Distribuição estratigráfica e proveniência de minerais pesados das Formações Ipixuna e Barreiras, região do Rio Capim, Sul da Sub-Bacia de Cametá

Abstract

Heavy mineral and paleocurrent analysis can play an important part in unraveling the extrabacinal (source and source area weathering) and intrabacinal processes (chemical weathering processes) that influence the formation of clastic rocks. Tertiary and cretaceous sandstones from the Cameta Sub-Basin were investigated for their transparent heavy minerals. The Ipixuna (Upper Cretaceous/Lower Tertiary) and Barreiras (Miocene) formations comprise 35m of clastic sedimentary rocks outcropping in the Capim River region, and were deposited in the fluvio-estuarine environments of incised-valleys systems. The Ipixuna Formation is represented by sandstones, claystones and intraformational conglomerates kaolinitic and the Barreiras Formation is composed of sandstones, claystones and conglomerates. The heavy minerals assemblages are composed of zircon, tourmaline, staurolite, kyanite and rutile. The Est/ZTR+Est index and surface textures shows that post-depositional processes less alter heavy mineral assemblage of Barreiras Formation than Ipixuna Formation. The provenance data are still limited, howere the mineralogical assemblages are derived from metamorphic, granitic and sedimentary rocks. The RuZi index and paleocurrent dates record changes in the provenance of sandstones of the Ipixuna and Barreiras formations. The variety of zircon and tourmaline indicate that Sao Luis Craton and Gurupi Mobile Belt were an important component of provenance to Barreiras Formation, but were insignificant source to the Ipixuna Formation rocks. The Araguaia-Tocantins Mobile Belt and Amazon Craton in the south portion of the Rio Capim Region was an important source to Ipixuna Formation. The RuZi index and dissolution features in the heavy minerals suggest that semi-flint and soft kaolin deposits have different sources and evolutionary history.