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.