Geological characteristics and genesis of the Hekoulinchang tin-polymetallic deposit in Baoqing, Heilongjiang Province
The Hekoulinchang porphyry tin-polymetallic deposit is located in the Wandashan epicontinental accretional terrane,which is a part of China's eastern margin in the Circum-Pacific Metallogenic Belt.On the basis of previous geological and geochemical studies,this paper first reports ICP-MS zircon U-Pb age of 121.4 ± 0.5 Ma for granite porphyry,which indicates that the deposit was formed in late period of Late Cretaceous.Geochemical analysis indicates that rock samples of the Hekoulinchang granite porphyry show high content of SiO2(61.21％ ～73.81％),K2O (3.74％ ～4.61％) and lower content of Na2O (0.06％ ～0.20％).The Hekoulinchang granite porphyry can be classified as high K calc-alkaline A-type granites.The magmatism in this area occurred in an extensional tectonic setting,and the diagrams of Yb-(La/Yb)N and Rb-K/Rb show that mantle-derived materials played an important role in the generation of the magma.The lithospheric thinning in eastern China took place in the Late Mesozoic,and maximally thinned in Early Cretaceous (130～120 Ma).It is thus considered that the lithospheric thinning was related to the subduction of paleo-Pacific plate in the east,which resulted in the lithospheric thickening and subsequent delamination,leading therefore to the direct contact between the asthenospheric mantle and the crust.The heating from the asthenosphere on the crust subsequently caused the W-Sn ore-related deep-seated magma to trigger the fluids to circulate and leach out ore-forming elements from sedimentary rocks underlain by the wall rock of the deposit,thus forming the Hekoulinchang porphyry tin-polymetallic deposit in endo-and exo-contact zone between the strata and the intrusion.The Hekoulinchang porphyry tin-polymetallic deposit is the first case in Wandashan epicontinental accretional belt which has an affinity with Sikhote-Alin tin province,and its discovery offers a new thought of tin exploration in Northeast China.
porphyry tin-polymetallic depositore genesisSikhote-Alin tin provinceWandashanHekoulinchang
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