Deep carbon cycle and early Earth´s oxygenation: evidence from ultra-high-pressure metamorphic rocks

Deep carbon cycle and early Earth´s oxygenation: evidence from ultra-high-pressure metamorphic rocks | 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 Article Deep carbon cycle and early Earth´s oxygenation: evidence from ultra-high-pressure metamorphic rocks Evilarde Uchôa Filho, Felipe dos Santos, Douglas Martins, Wagner Amaral, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6229822/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted You are reading this latest preprint version Abstract This study presents the oldest microdiamond and highly ordered graphite inclusions in garnet from Mn-rich metamorphic rocks of the Borborema Province, NE Brazil, providing strong evidence for Paleoproterozoic ultra-high-pressure metamorphism (UHPM). The biogenic origin of graphite suggests that organic matter was subducted to depths exceeding 3.7 GPa and temperatures above 900°C. Raman spectroscopy and isotopic modeling reveal a metamorphic transition from disordered graphite (~ 300–400°C) to highly ordered graphite (~ 850°C) and microdiamonds, indicating fluid-assisted recrystallization under changing redox conditions. The transformation of CH₄-dominated to CO₂-rich fluids during devolatilization highlights a link between deep carbon cycling and redox stabilization. Isotopic trends in COH fluids match those of Paleoproterozoic Mn-rich deposits and carbonates, supporting a connection between organic carbon burial, CO₂ release, and atmospheric evolution. These findings suggest that subduction and exhumation processes were already active in the Paleoproterozoic, facilitating the transfer of deep carbon and contributing to atmospheric oxygenation. This work provides one of the earliest records of UHPM-related microdiamonds, positioning the Borborema Province among the oldest known UHPM terranes and offering new insights into early plate tectonics and the emergence of conditions favorable to complex life. Earth and environmental sciences/Solid Earth sciences/Geology/Precambrian geology Earth and environmental sciences/Solid Earth sciences/Petrology Figures Figure 1 Figure 2 Figure 4 Introduction Non-cratonic microdiamond and graphite inclusions in garnet are reported in highly retrograded, metamorphic crustal rocks formed in Earth's ultra-high-pressure metamorphism (UHPM). All occurrences of microdiamond inclusions, except those partially replaced by graphite in garnet from the Precambrian supracrustal rocks of the Nagssugtoqidian Orogen in West Greenland (1.8 Ga), are associated with Phanerozoic orogens, with ages ranging from Paleozoic to Cenozoic 1 – 4 . Furthermore, the presence of coupled microdiamond and graphite inclusions within garnet indicates UHPM on Earth, often found in highly retrograded metamorphic crustal rocks (Fig. 1 A). The occurrence of microdiamond inclusions in garnets from rocks formed in UHPM terranes requires crystallization from a fluid phase under static conditions at pressures of ≥ 2.7–4.0 GPa, temperatures of ~ 700–1000°C, and subduction to depths of ≥ 90–120 km 5 . A classic example, characterized by extreme formation conditions, is the case of microdiamond inclusions in garnet from ultra-high-pressure metamorphic (UHPM) rocks of the Kokchetav massif in Kazakhstan, which comprise metamorphic rocks with sedimentary and volcanic protoliths (dating back to the 531 Ma UHPM event). Studies indicate that microdiamonds form at a pressure range of 6–9 GPa and a temperature range of 980–1200°C. It is believed that the protective nature of garnet crystals may have helped shield the diamond from undergoing total retrograde graphitization processes 1 , 5 . The hypothesis suggests that these diamonds were trapped in garnet during their growth and underwent graphitization during decompression, followed by granulite facies metamorphism. The occurrence of graphitized diamonds or the coexistence of diamond and graphite within garnet requires the involvement of CO 2 and/or C-O-H fluids during crystallization 4 , 7 – 11 . The subduction of surface-derived organic carbon to mantle depths, specifically around 90 km, leads to the transformation of disordered organic carbon into crystallized graphite at subarc depths, which can further transform into diamonds at lithospheric mantle depths exceeding 140 km 12 . The continued subduction of graphitized organic carbon plays a crucial role in forming diamonds with light carbon isotope compositions, indicating a biogenic origin. The light δ¹³C values observed in diamonds, especially those hosted in ophiolites, suggest incorporating subducted biogenic carbon 12 . The subduction of organic carbon to such depths has significant implications for the deep carbon cycle. This process indicates a mechanism for recycling surface carbon into the mantle, potentially influencing large-scale geological events such as the Great Oxidation Event (GOE) and the Lomagundi-Jatuli Event (LJE). The latter is usually characterized by an unusual increase in organic carbon deposition in marine sediments 12 – 15 . In the case of the LJE, one key question remains: What mechanism triggered such a significant disturbance in the global carbon cycle? Some alternative hypotheses 15 have recently suggested that the deep carbon cycle could be responsible for this unusual influx of organic carbon into the Paleoproterozoic oceans. In a recent study, Santos et al. 16 provided significant evidence of an ancient reservoir of organic carbon found in graphite rocks dated 2.1 billion years ago. These rocks are located in the northern Borborema Province. The authors suggest that this organic carbon was partially released during the metamorphic processes affecting these carbon-rich sediments, indicating a deep carbon cycle. They also propose a connection between these graphite rocks and manganese-rich sediments from the Paleoproterozoic era, which may have influenced the oxygenation of the oceans and the atmosphere. In line with these findings, we present our research from the Lagoa do Riacho deposit in northern Borborema Province, where we discovered microdiamonds within rocks containing manganese and graphite. This evidence suggests that they reached depths of approximately 150 kilometers beneath the Earth's crust before being exhumed. Moreover, given the 2.1 billion-year age of these rocks, we provide the earliest known evidence of microdiamonds discovered on Earth to date. Considering the paleoenvironmental importance of these findings, we propose a relationship between the deep carbon cycle, climate, tectonics, and oxygenation of the oceans and atmosphere during this ancient timeframe. Geological setting - Borborema Province The Borborema Province in Northeast Brazil is an essential piece in the puzzle of the orogenic system associated with assembling Western Gondwana during the Brasiliano/Pan-African orogeny, around 600 Ma 17 . Pre-drift reconstructions of the South Atlantic position the Borborema Province adjacent to the West African, Congo, and São Francisco cratons, reflecting its role as an internal segment of Western Gondwana 18 . This province comprises an Archean tonalite-trondhjemite-granodiorite (TTG) basement overlaid by metamorphosed and migmatized Palaeoproterozoic to early Mesoproterozoic rocks 19 – 27 . Neoproterozoic supracrustal rocks, granitoids, and shear zones (e.g., Senador Pompeu and Sobral Pedro II/Transbrasiliano) are common in this province 28 – 31 . The Borborema Province is divided into three structural subprovinces: (1) the Northern, (2) the Central, and (3) the Southern 32 , 33 . The Northern Borborema subprovince, especially in the Ceará Central Domain (CCD) (Fig. 1 B), which is the focus of this study, consists of an expressive Rhyacian high-grade metavolcanic-plutonic-sedimentary sequence 21 , 29 , 34 – 37 . On the CCD, in a 70 km N-NE linear extension, the Lagoa do Riacho manganese deposit (Figs. 1 C- 1 D) is composed of graphite-manganese-bearing rocks within the Paleoproterozoic unit of the Canindé do Ceará Complex, which includes migmatites, paragneisses, and peraluminous granitoids. Manganese-bearing minerals consist predominantly of spessartine, rhodonite-pyroxmangite, and minor tephroite, rhodochrosite, pyrophanite, manganese-amphibole, associated with graphite, sulfoarsenide, and sulfide minerals such as cobaltite, covellite, pyrite, and chalcopyrite. Massive ores record localized supergene enrichment with pyrolusite, manganite, cryptomelane, and todorokite 16 , 37 – 40 . U–Pb geochronological studies indicate that the sedimentary precursors of these mineralizations have a Rhyacian depositional age between 2.22 and 2.05 Ga, later reworked by high-grade metamorphism at 2.04 Ga and ultra-high temperature (UHT) metamorphism at 1.95 Ga 34 , 35 , 37 , 39 , 41 . These ages resemble other manganese formations associated with organic-matter-rich successions, including the Francevillian and Birimian groups in Gabon and Ghana, as well as those in the Brazilian territory, such as Serra do Navio, Azul, Buritirama, and Morro da Mina 42 – 48 . Results Mineralogy and textural features of the graphite-manganese-bearing rocks The studied lithologies include silicate manganese ore (SMO), oxidized manganese ore (OMO), graphite-bearing gondite, and graphite-bearing pelitic gneiss (see supplementary material). SMO primarily comprises tephroite, spessartine, and rhodonite, showing granoblastic texture, and is characterized by manganese-rich silicate layering, with siegenite, cobaltite, graphite, and manganese oxides as accessory minerals (Figs. 2 A-B). Graphite-bearing gondite exhibits a grano-lepidoblastic texture, characterized by the presence of graphite flakes and spessartine garnet, accompanied by quartz, potassium feldspar, baryte, and sulfides (Supplementary Material, Fig. 2 E). Graphite inclusions are common in spessartine, occurring as rounded to elongated forms (10–40 µm) (Fig. 2 E). OMO exhibits a distinct banded structure dominated by manganese oxides (pyrolusite, cryptomelane) intergrown with spessartine porphyroblasts containing aligned graphite, carbonate, and rare diamond micro-inclusions trails (Supplementary Material, Figs. 3 A and 3 C). Finally, graphite-bearing pelitic gneiss shows strong foliation, mainly composed of quartz, feldspar, almandine garnet, biotite, muscovite, and graphite, with frequent micro-inclusions of graphite, quartz, biotite, sulfides, and the occasional microdiamond within garnet porphyroblasts (Fig. 3 G) Graphite Raman mapping and thermometry In silicate manganese ore (SMO), graphite occurs intergrown with spessartine and rhodonite, forming irregular clusters along grain boundaries (Supplementary Material, Figs. 2 A- 2 B). It is frequently intergrown with sulfides and sulfoarsenides such as siegenite, cobaltite, and todorokite (Figs. 2 A- 2 C). Petrographic analyses of SMO samples in thin sections revealed the occurrence of highly disordered graphite associated with siegenite (Fig. 2 B), as well as graphite in association with cobaltite and todorokite (Fig. 2 D). Raman spectra indicate variations in graphite crystallinity, with characteristic bands at 1581 cm⁻¹ (G band), 1340 cm⁻¹ (D1 band), and 2720 cm⁻¹ (D2 band) (Fig. 2 B), with a full width at half maximum (FWHM) of 50 cm⁻¹, and a calculated and corrected temperature of 286°C using the method of Beyssac et al. 49 and Barzoi 50 . Another spectrum of highly disordered graphite exhibits bands at 1567 cm⁻¹ (G), 1340 cm⁻¹ (D1), and 2777 cm⁻¹ (D2) (Fig. 2 D), with a FWHM of 98 cm⁻¹ and a corresponding temperature of 362°C. Raman spectral mapping was performed on graphite inclusions in spessartine from graphite-bearing gondite. The Raman mapping of the G, D, and 2D bands (Figs. 2 F– 2 H) reveals heterogeneities in the crystallinity of graphite. The disorder in graphite is further confirmed by the presence of second-order bands such as S1, S2, and S3, which indicate structural defects and strain within the lattice 8 . Raman spectra of disordered graphite exhibit G bands at 1580 cm⁻¹, D1 bands at 1360 cm⁻¹, and additional second-order peaks (Fig. 2 I), with a full width at half maximum (FWHM) of 14 cm⁻¹ and a calculated temperature of 667°C. The highly ordered graphite exhibits G bands at 1579 cm⁻¹, D1 bands at 1353 cm⁻¹, and S1 and S2 peaks (Fig. 2 J), with a FWHM of 19 cm⁻¹ and a corresponding temperature of 853°C, consistent with high-temperature metamorphic conditions 8 . The progressive sharpening of the G-band and reduction in D1 intensity from disordered to highly ordered graphite follows the graphitization trend described by Zhang & Santosh 51 . Diamond Raman mapping and spectroscopy In oxidized manganese ore (OMO), graphite, microdiamond, and carbonate inclusions are frequently observed within anhedral spessartine crystals (Figs. 3 A- 3 C). These microcrystals form aligned trails of inclusions (Supplementary Material, Fig. 3 A). Microdiamond inclusions