"auto","created_at":"2025-11-22 18:39:04","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":1739041,"visible":true,"origin":"","legend":"\u003cp\u003ea) Representative outcrop photograph representing the visible stratigraphic succession along the fault surface. b) Simplified section (A-A’) showing the major units of the dome and graben, not to scale; photo taken from the southwestern part of the Gada’Ale volcano.\u003c/p\u003e","description":"","filename":"image4.png","url":"https://assets-eu.researchsquare.com/files/rs-7947350/v1/f1ef14a68ead4c5759594fa0.png"},{"id":96536275,"identity":"85a6494b-420b-4afe-bce6-bc707e6f39fe","added_by":"auto","created_at":"2025-11-22 18:39:04","extension":"jpeg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":327231,"visible":true,"origin":"","legend":"\u003cp\u003eRepresentative field photographs from the Gada’Ale area; a) blocky vesicular lava flows interlayered with rock salt at the bottom and aphanitic basalts at the top; b) highly exfoliated vesicular basalts making a sharp contact with the evaporite deposits; photo was taken from the periphery of the semi-collapsed caldera; c) jointed vesicular basalt, characterized by lava cave structure.\u003c/p\u003e","description":"","filename":"image5.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7947350/v1/37fed2e70696d17a0567e7e8.jpeg"},{"id":96536271,"identity":"3e892fa4-b1c5-473e-97b2-9c5fd7e9b333","added_by":"auto","created_at":"2025-11-22 18:39:03","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":1678668,"visible":true,"origin":"","legend":"\u003cp\u003eRepresentative field photos and photomicrographs showing typical minerals and textures of the analyzed basaltic rocks of the study area. (a) Blocky vesicular basalts characterized by rounded to subrounded vesicles. (b) Dark color vesicular basalts showing small lava caves. (c) Euhedral mega-phenocryst of clinopyroxene set in a coarse-grained plagioclase dominated groundmass of clinopyroxenes, few olivine and opaques. The elongated and laths-like plagioclase grains show polysynthetic twinning and are almost aligned. (d) Fine-grained plagioclase dominated groundmass of clinopyroxene, a few olivine, opaques, and vesicles. Tabular-elongated, randomly oriented micro-phenocrysts of albite and some polysynthetically twined plagioclase grains are common. (e) Mega phenocrysts of plagioclase set in a fine-grained plagioclase rich groundmass of clinopyroxene, few olivine and opaques. Plagioclase phenocrysts show polysynthetic twinning. (f) Fine-grained plagioclase and clinopyroxene dominated groundmass. Tabular-elongated meso-phenocrysts of polysynthetic plagioclase and few euhedral-subhedral olivine grains are present. All thin section photos were taken under crossed polars with a magnification of x50.\u003c/p\u003e","description":"","filename":"image6.png","url":"https://assets-eu.researchsquare.com/files/rs-7947350/v1/f99edbc74ff86dc61130ec69.png"},{"id":96536297,"identity":"79bf391b-8d88-4f80-8f07-6b9b1072dbbd","added_by":"auto","created_at":"2025-11-22 18:39:04","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":1862215,"visible":true,"origin":"","legend":"\u003cp\u003eRepresentative outcrop photos and thin-sections of the fine-grained lava flows from the Gada’Ale area. (a) Fine grain basalts characterized by pahoehoe lava flow and columnar joints. (b) Light gray color basalts. (c) Megaphenocrysts of albitic twinned plagioclase, imbedded in a medium-grained groundmass of randomly aligned plagioclase, pyroxene, and opaques. (d) A fine-grained, lath-like plagioclase-rich matrix exhibits flow texture, dominated by plagioclases with albite twinning, few pyroxenes and opaques. (e) Large subrounded olivine phenocryst set in a plagioclase dominated ground mass of clinopyroxene, opaque and few olivine. Olivine and clinopyroxene phenocrysts are fractured and altered. (f) Very fine-grained plagioclase-dominated ground mass with some pyroxenes and opaques. The plagioclase matrix shows flow texture. (g) Large grained plagioclase phenocryst embedded in a medium-grained groundmass of highly altered plagioclase, pyroxene, opaques and few vesicles. Euhedral plagioclase phenocrysts show polysynthetic twinning. (h) Fine-grained plagioclase rich ground mass, clinopyroxenes and opaques with few micro-phenocrysts of plagioclase and clinopyroxenes. All photos were taken under crossed polars with a magnification of x50.\u003c/p\u003e","description":"","filename":"image7.png","url":"https://assets-eu.researchsquare.com/files/rs-7947350/v1/3ca20c3e076642e7ef391274.png"},{"id":96536268,"identity":"005f71d4-fb43-4dd8-895e-009e8aaa84e1","added_by":"auto","created_at":"2025-11-22 18:39:03","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":235555,"visible":true,"origin":"","legend":"\u003cp\u003eDetailed structural map of the Gada'Ale area. The spatial distribution of contacts and structures were extracted from the Google Earth Image, 30 m resolution DEM, and 5 m resolution Landsat-5 ETM+ and SPOT Satellite images. To show the nature of the Gada’Ale dome and other associated structural features, two profile sections (a-a’ and b-b’) were constructed from the DEM data using Global Mapper 12. Fault traces and spatial orientations of the cross-sections were extracted from the structural map by overlaying the profiles in ArcGIS 10.4.1.\u003c/p\u003e","description":"","filename":"image8.png","url":"https://assets-eu.researchsquare.com/files/rs-7947350/v1/b01b24582cda1dafd3514781.png"},{"id":96604589,"identity":"78ab7e23-9436-463c-a709-a1e3521426f4","added_by":"auto","created_at":"2025-11-24 09:14:17","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":1130024,"visible":true,"origin":"","legend":"\u003cp\u003ea) DEM showing the geomorphological features of the Gada’Ale area; b) Landsat color composite image of Bands 7-5-1; showing the major extension fractures, collapse features (uplift and caldera collapse) and the Gada’Ale shield volcano; c) Topographic profiles (a-a’ and b-b’) across the Gada’Ale area in fig. 9a, showing various geomorphologic features.\u003c/p\u003e","description":"","filename":"image9.png","url":"https://assets-eu.researchsquare.com/files/rs-7947350/v1/2b022abd130d756a34985da4.png"},{"id":96604731,"identity":"018e26c3-4ac7-4a5c-b67e-da2f1490e52e","added_by":"auto","created_at":"2025-11-24 09:14:43","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":523466,"visible":true,"origin":"","legend":"\u003cp\u003eRepresentative field photos of extensional fractures of the western part of the Gada’Ale shield volcano (a-c), their orientations (d), opening direction (e) and the 84.4°, the angle between the fracture trend and extension direction (f) suggests a nearly orthogonal extension.\u003c/p\u003e","description":"","filename":"image10.png","url":"https://assets-eu.researchsquare.com/files/rs-7947350/v1/754ef63bcea58191c9fdb7f7.png"},{"id":96536278,"identity":"725f39db-8142-4055-ac9c-5270bb16d793","added_by":"auto","created_at":"2025-11-22 18:39:04","extension":"png","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":1118600,"visible":true,"origin":"","legend":"\u003cp\u003eField photographs of the Gada’Ale shield volcano: (a) broader view of the Gada’Ale volcano showing the morphological development of the shield and associated hydrothermal deposits; (b) side-wall volcanic collapse/caldera at the northwestern side of the shield; (c) circular crater at the top of the shield volcano.\u003c/p\u003e","description":"","filename":"image11.png","url":"https://assets-eu.researchsquare.com/files/rs-7947350/v1/d1549122447811078007c345.png"},{"id":96536286,"identity":"2971777a-74c3-4fa3-ad43-df8b09dc5b9f","added_by":"auto","created_at":"2025-11-22 18:39:04","extension":"png","order_by":12,"title":"Figure 12","display":"","copyAsset":false,"role":"figure","size":1936573,"visible":true,"origin":"","legend":"\u003cp\u003eRepresentative outcrop photographs of volcanic-related structures of the Gada’Ale area; (a) the structurally well-preserved maar volcano at the southeastern part of the Gada’Ale shield; taken from Google map 12/16/2018; (b) about 1.5 m in diameter lava tube with elliptical geometry, just south of the volcanic dome, the inset photo represents some of the near vent lava tubes at the upper side of the shield volcano; (c) ropy-shaped pahoehoe lava at the base of the shield volcano; RA ® Rift Axis; ‘A-A’” represents E-W profile of the maar volcano.\u003c/p\u003e","description":"","filename":"image12.png","url":"https://assets-eu.researchsquare.com/files/rs-7947350/v1/2b7721980fab90464e5065b6.png"},{"id":96604835,"identity":"40cdb9d0-afcd-4cfa-8e85-66dd89d00b22","added_by":"auto","created_at":"2025-11-24 09:15:11","extension":"png","order_by":13,"title":"Figure 13","display":"","copyAsset":false,"role":"figure","size":1069394,"visible":true,"origin":"","legend":"\u003cp\u003eb) Photograph showing the morphology of the rolling-over block; c) a sketch representing the development of listric fault and associated roll-over folds; a) SPOT image showing the curvi-linear geometry of the caldera structure; the yellow dashed line indicates the position of the photo in “b”.\u003c/p\u003e","description":"","filename":"image13.png","url":"https://assets-eu.researchsquare.com/files/rs-7947350/v1/3649c63789500675ef03fbde.png"},{"id":96536283,"identity":"19b9d421-f3a5-4988-982f-7ccb2915b79a","added_by":"auto","created_at":"2025-11-22 18:39:04","extension":"png","order_by":14,"title":"Figure 14","display":"","copyAsset":false,"role":"figure","size":815348,"visible":true,"origin":"","legend":"\u003cp\u003eSimplified Rose diagram showing the general geometric and kinematic relationships of the Gada’Ale extensional fractures with that of the Erta’Ale, and TMH rifts.\u003c/p\u003e","description":"","filename":"image14.png","url":"https://assets-eu.researchsquare.com/files/rs-7947350/v1/becba00327078eab2b583814.png"},{"id":96912952,"identity":"57dcc0af-1e5f-4cdb-8ab9-df69e0a7df4e","added_by":"auto","created_at":"2025-11-27 13:44:24","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":17673637,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7947350/v1/bf8adcd0-3383-4d86-8b01-fb3bd89fc540.