The Gurupi Belt is a Neoproterozoic orogen of NNW-SSE orientation developed at the southsouthwest margin of the San Luis Cratonic Fragment, of Paleoproterozoic age. The belt is composed of metavolcano-sedimentary sequences, gneisses and several generations of plutonic rocks representing reworked fragments of the cratonic border and portions of the basement on which the Gurupi Belt developed in the neoproterozoic. The Chega Tudo Formation, the main host for gold mineralization in the Gurupi belt, is a metavolcanosedimentary sequence that is characterized by being a narrow and elongated band in the NWSE direction. The rocks of this unit comprise an alternation metavolcanic, metavolcanoclastic and metassedimentary varieties, which are invariably schistose and/or mylonitic, and locally folded. Enche Concha is one of the gold prospects that occur in the Chega Tudo Formation and a better definition of it’s geological characteristics and genetic aspects is presented here. The host rocks are phyllites, dacites and breccia zones. The phyllites are rocks of blackish greenish colors, consisting essentially of quartz, micas and carbonate. Dacites are whitish gray-colored rocks consisting primarily of plagioclase and quartz. The breccias are fragmented, non-cohesive rocks, with no obvious tectonic fabric consisting of fragments of quartz and carbonate veins, and of fragments of phyllites. The types of hydrothermal alteration defined in the target was as follows: (i) silicification, (ii) sericitization, (iii) carbonatization and (iv) sulfidation, along with precipitation of gold. The sulfides are mainly pyrite, along with sphalerite and chalcopyrite. Gold occurs as inclusions in the three sulfide minerals, with concentrations of up to 6%, as identified by analyzes of Scanning Eletron Microscopy. The fluid inclusion were classified as type 1 (biphasic aqueous-carbonic - H2Oliquid - CO2liquid and H2Oliquid - CO2vapor) and type 2 (aqueous, single-phase and twophase H2Oliquid and H2Oliquid - CO2vapor). Type 1 inclusions provided CO2 melting temperature values (TfCO2) between -56.6 and -57.3ºC, which allows inferring that the main volatile component of the carbonic phase of these inclusions is CO2. The CO2 homogenization temperature values (ThCO2) are between 12 and 25.5ºC (global density between 0.7 and 1 g/cm3, CO2 density between 0.2 and 1 g/cm3). As for the melting temperature of the clathrate (TfClat), results were obtained between 6 and 8.4ºC, which gives salinities between 4.4 and 5.5 wt% NaCl equiv. The total homogenization temperature (Tht) of these inclusions varied between 251 and 369º, with homogenization occurring both for the liquid and vapor phases. Type 2 inclusions presented values of melting temperature of the ice (Tfg) between -0.1 and - 4.1 ºC, and Tht values between 167 and 342ºC,with homogenization occurring for the liquid phase. These inclusions presented low values of salinity, between 0.18 and 6.3 wt.% in NaCl equiv. weight, and global density between 0.7 and 0.9 g/cm3. The coexistence of aqueous and aqueous-carbonic inclusions over the same range of Tht, in addition to inclusions that homogenized for the liquid phase and for the vapor phase, suggest fluid immiscibility. The isotopic composition of oxygen and carbon was determined hydrothermal quartz and calcite, whereas hydrogen isotopic compositions were obtained from inclusion fluids. The values of δ18O in quartz vary from +15.25 to +17.74‰. The values of δ18O and δ13C in calcite range, respectively, from +14.32 and +16.24‰ and from -9.83 to -15.12‰. Values of δ13C bellow - 10‰ suggest contribution of organic C from the host rocks. Values of δD extracted from the inclusion fluids gave results of -25 and -28‰. The isotopic results suggest metamorphic composition for the mineralizing fluids at Enche Concha. The strontium isotopic composition was determined in hydrothermal calcite. The analyzed samples have low, little radiogenic 87Sr/86Sr ratios, ranging from 0.702699 and 0.705141. These results indicate origin of deep sources of the lower crust or mantle and should not have contribution of the regional rocks of the Gurupi Belt. As a whole, the integrated data indicate that the Enche Concha shares characteristics whit those of orogenic gold deposits, which are widespread in the Gurupi belt.
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