Geochemistry and geochronology of intermediate–basic rocks in the Galwan Valley area of the North Qiangtang terrane, Karakoram

This paper is the result of geological survey engineering.

Objective The Galwan Valley, which adjacent to the Huoshaoyun super large lead−zinc deposit, located in the Karakoram Mountains of the Northern Qiangtang terrane. A systematically lithogeochemistry and chronological studies was conducted on the newly discovered magmatic rocks in the Galwan Valley area to helps us deeply understanding the regional metallogenic dynamics and magmatic evolution history, providing a theoretical foundation for the study of regional magmatic−tectonic−mineralization processes.

Methods This study reports seven samples of intermediate−basic magmatic rocks in the Galwan Valley area, including basalt, diabase, and diorite. A systematic mineralogical, major and trace element, zircon U–Pb age, and trace element analyses were conducted on these samples.

Results The zircon U–Pb dating results indicate that the Bingdong diorite is emplaced at (98.9±1.2) Ma, and its whole−rock composition is characterized by low−potassium calc−alkaline features. In contrast, the zircon U–Pb dating results for the basalt show an eruption age of (232±9) Ma, with its whole−rock geochemical composition displaying calcium alkali or peralkaline characteristics. The zircon dating results show that both the diorite and basalt samples contain a large number of ~800 Ma inherited zircons, and both have age spectra featuring six distinct age peaks.

Conclusions The Bingdong diorite is a product of crust−mantle mixing under a crustal thickening background, related to the remote effect of the India–Asia collision orogeny following the closure of the Neo–Tethys Ocean. The existence of numerous ~800 Ma inherited zircons in the diorite and basalt indicates that they originated from the melting of Neoproterozoic basement material. The six distinct zircon age peaks in both the diorite and basalt reflect six periods of tectono–magmatic activity, ranging from the Mesoproterozoic crystalline basement and the breakup of the Rodinia supercontinent to the closure of the Neo–Tethys Ocean and subsequent collisional orogeny.