Beyssac, Olivier and Bollinger, Laurent and Avouac, Jean-Philippe and Goffé, Bruno (2004) Thermal metamorphism in the lesser Himalaya of Nepal determined from Raman spectroscopy of carbonaceous material. Earth and Planetary Science Letters, 225 (1-2). pp. 233-241. ISSN 0012-821X. http://resolver.caltech.edu/CaltechAUTHORS:20110111-092509212
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The determination of metamorphic conditions is critical to the understanding of the formation of mountain belts. However, all collisional mountain belts contain large volumes of accreted sediments generally lacking metamorphic index minerals and are therefore not amenable to conventional petrologic investigations. By contrast, these units are often rich in carbonaceous material, making it possible to determine thermal metamorphism through Raman spectroscopy of carbonaceous material (RSCM method), a technique that has been recently calibrated [Beyssac et al., J. Metamorph. Geol. 20 (2002) 859–871]. The Lesser Himalaya (LH) is one of these problematic cases with a very poor mineralogy, but a key structural position within the Himalayan system that makes LH considered as diagnostic of the overall thermal behaviour of the orogen. This work demonstrates the performance of the RSCM technique and shows that this technique might thus be used to detect inter-sample variations as small as ~10–15 °C, but absolute temperatures can only be determined to ±50 °C due to the uncertainty on the calibration. This study reveals that the LH has undergone a large-scale thermal metamorphism, with temperature decreasing progressively from about 540 °C at the top to less than 330 °C within the deepest exhumed structural levels.
|Additional Information:||© 2004 Elsevier B.V. Received 18 December 2003; received in revised form 6 May 2004; accepted 20 May 2004. Field work was organized with the friendly assistance of our colleagues at the Department of Mines and Geology in Katmandu. Raman spectroscopy measurements were performed at ENS Lyon (INSU national instrument). Maps were produced with GMT software. Constructive and sensitive comments by Michael Tice and Brigitte Wopenka as well as editorial handling by Ken Farley are gratefully acknowledged.|
|Group:||Caltech Tectonics Observatory, Caltech Tectonics Observatory. Indo-Asian Collision Zone|
|Subject Keywords:||Himalaya; graphitization; Raman spectroscopy; geothermometry; metamorphism|
|Other Numbering System:|
|Official Citation:||Olivier Beyssac, Laurent Bollinger, Jean-Philippe Avouac, Bruno Goffe, Thermal metamorphism in the lesser Himalaya of Nepal determined from Raman spectroscopy of carbonaceous material, Earth and Planetary Science Letters, Volume 225, Issues 1-2, 30 August 2004, Pages 233-241, ISSN 0012-821X, DOI: 10.1016/j.epsl.2004.05.023. (http://www.sciencedirect.com/science/article/B6V61-4CY0GP4-1/2/90ce2f41593ca9b83cd722ecbee2a7a7)|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Tony Diaz|
|Deposited On:||25 Jan 2011 18:40|
|Last Modified:||26 Dec 2012 12:50|
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