Geochemical Characteristics and Geological Significance of Late Triassic Intrusive Rocks in the Middle Reaches of Naling Guole River, Qinghai Province

The middle reaches of Naling Guole River is located in the western part of Qimantage area in East Kunlun Mountains, where a large number of granites are distributed. The study of the Late Triassic intrusive rocks in this area is of help to understand the Indosinian tectono-magmatic evolution history of the East Kunlun orogenic belt. Petrological, chronological and geochemical analyses of granites in the study area were carried out. The results show that the zircon LA-ICP-MS U-Pb ages of granodiorite and monzogranite porphyry in the study area are (225.7+1) Ma and (213.74+1) Ma respectively, which are the products of late Triassic magmatism. The results of petrogeochemical analysis show that the Late Triassic intrusive rocks in this area belong to the high-K calc-alkaline series. The saturated aluminium index shows that they are meta-aluminous to peraluminous, enriched with large ion lithophile elements such as Rb, Th, K and light rare earth elements, and obviously depleted with high field strength elements such as Nb, P and Ti. Granite is characterized by highly differentiated I-type granite and plate subduction stage. The analysis shows that the magmatite formed in the volcanic arc environment before plate collision.