Lead isotope ore provinces of eastern Transbaikalia and their relationships to regional structures: Results of high-precision MC-ICP-MS study of Pb isotopes

Lead isotopic composition was studied at 12 deposits of eastern Transbaikalia, which differ in type and scale of mineralization. The high-precision Pb-Pb data obtained using multicollector inductively coupled plasma mass-spectrometry allowed us to outline two large lead isotope provinces spatially coinciding with the West Stanovoi and Argun tectonic blocks. The difference in Pb isotopic composition of deposits in these provinces indicates that regional ore sources contrasting in geochemistry took part in ore formation. In the deposits at the southern margin of the West Stanovoi Block with predominance of Au and Mo mineralization, the lead role is played by a mixed mantle-type source, whereas the source of lead in the deposits of the Argun Block has U-Th-Pb isotopic characteristics inherent to a continental crust of orogenic type.