Modelagem metalogenética para prospecção de urânio nas rochas do núcleo da Anticlinal Abaíra-Jussiape, Chapada Diamantina, Bahia

Abstract

Revista Brasileira de GeociênciasArquivo digital disponível on-line no site www.sbgeo.org.br 203 41(2): 203-219, junho de 2011 Modelagem metalogenética para prospecção de urânio nas rochas do núcleo da Anticlinal Abaíra-Jussiape, Chapada Diamantina, Bahia Palavras-chave: Anticlinal, zona de cisalhamento, modelagem metalogenética, urânio. Abstract Metallogenetic modeling for uranium exploration in rocks of the Abaíra-Jussiape Anticlinal nucleus, Chapada Diamantina, Bahia.The NNW-SSE-trending Abaíra-Jussiape Anticlinal is an antiformal culmination of folding and shearing in the Paramirim Corridor of the Western Chapada Diamantina. In its core Paleoproterozoic, mylonitized Caraguataí Suite, tonalites-granodiorites, alkali-feldspar granites, syenites to quartz-syenites and Jussiape Suite granites crop out. Compressional and distensional stresses mark the structural geology of the area. The compressional structures are related to two distinct deformation phases, named D1a and D1b. The main compressional phase is ductile D1a, which is related to the nucleation of dextral to dextral-reverse shearing zones. Deformation and syn-D1a recrystallization involving plagioclase and the K-feldspar suggest deformation temperature conditions above 550ºC. The following phase D2 is of ductilebrittle nature and culminates in reverse shearing zones. The distensional structures correspond to the D3 phase and are represented by frontal shear zones with normal movement. The petrographic study helped identify a pre-D1a hydrothermal alteration process related to albitization and potassifi cation, syn-D1 oxidation process, and hydration and saussuritization related to phases D2 and D3. The integration of lithological, petrographic, structural and geophysical data by means of the logic Fuzzy, plus the existing information regarding structural and lithologic controls of the known uranium mineralization in the Paramirim Corridor, led us to identify two promising areas for radioactive element exploration in the nucleus of Abaíra-Jussiape Anticlinal.