Metal-bearing fluids and the age of the Panimba gold deposit (Yenisei Ridge, Russia)

Abstract

The Panimba gold deposit lies in the rocks of the epidote-amphibolite metamorphism facies and is confined to the exocontact zone of the Chirimba granitoid massif. Fluid inclusions in quartz and sulfides of two sites of the deposit, Mikhailovka and Zolotoi Brook, were studied by thermobarogeochemistry, gas chromatography, and chromatography-mass spectrometry. We have established that gold-quartz veins of the deposit were formed by metal-bearing Mg-Na-Cl-containing water-carbon dioxide-hydrocarbon fluids with salinity of 8-23 wt.% NaCl eq. at temperatures of 180 to 410 °C and pressures of 0.2 to 3.3 kbar. Hydrocarbons and nitrogen- and sulfur-containing compounds of the fluids can transport gold and might be positive indicators of the gold presence in quartz veins. Fluids with salinity of > 30-40 wt.% and sulfur isotope values (δ34S) of 0.9 to 6.7‰ of sulfides are the result of the action of postmagmatic solutions of the nearby Chirimba granitoid massif. The age of hydrothermal gold-sulfide mineralization of the Panimba deposit is within 817.2 ± 5.3-744 ± 17 Ma and falls in the time interval of crystallization of the Chirimba intrusion, 868.9 ± 6.5 to 721.4 ± 1.6 Ma, but it is considerably younger than the age of the regional metamorphism (996.0 ± 32-889.0 ± 26 Ma).