are characterized by their subhedral to euhedral shape (2–5 µm) and may be associated with graphite. Graphite also occurs in the rock matrix along grain boundaries and within fractures in spessartine, often associated with manganese oxides (Supplementary Material, Fig. 3 A). Petrographic analyses reveal the presence of carbonate and diamond inclusions in spessartine from the OMO (Fig. 3 A). The Raman spectrum of the microdiamond inclusion exhibits a characteristic sharp diamond peak at 1335 cm⁻¹, with a FWHM of 9.9 cm⁻¹ (Fig. 3 B), which falls within the expected range for metamorphic microdiamonds. A Raman mapping of a microdiamond inclusion in spessartine was performed (Figs. 3 D– 3 E). The Raman map revealed the occurrence of graphite associated with microdiamond, with the D1 (graphite) and sp³-bonded carbon (diamond) bands showing positional variations due to strain or minor compositional changes. The variation in the position of the G band of graphite is observable in Fig. 3 E. The obtained spectra show diamonds with a peak at 1338 cm⁻¹ and FWHM of 12.8 cm⁻¹, slightly broader than typical single-crystal diamonds, suggesting internal stress or size effects 9 . The G and 2D graphite bands can appear alongside the microdiamond spectrum (Fig. 3 F). In graphite-bearing pelitic gneiss, graphite occurs as medium-grained flakes within the foliation, intercalated with biotite and muscovite (Supplementary Material, Fig. 3 B). It is frequently found as inclusions within almandine porphyroblasts, where it forms aligned inclusion trails. Microdiamond inclusions (5–25 µm), with subhedral to euhedral shapes, also occur within almandine, coexisting with graphite inclusions (Fig. 3 G). Microdiamond inclusions are associated with quartz and biotite in almandine (Fig. 3 G). Backscattered electron (BSE) images reveal the details of these diamond and graphite inclusions within almandine, with biotite surrounding the inclusions (Fig. 3 H). Raman spectroscopy confirms the presence of microdiamonds, characterized by a peak at 1335 cm⁻¹ and a FWHM of 10.5 cm⁻¹ (Fig. 3 I), which aligns with previous reports of ultra-high-pressure metamorphic diamonds. Raman spectral mapping highlights the spatial distribution of graphite, almandine, and diamond within the almandine (Fig. 3 K). The coexistence of graphite with microdiamonds in ultra-high-pressure environments is further supported by a well-defined 2D band, indicating increased crystalline ordering at extreme pressures 51 . Core and rim microprobe data from garnet of graphite-bearing pelitic gneiss, represented in ternary diagrams, show compositional variations between XMg (pyrope) and XFe (almandine) (Figs. 3 M- 3 N). The distribution of analytical points plots near the fields of diamond-bearing paragneisses (core) and gneisses (rim), as well as along the transition from granulite facies (core) to upper amphibolite facies (rim). Isotopic modeling and speciation of COH fluids The isotopic and thermodynamic modeling of the COH system was conducted to evaluate the stability and compositional evolution of fluids responsible for diamond precipitation. The multicomponent Rayleigh fractionation between CH₄+CO₂ and diamond followed a progressive trend, starting from an initial fluid composition of δ¹³C = -29‰. As carbon was progressively incorporated into the solid phase (Fig. 4 A), the remaining fluid became enriched gradually in ¹³C, reaching a final value of δ¹³C = -10.0‰, while the precipitated diamond recorded a final isotopic composition of δ¹³C = -15.28‰. The COH ternary diagram (Fig. 4 B) indicates that the transition from graphite to diamond occurs under high-pressure conditions, with diamond stability prevailing above 3.7 GPa and 900°C. The mineral stability maps (Fig. 4 C) and fluid compositional evolution (Figs. 4 D– 4 F) reveal an increase in the molar fraction of CO₂ (Fig. 4 E) with increasing pressure and temperature. At the same time, H 2 O and CH₄ progressively decrease (Fig. 4 F), indicating an increasingly oxidizing environment. The rise in oxygen fugacity (Fig. 4 G) further supports this trend, allowing diamond stability. The isotopic evolution of the fluid (Fig. 4 H) shows a progressive enrichment in ¹³C. At the same time, the δ¹³C values of CO₂ and CH₄ (Figs. 4 I- 4 J) reveal significant isotopic fractionation, driven by exchange reactions between the fluid and solid phases. These results indicate that diamond formation from COH fluids under high-pressure (> 3.7 GPa) and high-temperature (~ 900°C) metamorphic conditions occurs with a well-defined isotopic fractionation trend, highlighting the role of fluid evolution and oxygen fugacity in diamond stabilization. Discussion Paleoproterozoic UHPM and plate tectonics Raman spectroscopy reveals a progressive metamorphic transformation of graphite from highly disordered forms (~ 300–400°C) to highly ordered graphite (~ 850°C) 51 , consistent with subduction-related recrystallization processes. The presence of microdiamonds within garnet, particularly in spessartine (manganese-rich oxidized ore) and almandine (graphite-bearing metapelitic gneiss), indicates metamorphic conditions exceeding 3.7 GPa and 900°C, reinforcing their formation under ultra-high-pressure conditions before exhumation 9 . Secondary Raman bands (S1, S2, S3) in graphite further suggest variable stress conditions linked to a convergent tectonic regime, where CO₂ reduction reactions govern carbon phase stability 8 . This process likely involved fluid-assisted recrystallization under fluctuating oxygen fugacity, driving the transformation of amorphous organic matter into graphite and diamond. Thermodynamic modeling indicates that diamond precipitation occurred during a transition from CH₄-dominated reducing fluids to CO₂-rich oxidizing conditions, aligning with global models of carbon recycling in subduction zones 5 . The increasing oxygen fugacity recorded in the model suggests a direct link between deep fluid evolution and the stabilization of diamond over graphite, highlighting the role of high-pressure metamorphism in carbon sequestration. These findings support the hypothesis that diamonds and graphite in the Lagoa do Riacho manganese-rich rocks are metamorphic products formed under extreme pressures, with estimated P-T conditions (~ 3.7 GPa and 900°C, respectively) consistent with other UHPM terrains 5 , 8 , 52 ). Successive metamorphic events were likely driven by plate convergence, crustal thickening, and exhumation 5 . Almadine containing microdiamond and graphite inclusions exhibit a pyrope-rich core and an almandine-rich rim, suggesting decompression-related chemical re-equilibration. The compositional shift from diamond-bearing gneiss and granulite stability fields in the core to upper amphibolite facies in the rim supports a multi-stage metamorphic evolution (see Figs. 4 M- 4 N, diagrams from Tolosan-Delgado et al. 53 and Schönig et al. 54 ). The occurrence of highly ordered graphite and microdiamonds in manganese-bearing rocks from the Borborema Province, specifically the Canindé do Ceará Complex, represents one of the earliest pieces of evidence of UHPM on Earth 4 , 5 , 55 , 56 . Geochronological data suggest that the sedimentary precursors of these rocks were deposited between 2.22 and 2.05 Ga, later subjected to high-grade metamorphism (~ 2.04 Ga), followed by UHT conditions (~ 1.95 Ga) 34 , 35 , 37 , 39 , 41 . These results contribute to growing evidence that plate tectonics was fully operational during the Paleoproterozoic (Orosirian, 2.05–1.80 Ga), challenging earlier models of a stagnant-lid regime (see Stern 56 ). The data from Lagoa do Riacho align with other UHPM terranes worldwide, where similar events occurred at comparable time intervals but with variable degrees of exhumation: Nagssugtoqidian Orogen, Greenland (~ 1.8 Ga): UHPM represented by graphitized diamond inclusions in garnet of gneisses formed at greater burial depths (~ 7 GPa, 970°C) 4 . Trans-Hudson Orogeny, Canada (~ 1.80 Ga): Eclogites and high-pressure granulites with no confirmed microdiamond record 57 , 58 . Democratic Republic of the Congo (~ 2.0 Ga): Paleoproterozoic eclogites and HP-LT granulites with evidence of deep subduction processes 55 . Deep carbon cycle and implications for early Earth oxygenation The findings of this study align with the broader context of Paleoproterozoic deep carbon cycling, where subduction and mantle processes may have influenced CO₂ degassing and fluctuations in ocean-atmosphere redox. The increasing oxygen fugacity recorded in isotopic models links deep fluid evolution to the stabilization of diamond over graphite, reinforcing the role of high-pressure metamorphism in carbon sequestration. This transition is significant in the GOE (~ 2.4 Ga) and the LJE (~ 2.3–2.1 Ga), as increased oxygen fugacity in subduction-related fluids may have contributed to the oxidation of surface environments. The GOE and LJE marked profound shifts in Earth's atmospheric and oceanic chemistry, influencing carbon burial, oxidative weathering, and the sedimentation of manganese. Isotopic modeling in this study indicates that the redox evolution of this period was also recorded in the metamorphic transformation of carbon, progressing from disordered graphite to highly ordered graphite and microdiamonds. This process reflects deep carbon recycling and its role in stabilizing atmospheric O₂ levels. The isotopic fractionation observed in the COH system parallels δ¹³C shifts in Paleoproterozoic carbonates and Mn-rich deposits, supporting a link between large-scale organic carbon burial, fluid evolution, and oxygenation (Fig. 5 ). The fate of subducted organic carbon has significant implications for the deep carbon cycle and Earth's redox state 59 . Graphitic carbon from organic precursors can persist to mantle depths (~ 90 km), influencing arc emissions and long-term carbon cycling 60 . This process may have been crucial in buffering atmospheric CO₂ levels over geological timescales and sustaining climate stability 13 . The oxidation of subducted carbon and its interaction with carbonate-bearing sediments further modulated the isotopic signature of volcanic emissions, contributing to the stabilization of atmospheric O₂ levels following the GOE, as noted by LJE 15 . During the Paleoproterozoic, volcanic CO₂ emissions played a crucial role in the Lomagundi-Jatuli Event (LJE), intensifying silicate weathering, nutrient influx, and organic carbon sequestration, thereby sustaining high atmospheric O₂ levels and influencing global climate perturbations and transient glaciations 15 . Following Paleoproterozoic glaciations, Mn-rich carbonates and oxides precipitated in response to ice retreat, reflecting a strong coupling between ocean stratification and evolving redox conditions 16 , 61 . During glaciations, Mn²⁺ accumulated in anoxic, ice-covered deep ocean waters, where it was later oxidized and deposited following ice retreat. Subduction-driven CO₂ degassing facilitated deglaciation and stabilized ocean chemistry, as observed similarly in Neoproterozoic Snowball Earth events, potentially aiding the rise of complex life 16 , 61 – 63 . Conclusions Five critical conclusions come from this study: Petrographic and spectroscopic data indicate a progressive metamorphism of graphite from disordered forms (300°C) to highly ordered graphite (~850°C), culminating in the formation of microdiamonds under ultra-high-pressure conditions (3.7–4.0 GPa). Microdiamond inclusions in garnet suggest that part of the buried biogenic carbon was subducted and recycled at mantle depths, influencing the deep carbon cycle. The findings suggest that the Borborema Province shares key characteristics with other Paleoproterozoic subduction terranes and may host the oldest record of metamorphic diamond formation associated with subduction processes. This discovery provides crucial evidence for the evolution of early Earth’s tectonics, reinforcing the role of subduction-exhumation cycles in controlling global carbon fluxes and influencing the composition of the Earth’s mantle and atmosphere. The coevolution of Earth's biosphere, atmosphere, and lithosphere during the Paleoproterozoic was fundamentally driven by the burial of organic carbon, manganese deposition, and fluctuations in redox conditions. The transition from an anoxic to an oxic world was marked by the interplay of enhanced photosynthetic productivity, volcanic CO₂ emissions, glacial-interglacial cycles, and deep carbon subduction. These processes collectively shaped the trajectory of Earth's carbon cycle and atmospheric oxygenation, ultimately paving the way for the emergence of complex life. Methods Methods are available as electronic Supplementary Material. Declarations Data availability All data generated or analyzed during this study are included in this published article, along with its Supplementary Material files. Acknowledgments This research was part of the first author’s Ph.D. thesis. ECUF is