Estudos de inclusões fluidas em veios de quartzo associados ao Granito Nhandu no Depósito de Ouro Trairão - Província Aurífera Alta Floresta MT

Abstract

The research focuses on field data, geochemical and hydrothermal host rock with a focus aimed at microthermometric studies of fluid inclusions in quartz veins in granite Nhandu central part of the Alta Floresta gold province. The Target Trairão shows evidence of intense sericitic alteration (sericite fine) completely obliterating the texture of the primary rocks. The studies allowed the recognition of the following stages of hydrothermal alteration and paragenetic evolution: pervasive silicification, pervasive muscovite fine, coarse muscovite pervasive; silicification fissure (late veins and veinlets of quartz). Based on the petrographic characteristics of fluid inclusions were classified into types such as single-phase liquid comprising type I, type II single-phase vapor, biphasic type III (L + V), Type IV saturated three-phase (L + V + S) and three-phase type IV aqueous-carbonic (LH2O LCO2 + + VCO2), rare. The fluid inclusions placed on the type III and IV, a primary, occurring in all samples, microthermometric studies were carried out in a platinum cooling / heating Chaixmec, apparatus Likan THMS/600, from -180 ° C to 600 ° C , respectively, for obtaining measurements of melting and homogenization of the phases. Platinum is coupled to a model microscrospio petrographic JENA Phol, which allows observation of the blade shaft bipolidas samples in all steps of the assay. From data microthermometric identified fluid inclusions belonging to the systems: a) - H2O + NaCl + CaCl2 H2O-NaCl (Type III - biphasic) distributed in groups of low salinity, intermediate and high salinities with (Thtot (v)) between 50 ° C to 180 ° C and fashion of 80 ° C to 90 ° C, b) - H 2 O + NaCl + CaCl 2, H 2 O, MgCl 2 (Type IV-three-phase saturated) showing a group of high salinity (Thtot (s)))) 120 240 ° C and modal frequency between 170 ° C to 240 ° C. This distribution can be interpreted as a mixture of fluids of different compositions, which represent inclusions of low salinity meteoric fluid inclusions intermediate as a mixture of meteoric and magmatic fluids, while the high salinity is defined as magmatic origin with decreasing temperature during its way ascension.