Lyell Collection

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (19) Citing Articles via Google Scholar Google Scholar Articles by WHITE, N. M. Articles by MAITHANI, A. Search for Related Content GeoRef GeoRef Citation

Metamorphism and exhumation of the NW Himalaya constrained by U–Th–Pb analyses of detrital monazite grains from early foreland basin sediments

¹ Department of Earth Sciences, Cambridge University, Downing Street, Cambridge CB2 3EQ, UK (e-mail: nicola{at}esc.cam.ac.uk)
² NERC Isotope Geosciences Laboratory, Kingsley Dunham Centre, Keyworth, Nottingham NG12 5GG, UK
³ Department of Geology and Geophysics, Edinburgh University, Grant Institute, Kings Buildings, West Mains Road, Edinburgh EH9 3JW, UK
⁴ Present address: Department of Geology and Geophysics, University of Calgary, 2500 University Drive, NW Calgary, Canada
⁵ Dept. of Geosciences, 539 Deike Building, Pennsylvania State University, University Park, PA 16802 USA
⁶ Remote Sensing Lab., Geology Division KDM Instt. of Petroleum Exploration, Oil and Natural Gas Corporation, Dehra Dun, 248 195 Uttar Pradesh, India

Scientific editing by Martin Whitehouse.

Single detrital monazite grains from the Dharamsala and Lower Siwalik Formations (early to mid-Miocene continental foreland basin sediments in NW India) have been dated by two techniques; isotope dilution thermal ionization multicollector mass spectrometry (ID-TIMS) and laser ablation plasma ionization multicollector mass spectrometry (LA-PIMMS). The results give U–Th–Pb isotopic ages of c. 400–1300 Ma and 28–37 Ma and suggest that the source of detritus shed from the uplifting Himalayan mountains and captured in the foreland basin included (1) the protolith to the High Himalayan Crystalline Series (HHCS), i.e. rocks unaffected by the Himalayan metamorphism, (2) Cambro-Ordovician granites and (3) HHCS affected by the M₁ phase of Barrovian metamorphism (Eo-Himalayan) related to the Indo-Asian collision. Deposition of the Dharamsala Formation was coeval with M₂ sillimanite grade Himalayan metamorphism and crustal melting.

The youngest monazite (c. 28–37 Ma) ages imply that Indian plate rocks, having experienced the earliest Himalayan metamorphic event which occurred within 10–20 Ma of collision were exhumed, eroded and deposited within c. 10–20 Ma of metamorphism. This indicates a minimum cooling rate of between 60 and 40°C Ma^–1 for the period 30–20 Ma. After 20 Ma our study suggests no change in source area and that this same sequence, comprising both metamorphosed and unmetamorphosed rocks, was supplying detritus and being progressively incised by erosion for at least a further 8 million years.

Keywords: Himalayas, Siwalik Range, monazite, exhumation, foreland basins.

This article has been cited by other articles:

				R. A. Cox, D. H.C. Wilton, and J. Kosler LASER-ABLATION U Th Pb IN SITU DATING OF ZIRCON AND ALLANITE: AN EXAMPLE FROM THE OCTOBER HARBOUR GRANITE, CENTRAL COASTAL LABRADOR, CANADA Can Mineral, 2003; 41: 273 - 291. [Abstract] [Full Text] [PDF]

				T. M. Harrison, E. J. Catlos, and J.-M. Montel U-Th-Pb Dating of Phosphate Minerals Reviews in Mineralogy and Geochemistry, 2002; 48: 524 - 558. [Full Text] [PDF]

• Home  |  
• Current issue  |  
• Table of contents  |  
• Archive  |  
• Search  |  
• Feedback

• Copyright policy  |  
• Permissions request   |  
• Terms of use   |  
• Feedback   |  
• HighWire Press