Geochemistry, zircon U-Pb age and Hf isotopic characteristics of two-mica monzonitic granites in Dujianshan area of Western Kunlun, Xinjiang

This paper is the result of geological survey engineering.

Objective The study aims to further understand the tectonic evolution of the back-arc basin of Bayankera, the northwestern margin of Songpan-Ganzi block, Western Kunlun.

Methods In this paper, the authors present petrographical, lithogeochemical, LA-ICP-MS zircon U-Pb geochronological and Hf isotopic data for the two-mica monzogranite in Dujianshan.

Results LA-ICP-MS zircon geochronology study reveals that the monzogranites in the Dujianshan area crystallized at (219.9±1.2)-(227.1±1.5) Ma, indicative of the Late Triassic plutons. The results of major elements, trace elements and Hf isotope reveal that the monzogranites are metaluminous-weakly peraluminous rocks, belongs to the high potassium calcium alkaline series and exhibit characteristics of island arc and collisional granites. The source rocks of granites were generated from partial melting of a mixture of crust-mantle materials.

Conclusions Combined with the regional tectonic evolution, it is speculated that the Dujianshan area is in a post collision extension environment at the end of the Late Triassic, and the island arc and syn-collision materials formed in the early ocean continent subduction stage partially melted to form post collision granite in the area.