Structural and Geophysical Modeling in an area with non-outcropping Copper Sulphide Deposits, Minas Do Seival Region, Sul-Riograndense Shield, Southern Brazil

Structural and Geophysical Modeling in an area with non-outcropping Copper Sulphide Deposits, Minas Do Seival Region, Sul-Riograndense Shield, Southern Brazil | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Structural and Geophysical Modeling in an area with non-outcropping Copper Sulphide Deposits, Minas Do Seival Region, Sul-Riograndense Shield, Southern Brazil Ana Flávia Araujo, César Augusto Moreira, Luiza Lima Alves, Lenon Melo Ilha, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5716993/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract This paper is based on the use of indirect investigation methods using geophysics as a tool for the search for non-outcropping deposits. The integration of the geophysical methods of DC Resistivity and Induced Polarization added to the analysis of structural data is adopted in the region of Minas do Seival, in the extreme south of Brazil, in an area with no signs of surface mineralization. The region is located in the context of the Sul-Riograndense Shield, with andesites, dacites and latites occur locally, in addition tuffs, lapilli tuffs and breccia tuffs, gathered in the Hilário Formation (Neoproterozoic). The structural survey was carried out at the Barita Mine, in outcropping lapilli tuffs where brecciation, argilization and carbonation were recognized in mineralized zones, with malachite and azurite. Next, 6 electrical tomography lines with 420m of length. The combined analysis of the 2D and 3D models allows the recognition of potentially mineralized zones characterized by high chargeability. The results indicate the existence of a deposit from 30m deep with a tendency to connect the mines, partly related to silicification processes (high chargeability + high resistivity) and partly related to argilization and propylitization (high chargeability + low resistivity), structurally controlled. mineral exploration sulfides copper electrical resistivity chargeability non-outcrop target Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 1 Introduction The mining sector contributes approximately 4% to Brazil's GDP (Gross Domestic Product) and assumes a pivotal role in sustaining a favorable trade balance, which amounts to US $ 32.5 billion, representing 63.8% of the country's balance [ 1 ]. It is indispensable in underpinning numerous production chains that shape the modern lifestyle of society and are of paramount importance in fulfilling its fundamental needs. The discovery of economically viable mineral deposits has become increasingly rare as consumer societies expand, driven by the unchecked urbanization of emerging countries and global technological advancements, which continue to place greater demand on commodities [ 2 ]. Mineral exploration represents a crucial phase aimed at identifying and thoroughly assessing deposits that meet the requisite economic, technical, and environmental criteria, in order to progress to the development and production stages of mining. Like iron and gold, copper stands as one of the most significant commodities in Brazil's trade balance, extensively used in the production of electrically conductive materials, including wires and cables, electric vehicle motors, and metal alloys [ 3 ]. To identify and incorporate new reserves, both direct investigative methods—such as drilling and chemical analysis—and indirect approaches, such as remote sensing and geophysical techniques, are employed. Mineral exploration carries a high inherent risk due to the activity's failure rates. As a result, direct methods are indispensable for confirming mineral occurrences, as they provide a realistic portrayal and reliable data through rigorous control and quality assurance measures. However, these methods are resource- and time-intensive, as a significant portion of boreholes and drill sample are often lost due to the lack of prior knowledge about the structure and morphology of mineralized targets, leading to drilling through sterile rocks and, consequently, wasting financial resources [ 2 – 4 ]. Alternatively, the application of geophysical methods is recommended due to their lower cost, ability to cover extensive areas, and effectiveness in delineating targets of interest for subsequent drilling and sampling, irrespective of rock exposures [ 5 ]. One strategy for identifying new targets involves exploring known mineralized regions, employing geological and structural controls to direct the search, and conducting surveys in areas lacking visible signs of mineralization [ 2 – 4 ]. Geoelectrical methods are widely employed in mineral exploration studies [ 6 – 7 – 8 – 9 ], with particular emphasis on sulfide deposits [ 10 – 11 – 12 – 13 – 14 ]. Therefore, the objective of this study is to evaluate the potential for discovering non-outcropping sulfide copper deposits between two abandoned mines in southern Brazil through the integration of geological mapping, structural analysis, and geophysical surveys. Electrical tomography data obtained from DC Resistivity and Induced Polarization methods, guided by geological controls, identified a promising target at a depth of 30 meters in an area devoid of surface mineralization. Its continuity at depth further suggests a possible connection between the abandoned mines, influenced by the regional structural framework, and highlights a target with significant potential for the resumption of mineral exploration projects in the region. 2 Study Area and Geological Settings The Seival Mines are located 324 km from Porto Alegre (RS) via the BR 290 highway, between the municipal boundaries of Caçapava do Sul and Lavras do Sul. The area hosts six copper-bearing mines: (1) Alcides; (2) Vila do Torrão; (3) Cruzeta; (4) Meio; (5) Morcego; (6) João Dahne; and (7) Barita. The study area is specifically situated between the Barita and João Dahne mines (Fig. 1 ). Historically, this region has been exploited for copper and gold mining for several years. Both private and state-owned companies documented occurrences from 1901 to 1931, when the E.F. and São Jerônimo Mines Company began shallow excavations. In the following years, various companies mined the area of the six mines, and between 1955 and 1962, more than 1,000 tons of ore were extracted per month, with an average grade of 1.6% total Cu [ 15 ]. The Seival Mines’ reserve was estimated at approximately 0.20Mt of ore, with an average of 1.40% Cu and 10–70 ppm of Ag [ 16 – 17 ]. At a regional scale, the area is geologically located in the southern sector of the Mantiqueira Province, which originated at the end of the Neoproterozoic and the beginning of the Paleozoic [ 18 ]. It corresponds to a complex geotectonic unit situated between the São Francisco and Rio de La Plata cratons, following the closure of the Adamastor Ocean [ 19 ]. The province is oriented NNE-SSW and extends for approximately 3,000km along the Atlantic coast, from Montevideo (Uruguay) to the south of Bahia [ 18 ]. The province is compartmentalized by the Dom Feliciano (southern Brazil to Uruguay), Araçuaí (Espírito Santo, eastern Minas Gerais, and southern Bahia), and Ribeira (states of Rio de Janeiro, Minas Gerais, São Paulo, and Paraná) belts [ 21 ]. In the Dom Feliciano Belt, rocks formed during the Transamazonian (2.26-2.00Ga) and Brasiliano (900-535Ma) orogenic cycles outcrop [ 22 ]. However, the latter orogenic cycle was responsible for the accretion, deformation, and reworking of pre-Cambrian crustal blocks, which define the current configuration of the region. On a smaller scale in the geological context, the state of Rio Grande do Sul is located in the Sul-Riograndense Shield (ESRG). This includes associations of metamorphic, igneous, and sedimentary rocks, distributed in a complex tectono-stratigraphic arrangement, compartmentalized into the tectonic units of the Vila Nova Belt (São Gabriel Terrane), Tijucas Belt (Tijucas Terrane), Dom Feliciano Belt (Pelotas Batholith), and Granulitic Complex [ 23 ]. Associated with the South Rio Grande Shield (ESRG) at a regional scale, the Camaquã Basin occurs, resting on its crystalline terrains. It trends N30E, with a length of approximately 100km and a width of up to 100km [ 24 ]. Its basement is composed of gneisses and metavolcanosedimentary rocks deformed with a NW-SE orientation [ 23 – 25 ]. The Camaquã Basin is compartmentalized into four groups, which are composed of several formations, divided into four events: i) Maricá Group, in a retroarc or foreland basin context [ 23 – 26 ]; ii) Bom Jardim Group, deposited in a transpressional strike-slip basin [ 27 – 28 ]; iii) Santa Bárbara Group, in a transtensional strike-slip context [ 29 – 30 ]; iv) Guaritas Group, formed in a transtensional subsidence event [ 30 – 31 ]. In the Seival Mines region, rocks from the Hilário Formation, part of the Bom Jardim Group, are present. This unit consists of intermediate volcanic rocks with calc-alkaline magmatism and shoshonitic affinity, such as andesites, dacites, and latites, as well as volcaniclastic rocks like tuffs, lapilli tuffs, and breccia tuffs [ 32 ]. The structural context of the Seival Mines indicates that the rocks are highly fractured, characteristic of ruptile tectonics, with subvertical fractures predominantly trending NE-SW and secondarily NW-SE. Some of these fractures result from reactivations of the NE-SW shear zones due to tectonic events that generated stress fields affecting the Sul-Riograndense Shield, while the NW-SE faults are correlatable with the Ibaré Lineament [ 15 ]. As a result, a strong structural control related to copper mineralizations is evident in the region, and ore zones are commonly associated with quartz veins rich in sulfides [ 33 ]. The sulfides occurring in the Seival Mines region include chalcopyrite, bornite, chalcocite, and covellite [ 34 ], which are part of the Cu-bearing mineralized veins that fill fractures and faults [ 15 ]. Since the 2000s, the Seival Mines have been targeted by multinational companies; however, due to insufficient investment, primarily based on a few drill holes, the research efforts have been incipient and unproductive [ 15 ]. 3 Materials and Methods The study followed a sequence of investigative steps. Initially, geological reconnaissance was conducted at rock outcrops in the Barita Mine, located at the northeastern boundary of the study area, where evidence of mineralization, including malachite and azurite impregnations, was identified (Fig. 2 ). Subsequently, structural measurements were taken at fractures and faults to define the main controls of the deposit, based on 200 measurements, which were processed in StereoNet software for subsequent graphical analysis. Based on clear indicators of mineralization identified in the Barita Mine, geological reconnaissance was conducted in the study area, corresponding to the interval between the Barita and João Dahne mines, where no evidence of copper mineralization was found (Fig. 3 ). The João Dahne mine was not visited due to years of abandonment and dense vegetation cover. The geophysical methods selected for this study were DC Resistivity and Induced Polarization. DC Resistivity determines the apparent resistivity of subsurface materials based on the injection of electrical current into the ground and the measurement of the resulting potential difference. The penetration depth of the method is proportional to the spacing between electrodes, and variations in electrode spacing provide information about stratification [ 35 – 36 – 37 ]. The method is grounded in Ohm’s Law, which enables the calculation of apparent resistivity (ρa) in a heterogeneous geological environment, incorporating a geometric factor (K) between two pairs of electrodes used for data acquisition, namely voltage (ΔV) (electrodes A and B) and electric current intensity (I) (electrodes C and D) (Eq. 1). The geometric factor (K) is calculated using Eq. 2, which accounts for the distances between electrodes AC, CB, AD, and DB (Eq. 2). These calculations facilitate the identification of mineralization and the recognition of subsurface geological structures [ 38 ]. Induced Polarization is a method based on the voltage response observed after the interruption of a continuous electrical current applied to the subsurface [ 38 ]. When electrical