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Geological, Petrographic, and Structural Investigation of Gada’Ale Volcano and Surrounding Areas, Northern Afar Depression, Ethiopia","fulltext":[{"header":"1 Introduction","content":"\u003cp\u003eThe Afar Depression, located at a triple plate junction above a hot mantle plume is characterized by active extensional deformation and a range of volcanic activity from basaltic to rhyolitic compositions. This region serves as the source from which the Red Sea, Gulf of Aden, and Main Ethiopian rifts radiate [1, 5; Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb]. The floor of the Depression is dominated by a variety of magmatic products and sediments filled in the basin. Volcanism was widespread in the region between ~\u0026thinsp;31 and 22 Ma, during which flood basalts, shield basalts, and associated felsic pyroclastic rocks were erupted [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. The Afar Depression as a whole, and the Danakil Depression in particular, are on the verge of transitioning to oceanic crust or proto-oceanic spreading [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e, \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]. The Danakil Depression represents a highly evolved segment of the East African Rift System (EARS) and is one of the most volcanically and tectonically active regions on Earth (38, 39). Although it is a low-lying area with an average elevation of ~\u0026thinsp;200 meters, it drops to ~\u0026thinsp;124 meters below sea level in the Dallol Depression. Despite this low elevation, the region is home to several prominent shield volcanoes, including Erta\u0026rsquo;Ale, Tat\u0026rsquo;Ale, and Alyata (Figs.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ec and \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e), characterized by intense seismicity, hydrothermal activity, and basaltic volcanism.\u003c/p\u003e\u003cp\u003eThe Erta'Ale range is one of the most volcanically and tectonically active segments in the region, consisting of seven volcanic centers aligned in an NNW-SSE direction [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e]. From north to south, these centers are Gada\u0026rsquo;Ale, Alu, Dalaffilla, Borale\u0026rsquo;Ale, Erta\u0026rsquo;Ale, AleBagu, and Hayli Gubi (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). The range is characterized by basaltic magmatism, extensional fractures/normal faults, volcanic structures, and fissure-fed lavas that are primarily transitional to tholeiitic in composition, with some interbedded felsic derivatives accompanying the basaltic flows [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Typically, basaltic fissure eruptions align along NNW-SSE belts (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e), reflecting the regional tectonic trend of the Red Sea rift, and produce the \u0026lt;\u0026thinsp;1\u0026nbsp;million years old shield volcanoes of the range [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e]. We utilized various types of remote sensing imageries and field data for geological and structural mapping in the Gada\u0026rsquo;Ale and surrounding areas. This paper presents petrological, petrographic, and structural data from the study area. These data are interpreted to understand the geology, petrographic, and structural features of the Gada\u0026rsquo;Ale and surrounding areas.\u003c/p\u003e\u003cp\u003eThe Danakil Depression is one of the unique sub-aerial exposures in the globe and allows direct observation of mid-ocean ridge volcano-tectonic processes. It provides an opportunity to investigate the relationship between petrology, volcanism, tectonism, and sedimentation. In comparison to other areas within the Danakil Depression, the Erta\u0026rsquo;Ale range demonstrates a more pronounced interaction between tectonism and magmatism, making it crucial for understanding the surface manifestations of active magmatism. Additionally, the Danakil Depression is characterized by thick evaporite deposits (~\u0026thinsp;1500 m) overlaying thin crustal materials [~\u0026thinsp;15 km; 28]. However, due to the hostile environment, poor infrastructure, and extremely high temperatures, geological and structural investigations have primarily been conducted at a regional scale and have mostly relied on remote sensing techniques [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e, \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e, \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. Furthermore, detailed field-based geological and structural investigations focused on individual shield volcanoes have yet to be carried out. Specifically, the geology, petrography, and structural features of the northern end of Erta'Ale volcanic range, particularly the Gada'Ale area (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e), remain unexplored.\u003c/p\u003e\u003cp\u003eThe Gada'Ale is an interesting area that separates the northern non-magmatic, hydrothermally active Dallol Depression from the southern magmatic range (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). It features a shield volcano with a diameter of ~\u0026thinsp;4 km and elevated from the Dallol salt crust by ~\u0026thinsp;300 m. Located\u0026thinsp;~\u0026thinsp;4 km southwest of the volcano's summit are a semi-circular crater that has collapsed and a geometrically remarkable salt dome. The main goal of this study is to conduct a comprehensive geological, petrographic, and structural investigation to constrain the field stratigraphic relationships, and volcano-tectonic features of the study area. This study aims to achieve the following objectives: (1) provide a detailed description of the lithologic units, (2) determine the mineralogy and fabric of the volcanic rocks, and (3) describe the volcano-tectonic structures and morphological features of the study area.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e"},{"header":"2 Regional geological setting","content":"\u003cp\u003eThe Afar Depression is a highly extended area located at the triple junction of the Red Sea, Gulf of Aden, and East African rifts [\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e]. Covering an area of ~\u0026thinsp;250,000 km\u0026sup2;, it is one of the few places on Earth where researchers can study the entire processes of mantle plume dynamics, rift-rift-rift triple junctions, and microplate formation on land [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. Magmatic activity in the depression commenced\u0026thinsp;~\u0026thinsp;4\u0026nbsp;million years after the peak volcanism in the Ethiopian Plateau [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. Since the Oligocene, the region has experienced 30\u0026nbsp;million years of mafic, felsic, and pyroclastic volcanism, with significant eruptions (notably the Stratoid series) linked to the initiation of sea-floor spreading in the Gulf of Aden and Red Sea rifts [\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e]. Pleistocene to Quaternary volcanism is mainly confined to the active tectonic and magmatic segments of the embryonic spreading centers [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e, \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eLocated in the northern tectonic-magmatic domain of the Afar Depression, the Danakil Depression is a well-defined active rift segment bordered by major faults and dissected escarpments (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e; [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e, \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]. The attenuated continental crust has a thickness of \u0026lt;\u0026thinsp;15 km, with shallow magma chambers (2\u0026ndash;5 km deep) located beneath its axial zones [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e, \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e]. Volcanic activity in the Danakil Depression has been intense since the Pliocene, primarily concentrated in the axial zone, where three prominent volcanic shields-Erta\u0026rsquo;Ale, Tat\u0026rsquo;Ali, and Alayta-are found [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. The NNW-SSE trending Erta\u0026rsquo;Ale volcanic range dominates the southern portion of the depression and is the focus of most Quaternary to Recent basalt activity in the Afar region [Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e; \u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e12\u003c/span\u003e]. A notable fissure eruption at the Alu-Dalafilla volcano in 2008, oriented sub-parallel to the rift axis, represents one of the recent volcanic activities in the Erta'Ale Volcanic Range [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThe shield volcanoes of the Erta\u0026rsquo;Ale axial range, which are \u0026lt;\u0026thinsp;1\u0026nbsp;million years old, are typically formed by basaltic fissure eruptions arranged in NNW-SSE belts that align with the regional tectonic trend of the Red Sea rift [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e]. The lowest areas of the Danakil Depression are often filled with recent lacustrine sediments and evaporite beds, underlain by fissure-fed basaltic lava flows. Over the past million years, widespread fissure-fed basaltic flows, basaltic shields, scoria cones, and alkaline to peralkaline silicic rocks have erupted along the dynamically expanding axial ranges of the Afar Depression [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e, \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e]. Volcanism across the axial ranges of the northern Afar Depression, such as Erta\u0026rsquo;Ale, has produced fissure-fed transitional-tholeiitic basalts with elemental and isotopic compositions similar to those of mid-ocean ridge basalts (MORBs) [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. These basalts, often referred to as \u0026lsquo;Aden Series\u0026rsquo; basalts, and are closely resemble MORBs [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. The presence of dyke intrusions in the Erta'Ale ridge, a shallow magma chamber beneath the evaporites in the Dallol area, and the occurrence of intense shallow seismicity [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e] suggest a north-northwestward propagation of the Erta\u0026rsquo;Ale magmatic and tectonic activity linked rifting.