Geological-Geochemical Features And Genesis Of Xiao Qinling Gold Deposit

Xiao Qinling gold field is the famous gold mineralization belt in China, it locates in the south of north China platform. Ore field lies in the greenstone belt of Archean, and it has the Xiao He fracture of south and Tai Yao fracture of north as its boundary. In this essay, several typical gold field, some main rock masses and the surrounding strata are considered as its subject, on the basis of abundant work in the field, synthetically using multidisciplinary theory and method, such as petrology, mineralogy, ore deposit geology, geochemistry, isotope geology and so on to do systemically research on the geochemical characters on Xiao Qinling gold field, and explore the genesis of Xiao Qinling gold deposit.In this area, the biotite plagioclase gneiss of Yang Zhaiyu formation belongs to intermediate-acid volcanic rocks, while the biotite granulites of Guan Yin tang formation equivalents with the average composition of intermediate-acid volcanic rocks of our country, and plagioclase amphibolite undergoes the affect of regional metamorphism and migmatization. Rare earth elements are rich in gneiss and granulites, with a large variable ranges and rich light rare earth elements, Eu negative anomaly is not obvious. The rare earth'distribution diagrams of the three rock bodies trend uniformly, according to the flat pattern with right deviation gradually, without obvious Eu anomaly. From plagioclase amphibolite,biotite plagioclase gneiss, biotite granulites to granulites, trace elements in them such as Cr,Co,Ni,V,Cu,Zn,Ti and so on, revealing an evolutionary trend from high to low; but for Pb and Mo, just an opposite trend; the ration of Ni and Co is more than one, which is obvious higher in plagioclase amphibolite than that of others.Gold bearing quartz veins of different mine are have almost the same components of H and O isotope, ore-forming fluid shows the same source and evolutionary history, that is, has the multi-source mixed fluid of magmatic water and meteoric water. The average contents ofδ¹³C are mostly concentrated between -2.1‰and 5.7‰, rich in heavy sulfur and a high homogeneity. The sulfur isotope sources of ores, granite and strata are identical, and rich in deep source sulfur. Pb isotopes distribute concentrated, and are very stable, whose components in gold deposit mines and Wen Yu granite of Tai Hua group are basically the same, and it has the similar evolutionary model with the mental and the lower crust. In some deposit mine,δ¹³C of carbonate minerals vary not greatly, and it is charactered as the deep source C isotopes.The metallogenic materials of Xiao Qinling gold mine such as Au , S, Pb, C and so on mainly come from Tai Hua group with mental substance and the crust below it. Ore-forming fluid is multi-source mixed fluid of magmatic water and meteoric water. This gold deposit mine belongs to middle-low temperature remelting post magmatic hydrothermal type gold mine, the formation of the gold mine has close relationship with the long period of metamorphism and deformation of Tai Hua group strata. The intrusion of granite in late Yan Shan period provides thermal dynamic and ore-hosting structure for the further activation and migration of gold, eventually contributes to concentration in gold ore-formation.