GEOLOGIC STRUCTURE OF THE MUKODEK GOLD FIELD (northern Transbaikalia) AND SOURCES OF MAtter (Pb-Pb and Sm-Nd data)
V.A. Vanin1, A.V. Chugaev2, E.I. Demonterova1, D.P. Gladkochub1, A.M. Mazukabzov1
1Institute of the Earth’s Crust, Siberina Branch of the Russian Academy of Sciences, ul. Lermontova 128, Irkutsk, 664033, Russia
2Institute of Geology of Ore Deposits, Petrography, Mineralogy and Geochemistry, Russian Academy of Sciences, Staromonetnyi per. 35, Moscow, Zh-17, 119017, Russia
Keywords: Gold mineralization, Mukodek gold field, gold-bearing metasomatites, Sm-Nd and Pb-Pb isotope data, northern Transbaikalia, Baikal-Muya belt
Abstract
The Mukodek gold field is located in the Yana zone of the Baikal-Muya fold belt (northern Transbaikalia). Its orebodies are gold-bearing metasomatites confined to the fault of NE strike. It is shown that pre-ore faults played a crucial role in the spatial localization of the orebodies, as they favored the concentration of ore-bearing fluids. Results of geological and structural studies, along with available geochronological data (40Ar-39Ar dates for micas in gold-bearing pyrite), testify to ore-forming processes in the ore field during two Late Paleozoic stages. Early gold-bearing metasomatites of sericite-chlorite-albite-ankerite-quartz composition formed at 320 Ma, and late gold-bearing vein metasomatites of ankerite(calcite)-quartz composition originated at 285 Ma. A Pb-Pb isotope study of gold mineralization has shown that ore lead was supplied into the mineral-forming system mainly from a mantle source, most likely, regional Neoproterozoic igneous rocks. According to Sm-Nd isotope data, these rocks formed with the participation of a material of mantle genesis.
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