grateful to the Geosciences Graduate Program from the Federal University of Ceará and the Geological Survey of Brazil for support throughout the thesis development and to geologist Renato Braz Sue (representing Libra Ligas do Brasil company) for providing full access to drill cores and fieldwork assistance. Prof. Dr. Felipe Holand FHS would like to thank the Society of Economic Geologists (SEG) for the Student Research Grant. WSA is funded by CNPq, under grant number (407255/2022-2). We genuinely appreciate anonymous reviewers' comments, suggestions, and criticisms that helped improve this manuscript's quality. Author contributions ECUF designed the study, developed the idea, performed the analyses, and wrote the manuscript. All authors discussed the results and participated in manuscript refinement. Competing interests The authors declare no competing interests. Additional information Supplementary Material References Sobolev NV, Shatsky VS (1990) Diamond inclusions in garnets from metamorphic rocks: a new environment for diamond formation. Nature 343:742–746 Massonne H-J, Kennedy A, Nasdala L, Theye T (2007) Dating of zircon and monazite from diamondiferous quartzofeldspathic rocks of the Saxonian Erzgebirge – hints at burial and exhumation velocities. Mineral Mag 71:407–425 Frezzotti M-L, Huizenga J-M, Compagnoni R, Selverstone J (2014) Diamond formation by carbon saturation in C–O–H fluids during cold subduction of oceanic lithosphere. Geochim Cosmochim Acta 143:68–86 Glassley WE, Korstgard JA, Sorensen K, Platou S (2014) W. A new UHP metamorphic complex in the 1.8 Ga Nagssugtoqidian Orogen of West Greenland. Am Mineral 99:1315–1334 Dobrzhinetskaya LF, O’Bannon EF, Sumino H (2022) Non-cratonic Diamonds from UHP Metamorphic Terranes, Ophiolites and Volcanic Sources. Rev Mineral Geochem 88:191–255 Dobrzhinetskaya L, Wirth R, Greenii H (2006) Nanometric inclusions of carbonates in Kokchetav diamonds from Kazakhstan: A new constraint for the depth of metamorphic diamond crystallization. Earth Planet Sci Lett 243:85–93 Mposkos ED, Kostopoulos DK (2001) Diamond, former coesite and supersilicic garnet in metasedimentary rocks from the Greek Rhodope: a new ultrahigh-pressure metamorphic province established. Earth Planet Sci Lett 192:497–506 Perraki M, Proyer A, Mposkos E, Kaindl R, Hoinkes G (2006) Raman micro-spectroscopy on diamond, graphite and other carbon polymorphs from the ultrahigh-pressure metamorphic Kimi Complex of the Rhodope Metamorphic Province, NE Greece. Earth Planet Sci Lett 241:672–685 Korsakov AV et al (2010) Diamond-Graphite Relationships in Ultrahigh-pressure Metamorphic Rocks from the Kokchetav Massif, Northern Kazakhstan. J Petrol 51:763–783 Sonin V, Leech M, Chepurov A, Zhimulev E, Chepurov A (2018) Why are diamonds preserved in UHP metamorphic complexes? Experimental evidence for the effect of pressure on diamond graphitization. Int Geol Rev 61:504–519 Korsakov A, Rezvukhina O, Jaszczak J, Rezvukhin D, Mikhailenko D (2019) Nat Graphite Cuboids Minerals 9:110 Hu H, Zhang L, Lan C, Liu Z (2023) Petrological evidence for deep subduction of organic carbon to subarc depths. Commun Earth Environ 4:418 Holland HD (2002) Volcanic gases, black smokers, and the great oxidation event. Geochim Cosmochim Acta 66:3811–3826 Lyons TW, Reinhard CT, Planavsky NJ (2014) The rise of oxygen in Earth’s early ocean and atmosphere. Nature 506:307–315 Eguchi J, Seales J, Dasgupta R (2020) Great Oxidation and Lomagundi events linked by deep cycling and enhanced degassing of carbon. Nat Geosci 13:71–76 Santos FH et al (2024) The origin and fate of organic carbon in graphite–manganese bearing rocks and implications for the Lomagundi–Jatuli Event. Sci Rep 14:21191 Almeida FFM, Hasui Y, De Brito Neves BB, Fuck RA (1981) Brazilian structural provinces: An introduction. Earth-Sci Rev 17:1–29 Neves SP (2003) Proterozoic history of the Borborema province (NE Brazil): Correlations with neighboring cratons and Pan-African belts and implications for the evolution of western Gondwana. Tectonics 22:2001TC001352 Sá JM, Bertrand JM, Leterrier J, Macedo MHF (2002) Geochemistry and geochronology of pre-Brasiliano rocks from the Transversal Zone, Borborema Province, Northeast Brazil. J South Am Earth Sci 14:851–866 Martins G, Oliveira EP, Lafon J-M (2009) The Algodões amphibolite–tonalite gneiss sequence, Borborema Province, NE Brazil: Geochemical and geochronological evidence for Palaeoproterozoic accretion of oceanic plateau/back-arc basalts and adakitic plutons. Gondwana Res 15:71–85 Hollanda MHBM, Archanjo CJ, Souza LC, Dunyi L, Armstrong R (2011) Long-lived Paleoproterozoic granitic magmatism in the Seridó-Jaguaribe domain, Borborema Province–NE Brazil. J South Am Earth Sci 32:287–300 Dantas EL et al (2013) Crustal growth in the 3.4–2.7Ga São José de Campestre Massif, Borborema Province, NE Brazil. Precambrian Res 227:120–156 Costa FGD, Palheta ESDM, Rodrigues JB, Gomes IP, Vasconcelos AM (2015) Geochemistry and U–Pb zircon ages of plutonic rocks from the Algodões granite-greenstone terrane, Troia Massif, northern Borborema Province, Brazil: Implications for Paleoproterozoic subduction-accretion processes. J South Am Earth Sci 59:45–68 Souza ZS et al (2016) Generation of continental crust in the northern part of the Borborema Province, northeastern Brazil, from Archaean to Neoproterozoic. J South Am Earth Sci 68:68–96 Ganade CE, Basei MAS, Grandjean FC, Armstrong R, Brito RS (2017) Contrasting Archaean (2.85–2.68 Ga) TTGs from the Tróia Massif (NE-Brazil) and their geodynamic implications for flat to steep subduction transition. Precambrian Res 297:1–18 Costa FG et al (2018) Geochemistry and U–Pb–Hf zircon data for plutonic rocks of the Troia Massif, Borborema Province, NE Brazil: Evidence for reworking of Archean and juvenile Paleoproterozoic crust during Rhyacian accretionary and collisional tectonics. Precambrian Res 311:167–194 Lages GA, De Lira Santos M, Brasilino LC, Rodrigues RG, J. B., Dantas EL (2019) Statherian-Calymmian (ca. 1.6 Ga) magmatism in the Alto Moxotó Terrane, Borborema Province, northeast Brazil: Implications for within-plate and coeval collisional tectonics in West Gondwana. J South Am Earth Sci 91:116–130 Vauchez A et al (1995) The Borborema shear zone system, NE Brazil. J South Am Earth Sci 8:247–266 Garcia MDG, Dos Santos S, T. J., Da Silva Amaral W (2014) Provenance and tectonic setting of neoproterozoic supracrustal rocks from the Ceará Central Domain, Borborema Province (NE Brazil): constraints from geochemistry and detrital zircon ages. Int Geol Rev 56:481–500 Ganade CE, Weinberg RF, Cordani UG (2014) Extruding the Borborema Province (NE -Brazil): a two‐stage Neoproterozoic collision process. Terra Nova 26:157–168 Pitombeira JPA, Amaral WDS, Santos TJSD, Dantas EL, Fuck R (2021) A. A new record of continental arc magmatism in the Ceará Central Domain, Borborema Province (NE Brazil): evidence from the Pacatuba-Maranguape Complex. Precambrian Res 359:106192 Van Schmus WR, Kozuch M, De Brito Neves BB (2011) Precambrian history of the Zona Transversal of the Borborema Province, NE Brazil: Insights from Sm–Nd and U–Pb geochronology. J South Am Earth Sci 31:227–252 Neves SP (2015) Constraints from zircon geochronology on the tectonic evolution of the Borborema Province (NE Brazil): Widespread intracontinental Neoproterozoic reworking of a Paleoproterozoic accretionary orogen. J South Am Earth Sci 58:150–164 da Costa FG, de Plaheta ES (2017) Geologia e recursos minerais das folhas Quixadá (SB.24-V-B-IV) e Itapiúna (SB.24-X-A-IV): estado do Ceará. CPRM - Serviço Geológico do Brasil Muniz RL, Santos D, Dantas TJS, E. L., Fuck RA (2022) Rhyacian-Orosirian Khondalite Belt in the Borborema Province (NE Brazil): An active margin setting based on U–Pb zircon and monazite constraints. Geol J 57:3808–3828 Amaral WDS et al (2023) Paleoproterozoic crustal evolution of the northern Borborema Province, NE Brazil: Insights from high-grade metamorphic rocks of the Canindé do Ceará Complex. Precambrian Res 384:106941 Santos FH, Da Silva Amaral W, Martins DT, De Souza AC (2023) B. Zircon U–Pb geochronology of manganese-rich rocks from the Borborema Province, Northeast Brazil: adding a new piece to the global inventory of Paleoproterozoic manganese mineralization. Min Deposita 58:531–551 Souza Filho S (1979) Tese de Doutoramento apresentada ao lnstituto de Geociências da Universidade de São Paulo Santos FHD et al (2021) Unraveling sedimentary precursors and metal enrichment of high-grade metamorphosed manganese-rich rocks from the Borborema Province, northeastern Brazil. Ore Geol Rev 137:104283 Santos FH, Da Silva Amaral W, Chi-Fru E, De Souza ACB, Bosco-Santos A (2022) Paleoproterozoic manganese oxide precipitation in oxic seawater surface and reductive enrichment in anoxic seafloor. Chem Geol 588:120655 Calado et al (2019) Evidence for ca. 2046 Ma high-grade metamorphism in Paleoproterozoic metasedimentary rocks of the northern Borborema Province, NE Brazil: constraints from U-Pb (LA-ICP-MS) zircon ages. J Geol Surv Braz 2:137–150 Nyame FK (2008) Petrography and geochemistry of intraclastic manganese–carbonates from the ∼2.2Ga Nsuta deposit of Ghana: Significance for manganese sedimentation in the Palaeoproterozoic of West Africa. J Afr Earth Sci 50:133–147 Chisonga BC, Gutzmer J, Beukes NJ, Huizenga JM (2012) Nature and origin of the protolith succession to the Paleoproterozoic Serra do Navio manganese deposit, Amapa Province, Brazil. Ore Geol Rev 47:59–76 Dubois M (2017) Environnement de dépôt et processus de formation des carbonates de manganèse dans les black shales paléoprotérozoiques du Bassin de Franceville (2.1 Ga; Gabon) Cabral AR et al (2019) Molybdenum-isotope signals and cerium anomalies in Palaeoproterozoic manganese ore survive high-grade metamorphism. Sci Rep 9:4570 Goto KT et al (2021) Progressive ocean oxygenation at ~ 2.2 Ga inferred from geochemistry and molybdenum isotopes of the Nsuta Mn deposit, Ghana. Chem Geol 567:120116 Salgado SS et al (2021) Metallogenetic Mn-model of the Rhyacian-aged Buritirama Formation, Carajás domain (Amazon Craton). Ore Geol Rev 138:104396 Costa M et al (2022) SEDIMENTARY MANGANESE DEPOSITS IN CARAJÁS, BRAZIL. Bol Mus Geociências Amaz 9:1–38 Beyssac O, Goffé B, Chopin C, Rouzaud JN (2002) Raman spectra of carbonaceous material in metasediments: a new geothermometer. J Metamorph Geol 20:859–871 Barzoi SC (2015) Shear stress in the graphitization of carbonaceous matter during the low-grade metamorphism from the northern Parang Mountains (South Carpathians) — Implications to graphite geothermometry. Int J Coal Geol 146:179–187 Zhang C, Santosh M (2019) Coupled laser Raman spectroscopy and carbon stable isotopes of graphite from the khondalite belt of Kerala, southern India. Lithos 334–335:245–253 Korsakov AV, Hutsebaut D, Theunissen K, Vandenabeele P, Stepanov AS (2007) Raman mapping of coesite inclusions in garnet from the Kokchetav Massif (Northern Kazakhstan). Spectrochim Acta Mol Biomol Spectrosc 68:1046–1052 Tolosana-Delgado R, Von Eynatten H, Krippner A, Meinhold G (2018) A multivariate discrimination scheme of detrital garnet chemistry for use in sedimentary provenance analysis. Sediment Geol 375:14–26 Schönig J, Von Eynatten H, Meinhold G, Lünsdorf NK (2019) Diamond and coesite inclusions in detrital garnet of the Saxonian Erzgebirge, Germany. Geology 47:715–718 François C, Debaille V, Paquette J-L, Baudet D, Javaux EJ (2018) The earliest evidence for modern-style plate tectonics recorded by HP–LT metamorphism in the Paleoproterozoic of the Democratic Republic of the Congo. Sci Rep 8:15452 Stern RJ (2023) The Orosirian (1800–2050 Ma) plate tectonic episode: Key for reconstructing the Proterozoic tectonic record. Geosci Front 14:101553 Weller OM, St-Onge MR (2017) Record of modern-style plate tectonics in the Palaeoproterozoic Trans-Hudson orogen. Nat Geosci 10:305–311 Toma J et al (2024) Nuna supercontinent assembly linked to carbon cycling in shear zones 1.9–1.7 billion years ago. Nat Geosci 17:1038–1045 Hu H, Zhang L, Lan C, Liu Z (2023) Petrological evidence for deep subduction of organic carbon to subarc depths. Commun Earth Environ 4:418 Tumiati S et al (2022) Subducted organic matter buffered by marine carbonate rules the carbon isotopic signature of arc emissions. Nat Commun 13:2909 Roy S (2006) Sedimentary manganese metallogenesis in response to the evolution of the Earth system. Earth-Sci Rev 77:273–305 Sekine Y et al (2011) Manganese enrichment in the Gowganda Formation of the Huronian Supergroup: A highly oxidizing shallow-marine environment after the last Huronian glaciation. Earth Planet Sci Lett 307:201–210 Mills BJW, Scotese CR, Walding NG, Shields GA, Lenton TM (2017) Elevated CO2 degassing rates prevented the return of Snowball Earth during the Phanerozoic. Nat Commun 8:1110 Atlas aerogeofísico do estado do Ceará . (Serviço Geológico do Brasil - CPRM, Fortaleza, CE, (2021) Bottinga Y (1969) Calculated fractionation factors for carbon and hydrogen isotope exchange in the system calcite-carbon dioxide-graphite-methane-hydrogen-water vapor. Geochim Cosmochim Acta 33:49–64 Miozzi F, Tumiati S (2020) Aqueous concentration of CO2 in carbon-saturated fluids as a highly sensitive oxybarometer. Geochem Perspect Lett 16:30–34 Duncan MS, Dasgupta R (2017) Rise of Earth’s atmospheric oxygen controlled by efficient subduction of organic carbon. Nat Geosci 10:387–392 Galvez ME, Fischer WW, Jaccard SL, Eglinton TI (2020) Materials and pathways of the organic carbon cycle through time. Nat Geosci 13:535–546 Additional Declarations There is NO Competing Interest. Supplementary Files ESMEMPADeepcarboncycleandearlyEarthXXsoxygenationevidencefromultrahighpressuremetamorphicrocks.xlsx Dataset 1 ESMRamanDeepcarboncycleandearlyEarthXXsoxygenationevidencefromultrahighpressuremetamorphicrocks.xlsx Dataset 2 ESMDeepcarboncycleandearlyEarthXXsoxygenationevidencefromultrahighpressuremetamorphicrocks.docx Supplementary Material Cite Share Download PDF Status: Under Review Version 1 posted 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. 