Research On The Genesis And Prospecting Direction Of Jilongshan Au-Cu Deposit In Yangxin County Of Hubei Province

Jilongshan Au-Cu deposit is a typical skarn deposit in Hubei province, which islocated in the Jiurui ore-clustered district of the Middle-Lower Yangtze RiverFe-Cu-Au metallogenic belt. But little study has been made in this deposit before.We have tried to make systematic research on this deposit from aspects of geneticmineralogy and geochemistry using the theories and techniques of trace elementgeochemistry, isotope geochemistry, fluid inclusions geochemistry, isotopechronology, etc.Granodiorite porphyry and quartz diorite porphyrite are the main rock ofJilongshan rock mass, which belongs to I-type granite series with characteristics ofhigh-K calc-alkalic and peraluminous. Jilongshan rock mass are the main source ofore-forming materials and fluid. Jilongshan rock mass, carbonate strata andstructures together form three major ore-controlling factors of Jilongshan Au-Cudeposit. Carbonate wall rocks are mainly composed by limestone or dolomiticlimestone of Daye Formation from Group 4 to 6 of Lower Triassic. Structuresare mainly composed by Zhulintang reverse duplex syncline belonging to nearlyEW-trending fold belt, the NW-trending pressure-shear fracture, the NWW-trendingtensional or tensional shear faults, and their composite structure parts.The metallogenesis of Jilongshan deposit can be divided into two majormetallogenic epochs of Skarn and Quartz-sulfide. Skarn epoch is made up of dryskarn stage and wet skarn stage formed in high–temperature conditions.Quartz-sulfide epoch is made up of quartz-molybdenite stage, gold-copper sulfidestage, gold-lead and zinc sulfide stage, gold-arsenic sulfide stage and carbonate stage,which are formed in middle - low temperature conditions.The study of trace elements, rare earth elements as well as sulfur andlead isotope shows that the ore-forming materials derive mainly fromthe ore-forming rock and little from the strata. The study of hydrogen, oxygen,nitrogen, helium, argon isotopes shows that the ore-forming fluids mainly derivefrom the magma, but which were significantly affected by crustal fluids and meteoric water in the late mineralization. The study of fluid inclusions shows that theore-forming fluids had the characteristics of weak reducing and the reducinggradually increased with the evolution of fluids.The wall rock alteration is extensive, and of which skarn alteration has theclosest relationship with mineralization. The metal mineralization in the contactzone shows an evolutionary trend from high temperature to low temperature, whichform a mineralization zoning of Cu-Mo~Cu-Au~Au-Cu~Au-Pb-Zn.Jilongshan orebodies show a cyclic variation from upper to deep level, which is (Au-Cu~Au~Cu-Mo)→(Cu-Au~Cu)→(Cu~Cu-Au)→(Au-Cu~Cu-Mo). The Zonation indicatesthat the Au-Cu ore body may continue to appear in deep level of Jilongshan Au-Cudeposit.Zircon U-Pb dating shows that the diagenetic age of Jilongshan rock mass is151.75±0.70 Ma, and molybdenite Re-Os dating shows that the metallogenic age is150.79±0.82 Ma. The diagenesis and mineralization of the deposit are almostsynchronous.Based on above research results, we improved the metallogenic model,summarize the prospecting criteria and give advice on prospecting direction in thispaper.