Contribuição geofísica ao estudo do batólito granítico Santa Helena, sudoeste do Cráton amazônico

Abstract

The Santa Helena batholith is subject of many controversies concerning its geographical extension, lithological constitution, geochemical characterization and geotectonic setting. This paper aims to contribute for a better understanding of this intrusion using geophysical data (gammaspectrometric and aeromagnetic). These data were obtained through surveys contracted by the Geological Survey of Brazil (CPRM) flown over the study region. Given the compositional variety of the rocks, we analyzed the susceptibility contrast (magnetometry) and distribution of radioelements (K, Th and U, measured by gammaspectrometry) in the batholith. The resulting geophysical signature is different when comparing the northern and southern parts of the body, suggesting the presence of two distinct suites. The boundary between these two suites coincides with the location of an approximately N75° W oriented fault system that extends through the batholith.