Accurate zircon U-Pb dating of Early Yanshanian molybdenum-tungsten mother rocks in Xingjiashan area of Jiaodong Peninsula and its significance

Abstract: This paper presents the magma zircon LA-ICP-MS U-Pb isotopic dating results of the Xingfushan granites. The weighted mean age (157±2 Ma) was obtained from 15 test points on the oscillatory zones. Inferred from the same test positions and the coincident dating result with Re-Os isotopic age of molybdenite from the Xingjiashan molybdenum-tungsten deposit, the granites here crystallized in this period. The other two captured zircons from the same assay at the separate age of (2798±13) Ma and (2250±18) Ma imply possible existence of Neoarchean-Paleoproterozoic intrusive basement, whereas No. 7 point at the age of (230±6) Ma implies possible Triassic magmatic activity. The consistent features of the tectono-magmatic activities in eastern China since Mesozoic (190?110 Ma) produced the corresponding varied metallogenesis here. The common granites of Linglong and Xingfushan units in Jiaodong Peninsular share almost the same geochemical features and ages, suggesting that this area might have hosted large-scale molybdenum polymetallic metallogenesis. Under heavy regional denudation by late tectonic uplifting, the left Xingjiashan molybdenum-tungsten deposit typically shows less denudation in Qixia-Fushan area since Mesozoic and better metallogenic condition, so more importance should be attached to the prospecting for hypabyssal deposits (porphyry-skarn, Carlin and organic hypabyssal deposits) here.