Geochemistry, LA-ICP-MS zircon U-Pb ages of the Meicaogou ophiolite in East Kunlun, and its geological significance

This paper mainly introduces the rock assemblage and geochemical characteristics of the Meicaogou ophiolite and attempts to discuss the tectonic background of the ophiolite which is located in Golmud City of Qinghai Province and lies in the western part of the East kunlun composite orogenic belt. The rock association is composed of metamorphic basic basalt and a small amount of diabase, gabbro, metamorphic peridotite and augite peridotite. The characteristics of main elements and trace elements indicate that the ophiolite is not related to subduction but belongs to N-MORB. In the past geological survey carried out by previous researchers, it was considered that the ophiolite was formed in Late Ordovician. The LA-ICP-MS zircon U-Pb dating of gabbro and basalt in the Weitogou ophiolite yielded the exact age data of 488.2±2Ma and 501.1±2.2Ma. The isotope data have filled the gaps of the ophiolite data in this area, and reflected the existence of remains of the ancient ocean in this area. The comprehensive regional geological characteristics suggest that the early period of the oceanic basin was at the initial stage, but at the late stage basalt was formed in an oceanic ridge expanding center environment. The Early Cambrian period was the flourishing period of the development of the oceanic basin, the late oceanic crust was formed in the late Ordovician period, and the late Silurian basin was basically closed together with later greenschist facies metamorphism.