current is injected into the subsurface, the potential increases rapidly and takes some time to reach its maximum value (Vp). Similarly, when the current ceases, the voltage between the potential electrodes takes a measurable amount of time to decay completely, as the medium temporarily stores the electrical charge [ 39 – 40 – 41 ]. Thus, when applied to a geological medium, the voltage measured by the electrodes does not dissipate immediately but remains stored in the subsurface as mechanical, electrical, or chemical energy, detectable as a residual (induced) polarization for a certain period. The quantification of induced polarization is measured by chargeability (M), as represented by Eq. 3 [ 38 ]. The acquisition of geophysical data was based on 6 electrical tomography lines in a Schlumberger configuration, with a length of 420m and 10m electrode spacing, to measure electrical resistivity and chargeability parameters. The lines were oriented in the N60W direction, with a spacing of 50m between lines 1–2 and 5–6, and 100m between lines 2–3, 3–4, and 4–5 (Fig. 3 ). Non-polarizable electrodes were used to avoid noise in the acquisition of Induced Polarization data, made of porous ceramic and filled with a CuSO 4 solution. The geophysical equipment used for data acquisition was the Swedish-made ABEM Terrameter LS resistivimeter, consisting of a transmission and reception module with 250W potency, a maximum current of 2.5A, and a resolution of 1µV [ 42 ]. The configuration adopted for the survey was 1A of current, 1s transmission time, 0.3s reading time after current cutoff, with readings taken in two 100ms windows, and chargeability recorded in mV/V. Data acquisition was preceded by contact resistance measurements and programming for the exclusion of data with a mean deviation above 4%. The equipment automatically records the data in the internal memory as a spreadsheet, allowing for subsequent processing. A statistical analysis is performed after data acquisition to eliminate negative (anomalous) values and minimize extreme values by comparing them with neighboring values using arithmetic mean. The processing was carried out using the Res2Dinv software, version 3.53 (Geotomo Software), to generate inversion models for resistivity and chargeability parameters, with topography adjustment based on data generated from a differential GPS (DGPS) system. The inversion models are presented in 2D sections, containing information about the depth and length of the acquisition line, with values expressed in a logarithmic color scale. The inversion models are mathematically based on the least-squares algorithm with smoothing (smoothness constrained least square method), such that the software processes the subsurface as rectangular blocks containing values for the modeled parameters [ 43 ], in order to reduce the difference between the apparent resistivity values and those measured in the field, with the quality of the fit expressed by the root mean square error, the Root Mean Squared (RMS) error [ 43 ]. Upon completion of the inversion, the data are organized into a single spreadsheet, presenting each of the sections in an ordered manner. The file includes the position of the readings along the lines, spacing, and depth (variables "x", "y", and "z", respectively), as well as the resistivity and chargeability values for generating 3D visualization models. For 3D modeling, the tabulated data are used in the Oasis Montaj software (Geosoft) with interpolation through kriging. Subsequently, the statistical method of minimum curvature is applied to smooth the central values at the expense of the extremes. In this way, a gridded sample mesh is generated for each point of the 3D model, making it possible to generate depth maps with sections at depths of 10m, 20m, 30m, 40m, 50m, 60m, 70m, and 80m. 4 Results and Discussion At the regional scale, topographic lineaments are indicative of potential geological structures and possibly the location of mineral deposits. The shear zones of the Sul-Riograndense Shield (ESRG) predominantly trend NE-SW (Fig. 4 ). According to Lopes et al. (2018) [ 15 ], the main orientations are divided as follows: ±62% in N31-90ºE, ± 18% in N0-30ºE, and ± 18% in N0-90ºW. More precisely, in the Seival Mines region, the lineaments have a preferential direction of N50E, and the oriented dykes and faults (± N50E/70-88NW) are parallel to the Cabritos-Perau Fault, located 5km north of the area. The structural data from this study are similar to those obtained in previous works, with an average direction of N44E/65NW (Fig. 5 A), corresponding to the fracture family with the highest representation in the locality. Furthermore, another maximum was determined with an average attitude of N55W/65NE, which corresponds to a second fracture family of lower magnitude. The Hilário Formation exhibits bedding with a preferential direction of N20E/15SE, and the lapilli tuffs with N70E/30NW. The mineralized fractures and faults correspond to veins with thicknesses ranging from 0.1 to 1 cm, either straight or irregular, with directions of NE-SW and NNE-SSW, and high dips [ 15 ]. This observation is confirmed by the measurements taken in this study, with mineralized fractures showing an average attitude of N62E/48NW and N69E/75NW (Fig. 5 B). The faults present in the Barita Mine have an average attitude of N19E/9NW, which maintain the characteristics of the regional structural trend with a general NE-SW orientation (Fig. 5 C). The electrical tomography data are presented in 2D tomography sections based on distance and depth, using a single logarithmic color scale and values aligned with the analyzed physical parameters. This approach facilitates comparative analysis between the survey lines. Regarding resistivity, the processed data reveal a value range between 10Ω.m and 20,000Ω.m (Fig. 6 ), while the chargeability data show a range from 0.5mV/V to 5mV/V (Fig. 7 ). For better visualization, warm colors represent high values, and cool colors correspond to low values of the aforementioned physical parameters. The 2D sections were analyzed based on geological, structural, and metallogenetic criteria, combined with evidence of mineralization identified in the region. Zones with high resistivity values (> 2280Ω.m) may be associated with silicified intervals formed during the deposit's development [ 12 – 13 ]. Medium resistivity values, ranging from > 87Ω.m to < 260Ω.m, indicate water-saturated rock. Zones with very low resistivity ( 2.59mV/V indicate areas with an accumulation of sulfide metallic minerals, such as chalcopyrite, chalcocite, and bornite, which were mined in the abandoned sites and are possibly disseminated in fractured intervals [ 12 – 13 ]. Conversely, zones with low chargeability (< 2.59mV/V) represent sterile rocks lacking mineralization. Line 1, located to the north of the area, shows highly contrasted results according to the resistivity parameter, with a central zone between 160m and 290m, from the surface to a depth of approximately 90m, and a less pronounced zone between 340m and 380m, at the end of the acquisition section, both zones are characterized by high resistivity (> 2280Ω.m). The chargeability section shows a positive anomaly (> 2.59mV/V) between 80m and 255m, from a depth of 30m to 85m. Line 2, located 50m from the aforementioned line, shows three distinct zones characterized by high resistivity (> 2280Ω.m): the first is irregular and occurs between approximately 80m and 115m, from the surface to 55m; the second occurs between 210m and 240m, from 75m to a depth of 85m; the third positive anomaly occurs near the end of the acquisition, between 295m and 350m, from about 30m to a depth of 55m. The chargeability section shows an extensive positive anomaly (> 2.59mV/V) between 70m and 385m, from the surface to 85m, with a distinct zone of lower chargeability between 160m and 275m, from the surface to 40m. Line 3, located 100m from the aforementioned line, is characterized by high contrast in resistivity parameters. Two distinct positive anomalies (> 2280Ω.m) occur: the first, irregular, is between 190m and 300m, from the surface to a depth of 90m, with the width increasing from 65m toward the start of the acquisition line; the second anomaly occurs between 330m and 385m, from the surface to 40m. The chargeability section shows a positive anomaly (> 2.59mV/V) between 225m and 315m, from 40m to a depth of 90m. Line 4, located 100m from the aforementioned line, is characterized by low to medium resistivity. The chargeability section shows a distinct positive anomaly (> 2.59mV/V) between 160m and 180m, from a depth of 80m to 90m. Line 5, located 100m from the aforementioned line, shows high contrast in the resistivity parameter. A large, irregular zone of high resistivity (> 2280Ω.m) occurs between 190m and 300m, from the surface to a depth of 90m, widening at the base of the anomaly, starting at 70m. The chargeability section shows a distinct zone of high chargeability (> 2.59mV/V) between 110m and 150m, from a depth of 50m to 75m. Line 6, located 50m from the aforementioned line, exhibits anomalies of low to medium resistivity. Two distinct high resistivity anomalies (> 2280Ω.m) appear at high depth, from 80m to a maximum depth of 90m. The chargeability section shows a positive anomaly (> 2.59mV/V) between 50m and 145m, from the surface to a depth of 50m. Based on the established parameters, the area presents two types of copper mineralization occurrences in the subsurface. The first refers to anomalies of high chargeability combined with high resistivity, characteristic of mineralization associated with local structuring linked to silicification, possibly hosted in breccias or veins, occurring in lines 1, 2, and 3. Silicified zones can be defined as areas characterized by high resistivity (> 2280Ω.m) due to the increased resistance to the passage of electrical current in this material. This process results from the precipitation of silica due to the interaction of hydrothermal fluids with rock, leading to the replacement of minerals and the filling of voids with quartz [ 15 ]. This mineralized zone, characterized by high chargeability and high resistivity, associated with silicification, occurs in line 1 between 200m and 255m, from 30m to 85m in depth. In line 2, all the high resistivity zones coincide with the high chargeability zone, such that the areas classified as highly resistive serve as the boundary delimiting the silicified mineralized zone. Finally, in line 3, this mineralization occurs between 225m and 260m, from a depth of 40m to 90m. The second type of mineral occurrence refers to anomalies of high chargeability combined with low resistivity, indicative of structurally controlled mineralization associated with metasomatic processes of argillization/propylitization, identified in lines 1, 3, 4, 5, and 6. The argillization/propylitization zone is a peripheral belt surrounding hydrothermal sulfide deposits and contains copper carbonates, along with concentrations of chlorite and sericite [ 13 ]. These processes involve mineralogical alteration as a result of fluid-rock interaction and promote the concentration of metals, such as copper, especially in the hydrothermal system [ 45 ]. As a result, zones of low resistivity are generated due to the ability of secondary minerals to absorb water and ions in their crystal structure. This enhances the electrical conductivity of the rock, leading to a decrease in resistivity [45 − 15]. The mineralized zone characterized by high chargeability and low resistivity, associated with argillization/propylitization, occurs in line 1 between 80m and 195m, from a depth of 25m to 75m. In line 3, it appears between 260m and 315m, from a depth of 40m to 75m. In line 4, there is a distinct interception of the established physical parameters marking the boundary of the positive chargeability anomaly, that is, between 160m and 180m, from a depth of 80m to 90m. Line 5 is similar to line 4, with the mineralization occurring between 110m and 150m, from a depth of 50m to 75m. Finally, in line 6, the mineralization occurs between 50m and 145m, from the surface to a depth of 50m. In order to enhance the data analysis and for comparative purposes of the physical parameters, pseudo-3D visualization models were generated. For this, a lateral interpolation of the 2D inversion sections from all the geophysical acquisition