Geological interpretation of the aeromagnetic survey, Las Petas District, Republic of Bolivia

Abstract

Significant information about the underground continuity of the surface geology of the Las Petas district has been obtained, and it is presented on a solid geology map. The newly defined lithomagnetic units range from Precambrian basement, largely beneath non-magnetic cover, to Cretaceous sandstones. The basement comprises three units, i.e. a high magnetic gradient, Lower Proterozoic unit of high-grade metamorphic rocks, a medium magnetic gradient, Middle Proterozoic unit of low- to medium-grade metamorphic rocks and a low magnetic gradient unit of Middle Proterozoic sediments and metasediments. In addition, a unit of Upper Proterozoic sediments is inferred to underlie the Quaternary sediments of the southeastern portion of the district. Two circular shaped, previously unrecognized Cretaceous alkaline bodies have been identified. An area of low magnetic gradient and high potassium content identified in the Middle Proterozoic gneisses would correspond to an aureole of hydrothermal alteration. New data also include structural information, particularly foliation/schistosity of the metamorphic rocks covered by laterite, as well as the positions of faults and fractures of various scales.