\u003c/p\u003e\u003cp\u003eThe northern Afar Depression is marked by intense tectonic and hydrothermal activities, alongside basaltic volcanism, primarily focused on several axial volcanic ranges aligned parallel to the Red Sea axis [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. Volcanic activity in the depression has been vigorous since the Pliocene and is currently concentrated in the axial zone, forming three prominent volcanic shields: Erta\u0026rsquo;Ale, Alayta, and Tat\u0026rsquo;Ali [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. The lavas erupted from these systems show an affinity with mid-ocean ridge basalts (MORB), with slight enrichment possibly attributed to the influence of the Afar plume [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. These axial volcanic ranges are distinguished by their predominantly basaltic nature, their alignment along fissures that follow the dominant N-NW regional trends, and their unique petrological and geochemical characteristics [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. The Erta\u0026rsquo;Ale volcanic range, with an area of ~\u0026thinsp;2500 km\u0026sup2; [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e], features NNW-SSE trending elevated volcanic centers with a mean elevation of ~\u0026thinsp;200 m (Fig.). It is an active area of basaltic magmatism, characterized by fissure-fed lavas with some felsic derivatives interbedded with the basaltic flows [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. The felsic derivatives, including trachytes and rhyolites, are believed to have originated from the fractional crystallization of basaltic magmas with little or no crustal contamination [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003c/p\u003e"},{"header":"3. Sampling and methods","content":"\u003cp\u003eOur sampling was mainly focused on the western part of the Gada\u0026rsquo;Ale shield volcano with only two rock samples taken from the eastern part, as it is inaccessible. Despite the challenges due to the remote location, we collected sixteen (16) fresh surface rock samples, each weighing\u0026thinsp;\u0026lt;\u0026thinsp;1 kg. These samples were chosen based on their spatial distribution, mineralogical and lithologic variations, and overall areal coverage. The majority of the samples were taken from the mafic lava flows with only three samples from pyroclastic layers, hydrothermally altered rocks, and evaporites. From the sixteen samples, ten (10) rock samples-six from fine-grained basalts and four from blocky vesicular basalts-were chosen for petrographic analysis. The sampling locations were recorded using GPS, and an outcrop photograph of each sample was taken. Detailed field observations were conducted to identify rock units, noting to their color, texture, mineralogy, morphological and structural features, and weathering. Lithological contacts and geological structures were traced and interpreted on Google Earth and thematic satellite imagery.\u003c/p\u003e\u003cp\u003eThin sections were prepared in the Geological Survey of Ethiopia laboratory center found in Addis Ababa, and mineralogical examinations were performed under a petrological microscope at Mekelle University. The thin sections were analyzed to identify modal proportions, textures, alterations, and microstructural features of the volcanic rocks under both plane-polarized light (PPL) and cross-polarized light (XPL). The modal proportion of minerals was estimated using the simple counting technique of [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e].\u003c/p\u003e"},{"header":"4 Results and discussion","content":"\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\u003ch2\u003e4.1 Geological description\u003c/h2\u003e\u003cp\u003eThe Danakil Depression, characterized by its below-sea-level land surface, presents a unique geological setting in East Africa. The deepest valley is filled with a thick sequence of ~\u0026thinsp;1500 m of siliciclastics, carbonates, and evaporites [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e], forming the highly evolved Dallol plain. These plain lacks volcanic materials, while the geological history of its southern part (the Gada\u0026rsquo;Ale area) is strongly influenced by volcanic activity and extensional tectonics during the late Quaternary/Holocene period.\u003c/p\u003e\u003cp\u003eThe Gada\u0026rsquo;Ale and surrounding area is primarily covered by Quaternary fissure basaltic lava flows, thin pyroclastic materials interlayered with halite-dominated evaporites, and recent sediments. Field stratigraphy of this study reveals that the recent sediments represent the youngest lithologic units, while the evaporites are the oldest rocks in the mapped area. These sediments are predominantly deposited in the southwestern parts of the area, confined to small depressions such as calderas and pit craters (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea). Detailed field and petrographic descriptions of each rock unit and/or stratigraphic succession of the study area, from young to old is presented here below. It has to be noted that all units are younger than 10 Ka and age comparison is so local.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003e4.1.1 Recent sediments: -\u003c/b\u003e The alluvial/lagoonal sediments are the youngest units in the study area. They are mainly deposited in the southwestern parts of the Gada\u0026rsquo;Ale volcano, and within the semi-circular caldera (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea). The sediments are composed of clay, silt, sand, gravel and boulders. The color of the sediments is ranging from white, light gray to dark gray (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea). They are reworked from the hydrothermal altered deposits. In some cases, since there is pyroclastic layering intercalated with the lava flows, a significant amount of the alluvial deposit is also derived from the weathered and eroded products of the western escarpment.\u003c/p\u003e\u003cp\u003eAt the central part of the semi-collapsed caldera, the lagoonal sediment is flat whereas the eastern and western side is covered by massive and vesicular basaltic volcanic rocks. The sediments are very fine and containing shales of some fossils. The presence of lacustrine sediments and thick evaporites might indicate the presence of ancient lakes in the study area.\u003c/p\u003e\u003cp\u003e\u003cb\u003e4.1.2 Hydrothermal related deposits: -\u003c/b\u003e They are exposed in the northeastern parts of the study area, mostly at the summit and southern flanks of the Gada\u0026rsquo;Ale volcano (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea). Most of the southern flanks of the Gada\u0026rsquo;Ale volcano (i.e., the western-southern rim), is covered by reworked pyroclastic materials with some sulfur precipitates whereas in the eastern flank of the crater (i.e., ENE rim), the altered materials are covered by young vesicular basalts. The hydrothermally altered rim of the crater exhibits no sign of sliding but the blocky basalts with NE-oriented fractures.\u003c/p\u003e\u003cp\u003eThe deposits at the summit of the Gada\u0026rsquo;Ale volcano are deeply altered by an intense hydrothermal activity, and transformed into soft clay-like materials. The young hydrothermally altered rocks are rich in sulfur, clay, volcanic ashes, and other reworked pyroclastic materials. They are highly jointed and/or fractured. The reworked alluvial sediments at the center of the crater, are highly altered as a result of an intense volcanic activities and fluid-rock interaction that might occurred in a long period of time. In most cases, the color of these materials is changed into yellowish, mainly because of the presence of sulfur precipitates. They are also commonly observed on the peripheries of the semi-circular calderas, and small local craters found in the whole flanks of the Gada\u0026rsquo;Ale volcano.\u003c/p\u003e\u003cp\u003e\u003cb\u003e4.1.3 Pyroclastic materials: -\u003c/b\u003e These rocks are very thinly bedded and cover a small portion of the study area. They are unmappable and only traced on profile-section (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb). They are mainly confined to the western parts, and southern flanks of the Gada\u0026rsquo;Ale volcano. In the western part of the shield volcano at the semi-circular ring, ~\u0026thinsp;1\u0026ndash;2.5 m thick reworked pyroclastic material is deposited underneath the blocky vesicular basalts (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb). They are mainly felsic pyroclastic materials, like volcanic ashes. The pyroclastic materials are commonly observed interlayered with the lava flows and the layered evaporite (halite). They are characterized by light weight, light gray color, soft nature and intense weathering and alteration. The intense weathering and alteration of these rocks is due to the hydrothermal activities taken place in the past. They look like very soft clay-like materials, thin and also consists of visible feldspars and quartz. They are horizontally layered, and show slight lateral variations in thickness, but are less readily differentiated.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cdiv id=\"Sec6\" class=\"Section3\"\u003e\u003ch2\u003e4.1.4 Basaltic lava flows\u003c/h2\u003e\u003cp\u003eBased on field observations and mineralogical analysis, two types of basaltic lava flows are recognized in the Gada\u0026rsquo;Ale and surrounding area: relatively older and younger mafic lava flows.