Ore genesis and vertical variations of ore-forming fluids in the Day-ingezhuang gold deposit,Jiaodong Peninsula:Constraints from fluid inclu-sions,ore forming elements,and H-O-S-Pb isotopes
Ore genesis and vertical variations of ore-forming fluids in the Day-ingezhuang gold deposit,Jiaodong Peninsula:Constraints from fluid inclu-sions,ore forming elements,and H-O-S-Pb isotopes
[Objective]The Dayingezhuang gold deposit in the middle of the Zhaoping metallogenic belt represents a typical altered-rock type deposit with a giant Au reserve of 283 tons on the Jiaodong Peninsula.The genetic type of the deposit is still controversial.[Methods]Based on detailed field observations,ore genesis and variations in ore-forming fluids from different depths were investigated in this study.[Results]Fluid inclusion studies show that the ore-forming fluids formed an H2O-CO2-NaC l±CH 4 system with moderate temperature,low salinity,and moder-ate-low density.Furthermore,the temperatures and salinities decrease gradually from the early to late mineraliza-tion stages(Ⅰ-Ⅳ),but the opposite occurs at densities.Hydrogen and O isotopic compositions show that the ore fluids were dominated by magmatic water in the early stage,with subordinate meteoric water input during the late stages.Fluid boiling occurred possibly during the main mineralization stages.Sulfur and Pb isotopes of pyrite indi-cate that the ore-forming materials were derived from deep crust-mantle mixed magma.Overall,the mineralization process and tectonic setting are similar to those of the other Jiaodong gold deposits in a craton-destruction environ-ment.[Conclusion]Comprehensive comparisons of ore fluids,Au and Ag contents,and gold fineness between shallow and deep ores show that ore fluids and mineralization intensity are consistent throughout the deposit.Gold precipitation has a broad and stable environment,indicating the great potential for mineral exploration in deep spaces.
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