Geologia e identificação da paragênese mineral na mina dourada e correlação com minas da borda leste do complexo intrusivo Lavras do Sul – RS

Abstract

Hydrothermal fluids may be defined as a hot aqueous solution containing solutes that are commonly precipitated as the physicochemical properties of the solution are changed. The importance of these fluids is their ability to catalyze, and concentrate transport elements (including Au, Ag, Cu, Zn, Pb, etc.) that were rented in the surrounding rocks or the retained residual magma. The gold-bearing district of Lavras do Sul is an example of environment where there was a concentration of elements with economic bias by hydrothermal processes. This district consists of several gold-bearing mineral prospects facing the Au-Cu extraction (± Pb, Zn, Ag) located in a Neoproterozoic Plutono-Volcanic sequence with emphasis on alkaline rocks from the Lavras do Sul Intrusive Complex (LSIC). For this study was selected the Dourada Mine which lies eight kilometers northeast of the city of Lavras do Sul-RS on the field of alkaline rocks and syenogranite perthite-granite LSIC. The objective of this study is to identify the mineral paragenesis of the Dourada Mine, qualitatively characterizing hydrothermal alteration processes for making a prospective model. The methods used are based on techniques related to the study of changes and paragenetic characterization of secondary minerals, and for this were carried out fieldwork, petrography optics, Diffraction of X-Rays and Scanning Electron Microscopy. In the first stage of this research has produced a geological map of detail (1: 500) of the Dourada Mine, highlighting structures such as shafts, trenches and lithological contacts. It was later performed the identification of mineral alteration paragenesis with the help of the tools of Diffraction of X-Rays and Scanning Electron Microscopy, which enabled the characterization of mineral phases of the metals Zn-Fe-Ti, silicate-alumina and rare earth . With the compilation of petrological data has identified a possible zone of potassic alteration surrounded by an advanced argílitica affected zone in the region of the Dourada Mine, this result grounded by the strong presence of various mineral contents, such as anhydrite, barite and goyazita accompanied by several other elements such as rare earths. Finally, we designed a prospective map of hydrothermal alteration zones in the eastern part of the LSIC using dedicated work of Mines Cerro Rico, Volta Grande and the results of this work in the Dourada Mine. This prospective map highlighted the presence of potassic alteration zones, Advanced Argílitica, Filítica and propylitic that together with the presence of mineral thermal indices such as corundum, tridymite and sillimanite enabled manufacture a genetic model for the eastern edge of LSIC. This model showed that the area that includes the Dourada Mines, Cerro Rico and Volta Grande possibly fall into tank Porphyry type, and the Dourada Mine by the presence of a potassic alteration zone is a zone of "raíz", causing that this area may have great interest for economic association with the occurrence of gold and other ore metals.