Geophysical Prospecting Over a Meta-Ultramafic Sequence with Indicators of Gold Mineralization in Rio Grande do Sul State, Southernmost Brazil

Abstract

This work investigates the occurrence of gold on meta-ultramafic rocks at Funcho Farm, São Sepé, Rio Grande do Sul state, southernmost Brazil. The presence of base metals in meta-ultramafic rocks whose origin is related to volcanic massive sulfide (VMS) deposits has only rarely been explored in the scientific literature. The gold was identified in geochemical prospecting of current sediments in previous works, and suggested that the host rock of the mineralization is the serpentinite of Funcho Farm. The methodology used to achieve the study objectives included geological field surveys, surveys of structural measurements and acquisition of geophysical data utilizing electrical resistivity (DC) and induced polarization (IP) methods, using electrical tomography, with the execution of dipole-dipole arrays. In this study, nine electrical tomography lines, each 400 m, were acquired. The data were processed in 2D electrical inversion and then interpolated for 3D visualization. The information acquired for interpretations during field studies revealed that the probable mineralization is hosted in structures such as fractures and hinges and is also associated with milky quartz veins. The data analysis allowed the 3D delimitation of possible deep sulfide mineralizations from hydrothermal fluids, probably from the intrusion of the São Sepé granite. The results presented in this work are very useful, because they can serve as an appropriate analogy of geological reality associated with a reliable deposit architecture, helping to outline a strategy for a future drilling campaign directed to the targets found.

Geophysical and structural survey in copper occurrence located in the northern region of the Camaquã basin (RS)

“…The step of acquiring data comprised a geophysical survey by land through the methods of DC Resistivity and Induced Polarization in the time domain. These have great applicability in mineral exploration of massive and/or disseminated sulfide bodies, and are independent methods, but present results of greater efficiency and safety when interpreted in conjunction (Cortês et al, 2019;Moreira et al, 2019a;Moreira et al, 2019b;Lenhare & Moreira, 2020).…”

Combined analysis of resistivity and induced polarization tomography for 3D modelling and preliminary volume estimation of the possible gold mineralization zones in the Simi locality, Adamawa, Cameroon

“…IP and ERT are commonly used in geological and mining prospecting to indicate the presence of metal sulphides, metal oxides, clays and other old buried mine sites in the ground (Bharti et al., 2016; Bharti et al., 2019; Claude et al., 2014; Das et al., 2017; Gündoğdu et al., 2022; Horo et al., 2020; Kayode et al., 2022; Moreira et al., 2019; Shirazi et al., 2022; Silva et al., 2022; Singh et al., 2019; Zaid et al., 2022). Other studies use these methods for the 3D modelling of geoelectric anomalies corresponding to the targets sought (Embeng et al., 2022; Kayode et al., 2022; Lenhare & Moreira, 2020; Martin et al., 2020; Moreira et al., 2019; Sağır et al., 2020; Ya‐wei et al., 2015). This modelling can be done either by 3D inversion of the tomography data using inversion software (Zondres3D, Res3DInv, UBC and others) or by 3D correlation of the interpretation results of the different inverted sections using specific software (Oasis montaj, GeoModeller, RockWorks, GeoScene3D and others).…”

“…Although several geophysical methods exist, in this study, the sensitivity of the method (for the detection and location of horizontal and vertical structures or bodies), the type of mineralization sought (metallic sulphides), the depth of the targets (near surface), the geological environment (site constituted by ancient sedimentary deposits) and geomorphological environment (topographic variation), the deposit mode (diffuse or disseminated) and the area of investigation are a set of factors that justify, as in most studies (Gouet et al., 2013; Gündoğdu et al., 2022; Liang et al., 2021; Sağır et al., 2020), the choice of the electrical method as the ideal approach for this study. The choice of using the direct current (DC) and induced polarization (IP) electrical methods over the self‐potential method is not only due to their good accuracy and depth of investigation but also to their affinity in the detection of a particular type of mineralization (clays, metal sulphides, graphite and certain metal oxides such as magnetite) (Chouteau, 2006; Claude et al., 2014; Gouet et al., 2013; Kayode et al., 2022; Lenhare & Moreira, 2020; Martin et al., 2020; Shirazi et al., 2022; Silva et al., 2022; Wang et al., 2022). Moreover, with these two methods, the electrical tomography technique (acquisition in vertical sections of electrical data) can be easily used, and the different tomographic sections obtained after data processing can be used in 3D modelling and preliminary estimation of the volume of anomalies (Embeng et al., 2022; Martin et al., 2020; Moreira et al., 2019; Yan et al., 2018; Ya‐wei et al., 2015).…”

“…In geological or mining prospecting, the use of a geophysical approach leads to the elaboration of subsurface imagery that should allow a better understanding of the spatial distribution of geophysical anomalies related to the sought geological formations (Blanchy et al., 2020; Claude et al., 2014; Gouet et al., 2015; Hasan et al., 2021; Moreira et al., 2019; Zaid et al., 2022). In the ERT and IP surveys, the resistivity and chargeability of the geological formations are studied in order to identify zones of low (or medium) resistivity and high chargeability that may represent potential zones of gold mineralization (Embeng et al., 2022; Gouet et al., 2013; Horo et al., 2020; Kayode et al., 2022; Lenhare & Moreira, 2020; Singh et al., 2019; Yan et al., 2018). The present study combines these two geophysical techniques (ERT and IP) in 3D modelling and preliminary estimation of the volume of geoelectrical anomalies that may correspond to potential primary gold mineralization targets in the Simi locality.…”