Contribution of crustal anatexis to the tectonic evolution of Indian crust beneath southern Tibet
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Research Article| January 01, 2011 Contribution of crustal anatexis to the tectonic evolution of Indian crust beneath southern Tibet Jess King; Jess King † 1Department of Earth Sciences, University of Hong Kong, Hong Kong SAR, China †E-mail: jessking@hkucc.hku.hk Search for other works by this author on: GSW Google Scholar Nigel Harris; Nigel Harris 2Department of Earth Sciences, The Open University, Milton Keynes MK7 6AA, UK Search for other works by this author on: GSW Google Scholar Tom Argles; Tom Argles 2Department of Earth Sciences, The Open University, Milton Keynes MK7 6AA, UK Search for other works by this author on: GSW Google Scholar Randall Parrish; Randall Parrish 3Department of Geology, University of Leicester, LE17, UK, and Natural Environment Research Council Isotope Geosciences Laboratory, British Geological Survey, Keyworth, Notts NG12 5GG, UK Search for other works by this author on: GSW Google Scholar Hongfei Zhang Hongfei Zhang 4State Key Laboratory of Geological Processes and Mineral Resources, Faculty of Earth Sciences, China University of Geosciences, Wuhan 430074, China Search for other works by this author on: GSW Google Scholar Author and Article Information Jess King † 1Department of Earth Sciences, University of Hong Kong, Hong Kong SAR, China Nigel Harris 2Department of Earth Sciences, The Open University, Milton Keynes MK7 6AA, UK Tom Argles 2Department of Earth Sciences, The Open University, Milton Keynes MK7 6AA, UK Randall Parrish 3Department of Geology, University of Leicester, LE17, UK, and Natural Environment Research Council Isotope Geosciences Laboratory, British Geological Survey, Keyworth, Notts NG12 5GG, UK Hongfei Zhang 4State Key Laboratory of Geological Processes and Mineral Resources, Faculty of Earth Sciences, China University of Geosciences, Wuhan 430074, China †E-mail: jessking@hkucc.hku.hk Publisher: Geological Society of America Received: 09 May 2009 Revision Received: 02 Dec 2009 Accepted: 07 Dec 2009 First Online: 08 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 © 2011 Geological Society of America GSA Bulletin (2011) 123 (1-2): 218–239. https://doi.org/10.1130/B30085.1 Article history Received: 09 May 2009 Revision Received: 02 Dec 2009 Accepted: 07 Dec 2009 First Online: 08 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Jess King, Nigel Harris, Tom Argles, Randall Parrish, Hongfei Zhang; Contribution of crustal anatexis to the tectonic evolution of Indian crust beneath southern Tibet. GSA Bulletin 2011;; 123 (1-2): 218–239. doi: https://doi.org/10.1130/B30085.1 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 This geochemical, geochronological, and structural study of intrusive rocks in the Sakya dome of southern Tibet has identified two distinct suites of anatectic granites that carry contrasting implications for the tectonic evolution of the India-Asia collision zone. The northern margin of the dome core was intruded by anastomosing, equigranular two-mica garnet granites between 28.1 ± 0.4 Ma and 22.6 ± 0.4 Ma, coeval with top-to-the-south shear. Trace-element and isotopic (Sr-Nd) characteristics indicate an origin from partial melting of a biotite-bearing source in the Indian crust under conditions of high-fluid-phase activity. These granites thus provide evidence for the melt weakening required by some thermo-mechanical models that predict the southward extrusion of a low-viscosity channel during the Oligocene. Evidence for subsequent shear-sense reversal may document initiation of this process. However, a younger suite of porphyritic two-mica granite plutons, emplaced between 14.5 ± 0.9 Ma and 8.81 ± 0.22 Ma, is derived from anatexis of muscovite-bearing metasediments of the High Himalayan Series under fluid-absent conditions. Ar-Ar cooling ages of 14.4–8.0 Ma from the Sakya dome postdate crystallization of the Oligocene granite suite by ∼10 m.y. but are coincident with mid-Miocene granite emplacement, suggesting uplift to depths of <10 km by the mid-Miocene. We propose that plate flexural response to Miocene slab steepening was a likely cause of dome uplift, and that this exhumation of midcrustal rocks triggered decompression melting at 15–9 Ma and emplacement of discrete granite plutons into the upper crust under brittle conditions. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.Keywords:
Geological survey
Fluvial fans represent one of the dominant sedimentary systems at the active margins of non-marine foreland basins. The Puig-reig anticline at the north-eastern margin of the Ebro Foreland Basin (SE Pyrenees, Spain) exposes continuous outcrops of Late Eocene-Early Oligocene fluvial deposits, from proximal to medial fluvial fan environments. The proximal deposits are found in the north limb of the anticline, especially in the northwest zone. These deposits are characterised by conglomerates with minor interbedded sandstones, with thick and wide sheet-like geometries with unscoured or variably scoured basal surfaces. These are interpreted to be the deposits of unconfined flash floods and wide-shallow channel streams. The medial deposits, covering the rest of the anticline, consist of interbedded conglomerates, sandstones and claystones. These are interpreted to have been deposited from braided to meandering channel streams and overbank areas. Distal deposits are found towards the south, beyond the anticline, and are characterised by sandstone and clay deposits of terminal lobes and lacustrine deltas. This study assesses the impact of the primary depositional characteristics, diagenesis and deformation of the most heterolithic portion of the system, with implications for increasing our understanding of folded fluvial reservoirs. Diagenetic processes, mainly mechanical compaction and calcite cementation, resulted in overall low intergranular porosity, with limited relatively high porosity developed in sandstone lithofacies in the medial deposits. Deformation associated with thrusting and fold growth resulted in the formation of abundant fractures, with relatively high fracture intensities observed in sandstone lithofacies in the anticline crest. This study shows that post-depositional processes can both improve and diminish the reservoir potential of basin proximal fluvial deposits, through the development of fracture networks and by compaction-cementation. The comparison of the Puig-reig anticline with other similar settings worldwide indicates that foreland basin margin locations may be potential areas for effective reservoirs, even in the case of low intergranular porosity.
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