Re-Os isotopic age of molybdeinte from the Shimensi tungsten polymetallic deposit in northern Jiangxi province and its geological implications

The Shimensi tungsten polymetallic deposit lies in the Mesozoic Cu-Mo-Au-Ag-Pb-Zn ore belt of Jiangnan block within Lower Yangtze metallogenic province. The Shimensi W deposit is related with Yanshanian granites, and is the northern ore block of the largest Dahutang W deposit which was recently prospected in China. In this study, six molybdenite samples of the ore-forming stage were collected for Re-Os isotope dating determine the chronology of the ore deposit. The analytical results yield an isochron age of 149.6Ma±1.2Ma (n=6, MSWD=1.6) and weighted average model age of 150.4Ma±1.4Ma (n=6, MSWD=1.3). This age indicates that the mineralization took place during Late Jurassic. Moreover, the Re contents of molybdenite samples is 334.4×10-9~22600×10-9, which indicate that the ore-forming materials are likely to come from the crust-or crust-mantle-derived ones. In combination with metallogenic geological background, we infer that the Shimensi W deposit is associated with the subduction of the Paleo-Pacific ocean plate beneath the Eurasian continent. It is proposed that the ore-forming materials were extracted by alkali metasomatism between the magma and the wall rock and then concentrated in the favourable areas.