LA-ICP-MS zircon U-Pb ages of the Shijiao-Huangshan intrusive rocks in Zhuji area,Zhejiang Province:implications for the petrogenesis of the ultramafic orbicular rocks

LA-ICP-MS zircon U-Pb dating work was carried out for the Shijiao-Huangshan intrusive rocks from Zhuji area of Zhejiang Province,which is also tectonically adjacent to the Jiangshan-Shaoxing fault of eastern Jiangnan orogen.The dating results indicate that the Shijiao amphibole pyroxenite and Huangshan quartz diorites were crystallized at 844±3 Ma and 818±6 Ma,respectively,suggesting that they,including the Shijiao orbicular perknites,were probably formed in different periods.Combined with other new available dating results,the authors hold that the Neoproterozoic diorites along the Jiangshan-Shaoxing fault might have been formed during the span of ca.930-810 Ma.Further studies of the petrology and petrogenesis of the ultramafic rocks and diorites will shed light on the Neoproterozoic amalgamation processes between the Yangtze and Cathaysia blocks.