\u003c/p\u003e\u003cp\u003e\u003cb\u003eYounger lava flows: -\u003c/b\u003e Throughout the Erta\u0026rsquo;Ale volcanic range, the basaltic outcrops are younger than 100 ka [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e], and are part of the Aden series basaltic eruptions. The young basaltic rocks, the most recent flows in the study area, cover a small portion of the mapped area, restricted only to the eastern, northeastern and southern parts of the Gada\u0026rsquo;Ale area (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea). The younger fissure eruptions that took place on the eastern and southeastern flanks of the Gada\u0026rsquo;Ale volcano (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea) are related with the extensional tectonic fissures of NNW-direction that affect the southeastern flank of the volcano. They display both fresh, less weathered pahoehoe and a\u0026rsquo;a lava types. The a\u0026rsquo;a lava flows are characterized by rough or thorny texture and dark color with mostly unweathered surfaces. Except for the northern part of the shield volcano, these fissure basalts are almost gently dipping, and in most cases, they flow radially away from the volcano. The fissures aligned commonly to NNW and some N-S are characterized by recent tectonic fractures and indicate active lava flowing in the area.\u003c/p\u003e\u003cp\u003e\u003cb\u003eOlder lava flows: -\u003c/b\u003e They are the most dominant basaltic rocks, constitute almost\u0026thinsp;\u0026gt;\u0026thinsp;70% of the mapped area. They represent relatively older fissure-fed basaltic lava flows of both a\u0026rsquo;a and pahoehoe types erupted through the NNW-aligned extensional fractures. The a\u0026rsquo;a lava flows are characterized by rough and dark color with mostly unweathered surfaces. Samples were collected from the southeastern part of the ring structure, located in the southwestern part of the Gada\u0026rsquo;Ale volcano. These outcrops are relatively fractured, weathered and altered compared to the young basaltic volcanic rocks. Based on field and petrographic observations, these are texturally classified into two; blocky vesicular basalts and aphanitic basalts.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eVesicular lava flows: -\u003c/b\u003e The vesicular basalts are characterized by a smooth surface, light-dark color and highly vesiculated texture, mostly filled with fresh argilic materials (Figs.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ea and b). The vesicles are rounded to subrounded in shape and are formed by the expansion of bubbles of gas that was trapped inside the lava. They have relatively low density and hardness compared to the fine-grained basalts, mainly due to the presence of vesicles.\u003c/p\u003e\u003cp\u003eThe vesicular lava flows are commonly found in the northern, northeastern sides of the summit of the crater, most flanks of the Gada\u0026rsquo;Ale volcano, and in the southwestern and most flat laying parts of the study area. In the western flanks of the volcano, the blocky vesicular basalts are interlayered with the evaporite and aphanitic basalts on top (e.g., Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea). In the western parts within the eastern side of the ring, blocky vesicular basalts of ~\u0026thinsp;7 m thick is overlain by ~\u0026thinsp;2 m thick fine grained lava flows. Most of the lava flows are collapsed and toppled down towards the semi-circular calderas, in the form of blocks and debris, to form talus deposits (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea and b). The toppling of these lava flows is considered to be mainly because of local uplift and subsidence. They are relatively weathered (e.g., exfoliation weathering), altered and characterized by blocky nature. Joints are common within these outcrops and this together with the highly vesiculated nature of these lavas lead to speedy water circulation and increased rate of weathering. Sometimes, the color and composition of these rocks are changed, due to an intense degree of alteration and weathering, especially near discontinuities.\u003c/p\u003e\u003cp\u003eThe highly weathered nature of these lava flows is, due to the presence of vesicles and fractures; which in turn leads to speedy water and/or fluids circulation. They are highly fractured, altered, sometimes changed into yellowish color and form small volcanic caves and lava tubes. The lava tubes might indicate flow of lava beneath the hardened lava flow down from the center of the shield volcano. They are highly fractured and faulted. In the southwest part of the Gada\u0026rsquo;Ale dome, there is one major fracture on the vesicular basalt and upper pahoehoe lava flow, with opening\u0026thinsp;~\u0026thinsp;5 m, oriented NNW with a dip amount of 85\u003csup\u003e0\u003c/sup\u003e, almost vertical. Samples were collected from both sides of the semi-collapsed caldera structure to distinguish the mineralogical makeup, and textural variations of the basalts.\u003c/p\u003e\u003cp\u003e\u003cb\u003eAphanitic lava flows: -\u003c/b\u003e Based on field observation, this volcanic rock is characterized by dark-brown color, and fine texture (Figs.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003ea and b). They appear mostly in the form of pahoehoe with some a\u0026rsquo;a nature. They are fresh, slightly altered and their lower successions are blocky and vesicular in nature. The lava sheets are twisted into rope-like shapes (pahoehoe) lavas. The a\u0026rsquo;a types are formed when the lava loses its dissolved gases; it becomes thick, brittle, forms rough, jagged blocks of rock. This volcanic rock sequence is also characterized by light yellowish color, slightly fractured, tilted, jointed (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003ea and c), and varied degree of weathering. They are relatively less weathered with local variations in weathering grades, thinner and massive compared to vesicular lava flows. The fine-grained basalts are highly jointed (e.g., columnar joints) and are characterized by open joints, mostly unfilled with secondary materials. In most flanks of the Gada\u0026rsquo;Ale volcano, they form lava tube structures.\u003c/p\u003e\u003cp\u003eThe massive basalts are mostly sitting on top of the blocky vesicular lava flows. They are characterized by highly fragmented rock debris, resulted from rock movement and block rotations that might occurred due to tectonic activities. Once the primary structures (e.g., columnar joints) were developed within the massive basaltic lava flows, tectonics gradually change the rocks into rock debris formed due to block movement. This movement may further result in the formation of many fractures, most of which are oriented NNW, NE to NNE and some N-S direction.\u003c/p\u003e\u003cp\u003eToppling of the basalts from the top to the bottom parts is common phenomenon observed in the field, mainly along the peripheries of the semi-collapsed caldera structures (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea). Especially, along the dome-caldera structure, most of the lava flows which were placed above the evaporite sequence, are presently collapsed and slumped down from the top mainly as a result of uplifting. This rock unit is also found in the flat-lying areas of the study area, alongside vesicular lava flows, creating a talus deposit at the lowest portions.\u003c/p\u003e\u003cp\u003e\u003cb\u003e4.1.5 Evaporite deposits: -\u003c/b\u003e Evaporites are the oldest rock units in the Gada\u0026rsquo;Ale area. The age comparison is basically based on field stratigraphic sequence. They are mainly exposed in the northwestern and southwestern parts of the Gada\u0026rsquo;Ale area (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea). They are characterized by thick, light gray in color, hard, sub-horizontally bedded and commonly representing the rock salt (halite) (e.g., Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). In the western part of the Gada'Ale volcano, there is \u003cb\u003e~\u003c/b\u003e\u0026thinsp;80 m thick halite, where the whole basaltic sequence is flowing on top of it (Figs.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea and b) forming\u0026thinsp;\u003cb\u003e~\u003c/b\u003e\u0026thinsp;2 km diameter dome-like structure. The formation of this uplifted salt ring structure is related to local uplifting, magmatism and faulting.\u003c/p\u003e\u003cp\u003eTwo-types of evaporites have been recognized: the first is a flat-lying and thinly bedded, whereas the second is very massive and recrystallized. The flat-lying evaporites, which are found in the northwestern portion of the mapped area are the southern extension of the Dallol evaporites. The recrystallized evaporite is basically exposed on the sides of the collapsed semi-circular caldera (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea). Although they are unmappable, they are also commonly observed at the most flanks of the Gada\u0026rsquo;Ale volcano interlayered with the lava flows. These evaporites are elevated from the flat-lying once by ~\u0026thinsp;70\u0026ndash;90 m. This indicates that magma-assisted uplifting placed these rocks in the mountainous areas, within the flanks of the volcano. The presence of such thick evaporites and the underlined young sediments (lacustrine) in the Gada'Ale area might indicate the presence of lakes in the past 100 Ka, because the basis for sodium chloride is considered to be oceans and/or sea water. The origin of halite is entirely associated with evaporation of lake or sea water resulting in the loss of water and increasing the concentrations of Na\u003csup\u003e+\u003c/sup\u003e and Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e in the remaining water.\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\u003ch2\u003e4.2 Petrographic description\u003c/h2\u003e\u003cp\u003eTen thin sections were prepared to investigate the mineralogical, textural, and microstructural properties of the basaltic volcanic rocks of the Gada\u0026rsquo;Ale area.