Isotopic constraints on the structural relationships between the Lesser Himalayan Series and the High Himalayan Crystalline Series, Garhwal Himalaya

Research Article| March 01, 2000 Isotopic constraints on the structural relationships between the Lesser Himalayan Series and the High Himalayan Crystalline Series, Garhwal Himalaya Talat Ahmad; Talat Ahmad 1Wadia Institute of Himalayan Geology, Dehra Dun 248001 (U.P.), India Search for other works by this author on: GSW Google Scholar Nigel Harris; Nigel Harris 2Department of Earth Sciences, Open University, Milton Keynes MK7 6AA, United Kingdom Search for other works by this author on: GSW Google Scholar Mike Bickle; Mike Bickle 3Department of Earth Sciences, University of Cambridge, Cambridge CB2 3EQ, United Kingdom Search for other works by this author on: GSW Google Scholar Hazel Chapman; Hazel Chapman 3Department of Earth Sciences, University of Cambridge, Cambridge CB2 3EQ, United Kingdom Search for other works by this author on: GSW Google Scholar Judith Bunbury; Judith Bunbury 3Department of Earth Sciences, University of Cambridge, Cambridge CB2 3EQ, United Kingdom Search for other works by this author on: GSW Google Scholar Christophe Prince Christophe Prince 2Department of Earth Sciences, Open University, Milton Keynes MK7 6AA, United Kingdom Search for other works by this author on: GSW Google Scholar Author and Article Information Talat Ahmad 1Wadia Institute of Himalayan Geology, Dehra Dun 248001 (U.P.), India Nigel Harris 2Department of Earth Sciences, Open University, Milton Keynes MK7 6AA, United Kingdom Mike Bickle 3Department of Earth Sciences, University of Cambridge, Cambridge CB2 3EQ, United Kingdom Hazel Chapman 3Department of Earth Sciences, University of Cambridge, Cambridge CB2 3EQ, United Kingdom Judith Bunbury 3Department of Earth Sciences, University of Cambridge, Cambridge CB2 3EQ, United Kingdom Christophe Prince 2Department of Earth Sciences, Open University, Milton Keynes MK7 6AA, United Kingdom Publisher: Geological Society of America Received: 25 Jun 1998 Revision Received: 08 Feb 1999 Accepted: 24 Feb 1999 First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (2000) 112 (3): 467–477. https://doi.org/10.1130/0016-7606(2000)112<467:ICOTSR>2.0.CO;2 Article history Received: 25 Jun 1998 Revision Received: 08 Feb 1999 Accepted: 24 Feb 1999 First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Tools Icon Tools Get Permissions Search Site Citation Talat Ahmad, Nigel Harris, Mike Bickle, Hazel Chapman, Judith Bunbury, Christophe Prince; Isotopic constraints on the structural relationships between the Lesser Himalayan Series and the High Himalayan Crystalline Series, Garhwal Himalaya. GSA Bulletin 2000;; 112 (3): 467–477. doi: https://doi.org/10.1130/0016-7606(2000)112<467:ICOTSR>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 SocietyGSA Bulletin Search Advanced Search Abstract Nd and Sr isotope systematics may provide important constraints on the location of major thrust systems that separate lithologically similar sedimentary sequences. The potential of the technique is illustrated by this isotopic study of the Main Central thrust system of the Himalaya. Nd isotope data from the Garhwal Himalaya indicate that metasedimentary rocks from the Vaikrita Group (ϵNd = −14 to −19) correlate closely with those from the High Himalayan Crystalline Series, which constitutes the hanging-wall lithologies of the Main Central thrust. In contrast, metasedimentary rocks from the Munsiari Group (ϵNd = −23 to −28) show marked similarities to the Lesser Himalayan Series in the footwall of the Main Central thrust. Sr isotopes support the correlations in that the Vaikrita Group shows partial reequilibration at 500 Ma, whereas the Munsiari Group has not undergone Sr isotope homogenization since 1800 Ma. Thus, the Vaikrita thrust that juxtaposes these two formations is recognized as the Main Central thrust in Garhwal Himalaya. The thrust coincides, approximately, with the location of the kyanite isograd, confirming that inverted metamorphism is characteristic of both hanging wall and footwall of the Main Central thrust.Along the Tons thrust (known locally as the Srinagar thrust) 50 km south of the Main Central thrust, low-grade quartzarenites with Nd-Sr isotope and trace element characteristics typical of Lesser Himalayan formations have been emplaced on phyllites and siltstones with geochemical characteristics of the High Himalayan Crystalline Series. The field relationships most probably result from out-of-sequence thrusting in which Lesser Himalayan Series rocks to the north were emplaced over low-grade equivalents of the High Himalayan Crystalline Series preserved in the external part of the orogen. This study establishes the value of isotope data for lithostratigraphic correlations within orogenic belts. 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