Geological and Geochemical Features of Hushan Gold Deposit in Qixia, Shandong Province
Journal of Jilin University(Earth Science Edition). 2020, 50 (5):
Hushan gold deposit is the largest gold deposit in the southern part of Douya fault. In order to reveal its genesis, based on the geological work of the deposit, the study of the surrounding rock element geochemistry and fluid inclusions of the ore body was carried out. The results show that a large-scale of hydrothermal alteration is developed along the NE-trending faults in Hushan Au deposit,with obvious surface hydrothemal alteration, low Au mineralization, and poor alteration zoning. The borehole logs show that the hydrothermal alteration along the Au ore-bodies is symmetrically developed, displaying sericite-quartz alteration and pyrite-sericite-quartz alteration with the increase of distance from ore-body. The ore-bodies are mainly hosted in the alteraltion zone of pyrite-sericite-quartz alteration at the footwall of Douya fault. The mass-balance calculation shows that the major and trace elements behaved complicatedly during fluid-rock interaction. In the stage of sericite-quartz alteration, Linglong biotite granite experienced the loss of SiO2, Al2O3, FeO,MnO, Na2O, K2O, P2O5, and enrichment of REEs and MgO, CaO, Fe2O3, Au, Ag, Cu, Pb, V, Cr, Co and Ni; in the stage of pyrite-sericite-quartz alteration, FeO, Fe2O3, MnO, MgO, CaO, Au, Ag, Cu, V, Cr, Co, and Ni enterred in the sericite- quartz altered granite, while SiO2, Al2O3, Na2O, K2O and P2O5 moved out. The petrographic, microthermometric, and laser Raman microspectroscopic analyses on the fluid inclusions show that the fluid inclusions are mainly two-phrase aqueous fluid inclusions and CO2-bearing three phase inclusions, which are low salinity (5.33%-13.29%) and medium temperature (260 to 300 ℃) CO2-NaCl-H2O system. The ore fluid experienced fluid immiscibility during the ore-forming process. We believe that the deposit should belong to mesothermal altered rock type Au deposit controlled by Douya fault, which is similar to Jiaojia Au deposit in Jiaodong area.
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