lines was performed. Initially, maps for resistivity and chargeability at depths of 10m, 20m, 30m, 40m, 50m, 60m, 70m, and 80m were produced. For illustrative purposes, the maps for the 30m and 80m levels of resistivity and chargeability are presented, showing the outlines marking the orientation of the mineralizations, partly related to silicification processes indicated by anomalies of high chargeability + high resistivity, and partly associated with argillization/propylitization with zones interpolated between the high chargeability + low resistivity parameters (Fig. 8 ). The depth maps reveal zones that can be associated with mineralizations predominantly starting from a depth of 30m, although there are areas near the surface in lines 2 and, occasionally, in line 6. The copper deposit does not show any signs of surface mineralization and, therefore, represents a non-outcropping deposit with a continuous anomaly indicative of a vertical structural control with a steep dip angle. The chargeability maps highlight two distinct zones, both with positive anomalies consistent with the regional trend, where approximately 18% of the structures correspond to the NW quadrant, oriented N0–90°W [ 15 ]. The first positive anomaly occurs in the upper portion with a N60W direction and coincides with areas of high resistivity, thus indicating the mineralized and silicified portion of the deposit. The second positive chargeability anomaly occurs in the southern portion of the maps, with a N10W direction, where part intersects low resistivity anomalies, indicative of mineralized zones with argillization/propylitization, and part intersects another positive resistivity anomaly, consistent with silicification processes. As depth increases, both anomalies tend to converge, and their continuity at depth suggests the possibility of a connection trend between the abandoned mines in this non-outcropping region. Geochemically, it is possible to distinguish the hydrothermal alterations of argillization and propylitization based on mineral chemistry [ 15 ]. However, in geophysical parameters, it is not possible to differentiate between these alterations as both have a low resistivity signature. Therefore, in this study, both are considered to belong to the same resistivity range, which implies that the second type of copper mineralization occurrence includes sulfide mineralization associated with these hydrothermal alterations, without differentiation. In a hydrothermal system, the pattern of regional faults facilitates the movement of metal-enriched fluids, and combined with the presence of a porous system, the morphological configuration of the deposit and its modes of occurrence become complex [ 45 ]. The geological environment allowed for the combination of metasomatic processes that affect the mineral composition of the deposit, generating opposing effects on the physical parameter of resistivity [ 12 – 13 ]. The characterization of hydrothermal alterations is enabled through the analysis of mineral assemblages [ 46 – 47 ]. Silicification involves the precipitation of silica, which increases the resistance to the flow of electrical current through the rock [ 5 ]. This process commonly occurs in breccias or veins at greater depths and higher temperatures, resulting in highly resistive material, typical in the geological context of porous rocks, such as the lapilli tuffs found in the Seival Mines [ 15 – 18 ]. For the Seival Mines region, hydrothermal zones of propylitic and argillic alteration were characterized through geochemical studies [17 − 15]. Argillic alteration involves the percolation of ion-rich fluids that replace primary minerals with clay minerals, which have a higher water absorption capacity, thus resulting in a less resistive character. In the Seival Mines, this alteration is based on concentrations of smectite and quartz [ 17 – 34 ]. Fe and Cu sulfides occur in the intergranular space or are mixed with clay minerals [ 34 ]. This hydrothermal alteration is commonly found in the more superficial zones of the deposit, exposed to weathering [ 5 ]. Propylitic alteration frequently occurs under low to moderate temperature conditions, characterized by the formation of a series of secondary minerals through rock-fluid interaction and hydrothermal fluid percolation with Cu enrichment in the Seival Mines [ 15 ]. In this hydrothermal alteration, chlorite (chloritization) forms along with a mineral assemblage of hematite, titanite, calcite, barite, and quartz, associated with pyrite, chalcopyrite, and bornite [ 15 ]. Chlorite minerals and the association of chlorite/smectite with sulfides are characteristic of hydrothermal deposits [ 46 – 47 – 48 ]. These minerals have been linked to the percolation of fluids composed of meteoric water or brine [ 15 ]. Furthermore, chloritized zones emphasize areas enriched in Cu with hydrothermal fluid percolation in faults, dikes, and in lapilli tuffs that possess intrinsic porosity [ 15 ]. In propylitic alteration, the formation of albite (albitization) also occurs, involving the transformation of andesine and labradorite into albite with a hydrothermal magmatic fluid rich in Na, with a neutral to slightly acidic character. According to Lopes et al. (2018) [ 15 ], based on thermodynamic modeling, late-stage albitization with temperatures < 350ºC was associated with the formation of primary pyrite and chalcopyrite, while chloritization with temperatures between 120ºC and 312ºC involved the generation of bornite and chalcocite. Therefore, it was concluded that the petrographic association of albite and chlorite with sulfide mineralization and Cu suggests that the processes of albitization and chloritization, associated with structural control, can serve as a prospective guide in Cu-enriched systems. 5 Conclusions From the 2D inversion models and 3D visualization, it was possible to analyze the associations between these physical parameters and interpret two types of Cu ore occurrences: one related to silicification processes, characterized by high chargeability and high resistivity, and the other related to argillization/propylitization, with high chargeability combined with low resistivity, both structurally controlled with a general NW-SE orientation. The silicified zone has a predominant orientation of N60W and, secondarily, N10W. It was defined for areas with high resistivity and chargeability, and it possibly occurs hosted in breccias or veins. The argillic/propylitic alteration zone has an N10W orientation, and the physical parameters involve high chargeability and low resistivity. There is a clear structural control in the area, whether by faults, fractures, or fracture joints. The presence of joints facilitates the ascent of hydrothermal fluids and surface mineralization, where the Barita and João Dahne mines are located. The region between the mines, with no indications of mineralization, likely indicates an area where structural interception is absent, thus preventing the ascent of hydrothermal fluids. The structural analysis conducted at the Barita Mine reveals the orientation of fractures, mineralized fractures, and faults consistent with the regional trend of NE-SW direction, and, subordinately, NW-SE. Although the NW-SE fracture family is considered secondary in the regional geological context, it plays a significant role locally in mineral occurrences. This direction coincides with the relaxation direction of the regional folding event, suggesting the hypothesis of fracture filling followed by mineralization. The target identified in the geophysical data shows no evidence of surface mineralization and, therefore, represents a prospective target for restarting mineral exploration projects. This study enabled the recognition of a target suitable for future investigation using direct methods and highlights the versatility of geophysics in detailed phases of mineral exploration, significantly reducing uncertainties and financial resources. Declarations Competing interests The authors declare no competing interests. Author Contribution AA and CM performed the conception of the work, methodology and final review. Data acquisition, analysis, and interpretation were performed by all authors. Acknowledgement The authors thank the Geology Department of São Paulo State University – UNESP - for the use of the geophysical equipment, Pampa Federal University – UNIPAMPA, Caçapava do Sul campus, Universidad de la Republica - UdelaR, Montevideo, Uruguay and Marcelo Spode, for granting us access to the study area. Data Availability The authors declare that the data supporting the findings of this study are provided in the manuscript. References IBRAM (Instituto Brasileiro de Mineração), Boletim do Setor Mineral, 2020 (outubro). Available online: http://antigo.mme.gov.br/web/guest/secretarias/geologia-mineracao-e-transformacao-mineral/publicacoes/boletim-do-setor-mineral/ (accessed on 23/09/2024) Moon, C.J.; Whateley, M.K.; Evans, A.M. Introduction to Mineral Exploration. Blackwell Publishing, Hoboken, 2006. DNPM - Departamento Nacional De Produção Mineral. Anuário Mineral Brasileiro – Brasília Ano – XXXVIII. Available online: https://www.gov.br/anm/pt-br . 2005. 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Reassessment of copper mineral occurrence through electrical tomography and pseudo 3D modeling in Camaquã Sedimentary Basin, Southern Brazil. Pure Appl Geophys 2018 176(2):737–750. https://doi.org/10.1007/s00024-018-2019-2 . Côrtes A. R. P.; Moreira C. A.; Paes R. A. S.; Veloso D. I. K. Geophysical and metalogenetic modelling of the copper occurrence in Camaquã Sedimentary Basin, Brazilian Southern. Pure Appl Geophys 2019 176: 4955–4968. https://doi.org/10.1007/s00024-019-02190-8 Ali, M.; Sun, S.; Qian, W.; Bohari, A. D.; Dusabemariya, C.; Faruwa, A.; Zhang, Y. Borehole Resistivity and Induced Polarization Tomography at the Canadian Shield for Mineral Exploration in North-Western Sudbury. E3S Web of Conferences 2020, 168, 00002. https://doi.org/10.1051/e3sconf/202016800002 . Lopes, R. W.; Mexias, A. S.; Philipp, R. P.; Bongiolo, E. M.; Renac, C.; Bicca, M. M.; Fontana, E. AuCuAg Mineralization Controlled by Brittle Structures in Lavras Do Sul Mining District and Seival Mine Deposits, Camaquã Basin, Southern Brazil. Journal of South American Earth Sciences 2018, 88, 197–215. https://doi.org/10.1016/j.jsames.2018.08.017 . Reischl, J. L. Mineralizações cupríferas associadas a vulcânicas da Mina Seival –RS. In Congresso Brasileiro De Geologia, 30., 1978. Recife. Anais[… Recife: SBG, 1978.v. 4, p. 1568–1582. Lopes, R.W., Fontana, E., Mexias, A.S., Gomes, M.E.B., Nardi, L.V.S., Renac, C. Caracterização petrográfica e geoquímica da sequência magmática da Mina do Seival, Formação Hilário (Bacia do Camaquã – Neoproterozoico), Rio Grande do Sul, Brasil. Pesquisas em Geociências (Portuguese – Brazil) 2014, 41, 51–64. Almeida, F. F. M. de. O pré-cambriano do Brasil/Fernando Flávio Marques de Almeida, Yociteru Hasui coordenadores, 1984. Hartnady, C.; Joubert, P.; Stowe, C. Proterozoic Crustal Evolution in Southwestern Africa. Episodes Journal of International Geoscience 1985, 8 (4), 236–244. https://doi.org/10.18814/epiiugs/1985/v8i4/003 . Google Earth, 2024. Available online: http://earth.google.com/ (accessed on 23/09/2024) Heilbron, M.; Machado, N. Timing of Terrane Accretion in the Neoproterozoic–Eopaleozoic Ribeira Orogen (Se Brazil). Precambrian Research 2003, 125 (1), 87–112. https://doi.org/10.1016/S0301-9268(03)00082-2 . Soliani Junior, E.; Cordani, U. G. Dados geocronológicos do escudo sul-riograndense e suas implicações de ordem geotectônica. 