\u003c/p\u003e\u003cp\u003e\u003cb\u003e4.2.1 Vesicular lava flows: -\u003c/b\u003e Petrographically, these rocks are represented by vesicular texture. They are fine grained basalts carrying few localized phenocrysts of plagioclase, clinopyroxene and some olivine (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ec-f). Olivine and some clinopyroxene phenocrysts mostly show curvi-linear fractures/cleavages and are highly altered. They are pale brown in color and form irregular or anhedral shape (Figs.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ec and f). They range up to 1 mm in size, and contains needle-like to granular crystals of opaque minerals. The plagioclase phenocrysts are characterized by polysynthetic and albitic twinning and mostly randomly oriented (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ec-f). Vesicles are also commonly observed in these samples. Proportion of the minerals in the vesicular basalts is; plagioclase (~\u0026thinsp;52%), clinopyroxene (~\u0026thinsp;27%), olivine (~\u0026thinsp;8.5%), and opaque minerals (~\u0026thinsp;12%) (Figs.\u0026nbsp;4.8c-f).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003e4.2.2 Aphanitic lava flows: -\u003c/b\u003e Minerals cannot be readily observed by necked eye except few plagioclase minerals, because of the fine texture of these volcanic rocks. High magnification lens was used to differentiate the high magnesian basalts. From a petrographic point of view, these rocks exhibit an aphyric texture with very few micro-phenocrysts of plagioclase and few olivine, set on plagioclase dominated groundmass of clinopyroxenes, and opaque minerals (Figs.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003ec, e and g). Olivine phenocrysts are highly fractured and altered. The fabrics of these samples, in general, are inequigranular with finely crystallized plagioclase-lath showing albitic-polysynthetic twinning (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003ec, f, g and h), and are mostly randomly oriented. Some highly elongated plagioclase micro-phenocrysts (e.g., samples GA-008 and GA-014A) show flow (trachytic) texture (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003ed and f). Mega-phenocrysts of plagioclase are common (e.g., sample GA-004) but mega-phenocrysts of clinopyroxene and olivine are rare. Euhedral to subhedral plagioclase phenocrysts show albitic twinning (Figs.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003ec, f and h). Plagioclase crystals are elongated to laths shaped (ranging from 0.2\u0026ndash;0.3 mm in size). The mineralogical composition of the fine-grained basalts includes\u0026thinsp;~\u0026thinsp;51.5% plagioclase, 26% clinopyroxene, 6.5% olivine, and 15% opaque minerals, and others (Figs.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003ec-h).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003e4.3 Structural and morphological features\u003c/h2\u003e\u003cp\u003eThe axial zone of the Danakil Depression imprints some important physiographic elements of incipient ocean basin. Intermittent shield volcanoes rising from ~\u0026thinsp;300 meters above sea level (e.g., the Gada\u0026rsquo;Ale shield volcano) to ~\u0026thinsp;615 meters above sea level (i.e., the Erta\u0026rsquo;Ale shield volcano) characterize the axial part of the Danakil Depression. Satellite images and DEMs show that Gada\u0026rsquo;Ale volcano is slightly elliptical/sub-circular (4.3 \u0026times; 3.9 km), with a NNW-trending long axis parallel to the axial range extensional fractures (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). The salt dome at the southwestern base of Gada\u0026rsquo;Ale volcano is also another morphological feature with a peak elevation of 300 m.a.s.l. or rising\u0026thinsp;~\u0026thinsp;150 m high over the salt crust of the Dallol plain.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe two topographic profiles (i.e., profiles a-a\u0026rsquo; and b-b\u0026rsquo;; Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e), constructed along the Gada'Ale area, indicate the geomorphological and structural patterns. The geological map along with constructed geological cross sections (x-x\u0026rsquo;, y-y\u0026rsquo;; Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea-c) provides two clearly distinct and highly elevated morphologies: a flat-topped dome (central) and a well-defined shield volcano. The majority of the extension fractures and faults are oriented parallel to the rim structure (i.e., non-tectonic origin), with some transverse structural trends of NE, NNE and E-W orientations (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eNormal faults with visible displacement are scarce, the only measurable fault throws are found on the western rims of the Gada\u0026rsquo;Ale dome. As we can see from the profile sections (Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003ea-c), the summit of the dome is described by subdued horst and graben morphology. The interpretation of remote sensing and DEM data sets, supported with field measurements, showed that the area has two distinct structural trends: the dominant and well clustered NNW - SSE- trending extensional fractures, aligned parallel to the axial rift trend, and the local curvilinear structures which in-turn developed half-graben and horst-type morphology (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e). The outer rim of the dome is characterized by single to imbricate listric normal faulting with reverse drag (Fig.\u0026nbsp;\u003cspan refid=\"Fig13\" class=\"InternalRef\"\u003e13\u003c/span\u003ea and c). At the northern and southern sides of the dome, the young pahoehoe lavas are dissected by swarms of parallel-aligned NNW \u0026ndash; SSE oriented fractures (i.e., N22\u0026deg;W) (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e). The average orientation of these fractures is similar (i.e., with only 2\u0026ndash;3\u0026deg; deviation) with the alignment of the rift axis (N24\u0026deg;W).\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\u003ch2\u003e4.4 Nature of structures in the axial zone\u003c/h2\u003e\u003cp\u003eStructural data have been collected along the entire Gada\u0026rsquo;Ale shield volcano and uplifted salt dome (for an area of ~\u0026thinsp;125 km\u003csup\u003e2\u003c/sup\u003e) of the northern EVR. The study along the salt dome and the axial segment of the Gada\u0026rsquo;Ale area permit to analogically explore the volcano-tectonics of an incipient oceanic crust. The structures have been measured and mapped at a considerable scale. Within the premises of the well-defined Gada\u0026rsquo;Ale salt dome, three sets of structures have been recognized: tectonic structures, volcanic structures and/or a combination of these two.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003e4.4.1 Tectonic structures: -\u003c/b\u003e The northern part of the Erta\u0026rsquo;Ale volcanic range (EVR) exhibits both regional and/ or local tectonics, and fracture trace analysis has been considered mandatory to outline the axial rift structures. In order to evaluate the Quaternary geometry and kinematics of the region, rift axis fracture data have been collected from the fissure basalts of the area. The area includes various tectonic elements, such as extensional fractures, elliptical shield volcanoes and craters, and ring structures. For a better understanding of the kinematics of the Gada\u0026rsquo;Ale area, only late Holocene to present extensional fractures were analyzed using stereo plots [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. All fractures from the salt dome were not involved in this analysis; because, they are more of non-tectonic in origin and formed during the local uplift and subsidence process.\u003c/p\u003e\u003cp\u003eA total of ~\u0026thinsp;50 fracture orientations and 10 asperities from the fissural basalts of the Gada\u0026rsquo;Ale area, were measured (e.g., Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003ea-c). All measured open fractures have an opening between 0.03 and 1 m and a length between 5 and 500 m; their depth of penetration, ~\u0026thinsp;700 m, is inferred from mechanical considerations [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. The asperities along the walls of open fractures were sharp, fresh and unaffected by erosion and other secondary deformation, as for example shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003ea - c. This characteristic, together with the late Holocene\u0026ndash;age of the rocks, confirms that the fractures were active features in the study area. The open fractures, which have clear asperities, were analyzed and all found to be consistent with an overall ENE-WSW (059.4\u0026deg;) extension direction of the open fractures orthogonal to the mean trend of the axial structures (i.e., 335\u0026deg;; Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003ef).\u003c/p\u003e\u003cp\u003e\u003cb\u003e4.4.2 Volcanic structures: -\u003c/b\u003e Gada\u0026rsquo;Ale is an area where most of its volcanic structures are young and well exposed. The major volcanic-related structures are shield volcano, lava tubes, volcanic caves, a\u0026rsquo;a and pahoehoe lavas, collapse structures of various sizes, and maar volcanic rings.