Método de eletrorresistividade integrado com dados aeromagnéticos e sondagem mecânica aplicado ao estudo de mármore calcítico na área da Mina Cerro da Cadeia em Vila Nova do Sul – RS

Abstract

The present work deals with an update of the geological-geophysical mapping of the calcitic marble mineral extraction area, of the company Calcário Andreazza Ltda. The study area is delimited by the following geographic longitudes and latitudes: 53°57'5"W - 53°56'29"W e 30°20'12"S - 30°19'7"S, located in the rural area of the municipality of Vila Nova do Sul, Rio Grande do Sul (RS). Calcitic marble is the ore under exploration in the aforementioned region and is presented in the form of lenses, with grayish tones, alternating between light and dark bands, embedded in gneissic rocks of Neoproterozoic age. The production of it, in addition to the animal feed industry, also benefits the fertilizer industries since the calcitic marble extracted in the company's mine is presented as an agricultural corrective rich in carbonate. The research consists of the integration of electrical resistivity data from terrestrial geoelectric surveys on a scale of detail approximately (1: 5,000), obtained with the acquisition techniques of Vertical Electrical Sounding (VES) and Electrical Resistivity Tomography (ERT), together with aeromagnetometric data from the Rio Grande do Sul Shield Aerogeophysical Project (CPRM, 2010) and mechanical drilling information provided by the company Calcário Andreazza Ltda. The processing of geoelectric data was based on obtaining 1D and 2D models, from the inversion of apparent resistivity data, obtained with SEV and ERT techniques. The processing of the aeromagnetometric data was carried out following a conventional methodology, using filtering techniques and enhancement of the residual magnetic field anomalies. The results of the 2D models of electrical resistivity, show intervals from 400 Ohm.m to 1300 Ohm.m, associated with the presence of quartzites with intercalations of calcitic marble layers, with thicknesses around 20 meters. The integration of the aforementioned data resulted in a better understanding of the tectonic-structural control associated with the presence of calcitic marble mineral bodies, delimited by faults inferred by geophysics, as well as the delimitation of a sector of occurrence of calcitic marble, and the final preparation of a block model, for the occurrence of calcitic marble in the area.