Petrogenic and Metallogenic Geochronology, Geochemical Characteristics and Its Geological Implications of Cuizhong Fe Polymetallic Deposit, Heilongjiang Province

Two main types of igneous rocks are distributed in the Cuizhong Fe polymetallic deposit, including the coarse-grained alkali-feldspar granite in the shallow part and the fine-grained alkali-feldspar granite at depth, whose relationships with ore mineralization have long been debated. Whole rock geochemistry, zircon U-Pb geochronology and Hf isotopic analyses are carried out for these two types of granitoids. Pb isotopic analyses are performed on both the granitoids and the sulfides. The coarse-grained alkali-feldspar granite and fine-grained alkali-feldspar granite yield weighted mean 206Pb/238U age of 503±2.9 Ma and 201±6.4 Ma respectively, indicating that they were formed during middle Caledonian and late Indosinian-early Yanshanian respectively.The Re-Os model age of molybdenite is 202±2.9 Ma, which is consistent with the crystallization age of the fine-grained alkali-feldspar granite.Zircons in the coarse-grained alkali-feldspar granite display ΕHf(t) values of -8.31 to 0.57, indicating that it was derived from partial melting of Mesoproterozoic crustal rocks. Zircon crystals in the fine-grained alkali-feldspar granite have ΕHf(t) values of 2.84 to 4.78, indicating that it was generated by reworking of newly-growing juvenile crustal material which was originated from depleted mantle. In combination with the metallogenic and petrologic ages, trend surface analysis of ore-forming elements, and the comparison of Pb isotopes, we suggest that the mineralization in the Cuizhong Fe polymetallic deposit is genetically associated with the fine-grained alkali-feldspar granite. The polymetallic mineralization was generated in a compressional tectonic setting in response to the subduction of the Jiamusi Block towards the Songnen Block. © 2020, Editorial Department of Earth Science. All right reserved.