Abstract:
The formation age of the Shangqihan volcanic rocks in West Kunlun has been under controversy for long time. LA-ICP-MS zircon U-Pb dating was used in this article to test the formation age of volcanic rocks. According to cathodeluminescence images of zircons, it have symmetrical oscillatory growth zonal structure. And most of the Th/U is over 0.4, referring to the characteristic of magmatic zircon. The results show zircons yield excellent concordant results with a weighted mean
206Pb/
238U age of 335±4.2 Ma. Therefore, the formation age of the Shangqihan volcanic rocks belongs to Carboniferous period. Furthermore, the Shangqihan volcanic rocks are divided into Aqiangyan Formation. Combining with regional geologic background, we can reasonably conclude that the tectonic setting of the Shangqihan volcanic rocks are referred to rift environment.