GEOLOGIA E GEOQUÍMICA DOS FILÕES DE FLUORITA SEGUNDA LINHA TORRENS E COCAL - SC

Abstract

In the fluorite province of Southern Brazíl (Santa Catarina State), the míneralízed veins are positioned in open NS to N30E trending faults. Those faults are open fractures in the crystalline basement (granites and quartz-monzonítes of the Upper Proterozoíc), that from a paleogeographíc hígh, límítíng the eastern edge of Paraná Basin. The mineralized faults also cut across Eocambrian porphyry-quartz dykes, Upper Carboniferous sediments of Itararé Group and Upper Cretaceous diabase dykes. The fluorite veíns show a symmetrícal and/or assymmetrícal simple zonation, characterized by banded fluorite, fine and coarse breccías, "cocardes" and associated geodes. Fluorite samples are green, light~yellow and white in color, and are found associated with chalcedony, quartz, barite, pyríte, kaolinite and more rarely galena. Precipitation of fluorite occur in melange zone between rising hydrothermal fluids and connate water in sedíments of the Itararé Group, that is underlaín by crystaltine basement. The formation of fluorite veins is linked to the evolution of the rifting event that separated the South-American and African contínents, probably from the end of Cretaceous to the beginning of Tertiary. The origin of fluids investigated by oxygen and sulphur isotope studies in barite, fluid inclusions in fluorite and rare earth dístribution in various types of fluorite samples, is related to convective circulations of superficial waters percolated at depth, which are then heated, starting the leaching of fluorine from basement rocks and depositing fluorite during the ascending process towards the surface.