Research Article| May 01, 2001 Coesite in Himalayan eclogite and implications for models of India-Asia collision P.J. O'Brien; P.J. O'Brien 1Bayerisches Geoinstitut, Universität Bayreuth, D-95440 Bayreuth, Germany Search for other works by this author on: GSW Google Scholar N. Zotov; N. Zotov 1Bayerisches Geoinstitut, Universität Bayreuth, D-95440 Bayreuth, Germany Search for other works by this author on: GSW Google Scholar R. Law; R. Law 2Geological Sciences, Virginia Tech, Blacksburg, Virginia 24061, USA Search for other works by this author on: GSW Google Scholar M.A. Khan; M.A. Khan 3Government College, Sargodha, Pakistan Search for other works by this author on: GSW Google Scholar M.Q. Jan M.Q. Jan 4National Centre of Excellence in Geology, University of Peshawar, Peshawar, Pakistan Search for other works by this author on: GSW Google Scholar Geology (2001) 29 (5): 435–438. https://doi.org/10.1130/0091-7613(2001)029<0435:CIHEAI>2.0.CO;2 Article history received: 17 Aug 2000 rev-recd: 02 Jan 2001 accepted: 21 Jan 2001 first online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation P.J. O'Brien, N. Zotov, R. Law, M.A. Khan, M.Q. Jan; Coesite in Himalayan eclogite and implications for models of India-Asia collision. Geology 2001;; 29 (5): 435–438. doi: https://doi.org/10.1130/0091-7613(2001)029<0435:CIHEAI>2.0.CO;2 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 SocietyGeology Search Advanced Search Abstract Coesite, recognized petrographically and confirmed by in situ Raman microprobe spectroscopy, is reported from an eclogite from the Kaghan valley, Pakistan, and represents the first record of ultrahigh-pressure metamorphism in the Himalaya. The formation conditions of >27 kbar implied by the presence of coesite are supported by garnet-pyroxene- phengite barometry (27–29 kbar, 690–750 °C). If, as seems likely from previous field and geochronologic studies, the eclogites represent metamorphosed dikes, sills, and lava flows of Permian age within the granitic gneiss-metapelite-marble sequence of the Higher Himalayan crystalline nappes, then continental crust—the leading edge of the Indian plate— must also have been subducted to coesite-forming depths (90–100 km). This more than doubles previous depth estimates and, on the basis of available geochronological data for this area, requires average exhumation rates at least twice as fast (∼10 mm/yr) as previously imagined. A further implication, based on interpretations of deep seismic data, is that the present-day shallow angle of subduction of Indian plate lithosphere beneath Tibet represents a significant change from an initially much steeper angle. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.