Zircon Dating And Geochemical Characteristics Of Xueshuigou Pluton In The North Qilian Orogenic Belt

Songshu Nangou Gold Mine is located in the North Qilian Mountains(Qinghai Province)on the south side.As a hot spot for gold mining research over the years,it has always attracted attention.In the North Qilian orogenic belt,through detailed field observation and on-site investigation,combined with modern analysis techniques,the chronological study of the Xueshuigou rock mass in the Songshu Nangou area was carried out,and the Xueshuigou rock mass was obtained.The weighted average age of the gray medium-grained quartz diorite zircon LA-MC-ICP-MS is 517±1 Ma,belonging to the Early Cambrian.The weighted average age of the gray medium-fine-grained diorite zircons is 494±1 Ma,which belongs to the Late Cambrian.According to the petrological and geochemical characteristics,the main elements of the rock mass in the study area show the content of Si O2(52.5%?63.9%),TFe₂O₃(4%?10.63%),Mg O(2.05%?6.68%),experimental petrology Studies have shown that the melt Mg#formed by the melting of the basic lower crust should be less than 45.The value of Mg#in this study area(Mg#value is between 57?81,with an average of 70).Therefore,from the characteristics of major elements,this area The Xueshuigou rock mass should be the product of partial melting of the mantle.Based on the content of TFe₂O₃ and Mg#,it is analyzed that the content of Mg and Fe in this area is relatively high,and the analyzed rock mass belongs to the neutral rock of para-aluminum-weak peraluminum,calc-alkaline-high potassium calc-alkaline series.Among the rare earth elements,light rare earth elements are relatively enriched,and heavy rare earth elements are relatively depleted,with mild europium anomalies(0.63%?1.23%).The large ion lithophile elements Rb and Ba are relatively enriched,and the relative depletion of Nb,Ti,Zr and Hf is not significant.Based on the structural discriminant diagrams of major,rare earth and trace elements,this paper believes that the Xueshuigou intrusion of Songshu Nangou Gold Mine was formed in the subduction environment of the Middle Qilian Block at the southern end of the North Qilian Ocean,and its genesis may be replaced by fluids in the oceanic subduction environment.Partial melting of the lithospheric mantle is related to.