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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-6229822","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":433083844,"identity":"92732166-15ba-4469-96d9-2306f37e2033","order_by":0,"name":"Evilarde Uchôa Filho","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABFElEQVRIiWNgGAWjYFACxsYDDAzMIBYbENswMEhAxBPwaGlA1pJGjBYGBmQthwlr4ZdIbjjwc4+1HINE8rMHH2rO28tHNzC/+NjGkGfegF2L5IzEhoM9z9KNGSTSzA1nHLuduPHOATbLmW0MxTIHsGsxOHOw4QDPgcOJDRI5bNI8bLcTDGcksBnznGFInIHDYfZALQf/HDhcD9Hy75w9QS0G7I0Nh4G2JDCAtPC2HWCcL5HA/JinArcWieNALTIH0g3beJ6ZSc7sS07cIHOwjXFGhUSxBK4Qa2Z/+PDNAWt5fvbkZxIfvtnZy89uPvzhg4FNHi4tcMAGd+oBxjYJeOwQBeQbGJg/kKB+FIyCUTAKhj8AABwJXF4GNIMGAAAAAElFTkSuQmCC","orcid":"https://orcid.org/0009-0008-6051-8553","institution":"Geological Survey of Brazil","correspondingAuthor":true,"prefix":"","firstName":"Evilarde","middleName":"Uchôa","lastName":"Filho","suffix":""},{"id":433083845,"identity":"bb23ef0d-85fa-4649-a26b-f086d4da7094","order_by":1,"name":"Felipe dos Santos","email":"","orcid":"","institution":"Federal University of Ceará","correspondingAuthor":false,"prefix":"","firstName":"Felipe","middleName":"dos","lastName":"Santos","suffix":""},{"id":433083846,"identity":"7481b65d-98c7-429f-91b3-945b478437eb","order_by":2,"name":"Douglas Martins","email":"","orcid":"","institution":"Federal Institute of Piauí","correspondingAuthor":false,"prefix":"","firstName":"Douglas","middleName":"","lastName":"Martins","suffix":""},{"id":433083847,"identity":"7b0cd175-dd44-4cdc-b4ad-928f710e0ea6","order_by":3,"name":"Wagner Amaral","email":"","orcid":"","institution":"State University of Campinas","correspondingAuthor":false,"prefix":"","firstName":"Wagner","middleName":"","lastName":"Amaral","suffix":""},{"id":433083848,"identity":"aa19bb89-f760-404b-9dba-6e422b3a6567","order_by":4,"name":"José Alberto do Vale","email":"","orcid":"","institution":"Geological Survey of Brazil","correspondingAuthor":false,"prefix":"","firstName":"José","middleName":"Alberto do","lastName":"Vale","suffix":""},{"id":433083849,"identity":"53493d1e-f16a-4eed-8663-37ef412560e7","order_by":5,"name":"Antônio Paulo Soares","email":"","orcid":"https://orcid.org/0009-0003-5903-8994","institution":"Federal University of Ceará","correspondingAuthor":false,"prefix":"","firstName":"Antônio","middleName":"Paulo","lastName":"Soares","suffix":""}],"badges":[],"createdAt":"2025-03-15 02:00:15","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6229822/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6229822/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":79161362,"identity":"5b0cc73a-876b-4abc-a168-69ceb4c6d2b6","added_by":"auto","created_at":"2025-03-25 07:26:56","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":28237952,"visible":true,"origin":"","legend":"\u003cp\u003e(\u003cstrong\u003eA\u003c/strong\u003e) Global distribution of non-cratonic microdiamond occurrences and Paleoproterozoic orogens (2.1–1.8 Ga), ophiolites, and granulitized eclogite occurrences highlighted (modified from Dobrzhinetskaya et al.\u003csup\u003e5\u003c/sup\u003e and Stern\u003csup\u003e56\u003c/sup\u003e). (\u003cstrong\u003eB\u003c/strong\u003e) The geological framework of the Northern Borborema Province highlights the study area in blue diamond, major lithological units, and structural domains. (\u003cstrong\u003eC\u003c/strong\u003e) Gamma-ray spectrometry map (ternary RGB) of the Ceará Central and Rio Grande do Norte domains highlighting manganese and graphite occurrences (modified from Sousa\u003csup\u003e64\u003c/sup\u003e). (\u003cstrong\u003eD\u003c/strong\u003e) A local map of the Lagoa do Riacho Mn deposit shows the distribution of drill cores and studied manganese-graphite-rich lithological groups. The maps were created using QGIS v3.28 software (https://qgis.org/en/site/). Figure (\u003cstrong\u003eA\u003c/strong\u003e) was designed using the ETOPO Global Relief data (\u003ca href=\"https://www.ncei.noaa.gov/products/etopo-global-relief-model\"\u003ehttps://www.ncei.noaa.gov/products/etopo-global-relief-model\u003c/a\u003e).\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-6229822/v1/cc8831d5489454bd6b1e5f7f.png"},{"id":79161359,"identity":"26952280-d5b8-4e2c-a5e4-286dfd5093ac","added_by":"auto","created_at":"2025-03-25 07:26:56","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":16133036,"visible":true,"origin":"","legend":"\u003cp\u003eGraphite petrography and Raman spectroscopy. (A) Disordered graphite is intergrown with siegenite. (B) Raman spectrum of disordered graphite showing G, D1, and D2 bands, FWHM = 50 cm⁻¹, T = ~286°C. (C–D) Graphite associated with cobaltite and todorokite; Raman spectrum with FWHM = 98 cm⁻¹, T = ~362 °C. (E) Graphite inclusions in spessartine. (F–H) Raman mapping of G, D1, and D2 bands of graphite inclusions. (I–J) Raman spectra of disordered graphite (T = ~667°C) and highly ordered graphite (T = ~853°C).\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-6229822/v1/67c1ac9627101e2d9045b609.png"},{"id":79162423,"identity":"eeb56bf5-371c-46e5-ab28-8032c816c974","added_by":"auto","created_at":"2025-03-25 07:42:56","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":3889083,"visible":true,"origin":"","legend":"\u003cp\u003eCOH isotopic and thermodynamic modeling. (\u003cstrong\u003eA\u003c/strong\u003e) Rayleigh fractionation: δ¹³Cfluid from -29‰ to -10‰, δ¹³Cdiamond = -15.28‰. (\u003cstrong\u003eB\u003c/strong\u003e) COH ternary diagram: Diamond stable at\u0026gt;3.7 GPa and ~900°C. (\u003cstrong\u003eC\u003c/strong\u003e) Graphite-diamond stability fields. (\u003cstrong\u003eD–F\u003c/strong\u003e) Fluid evolution: increasing CO₂ fraction, decreasing CH₄ and H₂O. (\u003cstrong\u003eG\u003c/strong\u003e) Oxygen fugacity increases, favoring the stability of diamond. (\u003cstrong\u003eH–J\u003c/strong\u003e) Carbon isotopic evolution (total, CO₂, CH₄) during diamond precipitation. Fractionation factors followed the parameters established by \u0026nbsp;Bottinga\u003csup\u003e65\u003c/sup\u003e and Miozzi \u0026amp; Tumiati\u003csup\u003e66\u003c/sup\u003e\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-6229822/v1/b61415841c155533aee31e2a.png"},{"id":79161349,"identity":"7a657e7d-f704-416b-b0d7-771f59fb242f","added_by":"auto","created_at":"2025-03-25 07:26:56","extension":"xlsx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":843603,"visible":true,"origin":"","legend":"Dataset 1","description":"","filename":"ESMEMPADeepcarboncycleandearlyEarthXXsoxygenationevidencefromultrahighpressuremetamorphicrocks.xlsx","url":"https://assets-eu.researchsquare.com/files/rs-6229822/v1/46b09ec3b4351c644312c64e.xlsx"},{"id":79161681,"identity":"432855a5-0ebe-4a16-aee3-66e82bd82517","added_by":"auto","created_at":"2025-03-25 07:34:56","extension":"xlsx","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":465887,"visible":true,"origin":"","legend":"Dataset 2","description":"","filename":"ESMRamanDeepcarboncycleandearlyEarthXXsoxygenationevidencefromultrahighpressuremetamorphicrocks.xlsx","url":"https://assets-eu.researchsquare.com/files/rs-6229822/v1/b075b79bf3d754640e10c688.xlsx"},{"id":79161370,"identity":"086f8667-49ec-4f3e-a7ef-827b4ccfd9f5","added_by":"auto","created_at":"2025-03-25 07:26:56","extension":"docx","order_by":3,"title":"","display":"","copyAsset":false,"role":"supplement","size":25872840,"visible":true,"origin":"","legend":"Supplementary Material","description":"","filename":"ESMDeepcarboncycleandearlyEarthXXsoxygenationevidencefromultrahighpressuremetamorphicrocks.docx","url":"https://assets-eu.researchsquare.com/files/rs-6229822/v1/0cfd0094ec089825ab313bfd.docx"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"Deep carbon cycle and early Earth´s oxygenation: evidence from ultra-high-pressure metamorphic rocks","fulltext":[{"header":"Introduction","content":"\u003cp\u003eNon-cratonic microdiamond and graphite inclusions in garnet are reported in highly retrograded, metamorphic crustal rocks formed in Earth's ultra-high-pressure metamorphism (UHPM). All occurrences of microdiamond inclusions, except those partially replaced by graphite in garnet from the Precambrian supracrustal rocks of the Nagssugtoqidian Orogen in West Greenland (1.8 Ga), are associated with Phanerozoic orogens, with ages ranging from Paleozoic to Cenozoic\u003csup\u003e\u003cspan additionalcitationids=\"CR2 CR3\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e. Furthermore, the presence of coupled microdiamond and graphite inclusions within garnet indicates UHPM on Earth, often found in highly retrograded metamorphic crustal rocks (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eA).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe occurrence of microdiamond inclusions in garnets from rocks formed in UHPM terranes requires crystallization from a fluid phase under static conditions at pressures of \u0026ge;\u0026thinsp;2.7\u0026ndash;4.0 GPa, temperatures of ~\u0026thinsp;700\u0026ndash;1000\u0026deg;C, and subduction to depths of \u0026ge;\u0026thinsp;90\u0026ndash;120 km\u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u003c/sup\u003e. A classic example, characterized by extreme formation conditions, is the case of microdiamond inclusions in garnet from ultra-high-pressure metamorphic (UHPM) rocks of the Kokchetav massif in Kazakhstan, which comprise metamorphic rocks with sedimentary and volcanic protoliths (dating back to the 531 Ma UHPM event). Studies indicate that microdiamonds form at a pressure range of 6\u0026ndash;9 GPa and a temperature range of 980\u0026ndash;1200\u0026deg;C.\u003c/p\u003e \u003cp\u003eIt is believed that the protective nature of garnet crystals may have helped shield the diamond from undergoing total retrograde graphitization processes\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e,\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u003c/sup\u003e. The hypothesis suggests that these diamonds were trapped in garnet during their growth and underwent graphitization during decompression, followed by granulite facies metamorphism. The occurrence of graphitized diamonds or the coexistence of diamond and graphite within garnet requires the involvement of CO\u003csub\u003e2\u003c/sub\u003e and/or C-O-H fluids during crystallization\u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e,\u003cspan additionalcitationids=\"CR8 CR9 CR10\" citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eThe subduction of surface-derived organic carbon to mantle depths, specifically around 90 km, leads to the transformation of disordered organic carbon into crystallized graphite at subarc depths, which can further transform into diamonds at lithospheric mantle depths exceeding 140 km\u003csup\u003e\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e. The continued subduction of graphitized organic carbon plays a crucial role in forming diamonds with light carbon isotope compositions, indicating a biogenic origin. The light δ\u0026sup1;\u0026sup3;C values observed in diamonds, especially those hosted in ophiolites, suggest incorporating subducted biogenic carbon\u003csup\u003e\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e. The subduction of organic carbon to such depths has significant implications for the deep carbon cycle. This process indicates a mechanism for recycling surface carbon into the mantle, potentially influencing large-scale geological events such as the Great Oxidation Event (GOE) and the Lomagundi-Jatuli Event (LJE). The latter is usually characterized by an unusual increase in organic carbon deposition in marine sediments\u003csup\u003e\u003cspan additionalcitationids=\"CR13 CR14\" citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e. In the case of the LJE, one key question remains: What mechanism triggered such a significant disturbance in the global carbon cycle? Some alternative hypotheses\u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e have recently suggested that the deep carbon cycle could be responsible for this unusual influx of organic carbon into the Paleoproterozoic oceans.