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

César Augusto Moreira,Henrique Pelorca Carneiro,Matheus Felipe Stanfoca Casagrande,Marco Antonio Fontoura Hansen,Marcos Eduardo Hartwig

doi:10.1590/0370-44672020740103

Abstract

The geophysical diagnosis of mineral deposits can be extremely useful in detailing mineralized zones and is a strategy for direct sampling by probing holes for content analysis. This study involves the combined use of Electrical geophysical methods (DC resistivity and Induced Polarization), geological recognition and structural field analysis, with a study of the mineralized occurrence of copper, previously described in a systematic geochemical survey carried out by the Geological Survey of Brazil (CPRM), located in the north of the Camaquã Basin, extreme south of Brazil. The mineral occurrence is partially outcropped and consists of quartz vein shafts with malachite and relic structures of sulfides, contained in schist. Structural data obtained in the field revealed the existence of a system of fracture pairs in the directions N40-50W and N70-80E. Such information is presented in the programming of the geophysical data acquisition scheme, which consisted of 6 lines of electrical tomography with 410m each, in azimuthal disposition and Schlumberger arrangement, where all lines cross a single center and are separated according to an angle of 30°, in an attempt to cover fractures in various orientations. The 2D results reveal the existence of high chargeability zones (>40mV/V) positioned below the 40m depth. These data were interpolated in 3D visualization models and generated resistivity and chargeability maps for several depths, which integrated with previous structural data, and indicate the existence of zones with potential sulfide concentration with strong structural control, in addition to clear target recognition for direct and objective probing evaluation, with rationalization of costs.

Highlights

The mineral resources are increasingly assuming a strong importance for the maintenance, development and economic growth of the population
The electrical resistivity and chargeability measurements were obtained by means of six lines of the electric tomography oriented in azimuthal direction with angular distance of 30°
The geological surveillance of the field allowed the characterization of mineral occurrence in the surface, represented by copper carbonate contained in fractures of sericite chlorite quartz schists belonging to the Vacacaí Metamorphic Complex, besides impregnations of oxidized sulfides associated with quartz veins

Summary

Introduction

The mineral resources are increasingly assuming a strong importance for the maintenance, development and economic growth of the population. They are raw material sources that have wide applications in the market, which are of great importance in the sector of technological development These mineral resources rely strictly on mineral research, responsible for the discovery of new occurrences and mineral deposits that are economically viable for the prospectus (Moon et al, 2006). The great challenge is the discovery of new exploratory frontiers or research in regions where metallogenetic conditions are favorable, but with no evidence of surface mineralization In these cases, where potential deposits are deep, unbound from the surface or even in a geological context of high structural complexity, the use of geophysics is a highly recommended alternative for diagnosis and individualization of promising targets (Moon et al, 2006; Dentith & Mudge, 2014)

Methods

Results

Conclusion