Geological And Geochemical Characteristics Of Orogenic Gold Deposits In The Northern Margin Of The Altun Tagh

Beiketan gold deposit is located in eastern of Ruoqiang county in Xinjiang province,the north of Altun Tagh orogenic belt,joint of Altun strike-slip fault and fracture of the Altun northern area,special tectonic position,superior metallogenic geological condition,characteristics are similar to typical gold deposit in north Qilian.Therefore,ore-forming fluid characteristics,sulfur and lead isotope tracer,ore deposit geochemistry,ore-forming chronology research are carried out to discuss the forming process of Au mineralization and orogenic evolution,then make a contrast with north Qilian typical gold deposits.Many achievements are obtained:According to the field geological characteristics and the characteristics of mineral paragenetic association and petrography,metallogenic stages of Beiketan gold deposits are divided into quartz early stage phase,quartz-pyrite main phase,quartzcalcite late stage.Ore bodies are distribution in green sericite chlorite schist,controlled by the Hongliugou-Beiketan ductile shear zone obviously.Two types of fluid inclusion are obverved: H₂O type,CO₂-H₂O type.homogenization temperature is assemble in 160²10?.Ore-forming fluid salinity focus on 6¹2 wt%?NaCleq?,with characteristics of low temperature,low salinity;Calculating the mineralization density is 0.83¹.02 g/cm³.Through hydrogen and oxygen isotope test of quartz vein ore samples,the ?18OH2O?‰?values change from 3.0 to 4.9,the ?DH2O?‰?values is-54^-74,it suggests that the ore-forming fluid is given priority to with magmatic water.?³⁴S value is 9‰¹1.4‰,showing the sulfur mainly comes from the crust and relate to ore rock,lead isotope characteristics indicate its shallow source and mainly comes from the orogenic belt with the mix of shallow strata.Isotope chronology results show that the quartz mineral inclusions Rb-Sr isochron age is?390±47?Ma,syenogranite zircon U-Pb age is?444±5?Ma.According to regional geological data,establishing metallogenic model,ore deposit type is low temperature hydrothermal quartz vein gold deposit with the characteristics of orogenic gold deposits.Baketan gold deposit is similar to Yingzuishan and Hanshan gold deposit,the latter which is in north Qilian mountain,both mineralization are related to early Paleozoic volcanic rocks,controlled by the ductile-brittle tectonic deformation zone.They are of good comparision and has a certain significance for gold deposit prospecting.