\u003c/p\u003e \u003cp\u003eIn a recent study, Santos et al.\u003csup\u003e\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e provided significant evidence of an ancient reservoir of organic carbon found in graphite rocks dated 2.1\u0026nbsp;billion years ago. These rocks are located in the northern Borborema Province. The authors suggest that this organic carbon was partially released during the metamorphic processes affecting these carbon-rich sediments, indicating a deep carbon cycle. They also propose a connection between these graphite rocks and manganese-rich sediments from the Paleoproterozoic era, which may have influenced the oxygenation of the oceans and the atmosphere.\u003c/p\u003e \u003cp\u003eIn line with these findings, we present our research from the Lagoa do Riacho deposit in northern Borborema Province, where we discovered microdiamonds within rocks containing manganese and graphite. This evidence suggests that they reached depths of approximately 150 kilometers beneath the Earth's crust before being exhumed. Moreover, given the 2.1\u0026nbsp;billion-year age of these rocks, we provide the earliest known evidence of microdiamonds discovered on Earth to date. Considering the paleoenvironmental importance of these findings, we propose a relationship between the deep carbon cycle, climate, tectonics, and oxygenation of the oceans and atmosphere during this ancient timeframe.\u003c/p\u003e\n\u003ch3\u003eGeological setting - Borborema Province\u003c/h3\u003e\n\u003cp\u003eThe Borborema Province in Northeast Brazil is an essential piece in the puzzle of the orogenic system associated with assembling Western Gondwana during the Brasiliano/Pan-African orogeny, around 600 Ma\u003csup\u003e\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u003c/sup\u003e. Pre-drift reconstructions of the South Atlantic position the Borborema Province adjacent to the West African, Congo, and S\u0026atilde;o Francisco cratons, reflecting its role as an internal segment of Western Gondwana\u003csup\u003e\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003e. This province comprises an Archean tonalite-trondhjemite-granodiorite (TTG) basement overlaid by metamorphosed and migmatized Palaeoproterozoic to early Mesoproterozoic rocks\u003csup\u003e\u003cspan additionalcitationids=\"CR20 CR21 CR22 CR23 CR24 CR25 CR26\" citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e. Neoproterozoic supracrustal rocks, granitoids, and shear zones (e.g., Senador Pompeu and Sobral Pedro II/Transbrasiliano) are common in this province\u003csup\u003e\u003cspan additionalcitationids=\"CR29 CR30\" citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eThe Borborema Province is divided into three structural subprovinces: (1) the Northern, (2) the Central, and (3) the Southern\u003csup\u003e\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e,\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e\u003c/sup\u003e. The Northern Borborema subprovince, especially in the Cear\u0026aacute; Central Domain (CCD) (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eB), which is the focus of this study, consists of an expressive Rhyacian high-grade metavolcanic-plutonic-sedimentary sequence\u003csup\u003e\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e,\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e,\u003cspan additionalcitationids=\"CR35 CR36\" citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eOn the CCD, in a 70 km N-NE linear extension, the Lagoa do Riacho manganese deposit (Figs.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eC-\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eD) is composed of graphite-manganese-bearing rocks within the Paleoproterozoic unit of the Canind\u0026eacute; do Cear\u0026aacute; Complex, which includes migmatites, paragneisses, and peraluminous granitoids. Manganese-bearing minerals consist predominantly of spessartine, rhodonite-pyroxmangite, and minor tephroite, rhodochrosite, pyrophanite, manganese-amphibole, associated with graphite, sulfoarsenide, and sulfide minerals such as cobaltite, covellite, pyrite, and chalcopyrite. Massive ores record localized supergene enrichment with pyrolusite, manganite, cryptomelane, and todorokite\u003csup\u003e\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e,\u003cspan additionalcitationids=\"CR38 CR39\" citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eU\u0026ndash;Pb geochronological studies indicate that the sedimentary precursors of these mineralizations have a Rhyacian depositional age between 2.22 and 2.05 Ga, later reworked by high-grade metamorphism at 2.04 Ga and ultra-high temperature (UHT) metamorphism at 1.95 Ga\u003csup\u003e\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e,\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e,\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e,\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e,\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e\u003c/sup\u003e. These ages resemble other manganese formations associated with organic-matter-rich successions, including the Francevillian and Birimian groups in Gabon and Ghana, as well as those in the Brazilian territory, such as Serra do Navio, Azul, Buritirama, and Morro da Mina\u003csup\u003e\u003cspan additionalcitationids=\"CR43 CR44 CR45 CR46 CR47\" citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003eMineralogy and textural features of the graphite-manganese-bearing rocks\u003c/h2\u003e \u003cp\u003eThe studied lithologies include silicate manganese ore (SMO), oxidized manganese ore (OMO), graphite-bearing gondite, and graphite-bearing pelitic gneiss (see supplementary material). SMO primarily comprises tephroite, spessartine, and rhodonite, showing granoblastic texture, and is characterized by manganese-rich silicate layering, with siegenite, cobaltite, graphite, and manganese oxides as accessory minerals (Figs.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eA-B). Graphite-bearing gondite exhibits a grano-lepidoblastic texture, characterized by the presence of graphite flakes and spessartine garnet, accompanied by quartz, potassium feldspar, baryte, and sulfides (Supplementary Material, Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eE). Graphite inclusions are common in spessartine, occurring as rounded to elongated forms (10\u0026ndash;40 \u0026micro;m) (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eE).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eOMO exhibits a distinct banded structure dominated by manganese oxides (pyrolusite, cryptomelane) intergrown with spessartine porphyroblasts containing aligned graphite, carbonate, and rare diamond micro-inclusions trails (Supplementary Material, Figs.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eA and \u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eC). Finally, graphite-bearing pelitic gneiss shows strong foliation, mainly composed of quartz, feldspar, almandine garnet, biotite, muscovite, and graphite, with frequent micro-inclusions of graphite, quartz, biotite, sulfides, and the occasional microdiamond within garnet porphyroblasts (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eG)\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eGraphite Raman mapping and thermometry\u003c/h3\u003e\n\u003cp\u003eIn silicate manganese ore (SMO), graphite occurs intergrown with spessartine and rhodonite, forming irregular clusters along grain boundaries (Supplementary Material, Figs.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eA-\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eB). It is frequently intergrown with sulfides and sulfoarsenides such as siegenite, cobaltite, and todorokite (Figs.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eA-\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eC).\u003c/p\u003e \u003cp\u003ePetrographic analyses of SMO samples in thin sections revealed the occurrence of highly disordered graphite associated with siegenite (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eB), as well as graphite in association with cobaltite and todorokite (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eD). Raman spectra indicate variations in graphite crystallinity, with characteristic bands at 1581 cm⁻\u0026sup1; (G band), 1340 cm⁻\u0026sup1; (D1 band), and 2720 cm⁻\u0026sup1; (D2 band) (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eB), with a full width at half maximum (FWHM) of 50 cm⁻\u0026sup1;, and a calculated and corrected temperature of 286\u0026deg;C using the method of Beyssac et al.\u003csup\u003e\u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e49\u003c/span\u003e\u003c/sup\u003e and Barzoi\u003csup\u003e\u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e50\u003c/span\u003e\u003c/sup\u003e. Another spectrum of highly disordered graphite exhibits bands at 1567 cm⁻\u0026sup1; (G), 1340 cm⁻\u0026sup1; (D1), and 2777 cm⁻\u0026sup1; (D2) (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eD), with a FWHM of 98 cm⁻\u0026sup1; and a corresponding temperature of 362\u0026deg;C.\u003c/p\u003e \u003cp\u003eRaman spectral mapping was performed on graphite inclusions in spessartine from graphite-bearing gondite. The Raman mapping of the G, D, and 2D bands (Figs.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eF\u0026ndash;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eH) reveals heterogeneities in the crystallinity of graphite. The disorder in graphite is further confirmed by the presence of second-order bands such as S1, S2, and S3, which indicate structural defects and strain within the lattice\u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e. Raman spectra of disordered graphite exhibit G bands at 1580 cm⁻\u0026sup1;, D1 bands at 1360 cm⁻\u0026sup1;, and additional second-order peaks (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eI), with a full width at half maximum (FWHM) of 14 cm⁻\u0026sup1; and a calculated temperature of 667\u0026deg;C. The highly ordered graphite exhibits G bands at 1579 cm⁻\u0026sup1;, D1 bands at 1353 cm⁻\u0026sup1;, and S1 and S2 peaks (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eJ), with a FWHM of 19 cm⁻\u0026sup1; and a corresponding temperature of 853\u0026deg;C, consistent with high-temperature metamorphic conditions\u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e. The progressive sharpening of the G-band and reduction in D1 intensity from disordered to highly ordered graphite follows the graphitization trend described by Zhang \u0026amp; Santosh\u003csup\u003e\u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e51\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\n\u003ch3\u003eDiamond Raman mapping and spectroscopy\u003c/h3\u003e\n\u003cp\u003eIn oxidized manganese ore (OMO), graphite, microdiamond, and carbonate inclusions are frequently observed within anhedral spessartine crystals (Figs.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eA-\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eC). These microcrystals form aligned trails of inclusions (Supplementary Material, Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eA). Microdiamond inclusions are characterized by their subhedral to euhedral shape (2\u0026ndash;5 \u0026micro;m) and may be associated with graphite. Graphite also occurs in the rock matrix along grain boundaries and within fractures in spessartine, often associated with manganese oxides (Supplementary Material, Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eA). Petrographic analyses reveal the presence of carbonate and diamond inclusions in spessartine from the OMO (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eA).\u003c/p\u003e \u003cp\u003eThe Raman spectrum of the microdiamond inclusion exhibits a characteristic sharp diamond peak at 1335 cm⁻\u0026sup1;, with a FWHM of 9.9 cm⁻\u0026sup1; (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eB), which falls within the expected range for metamorphic microdiamonds. A Raman mapping of a microdiamond inclusion in spessartine was performed (Figs.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eD\u0026ndash;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eE). The Raman map revealed the occurrence of graphite associated with microdiamond, with the D1 (graphite) and sp\u0026sup3;-bonded carbon (diamond) bands showing positional variations due to strain or minor compositional changes. The variation in the position of the G band of graphite is observable in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eE. The obtained spectra show diamonds with a peak at 1338 cm⁻\u0026sup1; and FWHM of 12.8 cm⁻\u0026sup1;, slightly broader than typical single-crystal diamonds, suggesting internal stress or size effects\u003csup\u003e\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003e. The G and 2D graphite bands can appear alongside the microdiamond spectrum (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eF).