Zircon U-Pb age and geochemistry of volcanic rock of Linzizong Group in Nanmulin area of Middle Gangdise belt, Tibet

The volcanic rocks of Linzizong Group are widely distributed in the Gangdise belt. Their petrological characteristics together with regional unconformity events are considered to be related to the transform from Tethys Ocean subduction to the collision of Indian-Asian continent. In this paper, LA-ICP-MS zircon U-Pb age and geochemistry were investigated for the volcanic rocks in Linzizong Group, and the result indicates that the LA-ICP-MS zircon U-Pb ages of Pana Formation volcanic rocks of Linzizong Group are 46.08 ±0.47Ma and 49.00 ±1.30Ma. Compared with the related age data of other regions of the Gangdese belt, the authors hold that the time of the India-Asia continent collision (in southern Tibet) in the eastern part may be earlier than that of the central and western regions. Additionally, the geochemical characteristics show that the Linzizong volcanic rocks were generated under the background of the crustal thickening after collision in the Nanmulin area of Gangdese belt, and were formed in the background from the transform from the new Tethys Ocean subduction to the collisional structure of the Indian-Asian continent.