1986. Chemale Junior, F. Evolução Geológica Do Escudo Sul-Rio-Grandense. Geologia e Estratigrafia do Rio Grande do Sul 2000, 3–44. Teixeira, A.L.; Gaucher, C.; Paim, P.S.G.; Fonseca, M.M.; Parente, C.V.P.; Silva Filho, W.F.S.; Almeida, A.R. Bacias do estágio de transição da plataforma sul-americana. In Neto, V.M.; Bartorelli, A.; Carneiro, C.D.; Brito-Neves, B.B. (Eds.). Geologia do Continente Sul-Americano: Evolução da Obra de Fernando Flávio Marques de Almeida. São Paulo, Editora Beca, 2004, p. 487–536. Saalmann, K.; Gerdes, A.; Lahaye, Y.; Hartmann, L. A.; Remus, M. V. D.; Läufer, A. Multiple Accretion at the Eastern Margin of the Rio de La Plata Craton: The Prolonged Brasiliano Orogeny in Southernmost Brazil. Int J Earth Sci (Geol Rundsch) 2011, 100 (2), 355–378. https://doi.org/10.1007/s00531-010-0564-8 . Borba, A. W.; Mizusaki, A. M. P.; Santos, J. O. S.; McNaughton, N. J.; Onoe, A. T.; Hartmann, L. A. U–Pb Zircon and 40Ar–39Ar K-Feldspar Dating of Syn-Sedimentary Volcanism of the Neoproterozoic Maricá Formation: Constraining the Age of Foreland Basin Inception and Inversion in the Camaquã Basin of Southern Brazil. Basin Research 2008, 20 (3), 359–375. https://doi.org/10.1111/j.1365-2117.2007.00349.x . Lima, E.; Sommer, C.; Nardi, L. Ovulcanismo Neoproterozóico-Ordoviciano No Escudo Sul-Rio-Grandense: Os Ciclos Vulcânicos Da Bacia Do Camaquã. Comunicação e Identidade 2007, 1, 79–95. Janikian, L.; De Almeida, R. P.; Da Trindade, R. I. F.; Fragoso-Cesar, A. R. S.; D′Agrella-Filho, M. S.; Dantas, E. L.; Tohver, E. The Continental Record of Ediacaran Volcano-Sedimentary Successions in Southern Brazil and Their Global Implications. Terra Nova 2008, 20 (4), 259–266. https://doi.org/10.1111/j.1365-3121.2008.00814.x . Paim, P. S. G.; Chemale Jr, F.; Lopes, R. da C. A Bacia Do Camaquã. Geologia do Rio Grande do Sul 2000, 231–274. Bicca, M.M., Chemale Jr., F., Jelinek, A.R., Oliveira, C.H.E., Guadagnin, F., Armstrong, R. Tectonic evolution and provenance of the Santa Bárbara Group, Camaquã Mines region, Rio Grande do Sul, Brazil. Journal of South American Earth Sciences 2013, 48, 173–192. de Oliveira, C. H. E.; Chemale, F.; Jelinek, A. R.; Bicca, M. M.; Philipp, R. P. U–Pb and Lu–Hf Isotopes Applied to the Evolution of the Late to Post-Orogenic Transtensional Basins of the Dom Feliciano Belt, Brazil. Precambrian Research 2014, 246, 240–255. https://doi.org/10.1016/j.precamres.2014.03.008 . Janikian, L.; Almeida, R.; FRAGOSO-CESAR, A.; CORRÊA, C.; PELOSI, A. Evolução Paleoambiental e Seqüências Deposicionais Do Grupo Bom Jardim e Formação Acampamento Velho (Supergrupo Camaquã) Na Porção Norte Da Sub-Bacia Camaquã Ocidental. Rev Bras Geoc 2005, 35, 245–256. https://doi.org/10.25249/0375-7536.2005352245256 . Mexias, A. S.; Berger, G.; Gomes, M. E. B.; Formoso, M. L. L.; Dani, N.; Frantz, J. C.; Bongiolo, E. M. Geochemical modeling of gold precipitation conditions in the Bloco do Butiá Mine, Lavras do Sul/Brazil. An. Acad. Bras. Ciênc. 2005, 77, 717–728. https://doi.org/10.1590/S0001-37652005000400010 . Fontana, E.; Mexias, A.; Christophe, R.; Nardi, L.; Lopes, R.; Barats, A.; Boscato Gomes, M. Hydrothermal Alteration of Volcanic Rocks in Seival Mine Cu–Mineralization – Camaquã Basin – Brazil (Part I): Chloritization Process and Geochemical Dispersion in Alteration Halos. Journal of Geochemical Exploration 2017. Dahlin, T. The Development of DC Resistivity Imaging Techniques. Computers & Geosciences 2001, 27 (9), 1019–1029. https://doi.org/10.1016/S0098-3004(00)00160-6 . Kearey, P.; Brooks, M.; Hill, I. An introduction to geophysical Exploration 2002. Tradução de Maria Cristina Moreira Coelho, 1st edn, São Paulo: Oficina de Textos, p 429 Milson, J. Field geophysics, 2003. Wiley, England, p 232 Telford, W. M.; Geldart, L. P.; Sheriff, R. E. Applied Geophysics. Higher Education from Cambridge University Press, 1990. https://doi.org/10.1017/CBO9781139167932 . Sumner, J.S. Principles of Induced Polarization for Geophysical Exploration; Elsevier, Amsterdam, 227, 1976. Reynolds, J. An Introduction to Applied and Environmental Geophysics, 1997. Milsom, J.; Eriksen, A. Field Geophysics, 2011 https://johnmilsom.online/project/field-geophysics/ (accessed 2024-12-12). ABEM. Terrameter LS - Instruction Manual. Sundyberg: ABEM Instruments, 2012. Loke, M.; Barker, R. D. Rapid Least-Squares Inversion of Apparent Resistivity Pseudosections Using a Quasi-Newton Method. Geophysical Prospecting 1996, 44, 131–152. https://doi.org/10.1111/j.1365-2478.1996.tb00142.x . Toniolo, J. A.; Gil, C. A. A.; Sander, A. Metalogenia Das Bacias Neoproterozóico-Eopaleozóicas Do Sul Do Brasil: Bacia Do Camaquã. 2007. Pirajno, F. Hydrothermal Processes and Mineral Systems; Springer Netherlands: Dordrecht, 2009. https://doi.org/10.1007/978-1-4020-8613-7 . Seedorff, E.; Dilles, J. H.; Proffett, J. M., Jr.; Einaudi, M. T.; Zurcher, L.; Stavast, W. J. A.; Johnson, D. A.; Barton, M. D. Porphyry Deposits: Characteristics and Origin of Hypogene Features. In One Hundredth Anniversary Volume; Hedenquist, J. W., Thompson, J. F. H., Goldfarb, R. J., Richards, J. P., Eds.; Society of Economic Geologists, 2005; p 0. https://doi.org/10.5382/AV100.10 . Sillitoe, R. H. Porphyry Copper Systems*. Economic Geology 2010, 105 (1), 3–41. https://doi.org/10.2113/gsecongeo.105.1.3 . Barnes, H. L. Geochemistry of Hydrothermal Ore Deposits, 2nd edition.; John Wiley & Sons Inc: New York, 1979. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted 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. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-5716993","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":401037033,"identity":"76423e7f-92e0-4a39-ae0e-d7e79aa0a74c","order_by":0,"name":"Ana Flávia Araujo","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA3ElEQVRIie3NsQrCMBCA4SuBdql0bQjUV6hLShF8lkJBF2dxcIhLpuouvodzIZCpD6Ao6NTJQRBEoYiV2rWpm2D+4cIdfARAp/vFUFo9YLHq4CuJGX2InX5JANyoJXE4GNfpTFgOPtPTpThAQNJm4kpAOJMC4fU46K14DuEyaiZwZICZKZC/H1PSYQL8TCG65S8P9izJLqOkKFoQX4KJ57wkW5sSMFuQnjR4OF+OEE6GE7zguR0mCuJJJHbs1o8dS2zce3HwAltBAAz2nvFnS9WgblCT1kKn0+n+pxdXRj/ZxpnrJgAAAABJRU5ErkJggg==","orcid":"","institution":"São Paulo State University (Universidade Estadual Paulista), Rio Claro (SP)","correspondingAuthor":true,"prefix":"","firstName":"Ana","middleName":"Flávia","lastName":"Araujo","suffix":""},{"id":401037034,"identity":"2ea7b414-0ad6-4a56-8255-261cb881b147","order_by":1,"name":"César Augusto Moreira","email":"","orcid":"","institution":"São Paulo State University (Universidade Estadual Paulista), Rio Claro (SP)","correspondingAuthor":false,"prefix":"","firstName":"César","middleName":"Augusto","lastName":"Moreira","suffix":""},{"id":401037035,"identity":"fa43dc30-a8ca-4c9e-bc7a-5904d376a0e1","order_by":2,"name":"Luiza Lima Alves","email":"","orcid":"","institution":"São Paulo State University (Universidade Estadual Paulista), Rio Claro (SP)","correspondingAuthor":false,"prefix":"","firstName":"Luiza","middleName":"Lima","lastName":"Alves","suffix":""},{"id":401037036,"identity":"285c516b-5be9-4b28-a370-999bb0a48dec","order_by":3,"name":"Lenon Melo Ilha","email":"","orcid":"","institution":"São Paulo State University (Universidade Estadual Paulista), Rio Claro (SP)","correspondingAuthor":false,"prefix":"","firstName":"Lenon","middleName":"Melo","lastName":"Ilha","suffix":""},{"id":401037037,"identity":"dbe877cb-b968-48b3-982e-7b54c547261e","order_by":4,"name":"Sissa Kumaira","email":"","orcid":"","institution":"Pampa Federal University – UNIPAMPA, Caçapava do Sul (RS)","correspondingAuthor":false,"prefix":"","firstName":"Sissa","middleName":"","lastName":"Kumaira","suffix":""},{"id":401037038,"identity":"d85f6813-c6d0-4828-a497-2161e1ee3083","order_by":5,"name":"Henri Masquelin","email":"","orcid":"","institution":"Universidad de La Republica","correspondingAuthor":false,"prefix":"","firstName":"Henri","middleName":"","lastName":"Masquelin","suffix":""},{"id":401037039,"identity":"04efe813-7828-4a4c-8d11-d91caf466662","order_by":6,"name":"Beatriz Guzzo Duz","email":"","orcid":"","institution":"São Paulo State University (Universidade Estadual Paulista), Rio Claro (SP)","correspondingAuthor":false,"prefix":"","firstName":"Beatriz","middleName":"Guzzo","lastName":"Duz","suffix":""}],"badges":[],"createdAt":"2024-12-26 15:23:08","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-5716993/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-5716993/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":73628880,"identity":"699da147-46de-4090-b05e-6ab4ba0bc926","added_by":"auto","created_at":"2025-01-13 06:02:43","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":739921,"visible":true,"origin":"","legend":"\u003cp\u003eStudy area location and access. A. Geological map of the Seival Mines region showing the abandoned mines and geological structures in the area (Modified from Lopes et al., 2014) [17]; B. Access routes and municipalities near the study area (Extracted from Google Earth, 2024) [20].\u003c/p\u003e","description":"","filename":"Fig1.tif.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5716993/v1/c5990ea2d10f536e5f1d422c.jpg"},{"id":73628873,"identity":"6227e48b-15c4-4ed7-afb5-36c743cd591d","added_by":"auto","created_at":"2025-01-13 06:02:42","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":1590846,"visible":true,"origin":"","legend":"\u003cp\u003eEvidence of copper mineralization in rocks from the Barita Mine. Malachite in greenish coloration and a localized occurrence of azurite highlighted in red.\u003c/p\u003e","description":"","filename":"Fig2.tif.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5716993/v1/a257f3d6153832d02c0d38e1.jpg"},{"id":73628869,"identity":"dd7fc0f5-43ad-4388-998e-2e3f30382c59","added_by":"auto","created_at":"2025-01-13 06:02:42","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":950576,"visible":true,"origin":"","legend":"\u003cp\u003eGeophysical line position\u003c/p\u003e","description":"","filename":"Fig3.tif.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5716993/v1/60494a12e16535dcf76b36f2.jpg"},{"id":73630167,"identity":"076a7eea-2c77-46a5-9d83-f947919f4f0e","added_by":"auto","created_at":"2025-01-13 06:10:43","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":1323423,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eA.\u003c/strong\u003e Map of lineaments marked at a scale of 1:10,000 on an ASTER digital elevation model of the South Rio Grande Shield (Modified from Toniolo et al., 2007) [44]. \u003cstrong\u003eB.\u003c/strong\u003e Highlight of the regional structure near the study area, marked in red. Shear zones: ISZ = Ibaré; CSSZ = Caçapava do Sul; DCSZ = Canguçu Ridge. Faults: CPF = Cabritos–Perau; SF = Segredo; PJF = Palma–Jacques.\u003c/p\u003e","description":"","filename":"Fig4.tif.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5716993/v1/cab3a9f6410df9d89b3b89c5.jpg"},{"id":73630168,"identity":"cf849b3f-13ab-4aa2-ba55-414f53f0cc81","added_by":"auto","created_at":"2025-01-13 06:10:43","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":370451,"visible":true,"origin":"","legend":"\u003cp\u003eStereograms of measurements taken at the Barita Mine. \u003cstrong\u003eA.\u003c/strong\u003e Fractures; \u003cstrong\u003eB.\u003c/strong\u003eMineralized fractures; \u003cstrong\u003eC.\u003c/strong\u003e Faults.\u003c/p\u003e","description":"","filename":"Fig5.tif.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5716993/v1/c8596e629c2ad9ef960fbae0.jpg"},{"id":73628881,"identity":"e7512566-56b1-457a-88be-389907bd30f9","added_by":"auto","created_at":"2025-01-13 06:02:43","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":624294,"visible":true,"origin":"","legend":"\u003cp\u003eResistivity inversion models, highlighting areas of high resistivity.\u003c/p\u003e","description":"","filename":"Fig6.tif.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5716993/v1/8802d8744f9c8a7aac22e0f3.jpg"},{"id":73630175,"identity":"9edb53cb-136d-42e8-ac8b-b7afadcd7875","added_by":"auto","created_at":"2025-01-13 06:10:43","extension":"jpg","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":511235,"visible":true,"origin":"","legend":"\u003cp\u003eChargeability inversion models, highlighting areas of high chargeability.\u003c/p\u003e","description":"","filename":"Fig7.tif.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5716993/v1/3bb4c6fb468b8b161c33f88a.jpg"},{"id":73630180,"identity":"6bb50641-d853-4feb-943c-8b9d06eeb63c","added_by":"auto","created_at":"2025-01-13 06:10:44","extension":"jpg","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":1357643,"visible":true,"origin":"","legend":"\u003cp\u003eMaps for the depths of 30m and 80m showing the orientation of the occurring mineralizations. \u003cstrong\u003eA.\u003c/strong\u003e 30m resistivity map with the geophysical lines; \u003cstrong\u003eB.\u003c/strong\u003e 30m chargeability map; \u003cstrong\u003eC.\u003c/strong\u003e80m resistivity map; \u003cstrong\u003eD.\u003c/strong\u003e 80m chargeability map.\u003c/p\u003e","description":"","filename":"Fig8.tif.