\u003c/p\u003e \u003cp\u003eIn graphite-bearing pelitic gneiss, graphite occurs as medium-grained flakes within the foliation, intercalated with biotite and muscovite (Supplementary Material, Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eB). It is frequently found as inclusions within almandine porphyroblasts, where it forms aligned inclusion trails. Microdiamond inclusions (5\u0026ndash;25 \u0026micro;m), with subhedral to euhedral shapes, also occur within almandine, coexisting with graphite inclusions (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eG).\u003c/p\u003e \u003cp\u003eMicrodiamond inclusions are associated with quartz and biotite in almandine (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eG). Backscattered electron (BSE) images reveal the details of these diamond and graphite inclusions within almandine, with biotite surrounding the inclusions (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eH). Raman spectroscopy confirms the presence of microdiamonds, characterized by a peak at 1335 cm⁻\u0026sup1; and a FWHM of 10.5 cm⁻\u0026sup1; (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eI), which aligns with previous reports of ultra-high-pressure metamorphic diamonds. Raman spectral mapping highlights the spatial distribution of graphite, almandine, and diamond within the almandine (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eK). The coexistence of graphite with microdiamonds in ultra-high-pressure environments is further supported by a well-defined 2D band, indicating increased crystalline ordering at extreme pressures\u003csup\u003e\u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e51\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eCore and rim microprobe data from garnet of graphite-bearing pelitic gneiss, represented in ternary diagrams, show compositional variations between XMg (pyrope) and XFe (almandine) (Figs.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eM-\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eN). The distribution of analytical points plots near the fields of diamond-bearing paragneisses (core) and gneisses (rim), as well as along the transition from granulite facies (core) to upper amphibolite facies (rim).\u003c/p\u003e\n\u003ch3\u003eIsotopic modeling and speciation of COH fluids\u003c/h3\u003e\n\u003cp\u003eThe isotopic and thermodynamic modeling of the COH system was conducted to evaluate the stability and compositional evolution of fluids responsible for diamond precipitation. The multicomponent Rayleigh fractionation between CH₄+CO₂ and diamond followed a progressive trend, starting from an initial fluid composition of δ\u0026sup1;\u0026sup3;C = -29\u0026permil;. As carbon was progressively incorporated into the solid phase (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eA), the remaining fluid became enriched gradually in \u0026sup1;\u0026sup3;C, reaching a final value of δ\u0026sup1;\u0026sup3;C = -10.0\u0026permil;, while the precipitated diamond recorded a final isotopic composition of δ\u0026sup1;\u0026sup3;C = -15.28\u0026permil;. The COH ternary diagram (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eB) indicates that the transition from graphite to diamond occurs under high-pressure conditions, with diamond stability prevailing above 3.7 GPa and 900\u0026deg;C. The mineral stability maps (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eC) and fluid compositional evolution (Figs.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eD\u0026ndash;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eF) reveal an increase in the molar fraction of CO₂ (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eE) with increasing pressure and temperature. At the same time, H\u003csub\u003e2\u003c/sub\u003eO and CH₄ progressively decrease (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eF), indicating an increasingly oxidizing environment. The rise in oxygen fugacity (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eG) further supports this trend, allowing diamond stability. The isotopic evolution of the fluid (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eH) shows a progressive enrichment in \u0026sup1;\u0026sup3;C. At the same time, the δ\u0026sup1;\u0026sup3;C values of CO₂ and CH₄ (Figs.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eI-\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eJ) reveal significant isotopic fractionation, driven by exchange reactions between the fluid and solid phases. These results indicate that diamond formation from COH fluids under high-pressure (\u0026gt;\u0026thinsp;3.7 GPa) and high-temperature (~\u0026thinsp;900\u0026deg;C) metamorphic conditions occurs with a well-defined isotopic fractionation trend, highlighting the role of fluid evolution and oxygen fugacity in diamond stabilization.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"Discussion","content":"\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003ePaleoproterozoic UHPM and plate tectonics\u003c/h2\u003e \u003cp\u003eRaman spectroscopy reveals a progressive metamorphic transformation of graphite from highly disordered forms (~\u0026thinsp;300\u0026ndash;400\u0026deg;C) to highly ordered graphite (~\u0026thinsp;850\u0026deg;C)\u003csup\u003e\u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e51\u003c/span\u003e\u003c/sup\u003e, consistent with subduction-related recrystallization processes. The presence of microdiamonds within garnet, particularly in spessartine (manganese-rich oxidized ore) and almandine (graphite-bearing metapelitic gneiss), indicates metamorphic conditions exceeding 3.7 GPa and 900\u0026deg;C, reinforcing their formation under ultra-high-pressure conditions before exhumation\u003csup\u003e\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003e. Secondary Raman bands (S1, S2, S3) in graphite further suggest variable stress conditions linked to a convergent tectonic regime, where CO₂ reduction reactions govern carbon phase stability\u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e. This process likely involved fluid-assisted recrystallization under fluctuating oxygen fugacity, driving the transformation of amorphous organic matter into graphite and diamond.\u003c/p\u003e \u003cp\u003eThermodynamic modeling indicates that diamond precipitation occurred during a transition from CH₄-dominated reducing fluids to CO₂-rich oxidizing conditions, aligning with global models of carbon recycling in subduction zones\u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u003c/sup\u003e. The increasing oxygen fugacity recorded in the model suggests a direct link between deep fluid evolution and the stabilization of diamond over graphite, highlighting the role of high-pressure metamorphism in carbon sequestration. These findings support the hypothesis that diamonds and graphite in the Lagoa do Riacho manganese-rich rocks are metamorphic products formed under extreme pressures, with estimated P-T conditions (~\u0026thinsp;3.7 GPa and 900\u0026deg;C, respectively) consistent with other UHPM terrains\u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e,\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e,\u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e52\u003c/span\u003e\u003c/sup\u003e). Successive metamorphic events were likely driven by plate convergence, crustal thickening, and exhumation\u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eAlmadine containing microdiamond and graphite inclusions exhibit a pyrope-rich core and an almandine-rich rim, suggesting decompression-related chemical re-equilibration. The compositional shift from diamond-bearing gneiss and granulite stability fields in the core to upper amphibolite facies in the rim supports a multi-stage metamorphic evolution (see Figs.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eM-\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eN, diagrams from Tolosan-Delgado et al.\u003csup\u003e\u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e53\u003c/span\u003e\u003c/sup\u003e and Sch\u0026ouml;nig et al.\u003csup\u003e\u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e54\u003c/span\u003e\u003c/sup\u003e). The occurrence of highly ordered graphite and microdiamonds in manganese-bearing rocks from the Borborema Province, specifically the Canind\u0026eacute; do Cear\u0026aacute; Complex, represents one of the earliest pieces of evidence of UHPM on Earth\u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e,\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e,\u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e55\u003c/span\u003e,\u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e56\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eGeochronological data suggest that the sedimentary precursors of these rocks were deposited between 2.22 and 2.05 Ga, later subjected to high-grade metamorphism (~\u0026thinsp;2.04 Ga), followed by UHT conditions (~\u0026thinsp;1.95 Ga)\u003csup\u003e\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e,\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e,\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e,\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e,\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e\u003c/sup\u003e. These results contribute to growing evidence that plate tectonics was fully operational during the Paleoproterozoic (Orosirian, 2.05\u0026ndash;1.80 Ga), challenging earlier models of a stagnant-lid regime (see Stern\u003csup\u003e\u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e56\u003c/span\u003e\u003c/sup\u003e).\u003c/p\u003e \u003cp\u003eThe data from Lagoa do Riacho align with other UHPM terranes worldwide, where similar events occurred at comparable time intervals but with variable degrees of exhumation:\u003c/p\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003eNagssugtoqidian Orogen, Greenland (~\u0026thinsp;1.8 Ga): UHPM represented by graphitized diamond inclusions in garnet of gneisses formed at greater burial depths (~\u0026thinsp;7 GPa, 970\u0026deg;C)\u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eTrans-Hudson Orogeny, Canada (~\u0026thinsp;1.80 Ga): Eclogites and high-pressure granulites with no confirmed microdiamond record\u003csup\u003e\u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e57\u003c/span\u003e,\u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e58\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eDemocratic Republic of the Congo (~\u0026thinsp;2.0 Ga): Paleoproterozoic eclogites and HP-LT granulites with evidence of deep subduction processes\u003csup\u003e\u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e55\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eDeep carbon cycle and implications for early Earth oxygenation\u003c/h3\u003e\n\u003cp\u003eThe findings of this study align with the broader context of Paleoproterozoic deep carbon cycling, where subduction and mantle processes may have influenced CO₂ degassing and fluctuations in ocean-atmosphere redox. The increasing oxygen fugacity recorded in isotopic models links deep fluid evolution to the stabilization of diamond over graphite, reinforcing the role of high-pressure metamorphism in carbon sequestration. This transition is significant in the GOE (~\u0026thinsp;2.4 Ga) and the LJE (~\u0026thinsp;2.3\u0026ndash;2.1 Ga), as increased oxygen fugacity in subduction-related fluids may have contributed to the oxidation of surface environments.