This paper reports on the comparative study of fluids trapped in inclusions in gold-bearing and barren quartz veins at the Sovetskoye gold deposit, Yeniseisky ridge, Siberia, Russia. The host rocks are greenschist facies metasedimentary rocks of Upper Proterozoic age. Within the deposit, some veins contain 10 to 25 ppm of Au (gold-bearing veins); others contain less than 1 ppm of Au (barren veins). Fluid inclusions trapped in barren veins are predominantly low-salinity-H2O (4.0-8.0 mass % NaCl equiv.) with variable contents of dissolved CO2 (12.5 mol %), CH4 (1.3 mol %), and N2 (1.7 mol %). Homogenization temperatures vary from 200° to 410°C, and the calculated pressures of entrapment are 1.5 kbars. Inclusion fluids trapped in the host schists are predominantly aqueous (97.6-99.3 mol % H2O), with CO2 contents below 2.4 mol percent. The fluids trapped in ore-bearing quartz inclusions are different. Inclusions show higher homogenization temperatures (up to 630°C) and salinity (up to 20-25 mass % NaCl equiv). Calculated pressures range from 0.7 to 2.0 kbars. Bulk gas chromatographic data of fluids extracted from native gold have contents of CO2 that range from 29.3 to 62.0 mol percent, N2 from 2.7 to 13.2 mol percent, and CH4 from 0.0 to 2.8 mol percent. In gold-bearing quartz the contents of CO2 range from 18.0 to 41.0 mol percent, N2 from 0.1 to 0.2 mol percent, and CH4 from 0.3 to 3.0 mol percent. Raman spectroscopic data of fluid from gold-bearing quartz revealed CO2 contents of individual inclusions as high as 98.2 mol percent, N2 up to 66.4 mol percent, and CH4 up to 88.7 mol percent. Fluids of the country-rock schists which host gold-bearing quartz veins are also enriched in CO2 (up to 49.5 mol %). The host rocks for both barren and gold-bearing quartz veins show consistent REE patterns characterized by a negative Eu anomaly. Fluids from barren quartz veins show similar REE patterns although with a less conspicuous negative Eu anomaly, whereas fluids from gold-b
Geochemical and isotopic properties of fluids from gold-bearing and barren quartz veins of the Sovetskoye Gold Deposit (Siberia, Russia).
Dallai L
2010
Abstract
This paper reports on the comparative study of fluids trapped in inclusions in gold-bearing and barren quartz veins at the Sovetskoye gold deposit, Yeniseisky ridge, Siberia, Russia. The host rocks are greenschist facies metasedimentary rocks of Upper Proterozoic age. Within the deposit, some veins contain 10 to 25 ppm of Au (gold-bearing veins); others contain less than 1 ppm of Au (barren veins). Fluid inclusions trapped in barren veins are predominantly low-salinity-H2O (4.0-8.0 mass % NaCl equiv.) with variable contents of dissolved CO2 (12.5 mol %), CH4 (1.3 mol %), and N2 (1.7 mol %). Homogenization temperatures vary from 200° to 410°C, and the calculated pressures of entrapment are 1.5 kbars. Inclusion fluids trapped in the host schists are predominantly aqueous (97.6-99.3 mol % H2O), with CO2 contents below 2.4 mol percent. The fluids trapped in ore-bearing quartz inclusions are different. Inclusions show higher homogenization temperatures (up to 630°C) and salinity (up to 20-25 mass % NaCl equiv). Calculated pressures range from 0.7 to 2.0 kbars. Bulk gas chromatographic data of fluids extracted from native gold have contents of CO2 that range from 29.3 to 62.0 mol percent, N2 from 2.7 to 13.2 mol percent, and CH4 from 0.0 to 2.8 mol percent. In gold-bearing quartz the contents of CO2 range from 18.0 to 41.0 mol percent, N2 from 0.1 to 0.2 mol percent, and CH4 from 0.3 to 3.0 mol percent. Raman spectroscopic data of fluid from gold-bearing quartz revealed CO2 contents of individual inclusions as high as 98.2 mol percent, N2 up to 66.4 mol percent, and CH4 up to 88.7 mol percent. Fluids of the country-rock schists which host gold-bearing quartz veins are also enriched in CO2 (up to 49.5 mol %). The host rocks for both barren and gold-bearing quartz veins show consistent REE patterns characterized by a negative Eu anomaly. Fluids from barren quartz veins show similar REE patterns although with a less conspicuous negative Eu anomaly, whereas fluids from gold-bI documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