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5716993/v1/eb73097e6afd5e72afd69df3.jpg"},{"id":76728638,"identity":"3abe3df0-6a2d-4d89-ab1c-e876ac3bc32b","added_by":"auto","created_at":"2025-02-20 06:02:53","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":8013508,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5716993/v1/f6dcebc8-59ed-4c9f-b738-3ba68639facd.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Structural and Geophysical Modeling in an area with non-outcropping Copper Sulphide Deposits, Minas Do Seival Region, Sul-Riograndense Shield, Southern Brazil","fulltext":[{"header":"1 Introduction","content":"\u003cp\u003eThe mining sector contributes approximately 4% to Brazil's GDP (Gross Domestic Product) and assumes a pivotal role in sustaining a favorable trade balance, which amounts to US\u003cspan\u003e$\u003c/span\u003e32.5\u0026nbsp;billion, representing 63.8% of the country's balance [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. It is indispensable in underpinning numerous production chains that shape the modern lifestyle of society and are of paramount importance in fulfilling its fundamental needs.\u003c/p\u003e \u003cp\u003eThe discovery of economically viable mineral deposits has become increasingly rare as consumer societies expand, driven by the unchecked urbanization of emerging countries and global technological advancements, which continue to place greater demand on commodities [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Mineral exploration represents a crucial phase aimed at identifying and thoroughly assessing deposits that meet the requisite economic, technical, and environmental criteria, in order to progress to the development and production stages of mining. Like iron and gold, copper stands as one of the most significant commodities in Brazil's trade balance, extensively used in the production of electrically conductive materials, including wires and cables, electric vehicle motors, and metal alloys [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eTo identify and incorporate new reserves, both direct investigative methods\u0026mdash;such as drilling and chemical analysis\u0026mdash;and indirect approaches, such as remote sensing and geophysical techniques, are employed. Mineral exploration carries a high inherent risk due to the activity's failure rates. As a result, direct methods are indispensable for confirming mineral occurrences, as they provide a realistic portrayal and reliable data through rigorous control and quality assurance measures. However, these methods are resource- and time-intensive, as a significant portion of boreholes and drill sample are often lost due to the lack of prior knowledge about the structure and morphology of mineralized targets, leading to drilling through sterile rocks and, consequently, wasting financial resources [\u003cspan additionalcitationids=\"CR3\" citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eAlternatively, the application of geophysical methods is recommended due to their lower cost, ability to cover extensive areas, and effectiveness in delineating targets of interest for subsequent drilling and sampling, irrespective of rock exposures [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. One strategy for identifying new targets involves exploring known mineralized regions, employing geological and structural controls to direct the search, and conducting surveys in areas lacking visible signs of mineralization [\u003cspan additionalcitationids=\"CR3\" citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Geoelectrical methods are widely employed in mineral exploration studies [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e], with particular emphasis on sulfide deposits [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eTherefore, the objective of this study is to evaluate the potential for discovering non-outcropping sulfide copper deposits between two abandoned mines in southern Brazil through the integration of geological mapping, structural analysis, and geophysical surveys. Electrical tomography data obtained from DC Resistivity and Induced Polarization methods, guided by geological controls, identified a promising target at a depth of 30 meters in an area devoid of surface mineralization. Its continuity at depth further suggests a possible connection between the abandoned mines, influenced by the regional structural framework, and highlights a target with significant potential for the resumption of mineral exploration projects in the region.\u003c/p\u003e"},{"header":"2 Study Area and Geological Settings","content":"\u003cp\u003eThe Seival Mines are located 324 km from Porto Alegre (RS) via the BR 290 highway, between the municipal boundaries of Ca\u0026ccedil;apava do Sul and Lavras do Sul. The area hosts six copper-bearing mines: (1) Alcides; (2) Vila do Torr\u0026atilde;o; (3) Cruzeta; (4) Meio; (5) Morcego; (6) Jo\u0026atilde;o Dahne; and (7) Barita. The study area is specifically situated between the Barita and Jo\u0026atilde;o Dahne mines (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eHistorically, this region has been exploited for copper and gold mining for several years. Both private and state-owned companies documented occurrences from 1901 to 1931, when the E.F. and S\u0026atilde;o Jer\u0026ocirc;nimo Mines Company began shallow excavations. In the following years, various companies mined the area of the six mines, and between 1955 and 1962, more than 1,000 tons of ore were extracted per month, with an average grade of 1.6% total Cu [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. The Seival Mines\u0026rsquo; reserve was estimated at approximately 0.20Mt of ore, with an average of 1.40% Cu and 10\u0026ndash;70 ppm of Ag [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eAt a regional scale, the area is geologically located in the southern sector of the Mantiqueira Province, which originated at the end of the Neoproterozoic and the beginning of the Paleozoic [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. It corresponds to a complex geotectonic unit situated between the S\u0026atilde;o Francisco and Rio de La Plata cratons, following the closure of the Adamastor Ocean [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. The province is oriented NNE-SSW and extends for approximately 3,000km along the Atlantic coast, from Montevideo (Uruguay) to the south of Bahia [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe province is compartmentalized by the Dom Feliciano (southern Brazil to Uruguay), Ara\u0026ccedil;ua\u0026iacute; (Esp\u0026iacute;rito Santo, eastern Minas Gerais, and southern Bahia), and Ribeira (states of Rio de Janeiro, Minas Gerais, S\u0026atilde;o Paulo, and Paran\u0026aacute;) belts [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. In the Dom Feliciano Belt, rocks formed during the Transamazonian (2.26-2.00Ga) and Brasiliano (900-535Ma) orogenic cycles outcrop [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. However, the latter orogenic cycle was responsible for the accretion, deformation, and reworking of pre-Cambrian crustal blocks, which define the current configuration of the region.\u003c/p\u003e \u003cp\u003eOn a smaller scale in the geological context, the state of Rio Grande do Sul is located in the Sul-Riograndense Shield (ESRG). This includes associations of metamorphic, igneous, and sedimentary rocks, distributed in a complex tectono-stratigraphic arrangement, compartmentalized into the tectonic units of the Vila Nova Belt (S\u0026atilde;o Gabriel Terrane), Tijucas Belt (Tijucas Terrane), Dom Feliciano Belt (Pelotas Batholith), and Granulitic Complex [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eAssociated with the South Rio Grande Shield (ESRG) at a regional scale, the Camaqu\u0026atilde; Basin occurs, resting on its crystalline terrains. It trends N30E, with a length of approximately 100km and a width of up to 100km [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. Its basement is composed of gneisses and metavolcanosedimentary rocks deformed with a NW-SE orientation [\u003cspan additionalcitationids=\"CR24\" citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. The Camaqu\u0026atilde; Basin is compartmentalized into four groups, which are composed of several formations, divided into four events: i) Maric\u0026aacute; Group, in a retroarc or foreland basin context [\u003cspan additionalcitationids=\"CR24 CR25\" citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]; ii) Bom Jardim Group, deposited in a transpressional strike-slip basin [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]; iii) Santa B\u0026aacute;rbara Group, in a transtensional strike-slip context [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]; iv) Guaritas Group, formed in a transtensional subsidence event [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIn the Seival Mines region, rocks from the Hil\u0026aacute;rio Formation, part of the Bom Jardim Group, are present. This unit consists of intermediate volcanic rocks with calc-alkaline magmatism and shoshonitic affinity, such as andesites, dacites, and latites, as well as volcaniclastic rocks like tuffs, lapilli tuffs, and breccia tuffs [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]. The structural context of the Seival Mines indicates that the rocks are highly fractured, characteristic of ruptile tectonics, with subvertical fractures predominantly trending NE-SW and secondarily NW-SE. Some of these fractures result from reactivations of the NE-SW shear zones due to tectonic events that generated stress fields affecting the Sul-Riograndense Shield, while the NW-SE faults are correlatable with the Ibar\u0026eacute; Lineament [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. As a result, a strong structural control related to copper mineralizations is evident in the region, and ore zones are commonly associated with quartz veins rich in sulfides [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]. The sulfides occurring in the Seival Mines region include chalcopyrite, bornite, chalcocite, and covellite [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e], which are part of the Cu-bearing mineralized veins that fill fractures and faults [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eSince the 2000s, the Seival Mines have been targeted by multinational companies; however, due to insufficient investment, primarily based on a few drill holes, the research efforts have been incipient and unproductive [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e].\u003c/p\u003e"},{"header":"3 Materials and Methods","content":"\u003cp\u003eThe study followed a sequence of investigative steps. Initially, geological reconnaissance was conducted at rock outcrops in the Barita Mine, located at the northeastern boundary of the study area, where evidence of mineralization, including malachite and azurite impregnations, was identified (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Subsequently, structural measurements were taken at fractures and faults to define the main controls of the deposit, based on 200 measurements, which were processed in StereoNet software for subsequent graphical analysis.\u003c/p\u003e\u003cp\u003eBased on clear indicators of mineralization identified in the Barita Mine, geological reconnaissance was conducted in the study area, corresponding to the interval between the Barita and Jo\u0026atilde;o Dahne mines, where no evidence of copper mineralization was found (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). The Jo\u0026atilde;o Dahne mine was not visited due to years of abandonment and dense vegetation cover.\u003c/p\u003e \u003cp\u003eThe geophysical methods selected for this study were DC Resistivity and Induced Polarization. DC Resistivity determines the apparent resistivity of subsurface materials based on the injection of electrical current into the ground and the measurement of the resulting potential difference. The penetration depth of the method is proportional to the spacing between electrodes, and variations in electrode spacing provide information about stratification [\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e]. The method is grounded in Ohm\u0026rsquo;s Law, which enables the calculation of apparent resistivity (ρa) in a heterogeneous geological environment, incorporating a geometric factor (K) between two pairs of electrodes used for data acquisition, namely voltage (ΔV) (electrodes A and B) and electric current intensity (I) (electrodes C and D) (Eq.