Metallogenic Characteristics in the Abrupt Change Zone of Tectono-physicochemical Parameters in the Dayin'gezhuang Gold Orefield,Jiaodong Peninsula
In the study of orefields with endogenetic metallogenesis,tectono-deformation lithofacies can not only reflect the characteristics of tectonic stress field during the formation of the deposit but also reveal their geoche-mical features and physicochemical conditions.The Jiaodong gold-concentration area has a unique characteristic among global gold deposits,with its scale of gold reserves ranking third in the world.It is noteworthy that the Dayin'gezhuang orefield is one of the super-large gold fields in this region.Based on previous research on tec-tonic alteration lithofacies,it is particularly necessary to clarify the relationship among the tectono-physicoche-mistry parameters and to delve into how tectonic processes can drive gold mineralization by influencing the phys-icochemical conditions of ore formation.This study selected tectono-physicochemical parameters representing the composition,temperature and pressure,properties of ore-forming fluids,and conditions of ore-forming structures in order to analyze tectonic diagenesis and mineralization.The results show that the tectono-physico-chemistry conditions represented by fluid inclusion components such as CO2/H2O,pH,oxygen fugacity(lgfO2),tectonic additional hydrostatic pressure(Ps),homogenization temperature of fluid inclusion,mini-mum pressure of fluid inclusion(Pmin),and other parameters have a significant influence on ore formation.The effect of the ore-forming fluid's composition,properties,temperature and pressure conditions,and the tec-tonic process represented by CO2/H2O,lgfO2,Ps,homogenization temperature,and Pmin are positively corre-lated,while the effect of pH shows a negative correlation;additionally,in the pyrite-sericite zone,the pyritic-sericitic granitic cataclastic zone,and the strong potassic feldspar granite belt of the ore field,the tectonic ad-ditional hydrostatic pressure(Ps),fluid inclusion component CO2/H2O,oxygen fugacity(lgfO2),minimum pressure of fluid inclusion(Pmin),and homogenization temperature of fluid inclusions exhibit a trend of initially increasing and then decreasing.The ore-forming physical and chemical conditions represented by fluid inclusion component Na+/K+and F-/Cl-have a negative correlation with ore formation.In the pyrite-sericite zone,pyritic-sericitic granitic cataclastic zone,and strong potassic feldspar granite belt,F-/Cl-demonstrate a grad-ually downward trend,while Na+/K+exhibits the opposite trend.Tectonic additional hydrostatic pressure(Ps)can drive ore-forming fluids to migrate from areas with higher Ps to lower Ps,leading to ore precipitation.There is a tectono-physicochemistry interface between the high and low values of tectono-physicochemical param-eters,with gold deposits primarily located in stress relaxation zones at this interface.
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