\u003c/p\u003e\u003cp\u003e\u003cb\u003eShield volcano: -\u003c/b\u003e The Gada\u0026rsquo;Ale volcano, with a peak elevation of 370 m from the crusted salt surface, is one of the youngest and best-preserved volcanic structures in the EVR. The slopes of the shield along its E-W profile are between 11\u0026deg; and 12\u0026deg; (Fig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e11\u003c/span\u003ea). At the top of the volcano, there is a well-preserved, about 80 m deep and 500 m diameter, circular crater (Fig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e11\u003c/span\u003ec). The southeastern rim of the crater is lower by ~\u0026thinsp;20 m, and most of the recent hydrothermal-related deposits (i.e., chimneys of sulfur, salt and reworked ash) are concentrated there and flow southwards up to the base of the volcano (Fig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e11\u003c/span\u003ea \u0026amp; c). The fresh pahoehoe and some a\u0026rsquo;a lavas are vesiculated on their upper layers. This single volcanic crater is filled with hydrothermally altered sulfur-rich soft clay-like materials. These materials are highly altered as a result of intense fumarolic activity and fluid-rock interaction. There are no recently erupted magmatic products on the shield volcano (i.e., like the Alu-Dallafilla and Erta\u0026rsquo;Ale shield volcanoes); however, fragile structures (e.g., fumaroles and chimneys of sulfur and salt) are still undisturbed indicating the presence of hydrothermal activities in the past few decades. Small local pit craters and side-wall caldera collapses of various size are also common all over the flanks of the shield volcano (e.g., Fig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e11\u003c/span\u003eb).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eLava tubes and Maar volcanoes: -\u003c/b\u003e Most of the volcanic rocks of Gada\u0026rsquo;Ale area are late Quaternary/Holocene in age, and hence meso-volcanic structures associated with the lava are fresh and undisturbed. Lava tubes and/or caves, pahoehoe and maar or ring structures, layered vesicles and other features are present. Most of the lava tubes are few centimeters in diameter, but some as large as 1.5 m in diameter (i.e., long axis; Fig.\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e12\u003c/span\u003eb). They developed in massive/thick lava flows and form perfectly elliptical tubes extending sub-horizontally for several kilometers. Most such structures are found at the periphery of the shield volcano and are radiating outwards for tens of kilometers.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eAs the lava tubes extend further from the vent, they generally become wider, with a more rounded to elliptical shape and smoother floor, due to the decreasing flow velocity and gradual cooling of the lava as they travel further downhill. In most cases, the size of the tube is inversely proportional from the vent and slope of the volcano; i.e., the smaller the lava tube is the closer to the eruptive center and steeper slope.\u003c/p\u003e\u003cp\u003eMaars, tuff rings, and scoria cones are also among the common volcanic structures in the area. The Maar volcano found at the southern part of Gada\u0026rsquo;Ale shield volcano forms a \u0026ldquo;negative\u0026rdquo; landform, characterized by a circular and well-defined crater with a floor below the elevation of the surrounding rift floor and well-preserved rims of accumulated tephra (also called tephra rings). The Maar volcanoes are commonly associated with the basaltic lava flows of the rift floor volcanoes and are entirely mafic in composition. The floor of the maar is filled by fragmented country rock and/or juvenile volcaniclastic material and is still lying\u0026thinsp;~\u0026thinsp;20 m below the normal surface (Fig.\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e12\u003c/span\u003e; profile A-A\u0026rsquo;). It is the youngest (late Holocene; most probably in the last 100 years) volcanic structure erupted at the center of the axial zone and very close to the lake Bikila, and representing the entire Afar maar structures. The position of the lake within 1.5 km distance and a shallow magma chamber underneath [~\u0026thinsp;2.4 km deep; 29] most probably enabled for the formation of such phreatomagmatic eruption. The southern rim of the maar is partly collapsed as a result of the very late scoria eruption.\u003c/p\u003e\u003cp\u003e\u003cb\u003eUplift and subsidence related structures: -\u003c/b\u003e At about 4 km WSW of the Gada\u0026rsquo;Ale shield volcano, there is 3.5 km in diameter evaporite deposit (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e) covered by a thin veneer (~\u0026thinsp;13-m-thick) of magmatic materials and bounded by arcuate-shaped (plan-view) outward dipping fault. The circular evaporite deposit, uplifted from the normal salt surface of the Dallol plain by about 130 m, is one of the unique geological features where you can observe pronounced dome, steep fault surfaces, well-defined half grabens and subdued horst and graben morphology on its summit (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ec and Fig.\u0026nbsp;\u003cspan refid=\"Fig13\" class=\"InternalRef\"\u003e13\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eListric faults and associated structures\u003c/strong\u003e\u003cp\u003e- At the northern, western and southern peripheries of the dome, steeply dipping (i.e., 80\u0026ndash;85\u0026deg;) semi-circular or curvilinear (plan view) faults with a measured throw of ~\u0026thinsp;100 m dominate the area. Underneath, the fault surface is covered by alluvium and the hanging wall block. The rolling-over geometry on the hanging-wall block and inverted dip of an originally vertical fractures indicate that the dome-bounding faults are listric in nature (Fig.\u0026nbsp;\u003cspan refid=\"Fig13\" class=\"InternalRef\"\u003e13\u003c/span\u003ec). Along the curved surface of the hanging wall block (i.e., rolled-over folded layer), fracture openings are very wide (i.e., up to 3 m) and converge inwards at the interface with the underlying salt layers. Fracture lengths and openings on the hanging wall block increase towards the fault surface.\u003c/p\u003e\u003c/p\u003e\u003cp\u003eA semi-circular half-graben, partly filled by recent sediments, separates the dome from the normal rift floor. This structure, ~\u0026thinsp;450 m wide and ~\u0026thinsp;6 km long, forms one of the visible extensional structures in the floor of the northern end of the EVR. The inner wall of the half-graben is a faulted surface cutting the overlying thin volcanic layer and underlying thick deposit of the evaporite sequence (upper halite; Fig.\u0026nbsp;\u003cspan refid=\"Fig13\" class=\"InternalRef\"\u003e13\u003c/span\u003eb \u0026amp; c). The outer wall of the half-graben is a rolled-over folded layer of the volcano-sedimentary sequence. Field observations showed that the underlying salt layers are not intensively fractured instead dragged and bended forming open folds. Salt layers have high ductility, meaning they can undergo significant plastic deformation without fracturing. The brittle deformation observed on the overlying volcanic rocks is, therefore, accommodated by crystal stretching in the underlying salt layers.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\u003ch2\u003e4.5 Structural comparison\u003c/h2\u003e\u003cp\u003eThe structures of the Gada\u0026rsquo;Ale area have two major average orientations; NNW and NE to NNE structural trends (Figs.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e). However, the NNW- striking extension structures are the dominant structural features in the mapped area; and are used to compare the Gada\u0026rsquo;Ale structures with regional structural trends around in the Region. Accordingly, the NNW- trending extensional fractures of the study area are oriented parallel to subparallel to the NNW- striking regional extensional fractures and normal faults of the Red Sea and northern Afar rifts [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. The orientation of the transverse structures, NE to NNE is, however, not related to any of the trend of the axial structures in the Erta\u0026rsquo;Ale rift segment. Instead, they are similarly oriented with the NNE- trending active extension fractures and normal faults of the MER structure (e.g., Wonji Fault Belt, WFB) and more similarly oriented with the transverse/transform structures of the northern Red Sea rift. They are aligned orthogonal/oblique to the NNW- trending extensional structures of the Gada\u0026rsquo;Ale area.\u003c/p\u003e\u003cp\u003eIn order to evaluate the Pleistocene-Recent rift-axis kinematics and geometry of the Erta\u0026rsquo;Ale range and TMH rifts, [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e] has collected structural data along the entire western part of the Erta\u0026rsquo;Ale range and central parts of the Tendaho graben. Because of their location on the axial range of the northern Afar Depression, parallel trend to the Erta\u0026rsquo;Ale range trend, and Pleistocene-Present age of the open fractures, their extension direction is considered to be resulted from the existing kinematics of the Ethiopian plateau and Danakil Microplate. The average extension direction of the TMH rift is N53\u003csup\u003e0\u003c/sup\u003eE; whereas that of the Erta\u0026rsquo;Ale and Gada\u0026rsquo;Ale rifts is N66\u003csup\u003e0\u003c/sup\u003eE and N59.4\u003csup\u003e0\u003c/sup\u003eE, respectively (Fig.\u0026nbsp;\u003cspan refid=\"Fig14\" class=\"InternalRef\"\u003e14\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eAs compared to the Erta\u0026rsquo;Ale, the orientations of the Gada\u0026rsquo;Ale extension fractures are deviated by 002\u003csup\u003e0\u003c/sup\u003e towards the west (Fig.\u0026nbsp;\u003cspan refid=\"Fig14\" class=\"InternalRef\"\u003e14\u003c/span\u003e), that is, the Erta\u0026rsquo;Ale range is oriented to N23\u003csup\u003e0\u003c/sup\u003eW [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e] and the average strike of the study area is N25\u003csup\u003e0\u003c/sup\u003eW. The geometric difference between the Gada\u0026rsquo;Ale and Erta\u0026rsquo;Ale extension fractures is, therefore, almost insignificant. The geometric difference with the TMH rift is, however, wide (i.e., 007\u003csup\u003e0\u003c/sup\u003e), with the TMH- trending to N32\u003csup\u003e0\u003c/sup\u003eW [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. The trend of the Gada\u0026rsquo;Ale area is, therefore, deviated by 007\u003csup\u003e0\u003c/sup\u003e to the east from the average trend of the Tendaho rift. All measured open fractures of the Erta\u0026rsquo;Ale range, TMH rift and the Gada\u0026rsquo;Ale area, are consistent with an overall ENE-WSW (066\u003csup\u003e0\u003c/sup\u003e, 053\u003csup\u003e0\u003c/sup\u003e and 059.4\u003csup\u003e0\u003c/sup\u003e) extension directions of the open fractures, orthogonal to the mean NNW-SSE (337\u003csup\u003e0\u003c/sup\u003e, 328\u003csup\u003e0\u003c/sup\u003e and 335\u003csup\u003e0\u003c/sup\u003e) trends, respectively (Fig.