Mineração artesanal de ouro em pequena escala na Serra do Espinhaço Meridional – Brasil, utilizando indução eletromagnética no domínio do tempo: prospecção, eficiência e aspectos ambientais

Abstract

The attempt to locate large deposits of native gold in nature is a long-dating practice in human history. Gold mining has profound ties to the history of Brazilian colonization and exploitation. This prospective heritage still takes place, with many communities involved with and dependent on artisanal and small-scale gold mining. The more relevant gold deposits in the Southern Espinhaço Range, Brazil are related to the occurrence of shear zones which mostly occur in the region between the cities Diamantina and Gouveia, Minas Gerais, affecting mostly the Gouveia Complex granite rocks, the Costa Sena Group schist sequences, and the Espinhaço Supergroup metasediments/metavolcanites. Former colonial-dated gold mines were depleted, however, the use of newer prospecting practices for gold mining has brought new interest in these areas. In this context, this study assesses the efficiency, environmental impacts and economic viability of using time-domain electromagnetic induction as a gold exploration method for small-scale gold prospecting in the Gouveia county, though the study is likely applicable to similar mining areas across the world. Additionally, this work provides a characterization of the local gold mineralization and mineralogy along the three chosen areas for exploration, as well as bringing awareness to the prospecting community regarding environmental and legal aspects of gold mining. The gold samples located have specific morphology, depth and weight that suggest a hypogenic origin for this mineralization with a low degree of transport at eluvial levels. From an environmental perspective, compared to the more archaic small-scale and artisanal mining methods, the time-domain electromagnetic induction equipment has presented less environmental impacts, related mostly to site-specific remobilization of the soil. This prospecting practice is important, both socially and economically, for the local community in the study area. Considering this, the conclusion is made that the utilization of geophysical methods for prospecting subsurface gold occurrences in the regolith levels through the use of portable equipment with simple operation is efficient, environmentally friendly and economically viable for the studied region and similar areas.