\u003c/p\u003e \u003cp\u003eThe GOE and LJE marked profound shifts in Earth's atmospheric and oceanic chemistry, influencing carbon burial, oxidative weathering, and the sedimentation of manganese. Isotopic modeling in this study indicates that the redox evolution of this period was also recorded in the metamorphic transformation of carbon, progressing from disordered graphite to highly ordered graphite and microdiamonds. This process reflects deep carbon recycling and its role in stabilizing atmospheric O₂ levels. The isotopic fractionation observed in the COH system parallels δ\u0026sup1;\u0026sup3;C shifts in Paleoproterozoic carbonates and Mn-rich deposits, supporting a link between large-scale organic carbon burial, fluid evolution, and oxygenation (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe fate of subducted organic carbon has significant implications for the deep carbon cycle and Earth's redox state\u003csup\u003e\u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e59\u003c/span\u003e\u003c/sup\u003e. Graphitic carbon from organic precursors can persist to mantle depths (~\u0026thinsp;90 km), influencing arc emissions and long-term carbon cycling\u003csup\u003e\u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e60\u003c/span\u003e\u003c/sup\u003e. This process may have been crucial in buffering atmospheric CO₂ levels over geological timescales and sustaining climate stability\u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e. The oxidation of subducted carbon and its interaction with carbonate-bearing sediments further modulated the isotopic signature of volcanic emissions, contributing to the stabilization of atmospheric O₂ levels following the GOE, as noted by LJE\u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eDuring the Paleoproterozoic, volcanic CO₂ emissions played a crucial role in the Lomagundi-Jatuli Event (LJE), intensifying silicate weathering, nutrient influx, and organic carbon sequestration, thereby sustaining high atmospheric O₂ levels and influencing global climate perturbations and transient glaciations\u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e. Following Paleoproterozoic glaciations, Mn-rich carbonates and oxides precipitated in response to ice retreat, reflecting a strong coupling between ocean stratification and evolving redox conditions\u003csup\u003e\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e,\u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e61\u003c/span\u003e\u003c/sup\u003e. During glaciations, Mn\u0026sup2;⁺ accumulated in anoxic, ice-covered deep ocean waters, where it was later oxidized and deposited following ice retreat. Subduction-driven CO₂ degassing facilitated deglaciation and stabilized ocean chemistry, as observed similarly in Neoproterozoic Snowball Earth events, potentially aiding the rise of complex life\u003csup\u003e\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e,\u003cspan additionalcitationids=\"CR62\" citationid=\"CR61\" class=\"CitationRef\"\u003e61\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR63\" class=\"CitationRef\"\u003e63\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eFive critical conclusions come from this study:\u003c/p\u003e\n\u003cul\u003e\n \u003cli\u003ePetrographic and spectroscopic data indicate a progressive metamorphism of graphite from disordered forms (300\u0026deg;C) to highly ordered graphite (~850\u0026deg;C), culminating in the formation of microdiamonds under ultra-high-pressure conditions (3.7\u0026ndash;4.0 GPa).\u003c/li\u003e\n \u003cli\u003eMicrodiamond inclusions in garnet suggest that part of the buried biogenic carbon was subducted and recycled at mantle depths, influencing the deep carbon cycle.\u003c/li\u003e\n \u003cli\u003eThe findings suggest that the Borborema Province shares key characteristics with other Paleoproterozoic subduction terranes and may host the oldest record of metamorphic diamond formation associated with subduction processes.\u003c/li\u003e\n \u003cli\u003eThis discovery provides crucial evidence for the evolution of early Earth\u0026rsquo;s tectonics, reinforcing the role of subduction-exhumation cycles in controlling global carbon fluxes and influencing the composition of the Earth\u0026rsquo;s mantle and atmosphere.\u003c/li\u003e\n \u003cli\u003eThe coevolution of Earth\u0026apos;s biosphere, atmosphere, and lithosphere during the Paleoproterozoic was fundamentally driven by the burial of organic carbon, manganese deposition, and fluctuations in redox conditions. The transition from an anoxic to an oxic world was marked by the interplay of enhanced photosynthetic productivity, volcanic CO₂ emissions, glacial-interglacial cycles, and deep carbon subduction. These processes collectively shaped the trajectory of Earth\u0026apos;s carbon cycle and atmospheric oxygenation, ultimately paving the way for the emergence of complex life.\u003c/li\u003e\n\u003c/ul\u003e"},{"header":"Methods","content":"\u003cp\u003eMethods are available as electronic Supplementary Material.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll data generated or analyzed during this study are included in this published article, along with its Supplementary Material files.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgments\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis research was part of the first author’s Ph.D. thesis. ECUF is grateful to the Geosciences Graduate Program from the Federal University of Ceará and the Geological Survey of Brazil for support throughout the thesis development and to geologist Renato Braz Sue (representing Libra Ligas do Brasil company) for providing full access to drill cores and fieldwork assistance. Prof. Dr. Felipe Holand FHS would like to thank the Society of Economic Geologists (SEG) for the Student Research Grant. WSA is funded by CNPq, under grant number (407255/2022-2). We genuinely appreciate anonymous reviewers' comments, suggestions, and criticisms that helped improve this manuscript's quality.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eECUF designed the study, developed the idea, performed the analyses, and wrote the manuscript. All authors discussed the results and participated in manuscript refinement.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAdditional information\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eSupplementary Material\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eSobolev NV, Shatsky VS (1990) Diamond inclusions in garnets from metamorphic rocks: a new environment for diamond formation. Nature 343:742\u0026ndash;746\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMassonne H-J, Kennedy A, Nasdala L, Theye T (2007) Dating of zircon and monazite from diamondiferous quartzofeldspathic rocks of the Saxonian Erzgebirge \u0026ndash; hints at burial and exhumation velocities. Mineral Mag 71:407\u0026ndash;425\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFrezzotti M-L, Huizenga J-M, Compagnoni R, Selverstone J (2014) Diamond formation by carbon saturation in C\u0026ndash;O\u0026ndash;H fluids during cold subduction of oceanic lithosphere. Geochim Cosmochim Acta 143:68\u0026ndash;86\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGlassley WE, Korstgard JA, Sorensen K, Platou S (2014) W. A new UHP metamorphic complex in the 1.8 Ga Nagssugtoqidian Orogen of West Greenland. Am Mineral 99:1315\u0026ndash;1334\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDobrzhinetskaya LF, O\u0026rsquo;Bannon EF, Sumino H (2022) Non-cratonic Diamonds from UHP Metamorphic Terranes, Ophiolites and Volcanic Sources. Rev Mineral Geochem 88:191\u0026ndash;255\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDobrzhinetskaya L, Wirth R, Greenii H (2006) Nanometric inclusions of carbonates in Kokchetav diamonds from Kazakhstan: A new constraint for the depth of metamorphic diamond crystallization. Earth Planet Sci Lett 243:85\u0026ndash;93\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMposkos ED, Kostopoulos DK (2001) Diamond, former coesite and supersilicic garnet in metasedimentary rocks from the Greek Rhodope: a new ultrahigh-pressure metamorphic province established. Earth Planet Sci Lett 192:497\u0026ndash;506\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePerraki M, Proyer A, Mposkos E, Kaindl R, Hoinkes G (2006) Raman micro-spectroscopy on diamond, graphite and other carbon polymorphs from the ultrahigh-pressure metamorphic Kimi Complex of the Rhodope Metamorphic Province, NE Greece. Earth Planet Sci Lett 241:672\u0026ndash;685\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKorsakov AV et al (2010) Diamond-Graphite Relationships in Ultrahigh-pressure Metamorphic Rocks from the Kokchetav Massif, Northern Kazakhstan. J Petrol 51:763\u0026ndash;783\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSonin V, Leech M, Chepurov A, Zhimulev E, Chepurov A (2018) Why are diamonds preserved in UHP metamorphic complexes? Experimental evidence for the effect of pressure on diamond graphitization. Int Geol Rev 61:504\u0026ndash;519\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKorsakov A, Rezvukhina O, Jaszczak J, Rezvukhin D, Mikhailenko D (2019) Nat Graphite Cuboids Minerals 9:110\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHu H, Zhang L, Lan C, Liu Z (2023) Petrological evidence for deep subduction of organic carbon to subarc depths. Commun Earth Environ 4:418\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHolland HD (2002) Volcanic gases, black smokers, and the great oxidation event. Geochim Cosmochim Acta 66:3811\u0026ndash;3826\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLyons TW, Reinhard CT, Planavsky NJ (2014) The rise of oxygen in Earth\u0026rsquo;s early ocean and atmosphere. Nature 506:307\u0026ndash;315\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eEguchi J, Seales J, Dasgupta R (2020) Great Oxidation and Lomagundi events linked by deep cycling and enhanced degassing of carbon. Nat Geosci 13:71\u0026ndash;76\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSantos FH et al (2024) The origin and fate of organic carbon in graphite\u0026ndash;manganese bearing rocks and implications for the Lomagundi\u0026ndash;Jatuli Event. Sci Rep 14:21191\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAlmeida FFM, Hasui Y, De Brito Neves BB, Fuck RA (1981) Brazilian structural provinces: An introduction. Earth-Sci Rev 17:1\u0026ndash;29\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNeves SP (2003) Proterozoic history of the Borborema province (NE Brazil): Correlations with neighboring cratons and Pan-African belts and implications for the evolution of western Gondwana. Tectonics 22:2001TC001352\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eS\u0026aacute; JM, Bertrand JM, Leterrier J, Macedo MHF (2002) Geochemistry and geochronology of pre-Brasiliano rocks from the Transversal Zone, Borborema Province, Northeast Brazil. J South Am Earth Sci 14:851\u0026ndash;866\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMartins G, Oliveira EP, Lafon J-M (2009) The Algod\u0026otilde;es amphibolite\u0026ndash;tonalite gneiss sequence, Borborema Province, NE Brazil: Geochemical and geochronological evidence for Palaeoproterozoic accretion of oceanic plateau/back-arc basalts and adakitic plutons. Gondwana Res 15:71\u0026ndash;85\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHollanda MHBM, Archanjo CJ, Souza LC, Dunyi L, Armstrong R (2011) Long-lived Paleoproterozoic granitic magmatism in the Serid\u0026oacute;-Jaguaribe domain, Borborema Province\u0026ndash;NE Brazil. J South Am Earth Sci 32:287\u0026ndash;300\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDantas EL et al (2013) Crustal growth in the 3.4\u0026ndash;2.7Ga S\u0026atilde;o Jos\u0026eacute; de Campestre Massif, Borborema Province, NE Brazil. Precambrian Res 227:120\u0026ndash;156\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCosta FGD, Palheta ESDM, Rodrigues JB, Gomes IP, Vasconcelos AM (2015) Geochemistry and U\u0026ndash;Pb zircon ages of plutonic rocks from the Algod\u0026otilde;es granite-greenstone terrane, Troia Massif, northern Borborema Province, Brazil: Implications for Paleoproterozoic subduction-accretion processes. J South Am Earth Sci 59:45\u0026ndash;68\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSouza ZS et al (2016) Generation of continental crust in the northern part of the Borborema Province, northeastern Brazil, from Archaean to Neoproterozoic. J South Am Earth Sci 68:68\u0026ndash;96\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGanade CE, Basei MAS, Grandjean FC, Armstrong R, Brito RS (2017) Contrasting Archaean (2.85\u0026ndash;2.68 Ga) TTGs from the Tr\u0026oacute;ia Massif (NE-Brazil) and their geodynamic implications for flat to steep subduction transition. Precambrian Res 297:1\u0026ndash;18\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCosta FG et al (2018) Geochemistry and U\u0026ndash;Pb\u0026ndash;Hf zircon data for plutonic rocks of the Troia Massif, Borborema Province, NE Brazil: Evidence for reworking of Archean and juvenile Paleoproterozoic crust during Rhyacian accretionary and collisional tectonics. Precambrian Res 311:167\u0026ndash;194\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLages GA, De Lira Santos M, Brasilino LC, Rodrigues RG, J. B., Dantas EL (2019) Statherian-Calymmian (ca. 1.6 Ga) magmatism in the Alto Moxot\u0026oacute; Terrane, Borborema Province, northeast Brazil: Implications for within-plate and coeval collisional tectonics in West Gondwana. J South Am Earth Sci 91:116\u0026ndash;130\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eVauchez A et al (1995) The Borborema shear zone system, NE Brazil. J South Am Earth Sci 8:247\u0026ndash;266\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGarcia MDG, Dos Santos S, T. J., Da Silva Amaral W (2014) Provenance and tectonic setting of neoproterozoic supracrustal rocks from the Cear\u0026aacute; Central Domain, Borborema Province (NE Brazil): constraints from geochemistry and detrital zircon ages. Int Geol Rev 56:481\u0026ndash;500\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGanade CE, Weinberg RF, Cordani UG (2014) Extruding the Borborema Province (NE -Brazil): a two‐stage Neoproterozoic collision process. Terra Nova 26:157\u0026ndash;168\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePitombeira JPA, Amaral WDS, Santos TJSD, Dantas EL, Fuck R (2021) A. A new record of continental arc magmatism in the Cear\u0026aacute; Central Domain, Borborema Province (NE Brazil): evidence from the Pacatuba-Maranguape Complex. Precambrian Res 359:106192\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eVan Schmus WR, Kozuch M, De Brito Neves BB (2011) Precambrian history of the Zona Transversal of the Borborema Province, NE Brazil: Insights from Sm\u0026ndash;Nd and U\u0026ndash;Pb geochronology. J South Am Earth Sci 31:227\u0026ndash;252\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNeves SP (2015) Constraints from zircon geochronology on the tectonic evolution of the Borborema Province (NE Brazil): Widespread intracontinental Neoproterozoic reworking of a Paleoproterozoic accretionary orogen. J South Am Earth Sci 58:150\u0026ndash;164\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eda Costa FG, de Plaheta ES (2017) Geologia e recursos minerais das folhas Quixad\u0026aacute; (SB.24-V-B-IV) e Itapi\u0026uacute;na (SB.24-X-A-IV): estado do Cear\u0026aacute;. CPRM - Servi\u0026ccedil;o Geol\u0026oacute;gico do Brasil\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMuniz RL, Santos D, Dantas TJS, E. L., Fuck RA (2022) Rhyacian-Orosirian Khondalite Belt in the Borborema Province (NE Brazil): An active margin setting based on U\u0026ndash;Pb zircon and monazite constraints. Geol J 57:3808\u0026ndash;3828\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAmaral WDS et al (2023) Paleoproterozoic crustal evolution of the northern Borborema Province, NE Brazil: Insights from high-grade metamorphic rocks of the Canind\u0026eacute; do Cear\u0026aacute; Complex. Precambrian Res 384:106941\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSantos FH, Da Silva Amaral W, Martins DT, De Souza AC (2023) B. Zircon U\u0026ndash;Pb geochronology of manganese-rich rocks from the Borborema Province, Northeast Brazil: adding a new piece to the global inventory of Paleoproterozoic manganese mineralization. Min Deposita 58:531\u0026ndash;551\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSouza Filho S (1979) Tese de Doutoramento apresentada ao lnstituto de Geoci\u0026ecirc;ncias da Universidade de S\u0026atilde;o Paulo\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSantos FHD et al (2021) Unraveling sedimentary precursors and metal enrichment of high-grade metamorphosed manganese-rich rocks from the Borborema Province, northeastern Brazil. Ore Geol Rev 137:104283\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSantos FH, Da Silva Amaral W, Chi-Fru E, De Souza ACB, Bosco-Santos A (2022) Paleoproterozoic manganese oxide precipitation in oxic seawater surface and reductive enrichment in anoxic seafloor. Chem Geol 588:120655\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCalado et al (2019) Evidence for ca. 2046 Ma high-grade metamorphism in Paleoproterozoic metasedimentary rocks of the northern Borborema Province, NE Brazil: constraints from U-Pb (LA-ICP-MS) zircon ages. J Geol Surv Braz 2:137\u0026ndash;150\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNyame FK (2008) Petrography and geochemistry of intraclastic manganese\u0026ndash;carbonates from the \u0026sim;2.2Ga Nsuta deposit of Ghana: Significance for manganese sedimentation in the Palaeoproterozoic of West Africa. J Afr Earth Sci 50:133\u0026ndash;147\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChisonga BC, Gutzmer J, Beukes NJ, Huizenga JM (2012) Nature and origin of the protolith succession to the Paleoproterozoic Serra do Navio manganese deposit, Amapa Province, Brazil. Ore Geol Rev 47:59\u0026ndash;76\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDubois M (2017) Environnement de d\u0026eacute;p\u0026ocirc;t et processus de formation des carbonates de mangan\u0026egrave;se dans les black shales pal\u0026eacute;oprot\u0026eacute;rozoiques du Bassin de Franceville (2.1 Ga; Gabon)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCabral AR et al (2019) Molybdenum-isotope signals and cerium anomalies in Palaeoproterozoic manganese ore survive high-grade metamorphism. Sci Rep 9:4570\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGoto KT et al (2021) Progressive ocean oxygenation at ~\u0026thinsp;2.2 Ga inferred from geochemistry and molybdenum isotopes of the Nsuta Mn deposit, Ghana. Chem Geol 567:120116\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSalgado SS et al (2021) Metallogenetic Mn-model of the Rhyacian-aged Buritirama Formation, Caraj\u0026aacute;s domain (Amazon Craton). Ore Geol Rev 138:104396\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCosta M et al (2022) SEDIMENTARY MANGANESE DEPOSITS IN CARAJ\u0026Aacute;S, BRAZIL. Bol Mus Geoci\u0026ecirc;ncias Amaz 9:1\u0026ndash;38\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBeyssac O, Goff\u0026eacute; B, Chopin C, Rouzaud JN (2002) Raman spectra of carbonaceous material in metasediments: a new geothermometer. J Metamorph Geol 20:859\u0026ndash;871\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBarzoi SC (2015) Shear stress in the graphitization of carbonaceous matter during the low-grade metamorphism from the northern Parang Mountains (South Carpathians) \u0026mdash; Implications to graphite geothermometry. Int J Coal Geol 146:179\u0026ndash;187\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhang C, Santosh M (2019) Coupled laser Raman spectroscopy and carbon stable isotopes of graphite from the khondalite belt of Kerala, southern India. Lithos 334\u0026ndash;335:245\u0026ndash;253\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKorsakov AV, Hutsebaut D, Theunissen K, Vandenabeele P, Stepanov AS (2007) Raman mapping of coesite inclusions in garnet from the Kokchetav Massif (Northern Kazakhstan). Spectrochim Acta Mol Biomol Spectrosc 68:1046\u0026ndash;1052\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTolosana-Delgado R, Von Eynatten H, Krippner A, Meinhold G (2018) A multivariate discrimination scheme of detrital garnet chemistry for use in sedimentary provenance analysis. Sediment Geol 375:14\u0026ndash;26\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSch\u0026ouml;nig J, Von Eynatten H, Meinhold G, L\u0026uuml;nsdorf NK (2019) Diamond and coesite inclusions in detrital garnet of the Saxonian Erzgebirge, Germany. Geology 47:715\u0026ndash;718\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFran\u0026ccedil;ois C, Debaille V, Paquette J-L, Baudet D, Javaux EJ (2018) The earliest evidence for modern-style plate tectonics recorded by HP\u0026ndash;LT metamorphism in the Paleoproterozoic of the Democratic Republic of the Congo. Sci Rep 8:15452\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eStern RJ (2023) The Orosirian (1800\u0026ndash;2050 Ma) plate tectonic episode: Key for reconstructing the Proterozoic tectonic record. Geosci Front 14:101553\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWeller OM, St-Onge MR (2017) Record of modern-style plate tectonics in the Palaeoproterozoic Trans-Hudson orogen. Nat Geosci 10:305\u0026ndash;311\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eToma J et al (2024) Nuna supercontinent assembly linked to carbon cycling in shear zones 1.9\u0026ndash;1.7 billion years ago. Nat Geosci 17:1038\u0026ndash;1045\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHu H, Zhang L, Lan C, Liu Z (2023) Petrological evidence for deep subduction of organic carbon to subarc depths. Commun Earth Environ 4:418\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTumiati S et al (2022) Subducted organic matter buffered by marine carbonate rules the carbon isotopic signature of arc emissions. Nat Commun 13:2909\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRoy S (2006) Sedimentary manganese metallogenesis in response to the evolution of the Earth system. Earth-Sci Rev 77:273\u0026ndash;305\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSekine Y et al (2011) Manganese enrichment in the Gowganda Formation of the Huronian Supergroup: A highly oxidizing shallow-marine environment after the last Huronian glaciation. Earth Planet Sci Lett 307:201\u0026ndash;210\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMills BJW, Scotese CR, Walding NG, Shields GA, Lenton TM (2017) Elevated CO2 degassing rates prevented the return of Snowball Earth during the Phanerozoic. Nat Commun 8:1110\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003e\u003cem\u003eAtlas aerogeof\u0026iacute;sico do estado do Cear\u0026aacute;\u003c/em\u003e. (Servi\u0026ccedil;o Geol\u0026oacute;gico do Brasil - CPRM, Fortaleza, CE, (2021)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBottinga Y (1969) Calculated fractionation factors for carbon and hydrogen isotope exchange in the system calcite-carbon dioxide-graphite-methane-hydrogen-water vapor. Geochim Cosmochim Acta 33:49\u0026ndash;64\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMiozzi F, Tumiati S (2020) Aqueous concentration of CO2 in carbon-saturated fluids as a highly sensitive oxybarometer. Geochem Perspect Lett 16:30\u0026ndash;34\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDuncan MS, Dasgupta R (2017) Rise of Earth\u0026rsquo;s atmospheric oxygen controlled by efficient subduction of organic carbon. Nat Geosci 10:387\u0026ndash;392\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGalvez ME, Fischer WW, Jaccard SL, Eglinton TI (2020) Materials and pathways of the organic carbon cycle through time. Nat Geosci 13:535\u0026ndash;546\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"nature-portfolio","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"","title":"Nature Portfolio","twitterHandle":"","acdcEnabled":false,"dfaEnabled":false,"editorialSystem":"ejp","reportingPortfolio":"","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-6229822/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6229822/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThis study presents the oldest microdiamond and highly ordered graphite inclusions in garnet from Mn-rich metamorphic rocks of the Borborema Province, NE Brazil, providing strong evidence for Paleoproterozoic ultra-high-pressure metamorphism (UHPM). The biogenic origin of graphite suggests that organic matter was subducted to depths exceeding 3.7 GPa and temperatures above 900\u0026deg;C. Raman spectroscopy and isotopic modeling reveal a metamorphic transition from disordered graphite (~\u0026thinsp;300\u0026ndash;400\u0026deg;C) to highly ordered graphite (~\u0026thinsp;850\u0026deg;C) and microdiamonds, indicating fluid-assisted recrystallization under changing redox conditions. The transformation of CH₄-dominated to CO₂-rich fluids during devolatilization highlights a link between deep carbon cycling and redox stabilization. Isotopic trends in COH fluids match those of Paleoproterozoic Mn-rich deposits and carbonates, supporting a connection between organic carbon burial, CO₂ release, and atmospheric evolution. These findings suggest that subduction and exhumation processes were already active in the Paleoproterozoic, facilitating the transfer of deep carbon and contributing to atmospheric oxygenation. This work provides one of the earliest records of UHPM-related microdiamonds, positioning the Borborema Province among the oldest known UHPM terranes and offering new insights into early plate tectonics and the emergence of conditions favorable to complex life.\u003c/p\u003e","manuscriptTitle":"Deep carbon cycle and early Earth´s oxygenation: evidence from ultra-high-pressure metamorphic rocks","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-03-25 07:26:51","doi":"10.21203/rs.3.rs-6229822/v1","editorialEvents":[],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"communications-earth-and-environment","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"commsenv","sideBox":"Learn more about [Communications Earth and Environment](https://www.nature.com/commsenv/)","snPcode":"","submissionUrl":"","title":"Communications Earth \u0026 Environment","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"ejp","reportingPortfolio":"Communications Series","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"fb623a1c-549a-4a2a-b91c-5c7ac485f281","owner":[],"postedDate":"March 25th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[{"id":46114615,"name":"Earth and environmental sciences/Solid Earth sciences/Geology/Precambrian geology"},{"id":46114616,"name":"Earth and environmental sciences/Solid Earth sciences/Petrology"}],"tags":[],"updatedAt":"2025-04-06T10:00:15+00:00","versionOfRecord":[],"versionCreatedAt":"2025-03-25 07:26:51","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6229822","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6229822","identity":"rs-6229822","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}