The Darasun gold deposit,Eastern Transbaikal region: Chemical composition,REE patterns,and stable carbon and oxygen isotopes of carbonates from ore veins |
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Authors: | V Yu Prokof’ev N S Bortnikov V A Kovalenker S F Vinokurov L D Zorina A D Chernova S G Kryazhev A N Krasnov S A Gorbacheva |
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Institution: | 1.Institute of Geology of Ore Deposits, Petrography, Mineralogy, and Geochemistry,Russian Academy of Sciences,Moscow,Russia;2.Vinogradov Institute of Geochemistry, Siberian Branch,Russian Academy of Sciences,Irkutsk,Russia;3.Moscow State University,Moscow,Russia;4.Central Research Institute of Geological Exploration for Base and Precious Metals,Moscow,Russia |
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Abstract: | The chemistry, REE patterns, and carbon and oxygen isotopic compositions of carbonates from ore veins of the Darasun deposit
are discussed. In addition to the earlier described siderite, calcite, and carbonates of the dolomite-ankerite series, kutnahorite
is identified. The total REE content in Fe-Mg carbonates of the dolomite-ankerite series (2.8–73 ppm) is much lower than in
later calcite (18–390 ppm). δ13C of Fe-Mg carbonates and calcite varies from +1.1 to −6.7‰ and from −0.9 to −4.9‰, respectively. δ18O of Fe-Mg carbonates and calcite varies from +17.6 to 3.6‰ and from +15.7 to −0.5‰, respectively. The REE sum and carbon
and oxygen isotopic compositions reveal zonal distribution relative to the central granodiorite porphyry stock. The correlation
between the carbon and oxygen isotopic compositions and REE sum reflects variations in the physicochemical formation conditions
and composition of ore-forming fluid. The isotopic composition of fluid is calculated, and possible sources of its components
are considered. Earlier established evidence for a magmatic source of ore-forming fluid and participation of meteoric water
in ore formation is confirmed. Geochemical evidence for interaction of ore-forming fluid with host rocks is furnished. The
relationships between the REE sum, on the one hand, and carbon and oxygen isotopic compositions of hydrothermal ore-forming
fluid, on the other, are established. |
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