Metallogenetic Series And Prospecting Assessment In Lesser Xing’an Range-Zhangguangcai Range Metallogenic Belt Of Heilongjiang Province

The Lasser Xing’an Range-Zhangguangcai Range metallogenic belt is composite orogen belt superposed by Paleoasia oceanic tectonic domain and circle Pacific tectonic domian, lying in the intersection area among east section of Central Asian-Mongolian-Hinggan orogenic belt and Siberian,North China blocks. In the two tectonic domain transformation period, large-scale mineralization and diagenesis occured.On the basis of study magmatic petrology and diagenesis mineralization chronology, to the division of metallogenic series of ore deposits, to the study of geology and geochemistry and fluid inclusion, establishing the model of metallogenic dynamics.(1) The metallogenic series of intermediate-acid granitoids polymetallic deposit in early Yanshan Period(I):including skarn type, porohyry type, hydrothermal vein type, compound deposit. The zircon U-Pb age of195-175Ma and molybdenite Re-Os age of180～175Ma was obtained from granite, indicating that the suite formed in the Late Triassic-Early Jurassic Epoch, diagenesis in Late Triassic and mineralization in Late Triassic, ended in172Ma. Granitoids related to the mineralization belong to calc-alkaline series to high kalium calc alkalic series, charactered by I and A type, diagenesis and mineralization occurred after orogenic period and lithospheric extension and thinning. Materials source of diagenesis and mineralization comes from crust and the ore-forming fluid is meanly from and magmatic and atmosphere precipitation. The metallogenic temperature of oxide is380～500℃, sulfide250～360℃, depth of2～3km. Fluid inclusion studies that different fluid mixing and boiling during the metallogenic process.(2) In the late Yanshanian, related with volcanism, Au-Ag-Pb-Zn deposit series (II):The epithermal gold deposit. Rhyolite zircon U-Pb age of110Ma and sillite hornblende Ar-Ar age of100Ma, was obtained, indicating that the formed in the120～100Ma, diagenesis in120Ma and gold mineralization in110～105Ma, ended in sillite and releated lead-zinc mine. Diagenesis and mineralization of the metallogenetic series occurred in tectonic environment of the subduction of pacific plate lead to crust thickening, material source of diagenesis and mineralization is from the lower crust or upper mantle and ore-forming fluid is derived meanly from atmospheric precipitation and partly magmatic. The ore-forming temperature of the epithermal gold deposit is150～280℃. The ore forming fluids had very low salinity, depth of1.2～2.0km.Summarizing metallogenic regularities, establishing prediction modles, adopting comprehensive information metallogenic prediction method, this paper evaluates ore-forming prospects. The metallogenetic series (Ⅰ) distributed in granite belt of the early Mesozoic, the character of metallogenic symbiosis stage, homology, superpositon and transitivity. Metallogenic stages of skarn type iron tungsten tin occurred earlier, and late porphyry molybdenum deposit and hydrothermal type copper lead and zinc deposit. Porphyry molybdenum deposit, skarn type polymetallic deposits and hydrothermal type copper lead and zinc deposit come from internal zone, contact zone outer contact zones respectively. The metallogenetic series (Ⅱ) distributed in active belt in the late Mesozoic, controlled by fissure-central volcanic types. The paper outlines8metallogenic prospects and proposes direction of further exploration.