Petrogenesis and Tectonic Implications of Daomuti Intrusive Rocks in East Kunlun Orogen: Constraints from the Geochronology and Geochemistry

The Daomuti intrusive rocks is located in the eastern section of the East Kunlun orogenic belt, and mainly includes monzogranite, granodiorite and diorite. In this paper, zircon U–Pb dating and petrogeochemical tests are performed on newly discovered diorite to determine its crystalline age and petrogenesis. Comprehensively analyse the petrogeochemical characteristics of monzogranite and granodiorite, and discuss the emplacement age, rock genesis and tectonic evolution of the Daomuti intrusive rocks. LA–ICP–MS zircon U–Pb dating analysis shows that the ²⁰⁶Pb/²³⁸U weighted average age of diorite is (244.6±1.8) Ma, and the crystallization age of the diorite is Early Triassic. The geochemical characteristics of the monzogranite and granodiorite show that the Ritman index is greater than 3.3 and has the characteristics of calcium alkalinity–high potassium calcium alkalinity; the aluminum saturation index A/CNK values are less than 1.1; the P₂O₅ content in the rocks is low, and its has a negative correlation with SiO₂ content; It is enriched with LILE such as K, Rb, La, and loses HFSE such as Nb, Ta, Ti and P. The above characteristics indicate that the Daomuti intrusive rocks belongs to type I granite. Based on the research results of this paper, it can be considered that the Daomuti intrusive rocks is a volcanic arc granite, its formed by partial melting of the lower crust rocks, and the Animaqing Ocean subduction continued to the Early–Middle Triassic The mantle magma underplating during the subduction process is the heat source that causes the melting of the lower crust, and the mantle source magma is mixed into the Daomuti intrusive rocks’ magma evolution, and during the Daomuti intrusive rocks’ magma evolution occurred fractional crystallization.