Petrogenesis and Geological Implications of Granitoids from Halasen,East Kunlun

He Cheng; Wang Liyuan; Tian Liming; Xu Jing

Abstract：A large amount of granites widely distributes in Halasen area in the East Kunlun Mountains.The study of the granites not only help us to understand the tectono-magmatic evolution history of East Kunlun orogenic belt in the Late Paleozoic and Early Mesozo-ic,but also provides constraints for the subduction and closed time limit of the Paleo-Tethys Ocean.In this paper,we constrain geo-chronology and petrogenesis of the Halasen granites by zircon U-Pb dating and geochemical analyses.The LA-ICP-MS U-Pb analyses show that the formation ages of K-feldspar granite and fine-grained monzogranite are 239.2±1.7 Ma(MSWD=0.19)and 232.4± 1.2 Ma(MSWD=0.76),respectively,which are the products of the Middle Triassic granitic magmatism.The geochemistry data show that granites are high-potassium calcalkaline-shoshonite,peraluminous rock which is characterized by high silicon and aluminum, enriched alkali,low titanium,as well as enriched light rare earth elements(LREE)and large ion lithophile elements(LILE,e.g.,K,Th and Rb),and depleted in high field-strength elements(HFSE,e.g.,Nb,Ti,P,and Ta)with obvious Eu negative anomaly(the value ofδEu is between 0.27 and 0.65).Halasen granites belong to highly fractionated I-type granite.It is suggested that the Halasen granites were most likely derived from parental magma by mixing of depleted mantle-derived magma and induced crustal-melted felsic magma in the deep crust,and then suffered further differentiation during magma ascent.The subduction of the East Kunlun Paleo-Tethys Ocean lasted to the Early Triassic,and the Middle Triassic witnessed the intracontinental collision.