\u0026nbsp;\u003cspan refid=\"Fig14\" class=\"InternalRef\"\u003e14\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eThe strike and extension direction of open fractures/normal faults of the Erta\u0026rsquo;Ale and TMH axial rift zones vary by 009\u003csup\u003e0\u003c/sup\u003e and 013\u003csup\u003e0\u003c/sup\u003e, respectively. The deviation in the general orientation of the central Tendaho graben by 009\u003csup\u003e0\u003c/sup\u003e to the west from the average trend of the Erta\u0026rsquo;Ale range shows that the involvement of the Gulf of Aden rift (E-W- oriented ridge) is higher than the MER [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. The extension direction of the Gada\u0026rsquo;Ale area varies by 6.6\u003csup\u003e0\u003c/sup\u003e and 6.4\u003csup\u003e0\u003c/sup\u003e from the opening directions of the Erta\u0026rsquo;Ale and TMH rifts, respectively (Fig.\u0026nbsp;\u003cspan refid=\"Fig14\" class=\"InternalRef\"\u003e14\u003c/span\u003e). The angle between the trends of the extensional fractures and extension direction in all cases is, however, similarly orthogonal (i.e., 89\u003csup\u003e0\u003c/sup\u003e, 84.4\u003csup\u003e0\u003c/sup\u003e and 85\u003csup\u003e0\u003c/sup\u003e) for the Erta\u0026rsquo;Ale, Gada\u0026rsquo;Ale, and TMH rifts, respectively.\u003c/p\u003e\u003c/div\u003e"},{"header":"5 Conclusions","content":"\u003cp\u003eThis study is the first to extensively examine the geological and structural features of the Gada\u0026rsquo;Ale area through field observations, remote sensing data, and petrographic investigations. The analysis reveals a narrow lithologic spectrum predominantly composed of basaltic lava flows, recent rift sediments, evaporites, and thinly bedded pyroclastic ash flows interbedded with the basaltic rocks. Petrographic results indicate that the volcanic rocks exhibit aphanitic and vesicular textures, primarily dominated by plagioclase, with average mineralogical proportions of ~\u0026thinsp;51.75%, clinopyroxene\u0026thinsp;~\u0026thinsp;26.5%, olivine\u0026thinsp;~\u0026thinsp;7.5%, and opaque minerals up to 13.5%). Additionally, this research explains the stratigraphic relationships among the rock units and highlighted the interplay between tectonism and magmatism in the study area.\u003c/p\u003e\u003cp\u003eThe structural features of the Gada\u0026rsquo;Ale area can be categorized into two main types: the prominent tectonic structures including columnar joints, fractures, normal faults, listric faults, and associated rollover folds; and volcanic structures such as domes, caldera collapses, lava tubes, maar volcanoes, as well as a\u0026rsquo;a and pahoehoe flows. The tectonic structures display well-defined patterns, predominantly oriented NNW-SSE, paralleling the main rift axis and the Red Sea rift, and accommodating nearly orthogonal extension. In contrast, NE to NNE-trending transverse fractures which connect the Gada\u0026rsquo;Ale dome with the shield volcano, aligns parallel to the axial fractures and normal faults of the Wonji Fault Belt in the Main Ethiopian Rift.\u003c/p\u003e\u003cp\u003eThe structural analysis confirms the predominance of NNW-SSE trending extensional fractures, highlighting the area's tectonic activity. These findings significantly enhance our understanding of the geological mechanisms shaping the northern Erta\u0026rsquo;Ale volcanic range and provide critical insights into the behavior of active volcanic systems. Continued research is essential to study ongoing geological events and deepen our understanding of the tectonic evolution of this significant region.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgments\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors would like to thank to the community of Afar and Tigray Regional states for their friendly support during the fieldwork. They are also thankful for the logistics support received from Aksum University and Mekelle University, Ethiopia.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contribution statement\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll authors contributed to the study\u0026rsquo;s conception and design. Teka Asresie performed the methodology, data curation, investigation, formal analysis, validation, and wrote the original draft of the manuscript. Miruts Hagos contributed to the conceptualization, methodology, data curation, investigation, funding acquisition, resources, project administration, software, supervision, and wrote the review and editing. All authors read and approved the final manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis research was supported by Aksum University and Mekelle University.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets generated and/or analyzed during this study are available based on a reasonable request from the corresponding author.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthical approval and consent to participate\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no known conflicts of interest.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eAbbate E, Passerini P, Zan L. Strike-slip faults in a rift area: a transect in the Afar Triangle, East Africa. Tectonophysics. 1995;241(1\u0026ndash;2):67\u0026ndash;97.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eAcocella V, Korme T. Holocene extension direction along the main Ethiopian Rift, East Africa. Terra Nova. 2002;14(3):191\u0026ndash;7.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eAcocella V. Regional and local tectonics at Erta Ale caldera, Afar (Ethiopia). J Struct Geol. 2006;28(10):1808\u0026ndash;20.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eAmelung F, Oppenheimer C, Segall P, Zebker H. Ground deformation near Gada \u0026lsquo;Ale Volcano, Afar, observed by radar interferometry. Geophys Res Lett. 2000;27(19):3093\u0026ndash;6.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eAudin L, Quidelleur X, Couli\u0026eacute; E, Courtillot V, Gilder S, Manighetti I, Gillot PY, Tapponnier P, Kidane T. Palaeomagnetism and K-Ar and 40Ar/39Ar ages in the Ali Sabieh area (Republic of Djibouti and Ethiopia): constraints on the mechanism of Aden ridge propagation into southeastern Afar during the last 10 Myr. Geophys J Int. 2004;158(1):327\u0026ndash;45.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eAyalew D, Barbey P, Marty B, Reisberg L, Yirgu G, Pik R. Source, genesis, and timing of giant ignimbrite deposits associated with Ethiopian continental flood basalts. GeochimicaetCosmochimicaActa. 2002;66(8):1429\u0026ndash;48.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBaker JA, Thirlwall MF, Menzies MA. Sr- Nd- Pb isotopic and trace element evidence for crustal contamination of plume-derived flood basalts: Oligocene flood volcanism in western Yemen. GeochimicaetCosmochimicaActa. 1996;60(14):2559\u0026ndash;81.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBarberi F, Varet J. The Erta Ale volcanic range (Danakil depression, northern afar, Ethiopia). Bull Volcanologique. 1970;34(4):848\u0026ndash;917.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBarberi F, Varet J. Volcanism of Afar: Small-scale plate tectonics implications. Geol Soc Am Bull. 1977;88(9):1251\u0026ndash;66.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBarberi F, Ferrara G, Santacroce R, Varet J. Structural evolution of the Afar triple junction, in Afar depression. Ethiopia. 1975;1:39\u0026ndash;54.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBarberi F, Tazieff H, Varet J. Volcanism in the Afar depression: its tectonic and magmatic significance. Tectonophysics. 1972;15(1\u0026ndash;2):19\u0026ndash;29.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBarrat JA, Fourcade S, Jahn BM, Cheminee JL, Capdevila R. Isotope (Sr, Nd, Pb, O) and trace-element geochemistry of volcanics from the Erta'Ale range (Ethiopia). J Volcanol Geoth Res. 1998;80(1\u0026ndash;2):85\u0026ndash;100.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBastow ID, Keir D. The protracted development of the continent\u0026ndash;ocean transition in Afar. Nat Geosci. 2011;4(4):248\u0026ndash;50.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBoccaletti M, Bonini M, Mazzuoli R, Abebe B, Piccardi L, Tortorici L. Quaternary oblique extensional tectonics in the Ethiopian Rift (Horn of Africa). Tectonophysics. 1998;287(1\u0026ndash;4):97\u0026ndash;116.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBonatti E, Gasperini E, Vigliotti L, Lupi L, Vaselli O, Polonia A, Gasperini L. Lake Afrera, a structural depression in the northern Afar Rift (Red Sea). Heliyon. 2017;3(5):e00301.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eEagles G, Gloaguen R, Ebinger C. Kinematics of the Danakil microplate. Earth Planet Sci Lett. 2002;203(2):607\u0026ndash;20.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eEbinger CJ, Keir D, Ayele A, Calais E, Wright TJ, Belachew M, Hammond JO, Campbell E, Buck WR. Capturing magma intrusion and faulting processes during continental rupture: seismicity of the Dabbahu (Afar) rift. Geophys J Int. 2008;174(3):1138\u0026ndash;52.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eHagos GM. 2011. \u003cem\u003eGeochemical and petrographic studies of the volcano-tectonic evolution of northern Afar\u003c/em\u003e (Doctoral dissertation, uniwien).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eHagos M, Koeberl C, de Vries BVW. The Quaternary volcanic rocks of the northern Afar Depression (northern Ethiopia): Perspectives on petrology, geochemistry, and tectonics. J Afr Earth Sc. 2016b;117:29\u0026ndash;47.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eHofmann C, Courtillot V, Feraud G, Rochette P, Yirgu G, Ketefo E, Pik R. Timing of the Ethiopian flood basalt event and implications for plume birth and global change. Nature. 