\u0026nbsp;1). The geometric factor (K) is calculated using Eq.\u0026nbsp;2, which accounts for the distances between electrodes AC, CB, AD, and DB (Eq.\u0026nbsp;2). These calculations facilitate the identification of mineralization and the recognition of subsurface geological structures [\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003cimg 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NSoZgu/fxqOnrwQlL+KURDy8fw+3b9/BnTvaJSDgFp6GRkCm/LfYWw7Ie6BSqfiF8X7cPH+EbNl3nhT1zGnU2i2f3jxOmtT0IhdDYvn10oJGo+b/bls4hfTs/xWJzFDw66WFN8cnenqLeHlUJ7tvhPHrpQm1cI3Dbxwl3p7exD9Swq8XlfiIZ2Tzhn9ISES8oLw/8kwx+XHEYHIzPEVQyjZv/EnXwiI6PRMfGoCjl0PQt08nlBO0wjAyFrZUcZFIKWxAMTLSfm3UmtLXNkfJPj5CH+T8v0sbxsI1Vn3gOaxUvQ48q9jA58JliKQf9hrGJqZo2bEznCuYC4rhwoxOr8iwft02eHf5DM7WZoLGYJQMbdq3QezTQPjdfCAo74eJmTn6j/oK1R3LC4rhwoxOj4T6n8NTsR26tqgjKAxGyVHOxhWdGrrA5+w5JGV8WM+8haUlyhkbfr8rMzq9QXBg/3F4t2gChwpWgsZglCw9B/dH4rN7uB8SISgMXejF6FRKBTIyxFCps9tHaJd4SlIyJFKFoBg2aS/uwP9ZPBrWrwsz9jhh6IsKHmheyxoHz1xHKUxnfC+ioqI438gQ1rSoVCqkp6dDqVQKiha6HhERgbS0NEEpGL3cgo9u+WLF2k2IF2uTIOm4uuM7/sKiFRsRJyr55E21Qoq7/pexbcsGrF77N3yv3IZE/r9NKbh5MwBZqICa7i6C8v4Q7j+FhpTazHWaEkGPr7Q2+NM8MYVCUaoz/wk9Ru74inOMbT5tgZvnTnP3W+lLLC8qwcHBmDVrFsLDw/l1et327NmDmTNn4ocffsCUKVOwefNmXqfQ79yGDRv4pSjfPz0YnRL3/S/hxv1nMLM05ZVTu//CkvUHUbdRM9Rwsee1kuTCkZ1Yvupv+Afcx61rF/DT9ElYvnEfMnM/BIrF+93MagQ/fgQbZ3c4Onz45y1vUxGNG3nBrnzp7BWrVKUaGtatCXOT0hmympSvgKYtWsDJxlJQig/9HhTDk/JgaeOIJt4NUcG8qH3yeann7Q1NUgjuBMcKStlCLpdj9erVsLW1hZeXF6+tXLkSEyZMQGxsLLy5z0e3mTZtGn755Re+3MzMDN26dcPhw4cREBDAawXCXbgi8yYnpSDUGQlk1tcDyNezl/Prl/evJ82atyY7Tl8n3FNLLwTdu0lu33tEUkUZJCMtkaxZMIXUqtuKXHnwUtii+Oxet4b4XLlXpM+gEseTr/t1JF/9dw3JLMaHlmeJSdTrSJIlL525ixmpSSQmLoEo1fq6ssVDJZeSyNevSIZULijFRUU2/PZf4nPjhbBefBRZEu4YI4lUqc39+yDEkaRlvZpk1l9HBKFsceXKFVKnTh3i5+fHr3PVV8KZHhk7diyRyWS8plaryeTJk4mNjQ158SL7/A8dOpSMHj2aZGVl5cqbe3cp8UexiKszv4xOxieedRB48RDmr96H8TMXYnTvtnpLCWvQtBVaNPWCvZ0NbGyd0L5LN1gZZSI2JkHYIhu1WsWHvwqujs//5Zai5IM9DXyAV9EJRRoFkJGSgOjIdFR1cUX5YnxoM0trVKnqDkuzD3/a6xMbe0e4VnaGSSnttStnZgH3qtVgY1FyqT0PA64hIiZdWCs+ppZW3DG6w6I4UbG1IzzsLREWFCYIZQfOyLBr1y7Ur18fHTt25LXMzEz07dsXXbt2hbm5tjZjbGyMhg0b8v++f/8+/5cyZMgQ+Pj44NWr/EeJUErc6NJT45EoykTi81uYNm8VRvw4F+MHdxFKdcNFLrh38yp8L1zAxYsXdSwXcOGiP5KLODg7IzURRuZWcHDKrjamJ8Vh/z9rMOTzPujVpy/69PoMvXv3xuBhI3H2dqiwVf6YmJqiXLmiGU56qgiJGQo4ONoJCsMwMIKJiSlMypW2qrolKrnZITE2utQNxyuMpKQknD59Go0bNxYUoFKlSti6dSu++OILQdFC2+9MTEzQtm1bQQF69OjBb79lyxZB0U2JX7GU+EgEhTzHjWvXERYjgpVNhUIjOXFaAnZvXo3Fi5dg6dKleZYlS37D0t/X85FiYSjEyTh57BSqerVB0waevKaUiXH31i2EPH+NTFU5dOnTDyYKGRo2b4sB/QeiUS13frucaDRqfoykWk2jPQI10WjXuW8S7UGm/9bkM0AxI0uCVBMNrG3zbxviom5uf02JLPS1dEF17WcoYOH2zw9d7/W+S37Hxp9TXceTY6H758e771PcJb/jpGVvjoe2P785pzmPP7+OBLrtu+/zoUv+51GLlb0dksTx3BGWLRITE/laVYsWLQSFjmwxguk7gcXRo0f5zogRI0bAxSW7g8/a2hr29vaFttMZcSew4DOYA+0F5qoE+UU2RIUDa+Zj8qqz2LF3G+4dWImLMXY4tP0POFrpv0GdqBXYuXoR/j52B0tXr0enJjV4XSmTQG1khpvnDsEnMBkLZgzClDmbMXP2RNSo4sRvkxsNTu7ZhFvBr/nhRNw5x6VTZ2FbtQ686tfiTpoaKpUJWnf4DP17txb2yeae32EMmPATlv29G8O6NBfU3FwQoleVSsVf2A+F7t+8eXMMHjz4bZj/hszYMGzadQjxIjHKcaH/u9ALX7t5d4wdoK0y5EQqlWLhwoV5uvXfB3qDenp6YuzYsXzjcU6UkkRsXLcZMSIJjHRUfTXECLW9WmHs8D55HpRisRjr169HfHw8X6UpDvQYraysMGjQIDRq1EhQtSilYpw9tg/XH7yAmWk57jqp4Xt4P5zqd0GTT1z4fRVyMwwZMwYtvTyEvbKhkcqVK1d4kyrONabXgBoBPUYLCwtBzc3CH4di0y0JQgLOwObD3+qjs2zZMixfvhz79u1Dp06dBDUbeu5oh8OkSZNQp04dHDp0CM7OzkKplpEjR2Lv3r38vZAfJWp0akUmfv5hHB5Ka+LMjsUI9z+OPl/9hN+2HsSg9vWFrfKSJRbh2uULiE+T6c7SptPJGFVAlx6d4OacX3VQg0Mb/sDv/5zFtMXLMLx7S0HXkpkah1/nzESVbt+gqclz+MZaY/LYQbCz0HWjaOBzeBfuhETyRmfGGd25I8dhV6M+mnh58kanVpugeesu6NUt+0n0hruXD2HAdz/hz/V7MKyzbqOjF5Z2nxfX6OjTsHv37vwXoXz53EN5suJfYNfBE9x5leRrdDWbdMKIXm20Qg4kEglGjRrFt6F86PHR70vTpk0xf/78PDeoSpKMHdt2IjYtU+frU6PzqN8cowZ2F5RsUlNTMXv2bL5dpqjNCflBj5H29tHz1759e0HVQh+QF88cRUBQBExNqNFpcGrvdrh4f4bmDVy1RqcwRf9hwznjqybslc0///zD36TFNTra49izZ098//33vCnrYuHkodhwIwMhd87BtsTrafqBnvuJEyfi5MmT2L9/P9q1ayeUaKHlO3fuxNSpU3mj37ZtG1xdXYXSbGgKCjVLei/kR4kaXVZ6AsYPHwLnTt9j5YyhnCLFdwN7IaZiBxzd9AtM8rnWosQobP5rJUJjxTrbP+gkisTYCT9Mn4SGtfJ+UBA5dqz5HZuPXMfEn37FsB6fCgXZBF48iB8X/oON+/fgwPLf4Nl1AEZ81g4SmQrWFibCVvmzgLsgNbsMwcgBHQqtigdeO4F+42fhtzXbMVrHsVCogdCluNDLR6MlanLFuZnehb4uTd58j6+HTmibCr05S/LYqMFQI6Z/SwJ6bJaWlnmiTl1M/aIbGn35F0b3LXxYH42KqUkVF3oNaLROjzG/8/jz//XH7iCCp9x3z6LkTrVeodeP5sjRaik1upwPGhoArFmzho/4Bg4ciAULFsDR0VEozQ3NsaPpKQXWPriTWGS4N+eX/EiOCibtvOuRf3xDBIWQhz7bSbXqDYjf0/ynk1Fzr5mWmkKSkpNJcr5LKpErdb23jGxdPpc4OVQi385ZQs75XCDnz58lp06dJ+Gv4/gtAq+dJZ+1b0lGz/yL2zyOfN6rF1my+QAJuHWbJEm03deFMe/b8WTL3nOkKEkAYbcvkrq16pO/j2q7yxmGgopMHNiJbD78UFgvPcwY1YU0+2xskacCKy2cOnWKODk5kUuXLgmKlo0bN5KKFSuSX3/9tUDPofTu3ZvY2dm99SddS4kGuVlpybCyr4mm9asKCuDV8XP0bF4Vp85eEpS8GHMRoq29AxwrVgT34fJZ7GHGVR/eRZUUAT//2zC1ssCN0/swc/pUTJ8+HT9MmYVLt4I4J5di2fwFSIAL5kz5muYcoLqTOTZxT4rnySo46KHt0NauApy4Y01LKdqMwox/D8WLj/NDhdS4VDg7VSnyVGClBdruRms2tPf1DS9fvsTkyZP5TodatWrx7XK0mYcutC0uLCx3Gk1KSgr69OkjrOmmRKuu9KXoixnnCa9p7xMpdsNxftAQmIb0734UqtFDiX0dDpW5I6pWduD1hNhISBTGqObuxlWVixbnn967G/aejdG6Wf1Cq66y1NcYM3Q4Krb/GivnjUdRrDQp+iXOnj4D5wbt0aWVN3Slzskk6QgNDcGL5xGIT06BhbUdPDzroXljL1hZaEeh6AWiRnz0KzwJeYaoqBhkKoBKLq7watIUnlVd8Pr5UzwOeoLE5FQoYQpXVzc08GqEGu6VCj1XJYFanIC9h04BdtUwcmC3XKkEqqw0XL91B/Fx8cgQZ8HE0pozhIqoUs0D9erWfs/8NQ0ObFyNKi2GoE3jKoJWMEQtx93bAYiKjkWqKB0aYzM4OzvBxa0qf5Pb27xpu9QgPCQIj4OfIYW7tsbmVqjsVgXeXt5wd9FdZXuLMgldmrZF7aFzsOGnrwSxbCASifg0r3r16vFtmhTau0o7wt40Tby5r+lf2htLy776Svs57927hwEDBvDZGcOGDeM1XZRsrytDCxdFzpswGo+Unti6dhEcrQq/3Y9tWYbR42fCo8d4nNq5HFWdbYQSLQlRYfhr+TJcvvMUto7OKM85oUKWCafaLTB31hTUqKyfnD2ikuPSyf1Ys2kn0riHg5ODLd8Zk6U2Rb8R4zHhi25YMe9b/Ln7Cjq2bs4/OBJjIqGyrIJff1uEVl7anm99cu/EJvT7di5kJm64GhiAhs7ZjxbRc3/UbzMYnk1aozo9p9yTT5KegvjEdLToMRDTJn4DNwf9zcemkcSjTbv2EJerjGYNPLibFVBIxYiLT0SVeq0wfeYUNKpJ0yWkmPbtWOz1fYSOrZpwtRcjxEZHwszBE4uW/IrGtStrX1AHWdGP0KLjAExacRjf9msiqGWHFStW8G10tK2uSpUqfG96dHS0UJobGrzQbWjuHIXuS43Rz88PXBWY13RCja6ovKnvMgpn79oFpE3X4SQ0qvBpqmWiWPLjf0aR3r37ksYtOpDj14OEEi2ZSa/IhKG9SMuuA8kRn2skTWhXVMqySHJSCpEr9HVN1MTv8BbSyLsx+WHecvIsIkYYAqchGWlpJFWknf57ycwxpGm/794OVRNFBZG+rRuRMbNXEkkxRjYVlbnfDCL9x04hrRvWIQs2+wqqlpRQP1K5cjVy+lF2G3FWhoicO7CFNK5VlXw55Q8i1eMINpU4hjRrUIvMWpU9PEspyyR3/M6Qvu0ak9Z9x5JXKfR6SsmEkX1J3/HzSLpUe9IiHvmTdl6fkP/75S9+PT+CL+0jHp4tSGBUmqCULUJDQ0nz5s3J9u3bBaVo0KFiHTp0IMuWLePXc7bJvbvopy7JQOuWLWEkS0JETLyg5E/Uq3AEhcdj9DeTUN9Bgwt+t6HM0aF49tAO+D1Jw69L/8DA7u1gK7QrmphboqKjA5/jpQ9EcRFYvWYD6rTtj99+noo61V2FqqgRbGxtYW/3JtXBCJz3cX+1lQO7KlXh6eEKqTQLfL61HpEmhOBaYBT6DByCnq0bwu/cceTu5+SOjT8+bW2EYmljh55fjMPyBZPhu2c9fO++Fkr0BG0/yVFxMjEvj+Yde2HV8sWICTiF3cevUpWPVohaxW2qPWlOLtVQw60ipLIsrmKbP/fv3kWN5p1Rt5K1oJQtaK7l6NGj+YguJiZGUAuHM0a+N3r48OGCkj/M6PREtebt0aRaBQQ9CUP2LaYLDZ4EcsZm5oROfbuhZ/vGuHn1MtIyhV9Pl8Thku81NGjbHS0b1tRqH4nI8EcIicxEvz4DYVVABg41P41awY9RpEMAd65ZhbvRRhg1sC8qFJ65UyzuXLsMeYXq6NCkDj4f3A8xj2/jwcu8Pw/JPfCFf2Xzac+BcLFX4aJ/EWa/KDZ5379aow7cNXXFzYAb3BrN0zOCUiHnz6MoMQbbN61FhMIBI78YVMCNKsf1m6EY8HkPWOjpgfcxGDNmDN/WRlNyigLtwKCdlDRH083NTVDzhxmd3rDEiCG9cDvgLtIy8r94crEIVy9fQ8O2neDEOUb3/gMgi3yMG8+0P40oSk7Fq/hUuHu4w+oj/+xESvQrSM1t4VKruqDohv6Yz4sbh9H605Zo0aINZv+xDQ3bd0fbpvqeQl6BCxe4h0DTZnBxckDNpp1Q39UIZ32uC+VvyI42c2JiYYuKNjaITSg86v5g8r7tW4yNTVHVpRISU7VDG80tzHHx0AZ0atsSLVu3w5JNR9C+90C0aph/O2fs/UtItXRDp5aFd5KVZmy460AT1D088o4w0QXNeaQD+lu1aiUoBcOMTo+07DUYzlmvcfVxhKDkJTk6lIsoHsO8nBLXrl3F49dpsDER4+BBH76cPuXpRdKoNAXdM3qBGhhRqaFSFDwMjCZ012j5OXwvXMLVa9ewbfV8PDy1Fb+s3F6icwK+S3J4EG4+CIURkeLW9Su4ERAIS2sLXPU5j/RcJ4taQF4b0KjlyFIo4Ginx8kXCnAfWkVNE0tgb63teFLIFOjYfxxOn7+Ea1evYO2iqTi/7U8sXrUT+Q1uOnTyClcN7gwPtwIa4ssINLm8qJkZdDvaA0vvj6LAjE6fmNpiyqThuHDsKDLkultZ7l+7iEixCsE3TuPXXxfh95XrQcqZIeDSSSTIADtnJ3i4O+LJ46cQSfIfy6cPnNw9YCZLRsTTJ4KiG1orNDG3QqXKlVDZ1Q09Bn2Fyf8ZhGN79uDZ66L9aPeH8PBRIOJFGQgOuIJlS37D8lXr8DIhHbEvH+Legyhhq/yJC3+AuEQZPm2qe5ievpGlRuJRcCS8GtCeUg00nPFZWlnDuRJ3Ht2qYsCX3+D7YZ1x7MABPIvKOzVUdMhdJBo5oVf3jrBgiRAFwoxOz9Rq2Rs9vSrihM8tQclGo8zEidMX0H3EVPicPcsP9Pf18cGhzX9AFRcMv4BnXA3YCT16dUfYzTM45uv/UaM699peaFbXEbt2bUV0aiFTZL3zYDU1NYdKJoeK/jatPtBk4eb1G6jZZjBO+lyGj68vPy/ZoT1b4UzScOOW9nzTBz49tHdzO6WiWKxY+iccGnREr3Z1BVU/0HfOM3GBOgvb161CjLELhvTvzAlvHmL81tp/crcnbWxXyhVQKnM/5FTSdPgHPELr9u3h5aFNtWDkDzO6j0DvL4bBShqFeyGRgqIl9fUj+D+ORt9B/QRFS7UWndG0RgUcOXGOX+8xaDS+7O6NJbMmYdYvy3Hn0VMkJCQg5PE9+F2/BZG4aA2474utczXMnDML8pf+GPXlOOw77otXUTGIjXoF/+vXEPj0Jb8dbehXKWSQyeWQStK5aPQYVm3ciZbdu6GWu35uwsRXYQgIDMGnbVvDKUcaXJWqHmjfwhP+/v5IUYCfJEJDVBCliSDNFPPJ4j7H9mH812Nw/jnB0t/mwdlSv7eBWqOGJCMDMpkUyckJuOV3HlO/G48VB29g3m9L0bIWTQimUzFpuHMog0LBVakzRLh8fDdWbz+OT7t1hme1itoXo6iVeBL4EBbOtdC+TTNBZBQESxj+SEjFKYhPlaFGteweogN/TsFP+59xkcmZPDfb7j9+xLzdQbh44yJq2hhBnByLw/t24ujZy0gXZyFLpoSdfQXU/7QbZkz+DlUccycYlxicSQTdvopNW3Yg+HkksjIlMLe0RgXnKhg+9juM7NUGm5fNwootx2BpbYdKzs4wNTOFxydNMeG7b1C3au4pdUqKK0c2YNKC7Vi76wA6eueeOeT8ntX48Y8j2Lh7L1pVTELLHqOgMTaHmbkZnJwdUZ47/tr1G2PQkC/QrL5+E5rVmYkYOGAAQmPSYW1pCfuKTrCxLg+XqrXRb+BgdGvXVIg2ZFg0Zyo27j0HZ+dK3OIIczNz1G3cFt988xU8KmdPIqtSyhEfEwdrR1fYsR9Gf8sbf9IFM7qPCT3VOapQKQkxkKhMUM0tb9Qjk6QhJjENLu7VUN5Uuw/NBUvnIhNRWjr35FfCsrwVKtjawraCjd5/hFgmzYQoNRUZ4kwYm5jCysoadg72KM+ZhyQjDampIoglWTCzsICVtTUcHBxgQee30hPitBSkpGfB1c0NZu8M45JlSRCXkALHSpVhbWGE+PhE7hjF/C+WWVpawcrGGvZ2djrHTpc0NEpLTkqEmHv/LK4Kas6fHxvY29rBMtcU74S/tnTcplTGbceZopWVDXce7WFumjdHh072mXeo5b8bZnQMBsPgKcjoWBsdg8EwcID/B10jq3QmrFOKAAAAAElFTkSuQmCC\" width=\"314\" height=\"102\"\u003e\u003c/p\u003e \u003cp\u003eInduced Polarization is a method based on the voltage response observed after the interruption of a continuous electrical current applied to the subsurface [\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e]. When electrical current is injected into the subsurface, the potential increases rapidly and takes some time to reach its maximum value (Vp). Similarly, when the current ceases, the voltage between the potential electrodes takes a measurable amount of time to decay completely, as the medium temporarily stores the electrical charge [\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e]. Thus, when applied to a geological medium, the voltage measured by the electrodes does not dissipate immediately but remains stored in the subsurface as mechanical, electrical, or chemical energy, detectable as a residual (induced) polarization for a certain period. The quantification of induced polarization is measured by chargeability (M), as represented by Eq.\u0026nbsp;3 [\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003cimg 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\" width=\"349\" height=\"58\"\u003e\u003c/p\u003e\u003cp\u003eThe acquisition of geophysical data was based on 6 electrical tomography lines in a Schlumberger configuration, with a length of 420m and 10m electrode spacing, to measure electrical resistivity and chargeability parameters. The lines were oriented in the N60W direction, with a spacing of 50m between lines 1\u0026ndash;2 and 5\u0026ndash;6, and 100m between lines 2\u0026ndash;3, 3\u0026ndash;4, and 4\u0026ndash;5 (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). Non-polarizable electrodes were used to avoid noise in the acquisition of Induced Polarization data, made of porous ceramic and filled with a CuSO\u003csub\u003e4\u003c/sub\u003e solution.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe geophysical equipment used for data acquisition was the Swedish-made ABEM Terrameter LS resistivimeter, consisting of a transmission and reception module with 250W potency, a maximum current of 2.5A, and a resolution of 1\u0026micro;V [\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e]. The configuration adopted for the survey was 1A of current, 1s transmission time, 0.3s reading time after current cutoff, with readings taken in two 100ms windows, and chargeability recorded in mV/V. Data acquisition was preceded by contact resistance measurements and programming for the exclusion of data with a mean deviation above 4%. The equipment automatically records the data in the internal memory as a spreadsheet, allowing for subsequent processing. A statistical analysis is performed after data acquisition to eliminate negative (anomalous) values and minimize extreme values by comparing them with neighboring values using arithmetic mean.