Aplicação de técnicas de geologia e geoquímica na região de Ibaré/RS e no filão cocal de Fluorita/SC.

Abstract

The district of Ibaré, located in the municipality of Lavras do Sul, has its geology composed by lithostratigraphic units with ages from the Pre-Cambrian to the Fanerozoic. The Ultramafic Complex is divided into the Bela Vista and the Corticeira Sequences, intruded by granitic rocks related to tectonic and magmatic events from Late Proterozoic to Eo-Paleozoic (Santa Rita Monzogranite and Jaguari Granite). Although some studies had already been carried out in this area, the option was for a detail research, starting with a geological mapping, followed by petrology and geochemical (major and trace elements, and REE) studies, in order to test modern techniques not yet used for the rocks of these units. The mapping showed features not yet described, specially related to the Jaguari Granite, changing the interpretation of the metamorphic events in the region. The petrological and geochemical data showed that the intense metamorphism and metasomatism that affected Ultramafic Complex obliterated its original textures, making it hard to identify the protolith. However, the geochemical data obtained suggest a komatiitic affinity for these rocks. The granitic rocks, Santa Rita Monzogranite and Jaguari Granite, are peraluminous to metaluminous, calcic, and were developed under a volcanic arc and intraplate geotectonic environments, respectively. The Jaguari Granite was responsible for the contact metamorphism printed in the ultramafic rocks, as well as for the development of the metasomatites (rodingites and tourmalinites). The tourmalines of the tourmalinite were classified as oxy-dravites and are compositionally similar to those found in deposits related to metamorphic rocks.