1997;389(6653):838\u0026ndash;41.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eHurman GL, Keir D, Bull JM, McNeill LC, Booth AD, Bastow ID. 2023. Quantitative analysis of faulting in the Danakil depression rift of Afar: The importance of faulting in the final stages of magma-rich rifting. \u003cem\u003eTectonics\u003c/em\u003e, \u003cem\u003e42\u003c/em\u003e(6), p.e2022TC007607.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eHutchinson RW, Engels GG. 1970. Tectonic significance of regional geology and evaporite lithofacies in northeastern Ethiopia. Philosophical Trans Royal Soc Lond Ser Math Phys Sci, pp.313\u0026ndash;29.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eKieffer B, Arndt N, Lapierre H, Bastien F, Bosch D, Pecher A, Yirgu G, Ayalew D, Weis D, Jerram DA, Keller F. Flood and shield basalts from Ethiopia: magmas from the African superswell. J Petrol. 2004;45(4):793\u0026ndash;834.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eLahitte P, Gillot PY, Kidane T, Courtillot V, Bekele A. 2003. New age constraints on the timing of volcanism in central Afar, in the presence of propagating rifts. J Geophys Research: Solid Earth, \u003cem\u003e108\u003c/em\u003e(B2).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eL\u0026oacute;pez-Garc\u0026iacute;a JM, Moreira D, Benzerara K, Grunewald O, L\u0026oacute;pez-Garc\u0026iacute;a P. 2020. Origin and evolution of the halo-volcanic complex of Dallol: proto-volcanism in Northern Afar (Ethiopia). \u003cem\u003eFrontiers in Earth Science\u003c/em\u003e, \u003cem\u003e7\u003c/em\u003e, p.351.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMagee C, Bastow ID, van Wyk de Vries B, Jackson CAL, Hetherington R, Hagos M, Hoggett M. Structure and dynamics of surface uplift induced by incremental sill emplacement. Geology. 2017;45(5):431\u0026ndash;4.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMaguire PKH, Keller GR, Klemperer SL, Mackenzie GD, Keranen K, Harder S, O\u0026rsquo;reilly B, Thybo H, Asfaw L, Khan MA, Amha M. Crustal structure of the northern Main Ethiopian Rift from the EAGLE controlled-source survey; a snapshot of incipient lithospheric break-up. Geol Soc Lond Special Publications. 2006;259(1):269\u0026ndash;92.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMakris J, Ginzburg A. The Afar Depression: transition between continental rifting and sea-floor spreading. Tectonophysics. 1987;141(1\u0026ndash;3):199\u0026ndash;214.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eNobile A, Pagli C, Keir D, Wright TJ, Ayele A, Ruch J, Acocella V. 2012. Dike-fault interaction during the 2004 Dallol intrusion at the northern edge of the Erta Ale Ridge (Afar, Ethiopia). \u003cem\u003eGeophysical Research Letters\u003c/em\u003e, \u003cem\u003e39\u003c/em\u003e(19).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003ePagli C, Wright TJ, Ebinger CJ, Yun SH, Cann JR, Barnie T, Ayele A. Shallow axial magma chamber at the slow-spreading Erta Ale Ridge. Nat Geosci. 2012;5(4):284\u0026ndash;8.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eRime V, Foubert A, Ruch J, Kidane T. 2023. Tectonostratigraphic evolution and significance of the Afar Depression. \u003cem\u003eEarth-Science Reviews\u003c/em\u003e, \u003cem\u003e244\u003c/em\u003e, p.104519.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eTefera M, Chernet T, Haro W. Explanation of the geological map of Ethiopia. Geological Survey of Ethiopia; 1996.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eTerry RD, Chilingar GV. Summary of Concerning some additional aids in studying sedimentary formations, by MS Shvetsov. J Sediment Res. 1955;25(3):229\u0026ndash;34.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eTesfaye S, Harding DJ, Kusky TM. Early continental breakup boundary and migration of the Afar triple junction, Ethiopia. GSA Bull. 2003;115(9):1053\u0026ndash;67.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eThurmond AK, Abdelsalam MG, Thurmond JB. Optical-radar-DEM remote sensing data integration for geological mapping in the Afar Depression, Ethiopia. J Afr Earth Sc. 2006;44(2):119\u0026ndash;34.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eVaret J, Gasse F. Geology of central and southern Afar (Ethiopia and Djibouti Republic): Paris. Editions du Centre National de la RechercheScientifique, Report; 1978.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eVidal P, Deniel C, Vellutini PJ, Piguet P, Coulon C, Vincent J, Audin J. Changes of mantle sources in the course of a rift evolution: the Afar case. Geophys Res Lett. 1991;18(10):1913\u0026ndash;6.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eWaltham T. Extension tectonics in the Afar Triangle. Geol Today. 2005;21(3):101\u0026ndash;7.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eWolfenden E, Ebinger C, Yirgu G, Deino A, Ayalew D. Evolution of the northern Main Ethiopian rift: birth of a triple junction. Earth Planet Sci Lett. 2004;224(1\u0026ndash;2):213\u0026ndash;28.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eWolfenden E, Ebinger C, Yirgu G, Renne PR, Kelley SP. Evolution of a volcanic rifted margin: Southern Red Sea, Ethiopia. Geol Soc Am Bull. 2005;117(7\u0026ndash;8):846\u0026ndash;64.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eWright TJ, Ebinger C, Biggs J, Ayele A, Yirgu G, Keir D, Stork A. Magma-maintained rift segmentation at continental rupture in the 2005 Afardyking episode. Nature. 2006;442(7100):291\u0026ndash;4.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eYirgu G, Ebinger CJ, Maguire PKH. 2006. The afar volcanic province within the East African Rift System: introduction. \u003cem\u003eGeological Society, London, Special Publications\u003c/em\u003e, \u003cem\u003e259\u003c/em\u003e(1), pp.1\u0026ndash;6.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"discover-geoscience","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [Discover Geoscience](https://www.springer.com/journal/44288)","snPcode":"44288","submissionUrl":"https://submission.nature.com/new-submission/44288","title":"Discover Geoscience","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Discover Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Geology, shield volcano, Gada’Ale, petrography, volcano-tectonic","lastPublishedDoi":"10.21203/rs.3.rs-7947350/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7947350/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe geology, petrography, and structure of the Gada\u0026rsquo;Ale area has not yet been explored. This study presents a detailed geological, petrographic, and structural analysis of the Gada\u0026rsquo;Ale and surrounding areas in the northern Afar Depression, Ethiopia. The research highlights significant geological formations, including basaltic volcanic rocks, recent sediments, hydrothermally altered deposits, and evaporites. Petrographic results of this study indicate that the volcanic rocks exhibit aphanitic and vesicular textures, with average mineralogical proportions of ~\u0026thinsp;51.75% plagioclase, ~\u0026thinsp;26.5% clinopyroxene, ~\u0026thinsp;7.5% olivine, and opaque minerals up to 13.5%). Additionally, this research explains the stratigraphic relationships among the rock units and the interplay between tectonism and magmatism in the study area. Using remote sensing data and field observations, we mapped the lithological units, and volcano-tectonic structures of the study area. Our findings reveal various volcanic and tectonic features, such as shield volcanoes, fractures and faults, a salt dome, a collapsed caldera, lava tubes, and maar volcanoes, emphasizing the interactions between magmatism and tectonism. Notably, the study identifies the prevalence of NNW-SSE trending extensional fractures that align with regional tectonic patterns (The Red Sea Rift Trend). This research enhances our understanding of the geological evolution of the Afar region and highlights the significance of ongoing geological activity in the Gada\u0026rsquo;Ale area for future studies of the region's geological evolution.\u003c/p\u003e","manuscriptTitle":"Geological, Petrographic, and Structural Investigation of Gada’Ale Volcano and Surrounding Areas, Northern Afar Depression, Ethiopia","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-11-22 18:38:58","doi":"10.21203/rs.3.rs-7947350/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-12-11T07:42:17+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-12-05T04:36:54+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-11-30T13:38:46+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-11-28T08:30:04+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"91026110328022890330658976693404356777","date":"2025-11-16T20:09:45+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"1183024305507608121570593685038459821","date":"2025-11-14T05:45:37+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-11-11T18:52:17+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-11-11T18:36:18+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2025-11-07T03:04:30+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-11-06T08:35:22+00:00","index":"","fulltext":""},{"type":"submitted","content":"Discover Geoscience","date":"2025-11-06T08:30:38+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"discover-geoscience","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [Discover Geoscience](https://www.springer.com/journal/44288)","snPcode":"44288","submissionUrl":"https://submission.nature.com/new-submission/44288","title":"Discover Geoscience","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Discover Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"3e875782-d02d-4410-a3ec-050c350a0d62","owner":[],"postedDate":"November 22nd, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-01-24T11:40:32+00:00","versionOfRecord":[],"versionCreatedAt":"2025-11-22 18:38:58","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7947350","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7947350","identity":"rs-7947350","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}