Geochemistry of Eocene high-Mg# adakitic rocks in the northern Qiangtang terrane, central Tibet: Implications for early uplift of the plateau

Abstract

Research Article| November 01, 2013 Geochemistry of Eocene high-Mg# adakitic rocks in the northern Qiangtang terrane, central Tibet: Implications for early uplift of the plateau JianLin Chen; JianLin Chen † 1State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China †E-mails: lzdxchen@gig.ac.cn; jifengxu@gig.ac.cn Search for other works by this author on: GSW Google Scholar JianBin Wu; JianBin Wu 1State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China2University of Chinese Academy of Sciences, Beijing 100049, China Search for other works by this author on: GSW Google Scholar JiFeng Xu; JiFeng Xu † 1State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China †E-mails: lzdxchen@gig.ac.cn; jifengxu@gig.ac.cn Search for other works by this author on: GSW Google Scholar YanHui Dong; YanHui Dong 3Key Laboratory of Submarine Geosciences, Second Institute of Oceanography, State Oceanic Administration, Hangzhou 310012, China Search for other works by this author on: GSW Google Scholar BaoDi Wang; BaoDi Wang 4Chengdu Institute of Geology and Mineral Resources, Chengdu 610081, China Search for other works by this author on: GSW Google Scholar ZhiQiang Kang ZhiQiang Kang 5Guilin University of Technology, Guilin 541004, China Search for other works by this author on: GSW Google Scholar GSA Bulletin (2013) 125 (11-12): 1800–1819. https://doi.org/10.1130/B30755.1 Article history received: 26 Jun 2012 rev-recd: 14 May 2013 accepted: 24 Jul 2013 first online: 08 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation JianLin Chen, JianBin Wu, JiFeng Xu, YanHui Dong, BaoDi Wang, ZhiQiang Kang; Geochemistry of Eocene high-Mg# adakitic rocks in the northern Qiangtang terrane, central Tibet: Implications for early uplift of the plateau. GSA Bulletin 2013;; 125 (11-12): 1800–1819. doi: https://doi.org/10.1130/B30755.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract It is generally believed that the Tibetan Plateau is the result of crustal thickening in response to the collision of the Asian and Indian plates. However, the specific timing and uplift mechanism remain controversial. The widespread occurrence of Cenozoic lavas in the northern Qiangtang terrane provides a unique opportunity to constrain the dynamic processes that resulted in uplift of the northern Tibetan Plateau. Eocene lavas from the northern Qiangtang terrane display adakitic geochemical characteristics, such as high SiO2 and Al2O3 contents, low Y and Yb contents, positive Sr anomalies, and high Sr/Y and La/Yb ratios, in combination with high Mg# (43–69) and negative anomalies for Nb and Ta, which suggest a garnet + rutile-in and plagioclase-free source residue. The same samples also have high K2O and Th contents, high Th/Ce ratios, and low Nb/U, Ce/Pb, Ti/Eu, and Nd/Sm ratios, as well as high 87Sr/86Sr(i) (0.7062–0.7075) and low εNd(t) (–6.3 to –2.9), which show a clear continental crust affinity. These high-Mg# adakitic rocks, combined with other characteristics of Tibetan Cenozoic lavas, indicate that they were derived from partial melting of delaminated lower continental crust, which subsequently reacted with surrounding mantle peridotites during ascent to crustal depths. The Eocene high-Mg# adakitic rocks (46–38 Ma), north-south–trending shoshonitic dikes (47–38 Ma), and contemporaneous mantle-derived Mg-rich potassic and shoshonitic lavas indicate that the thickness of the crust was at least 50 km before ca. 46 Ma, at which time rapid uplift and extension occurred, most likely caused by small-scale delamination of the lithospheric mantle at 46–38 Ma (Eocene) in central Tibet. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.