Análise geoestatística aplicada à prospecção geoquímica de ouro nos sedimentos de solo, na zona sudoeste da província de Cabo Delgado, distrito de Namuno – área 5240 AD

Abstract

A geochemical analysis of soils is essential in gold prospecting, as it identifies patterns of mineral concentration and indicator elements, optimizing the search for profitable gold deposits. The occurrence of gold mineralization in the study region is attractive, leading to the establishment of geochemical prospecting programs. In this context, processed data resulted from a geochemical survey campaign conducted by the National Mining Institute (INAMI), as part of the Geological Research Project in support of Artisanal and Small-Scale Mining (MAPE), carried out in 2017 and available through the Mine Technology and Environment Project Services (SPTMA). Soil sampling was conducted on a 200x200 meter grid covering an area of 16,500 km², with 425 soil samples collected from the B horizon, each weighing 1.5 kg (Macuácua et al., 2017). In-situ analyses were performed using the portable XRF device X-MET 8000 Expert Geo. However, advanced studies utilizing geostatistical analysis techniques for elements in the study area, specifically for gold geochemical prospecting of soil samples, had not been conducted. In this context, the present work integrates geochemical and geological data to delineate areas favorable to Au mineralization. This is achieved through multielemental analysis of indicator elements Zn, Co, Ni, Cu, Sb, and Pb (Korshunova et al., 2019) and other elements such as Cr, Fe, Rb, Sb, Ti, and K, revealing the geochemical and mineralogical characteristics of the study area processed in oxides. Geochemical thresholds were determined using probability plots. Spatial representation of point geochemical concentrations was achieved through graduated symbols. For determining geochemical associations of elements, cluster analysis was employed through factorial analysis, distinguishing five factors: Factor 1 (Cr₂O₃-NiO-CuO-Sb₂O₃), Factor 2 (V₂O₅-PbO-K₂O), Factor 3 (Fe₂O₃-ZnORb₂O-Au), Factor 4 (TiO₂), and Factor 5 (CoO), occurring in meta-arenites and amphibolitic gneisses in the study area (Norconsult Consortium, 2007). To indicate the zones of occurrence of geochemical associations defined by factorial analysis, indicative kriging was performed. Geostatistical analysis was utilized for interpolating geochemical data through ordinary kriging, it allowed for create maps of spatial distribtion. The mineralogical analysis allowed for the identification of the main minerals in the area such as quartz, kaolinite, hornblende, albite, and chrysotile