\u003c/p\u003e \u003cp\u003eThe processing was carried out using the Res2Dinv software, version 3.53 (Geotomo Software), to generate inversion models for resistivity and chargeability parameters, with topography adjustment based on data generated from a differential GPS (DGPS) system. The inversion models are presented in 2D sections, containing information about the depth and length of the acquisition line, with values expressed in a logarithmic color scale. The inversion models are mathematically based on the least-squares algorithm with smoothing (smoothness constrained least square method), such that the software processes the subsurface as rectangular blocks containing values for the modeled parameters [\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e], in order to reduce the difference between the apparent resistivity values and those measured in the field, with the quality of the fit expressed by the root mean square error, the Root Mean Squared (RMS) error [\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e]. Upon completion of the inversion, the data are organized into a single spreadsheet, presenting each of the sections in an ordered manner. The file includes the position of the readings along the lines, spacing, and depth (variables \"x\", \"y\", and \"z\", respectively), as well as the resistivity and chargeability values for generating 3D visualization models.\u003c/p\u003e \u003cp\u003eFor 3D modeling, the tabulated data are used in the Oasis Montaj software (Geosoft) with interpolation through kriging. Subsequently, the statistical method of minimum curvature is applied to smooth the central values at the expense of the extremes. In this way, a gridded sample mesh is generated for each point of the 3D model, making it possible to generate depth maps with sections at depths of 10m, 20m, 30m, 40m, 50m, 60m, 70m, and 80m.\u003c/p\u003e"},{"header":"4 Results and Discussion","content":"\u003cp\u003eAt the regional scale, topographic lineaments are indicative of potential geological structures and possibly the location of mineral deposits. The shear zones of the Sul-Riograndense Shield (ESRG) predominantly trend NE-SW (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). According to Lopes et al. (2018) [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e], the main orientations are divided as follows: \u0026plusmn;62% in N31-90\u0026ordm;E, \u0026plusmn;\u0026thinsp;18% in N0-30\u0026ordm;E, and \u0026plusmn;\u0026thinsp;18% in N0-90\u0026ordm;W. More precisely, in the Seival Mines region, the lineaments have a preferential direction of N50E, and the oriented dykes and faults (\u0026plusmn;\u0026thinsp;N50E/70-88NW) are parallel to the Cabritos-Perau Fault, located 5km north of the area. The structural data from this study are similar to those obtained in previous works, with an average direction of N44E/65NW (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eA), corresponding to the fracture family with the highest representation in the locality. Furthermore, another maximum was determined with an average attitude of N55W/65NE, which corresponds to a second fracture family of lower magnitude.\u003c/p\u003e \u003cp\u003eThe Hil\u0026aacute;rio Formation exhibits bedding with a preferential direction of N20E/15SE, and the lapilli tuffs with N70E/30NW. The mineralized fractures and faults correspond to veins with thicknesses ranging from 0.1 to 1 cm, either straight or irregular, with directions of NE-SW and NNE-SSW, and high dips [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. This observation is confirmed by the measurements taken in this study, with mineralized fractures showing an average attitude of N62E/48NW and N69E/75NW (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eB). The faults present in the Barita Mine have an average attitude of N19E/9NW, which maintain the characteristics of the regional structural trend with a general NE-SW orientation (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eC).\u003c/p\u003e \u003cp\u003eThe electrical tomography data are presented in 2D tomography sections based on distance and depth, using a single logarithmic color scale and values aligned with the analyzed physical parameters. This approach facilitates comparative analysis between the survey lines. Regarding resistivity, the processed data reveal a value range between 10Ω.m and 20,000Ω.m (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e), while the chargeability data show a range from 0.5mV/V to 5mV/V (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e). For better visualization, warm colors represent high values, and cool colors correspond to low values of the aforementioned physical parameters.\u003c/p\u003e \u003cp\u003eThe 2D sections were analyzed based on geological, structural, and metallogenetic criteria, combined with evidence of mineralization identified in the region. Zones with high resistivity values (\u0026gt;\u0026thinsp;2280Ω.m) may be associated with silicified intervals formed during the deposit's development [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. Medium resistivity values, ranging from \u0026gt;\u0026thinsp;87Ω.m to \u0026lt;\u0026thinsp;260Ω.m, indicate water-saturated rock. Zones with very low resistivity (\u0026lt;\u0026thinsp;87Ω.m) reveal water-saturated areas, corresponding to aquifer intervals [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIn the case of chargeability, intervals\u0026thinsp;\u0026gt;\u0026thinsp;2.59mV/V indicate areas with an accumulation of sulfide metallic minerals, such as chalcopyrite, chalcocite, and bornite, which were mined in the abandoned sites and are possibly disseminated in fractured intervals [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. Conversely, zones with low chargeability (\u0026lt;\u0026thinsp;2.59mV/V) represent sterile rocks lacking mineralization.\u003c/p\u003e \u003cp\u003eLine 1, located to the north of the area, shows highly contrasted results according to the resistivity parameter, with a central zone between 160m and 290m, from the surface to a depth of approximately 90m, and a less pronounced zone between 340m and 380m, at the end of the acquisition section, both zones are characterized by high resistivity (\u0026gt;\u0026thinsp;2280Ω.m). The chargeability section shows a positive anomaly (\u0026gt;\u0026thinsp;2.59mV/V) between 80m and 255m, from a depth of 30m to 85m.\u003c/p\u003e \u003cp\u003eLine 2, located 50m from the aforementioned line, shows three distinct zones characterized by high resistivity (\u0026gt;\u0026thinsp;2280Ω.m): the first is irregular and occurs between approximately 80m and 115m, from the surface to 55m; the second occurs between 210m and 240m, from 75m to a depth of 85m; the third positive anomaly occurs near the end of the acquisition, between 295m and 350m, from about 30m to a depth of 55m. The chargeability section shows an extensive positive anomaly (\u0026gt;\u0026thinsp;2.59mV/V) between 70m and 385m, from the surface to 85m, with a distinct zone of lower chargeability between 160m and 275m, from the surface to 40m.\u003c/p\u003e \u003cp\u003eLine 3, located 100m from the aforementioned line, is characterized by high contrast in resistivity parameters. Two distinct positive anomalies (\u0026gt;\u0026thinsp;2280Ω.m) occur: the first, irregular, is between 190m and 300m, from the surface to a depth of 90m, with the width increasing from 65m toward the start of the acquisition line; the second anomaly occurs between 330m and 385m, from the surface to 40m. The chargeability section shows a positive anomaly (\u0026gt;\u0026thinsp;2.59mV/V) between 225m and 315m, from 40m to a depth of 90m.\u003c/p\u003e \u003cp\u003eLine 4, located 100m from the aforementioned line, is characterized by low to medium resistivity. The chargeability section shows a distinct positive anomaly (\u0026gt;\u0026thinsp;2.59mV/V) between 160m and 180m, from a depth of 80m to 90m.\u003c/p\u003e \u003cp\u003eLine 5, located 100m from the aforementioned line, shows high contrast in the resistivity parameter. A large, irregular zone of high resistivity (\u0026gt;\u0026thinsp;2280Ω.m) occurs between 190m and 300m, from the surface to a depth of 90m, widening at the base of the anomaly, starting at 70m. The chargeability section shows a distinct zone of high chargeability (\u0026gt;\u0026thinsp;2.59mV/V) between 110m and 150m, from a depth of 50m to 75m.\u003c/p\u003e \u003cp\u003eLine 6, located 50m from the aforementioned line, exhibits anomalies of low to medium resistivity. Two distinct high resistivity anomalies (\u0026gt;\u0026thinsp;2280Ω.m) appear at high depth, from 80m to a maximum depth of 90m. The chargeability section shows a positive anomaly (\u0026gt;\u0026thinsp;2.59mV/V) between 50m and 145m, from the surface to a depth of 50m.\u003c/p\u003e \u003cp\u003eBased on the established parameters, the area presents two types of copper mineralization occurrences in the subsurface. The first refers to anomalies of high chargeability combined with high resistivity, characteristic of mineralization associated with local structuring linked to silicification, possibly hosted in breccias or veins, occurring in lines 1, 2, and 3. Silicified zones can be defined as areas characterized by high resistivity (\u0026gt;\u0026thinsp;2280Ω.m) due to the increased resistance to the passage of electrical current in this material. This process results from the precipitation of silica due to the interaction of hydrothermal fluids with rock, leading to the replacement of minerals and the filling of voids with quartz [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThis mineralized zone, characterized by high chargeability and high resistivity, associated with silicification, occurs in line 1 between 200m and 255m, from 30m to 85m in depth. In line 2, all the high resistivity zones coincide with the high chargeability zone, such that the areas classified as highly resistive serve as the boundary delimiting the silicified mineralized zone. Finally, in line 3, this mineralization occurs between 225m and 260m, from a depth of 40m to 90m.\u003c/p\u003e \u003cp\u003eThe second type of mineral occurrence refers to anomalies of high chargeability combined with low resistivity, indicative of structurally controlled mineralization associated with metasomatic processes of argillization/propylitization, identified in lines 1, 3, 4, 5, and 6. The argillization/propylitization zone is a peripheral belt surrounding hydrothermal sulfide deposits and contains copper carbonates, along with concentrations of chlorite and sericite [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. These processes involve mineralogical alteration as a result of fluid-rock interaction and promote the concentration of metals, such as copper, especially in the hydrothermal system [\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e]. As a result, zones of low resistivity are generated due to the ability of secondary minerals to absorb water and ions in their crystal structure. This enhances the electrical conductivity of the rock, leading to a decrease in resistivity [45\u0026thinsp;\u0026minus;\u0026thinsp;15].\u003c/p\u003e \u003cp\u003eThe mineralized zone characterized by high chargeability and low resistivity, associated with argillization/propylitization, occurs in line 1 between 80m and 195m, from a depth of 25m to 75m. In line 3, it appears between 260m and 315m, from a depth of 40m to 75m. In line 4, there is a distinct interception of the established physical parameters marking the boundary of the positive chargeability anomaly, that is, between 160m and 180m, from a depth of 80m to 90m. Line 5 is similar to line 4, with the mineralization occurring between 110m and 150m, from a depth of 50m to 75m. Finally, in line 6, the mineralization occurs between 50m and 145m, from the surface to a depth of 50m.\u003c/p\u003e \u003cp\u003eIn order to enhance the data analysis and for comparative purposes of the physical parameters, pseudo-3D visualization models were generated. For this, a lateral interpolation of the 2D inversion sections from all the geophysical acquisition lines was performed. Initially, maps for resistivity and chargeability at depths of 10m, 20m, 30m, 40m, 50m, 60m, 70m, and 80m were produced. For illustrative purposes, the maps for the 30m and 80m levels of resistivity and chargeability are presented, showing the outlines marking the orientation of the mineralizations, partly related to silicification processes indicated by anomalies of high chargeability\u0026thinsp;+\u0026thinsp;high resistivity, and partly associated with argillization/propylitization with zones interpolated between the high chargeability\u0026thinsp;+\u0026thinsp;low resistivity parameters (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe depth maps reveal zones that can be associated with mineralizations predominantly starting from a depth of 30m, although there are areas near the surface in lines 2 and, occasionally, in line 6. The copper deposit does not show any signs of surface mineralization and, therefore, represents a non-outcropping deposit with a continuous anomaly indicative of a vertical structural control with a steep dip angle.