Airborne gamma-ray spectrometry signatures of Ediacaran granitic rocks in the Transversal Zone of Borborema Province - NE-Brazil

Abstract

High-resolution gamma ray spectrometry was exploited to identify and classify the main granitic intrusions present in Transversal Zone domain, Northeastern Brazil due to the fact that this rock type tend to have relatively high levels of gamma radiation from the decay of potassium, uranium and thorium, elements present in its mineral composition. The granitic suites were grouped according to the data compilation present in literature and the results revealed interesting patterns for the epidote bearing calc-alkalic, high-K calc-alkalic and ultrapotassic peralkalic series. Also, high-K metaluminous and post-orogenic/A-type suites have a distinct gamma-ray signature, even though there are few mapped occurrences in study area. On the other hand, the results for shoshonitic, high-K calc-alkalic and Trondhjemitic-affinity suites are ambiguous, since they do not present gamma-ray signatures that allow their clear differentiation between them.