Geochemical Characteristics And Genesis Of Acidic Rock Mass In Zhangcun,Wuyuan Jiangxi Province

Zhangcun acidic rock mass is located in wuyuan county,jiangxi province.It is located in the middle part of the south China land mass,the transfer site of yangzi plate and huaxia plate,and the core part of the qinhang ligand belt.There are abnormal combinations of W,Mo,Cu and Au around the rock mass.Zhangcun acidic rock mass as the research object,this article selects the petrography,zircon U-Pb in situ Hf isotopic chronology and zircon,rock geochemistry research,which determine the formation of acidic rock era,genetic types,source rock characteristics and diagenetic tectonic background.It provide data and theoretical support for that study of the magmatic activities and geodetic structure in the Yanshan phase in the Qinhang metallogenic belt,and provides a theoretical basis for the prediction of mineralization potential in the area.Through experiment of LA-ICP-MS zircon U-Pb,the formation age of granodiorite porphyry is 132.65±1.3Ma,the formation age of granite porphyry is 134.25±0.99Ma,Zhangcun acidic rock mass can be judged from the formation age belongs to late yanshan period.The characteristics of Hf isotopic composition of the Zhangcun acidic rock mass show that the value of the εHf(t)of granodiorite porphyry is between-8.47 and 0.18,and the corresponding crustal model age is between 1.41Ga and 1.15Ga.The value of the εHf(t)of granite porphyry was between-16.01～0.04,and the corresponding crustal model was between 2.17Ga and 1.16Ga,with an average value of 1.29Ga.Hf isotopic composition is relatively uniform,epsilon εHf(t)mostly negative,ancient crustal model age is mesoproterozoic,Zhangcun acidic granite is mainly composed of mature in mesoproterozoic crust molten material components.The geochemical characteristics of the main elements of the acidic rock mass in zhangcun are basically the same,which belong to the high potassium and calc-alkaline granite,the content of SiO2 is high,and the value of the aluminum saturation index A/CNK is less than 1.1,which belongs to the typical I type granite.The geochemical characteristics of trace elements are characterized by the enrichment of large ionic lithophile elements Rb,La,U and Ce,and the relative loss of high field strong elements Ti,P,Ta,Nb and Th.The characteristics of rare earth elements are consistent,both of which are rich in light rare earth elements and heavy rare earth elements.The differentiation of heavy and heavy rare earth is very obvious.The Eu losses are not obvious.in the rare earth element distribution figure chondrite standardized curve is steep dip type to the right.The source rock of zhangcun acid rock mass is from the lower crust,and its residual phase is mainly garnet.Moreover,the acid rock mass of zhangcun has the characteristics of typical adakite rock,which is a low Mg#adakite rock system.The origin depth of zhangcun adakite acid melt is more than 50km and the forming pressure is more than 1.5GPa.The geochemical characteristics of the trace elements of the acidic rock mass in zhangcun are similar to those of the granites associated with subduction,indicating that the formation of acidic rock mass in zhangcun may be related to the subduction of the plate.The Zhangcun acidic rock mass is formed in the system of thinning and thinning when the crust is thickened under the impact of the collision.The production environment is a mountain environment for the land,and the Pacific plate is stretching the back of the arc of the south China and the formation of the lithosphere.