GP002-0011
When and where did the Tibetan Plateau uplift to its maximum altitude：Evidence from north–south trending dikes in South Tibet
Monday, 14 December 2020
Poster
Yiming Ma1, Qiang Wang2, Huapei Wang3, Tianshui Yang4, Shihong Zhang5, Jun Wang2, Xiao Liu2 and Di Zou6, (1)China University of Geosciences Wuhan, Wuhan, China, (2)Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, Guangzhou, China, (3)Massachusetts Institute of Technology, Department of Earth, Atmospheric and Planetary Sciences, Cambridge, United States, (4)China University of Geosciences, Beijing, Beijing, China, (5)China University of Geosciences, Beijing, China, (6)China University of Geosciences, Wuhan, Wuhan, China
Abstract:
The uplift of the Tibetan plateau has a profound impact on climate change in Asia. However, when and where the Tibetan plateau uplift to its maximum elevation remain controversial. Because the north-south trending normal fault systems are widely believed to be related to the gravitational collapse of the Tibetan plateau, the latest uplift time of the Tibetan plateau can be dated at ~14 Ma based on the active time of these faults. The east-west extension of southern Tibet has also been proved to be related to the uplift of the plateau. A recent study showed a considerable decrease in the latitudinal convergence within Asia since 26 Ma, which has been interpreted as a transition from compression to extension within the Tibetan plateau. Notably, the appearance of north-south trending dikes in southern Tibet can be used to indicate the east-west extension, i.e., the collapse of the Tibetan plateau after it uplifted to the maximum elevation. Paleomagnetism of the north-south trending dikes from the southern Tibet may help us to unravel the mystery of when and where the Tibetan plateau uplifted to its maximum elevation.
We have conducted a combined palaeomagnetic and geochronological study on at least 10 independent north-south trending dikes in the Shigatse area. Our results show that the sampling dikes were formed in a paleolatitude of ~29°N at ~12 Ma, which is well consistent with their present latitude, indicating that there has been no significant latitudinal movement since ~12 Ma. Therefore, there was no significant crustal shortening to the north of the Shigaze area within the Tibetan plateau since ~12 Ma. The plateau most likely uplifted to its maximum elevation at this time, after which the plateau began its collapse caused by a transition from N-S compression to E-W extension, leading to the formation of a large number of the north-south trending dikes.
