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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