Integrated geophysical investigation of a possible new alkaline occurrence in SE Brazil

Airborne geophysical data by the Brazilian Geological Survey (CPRM) reveal the presence of a magnetic anomaly with no geological expression at the surface but with characteristics similar to those associated with alkaline complexes that outcrop in the same area. This observation motivated an attempt to characterize the anomaly source using various geophysical methods. This article presents satellite images for different spectral bands, as well as the results of a seismic survey, gravity and ground magnetic surveys along a profile crossing the anomaly, and density and susceptibility measurements of different lithologies in the area. The obtained information was used to constrain 2½-dimensional simultaneous gravity and magnetics and three-dimensional magnetics only models. The modeling results converge to indicate the presence of a body of approximately 3.3×109 metric tons, whose top is approximately 40 m from the surface and that has 1 km of maximum depth.