Delimitation of massive sulphide bodies – Mise‐à‐la‐masse method associated with induced polarization (IP) – A case history from Brazil

Abstract

This paper presents a successful application of the mise-à-la-masse (MALM) or applied potential method in association with induced polarization (IP). MALM is known, since 1920, to be able to delimit electrically conductive massive mineralization. The method is used at the point where a drill hole intercepts a massive, mineralized body, to estimate its extent and shape. It is thus used as a complementary mineral exploration tool. IP is normally used in conjunction with resistivity. However, the acquisition of IP data together with the MALM method is rarely found in the literature. This survey shows that it is possible to successfully detect and delimit areas of disseminated sulphides using MALM with IP. In this paper, the MALM method is presented and discussed in detail. A short description of the IP method is also provided. Data are from the Camaquã Project (Caçapava do Sul, RS, Brazil) and the Santa Maria (lead, zinc and associated silver) deposit, 5 km south of Caçapava do Sul. In a well that intercepted a massive mineralization (borehole 8011) with electrical continuity, ∆V measurements delineated the extent, shape and orientation (NS) of a conductive sulphide body. Mineralization intercepted by other two wells (8011 and 8103) did not present enough electrical continuity to exhibit potential contours that could be associated to massive sulphides; it was, however, successfully detected by IP.