Metamorphic rocks in central Tibet: Lateral variations and implications for crustal structure

Abstract

Research Article| March 01, 2011 Metamorphic rocks in central Tibet: Lateral variations and implications for crustal structure Alex Pullen; Alex Pullen † 1Department of Geosciences, University of Arizona, Tucson, Arizona 85721, USA †E-mail: apullen@email.arizona.edu Search for other works by this author on: GSW Google Scholar Paul Kapp; Paul Kapp 1Department of Geosciences, University of Arizona, Tucson, Arizona 85721, USA Search for other works by this author on: GSW Google Scholar George E. Gehrels; George E. Gehrels 1Department of Geosciences, University of Arizona, Tucson, Arizona 85721, USA Search for other works by this author on: GSW Google Scholar Lin Ding; Lin Ding 2Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100029, China Search for other works by this author on: GSW Google Scholar Qinghai Zhang Qinghai Zhang 2Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100029, China Search for other works by this author on: GSW Google Scholar GSA Bulletin (2011) 123 (3-4): 585–600. https://doi.org/10.1130/B30154.1 Article history 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 Alex Pullen, Paul Kapp, George E. Gehrels, Lin Ding, Qinghai Zhang; Metamorphic rocks in central Tibet: Lateral variations and implications for crustal structure. GSA Bulletin 2011;; 123 (3-4): 585–600. doi: https://doi.org/10.1130/B30154.1 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 Insights about lateral variations in the age, composition, and structure of the central Tibetan crust are provided by geologic investigations of metamorphic rocks in the Qiangtang terrane. Previous studies have shown that a tectonic mélange of Triassic age with blueschist- and eclogite-bearing blocks within a greenschist-facies matrix is exposed over an E-W distance of ∼600 km in the central Qiangtang terrane. New mapping shows that the mélange extends over a N-S distance of ∼150 km, nearly to the trace of the early Mesozoic Jinsha suture in the north. The mélange, exposed structurally beneath Upper Paleozoic to Mesozoic strata in the footwalls of early Mesozoic normal faults, is composed mostly of Paleozoic metasedimentary and crystalline rocks. These findings support the hypothesis that a large part of the central and northern Qiangtang terrane crust is composed of supracrustal rocks. The Duguer Range, <25 km south of the southernmost mélange, exposes high-temperature, low-pressure metasedimentary rocks and orthogneisses with 476–471 Ma U-Pb crystallization ages that represent continental basement of the Qiangtang terrane. The boundary at the surface between mélange and Gondwanan basement corresponds closely with abrupt changes in crustal geophysical properties, and allows us to extrapolate this relationship to depth. The resultant crustal structure can be explained by development of major Mesozoic structures documented in surface geology. Antiformal geophysical features imaged in the midcrust are likely inherited from Mesozoic tectonics, suggesting that the crust may not have been as mobile as that required by models invoking large-scale lower-crustal flow beneath the central Tibet Plateau during the Cenozoic India-Asian collision. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.