CARBONATES AND SOURCES OF FLUIDS IN ORES AND METASOMATITES OF THE ERMAKOVKA FLUORITE-BERTRANDITE-PHENACITE DEPOSIT (western Transbaikalia)
G.S. Ripp, I.A. Izbrodin, A.G. Doroshkevich, M.O. Rampilov, E.I. Lastochkin, V.F. Posokhov
Geological Institute, Siberian Branch of the Russian Academy of Sciences, ul. Sak'yanovoi 6a, Ulan-Ude, 670047, Russia
Keywords: F-Be ores, skarns, oxygen and hydrogen isotope compositions, western Transbaikalia
Abstract
We present results of isotope-geochemical study of the Ermakovka F-Be deposit, including data on the oxygen and carbon isotope compositions in dolomite and calcite marbles and in carbonates accompanying skarns, of early and late stages of ore formation and of post-ore parageneses. To elucidate the sources of fluids participated in the ore formation, we calculated the oxygen isotope composition in water and the hydrogen isotope composition in hydroxyl-containing minerals. Phlogopite in marbleized dolomites, vesuvianite and amphibole in skarns, eudidimite and bertrandite in ore parageneses, and bavenite formed during post-ore processes are analyzed. Most of the ore-stage minerals are depleted in heavy oxygen. Their δ18O values are lower than 5-6‰ (SMOW). Oxygen in carbonate minerals of the initial stage (dolomite and bastnaesite) is heavier (1.3-4.9‰) than that in calcite (+2.0 to -3.7‰). The δ18O values of water in equilibrium both with carbonate and with silicate minerals (-4 to -14‰) suggest the contribution of meteoric water to the mineral formation. A magmatic fluid (δ18O from +6 to +9‰) participated in the skarn formation at the initial stage, and a meteoric fluid, (δ18O from -1 to -9‰) at the final stage. A meteoric source is confirmed by the depleted hydrogen isotope composition in combined water in minerals (δD from -119 to -192‰).
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