Geoquímica isotópica do Sr no distrito fluorítico de Santa Catarina: implicações na fonte dos fluidos mineralizantes de fluorita

Abstract

In this work, we present the results of Sr analyses of fluorites, barites and disseminated fluorite with the objective to identify the source of the mineralizing fluids of the Santa Catarina Fluorite District. The sampling was divided among south and north parts of the district, Segunda Linha Torrens and Grao-Para sub-districts, respectively. In the Segunda Linha Torrens sub-district, the constancy of the 87 Sr/ 86 Sr reasons confirms the model of meteoric fluids involved in 3 successive hidrothermal circuits that drained, all the 3, a same rock source or a same composition of rocks source. It can be admitted that the Tabuleiro granite has been an important source of F, maybe the most important, because it was very rich in F in the form of disseminated fluorite of magmatic origin. However, we can´t exclude the contribution of the Pedras Grandes granite, the most abundant, and in which happens also disseminated fluorite (of secondary origin) away in smaller amount. In the Grao-Para sub-district, the 87 Sr/ 86 Sr reasons decrease clearly from the earlier fluorite to the late paragenesis and it´s easily to establish correlations among the fluorite of the several veins. During the mineralization process, the source and the origin of fluids changes. For the phase 1 of mineralization, it can be conceived a hidrothermalism in which the meteoric fluids drain the host granitic rocks and they leach F. The 87 Sr/ 86 Sr reasons of the vein fluorite indicate a strong influence of the Pedras Grandes granite that it might have been drained in depth. In the phase 2, the fluid gradually raisin to a descending fluid, saline, saturated in halite, originated from the sedimentary covering.