Origin of carbonatites of eastern taimyr deduced from an isotopic and geochemical study of zircons |
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| Authors: | V F Proskurnin O V Petrov E A Bagdasarov M I Rozinov E V Tolmacheva A N Larionov I V Bil’skaya A V Gavrish I N Mozoleva B S Petrushkov |
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| Institution: | 1.Russian Geological Research Institute,St. Petersburg,Russia |
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| Abstract: | Injection carbonatites of volcanic-plutonic origin with Au-bearing base-metal sulfide mineralization were established in 2006–2007 along the southern slope of the Byrranga Range in the Russian continental sector of the Arctic. According to thermobarogeochemical data, carbonatites were formed at a temperature not lower than 380–410°C from boiling gas-liquid H2O-CO2-salt fluids under decompression. The REE concentrations and patterns of sedimentary and magmatic carbonates are sharply distinct. Carbonatites are enriched in REE as compared to carbonates from limestone and are characterized by an REE distribution close to MORB. The geochronological and isotopic geochemical study of zircons has shown that carbonatite bodies (lavas?) were formed 238–219 Ma ago (Middle-Late Triassic); zircon crystallized at a high temperature. Detrital zircons from the Lower Carboniferous crinoid limestone are not younger than 594 Ma. The absolute predominance of Precambrian zircons, which are variable in age, indicates that they were captured from the crust, when carbonatitic magma ascended from subcrustal depths. |
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