\u003c/p\u003e \u003cp\u003eThe chargeability maps highlight two distinct zones, both with positive anomalies consistent with the regional trend, where approximately 18% of the structures correspond to the NW quadrant, oriented N0\u0026ndash;90\u0026deg;W [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. The first positive anomaly occurs in the upper portion with a N60W direction and coincides with areas of high resistivity, thus indicating the mineralized and silicified portion of the deposit. The second positive chargeability anomaly occurs in the southern portion of the maps, with a N10W direction, where part intersects low resistivity anomalies, indicative of mineralized zones with argillization/propylitization, and part intersects another positive resistivity anomaly, consistent with silicification processes. As depth increases, both anomalies tend to converge, and their continuity at depth suggests the possibility of a connection trend between the abandoned mines in this non-outcropping region.\u003c/p\u003e \u003cp\u003eGeochemically, it is possible to distinguish the hydrothermal alterations of argillization and propylitization based on mineral chemistry [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. However, in geophysical parameters, it is not possible to differentiate between these alterations as both have a low resistivity signature. Therefore, in this study, both are considered to belong to the same resistivity range, which implies that the second type of copper mineralization occurrence includes sulfide mineralization associated with these hydrothermal alterations, without differentiation.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIn a hydrothermal system, the pattern of regional faults facilitates the movement of metal-enriched fluids, and combined with the presence of a porous system, the morphological configuration of the deposit and its modes of occurrence become complex [\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e]. The geological environment allowed for the combination of metasomatic processes that affect the mineral composition of the deposit, generating opposing effects on the physical parameter of resistivity [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe characterization of hydrothermal alterations is enabled through the analysis of mineral assemblages [\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e]. Silicification involves the precipitation of silica, which increases the resistance to the flow of electrical current through the rock [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. This process commonly occurs in breccias or veins at greater depths and higher temperatures, resulting in highly resistive material, typical in the geological context of porous rocks, such as the lapilli tuffs found in the Seival Mines [\u003cspan additionalcitationids=\"CR16 CR17\" citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eFor the Seival Mines region, hydrothermal zones of propylitic and argillic alteration were characterized through geochemical studies [17\u0026thinsp;\u0026minus;\u0026thinsp;15]. Argillic alteration involves the percolation of ion-rich fluids that replace primary minerals with clay minerals, which have a higher water absorption capacity, thus resulting in a less resistive character. In the Seival Mines, this alteration is based on concentrations of smectite and quartz [\u003cspan additionalcitationids=\"CR18 CR19 CR20 CR21 CR22 CR23 CR24 CR25 CR26 CR27 CR28 CR29 CR30 CR31 CR32 CR33\" citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]. Fe and Cu sulfides occur in the intergranular space or are mixed with clay minerals [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]. This hydrothermal alteration is commonly found in the more superficial zones of the deposit, exposed to weathering [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e].\u003c/p\u003e \u003cp\u003ePropylitic alteration frequently occurs under low to moderate temperature conditions, characterized by the formation of a series of secondary minerals through rock-fluid interaction and hydrothermal fluid percolation with Cu enrichment in the Seival Mines [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. In this hydrothermal alteration, chlorite (chloritization) forms along with a mineral assemblage of hematite, titanite, calcite, barite, and quartz, associated with pyrite, chalcopyrite, and bornite [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. Chlorite minerals and the association of chlorite/smectite with sulfides are characteristic of hydrothermal deposits [\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e]. These minerals have been linked to the percolation of fluids composed of meteoric water or brine [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. Furthermore, chloritized zones emphasize areas enriched in Cu with hydrothermal fluid percolation in faults, dikes, and in lapilli tuffs that possess intrinsic porosity [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIn propylitic alteration, the formation of albite (albitization) also occurs, involving the transformation of andesine and labradorite into albite with a hydrothermal magmatic fluid rich in Na, with a neutral to slightly acidic character. According to Lopes et al. (2018) [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e], based on thermodynamic modeling, late-stage albitization with temperatures\u0026thinsp;\u0026lt;\u0026thinsp;350\u0026ordm;C was associated with the formation of primary pyrite and chalcopyrite, while chloritization with temperatures between 120\u0026ordm;C and 312\u0026ordm;C involved the generation of bornite and chalcocite. Therefore, it was concluded that the petrographic association of albite and chlorite with sulfide mineralization and Cu suggests that the processes of albitization and chloritization, associated with structural control, can serve as a prospective guide in Cu-enriched systems.\u003c/p\u003e"},{"header":"5 Conclusions","content":"\u003cp\u003eFrom the 2D inversion models and 3D visualization, it was possible to analyze the associations between these physical parameters and interpret two types of Cu ore occurrences: one related to silicification processes, characterized by high chargeability and high resistivity, and the other related to argillization/propylitization, with high chargeability combined with low resistivity, both structurally controlled with a general NW-SE orientation.\u003c/p\u003e \u003cp\u003eThe silicified zone has a predominant orientation of N60W and, secondarily, N10W. It was defined for areas with high resistivity and chargeability, and it possibly occurs hosted in breccias or veins. The argillic/propylitic alteration zone has an N10W orientation, and the physical parameters involve high chargeability and low resistivity.\u003c/p\u003e \u003cp\u003eThere is a clear structural control in the area, whether by faults, fractures, or fracture joints. The presence of joints facilitates the ascent of hydrothermal fluids and surface mineralization, where the Barita and Jo\u0026atilde;o Dahne mines are located. The region between the mines, with no indications of mineralization, likely indicates an area where structural interception is absent, thus preventing the ascent of hydrothermal fluids.\u003c/p\u003e \u003cp\u003eThe structural analysis conducted at the Barita Mine reveals the orientation of fractures, mineralized fractures, and faults consistent with the regional trend of NE-SW direction, and, subordinately, NW-SE. Although the NW-SE fracture family is considered secondary in the regional geological context, it plays a significant role locally in mineral occurrences. This direction coincides with the relaxation direction of the regional folding event, suggesting the hypothesis of fracture filling followed by mineralization.\u003c/p\u003e \u003cp\u003eThe target identified in the geophysical data shows no evidence of surface mineralization and, therefore, represents a prospective target for restarting mineral exploration projects. This study enabled the recognition of a target suitable for future investigation using direct methods and highlights the versatility of geophysics in detailed phases of mineral exploration, significantly reducing uncertainties and financial resources.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e \u003ch2\u003eCompeting interests\u003c/h2\u003e \u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e \u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eAA and CM performed the conception of the work, methodology and final review. Data acquisition, analysis, and interpretation were performed by all authors.\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eThe authors thank the Geology Department of S\u0026atilde;o Paulo State University \u0026ndash; UNESP - for the use of the geophysical equipment, Pampa Federal University \u0026ndash; UNIPAMPA, Ca\u0026ccedil;apava do Sul campus, Universidad de la Republica - UdelaR, Montevideo, Uruguay and Marcelo Spode, for granting us access to the study area.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eThe authors declare that the data supporting the findings of this study are provided in the manuscript.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eIBRAM (Instituto Brasileiro de Minera\u0026ccedil;\u0026atilde;o), Boletim do Setor Mineral, 2020 (outubro). 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Geochemistry of Hydrothermal Ore Deposits, 2nd edition.; John Wiley \u0026amp; Sons Inc: New York, 1979.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"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":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"mineral exploration, sulfides, copper, electrical resistivity, chargeability, non-outcrop, target","lastPublishedDoi":"10.21203/rs.3.rs-5716993/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5716993/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThis paper is based on the use of indirect investigation methods using geophysics as a tool for the search for non-outcropping deposits. The integration of the geophysical methods of DC Resistivity and Induced Polarization added to the analysis of structural data is adopted in the region of Minas do Seival, in the extreme south of Brazil, in an area with no signs of surface mineralization. The region is located in the context of the Sul-Riograndense Shield, with andesites, dacites and latites occur locally, in addition tuffs, lapilli tuffs and breccia tuffs, gathered in the Hil\u0026aacute;rio Formation (Neoproterozoic). The structural survey was carried out at the Barita Mine, in outcropping lapilli tuffs where brecciation, argilization and carbonation were recognized in mineralized zones, with malachite and azurite. Next, 6 electrical tomography lines with 420m of length. The combined analysis of the 2D and 3D models allows the recognition of potentially mineralized zones characterized by high chargeability. The results indicate the existence of a deposit from 30m deep with a tendency to connect the mines, partly related to silicification processes (high chargeability\u0026thinsp;+\u0026thinsp;high resistivity) and partly related to argilization and propylitization (high chargeability\u0026thinsp;+\u0026thinsp;low resistivity), structurally controlled.\u003c/p\u003e","manuscriptTitle":"Structural and Geophysical Modeling in an area with non-outcropping Copper Sulphide Deposits, Minas Do Seival Region, Sul-Riograndense Shield, Southern Brazil","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-01-13 06:02:37","doi":"10.21203/rs.3.rs-5716993/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"84872665-2acb-42e1-9378-e8d9ff7a9b7e","owner":[],"postedDate":"January 13th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-02-20T05:38:44+00:00","versionOfRecord":[],"versionCreatedAt":"2025-01-13 06:02:37","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-5716993","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5716993","identity":"rs-5716993","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}