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Age of metamorphism in the Lesser Himalaya and the Main Central Thrust zone, Garhwal India: results of illite crystallinity, 40Ar–39Ar fusion and K–Ar studies

Published online by Cambridge University Press:  01 May 2009

G. J. H. Oliver ,
M. R. W. Johnson  and
A. E. Fallick
G. J. H. Oliver
Affiliation:
Geology Department, St Andrews University, St Andrews, Fife KYI6 9ST, UK
M. R. W. Johnson
Affiliation:
Department of Geology & Geophysics, Grant Institute, University of Edinburgh, West Mains Road, Edinburgh EH9 3JW, UK
A. E. Fallick
Affiliation:
Scottish Universities Research & Reactor Centre, East Kilbride, Glasgow G75 0QU, UK
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Abstract

Illite crystallinity data from the Lesser Himalaya of Garhwal show that the upper Paleocene-lower Eocene Subathu Formation, deposited immediately prior to or early in the Himalayan collision, has not suffered significant regional metamorphism. The regional metamorphism in the upper Precambrian–lower Palaeozoic Lesser Himalaya must therefore be precollisional. Illite crystallinity results from Lesser Himalayan fossiliferous Permian strata show grades of metamorphism intermediate between upper Paleocene–lower Eocene and Proterozoic–lower Palaeozoic strata indicating a pre-Permian regional metamorphism for the latter.

K–Ar whole rock cooling ages provide supporting evidence for pre-collisional regional metamorphism in the Lesser Himalaya. Slates and phyllites below the Main Central Thrust (MCT) show pre-Cenozoic whole rock ages, as old as Ordovician (486 Ma). Whilst resetting of K–Ar whole rock ages has occurred locally in pervasively cleaved Palaeozoic strata (near thrusts?), fracture cleaved Permian and upper Paleocene–lower Eocene sediments give whole rock ages compatible with diagenesis. The illite crystallinity results confirm that these sediments have not been heated above mica blocking temperatures.

Muscovite 40Ar–39Ar and K–Ar mineral ages within the 5 km thick MCT zone are as young as 8 Ma indicating that temperatures of above ~ 350°C were maintained in the MCT zone for over 10 Ma after high temperature (~ 550°C) shearing on the MCT. This heating did not affect the MCT footwall Lesser Himalaya to any regional extent, where pre-Permian low grade regional metamorphism has not been overprinted.

Type
Articles
Information
Geological Magazine , Volume 132 , Issue 2 , March 1995 , pp. 139 - 149
Copyright
Copyright © Cambridge University Press 1995

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References

Archbold, N. W., & Singh, T. In press. Early Permian brachiopods from Lower Bijni unit, near Dugadda, Garhwal Lesser Himalaya. Himalayan Geology.Google Scholar
Azmi, R. J. 1983. Microfauna and age of the Lower Talm phosphorite of Mussoorie syncline, Garhwal Lesser Himalaya, India. Himalayan Geology 11, 373–409.Google Scholar
Azmi, R. J. & Pancholi, V. P. 1983. Early Cambrian (Tommotian) conodonts and other shelly microfaunas from the Upper Krol of Mussoorie Syncline, Garhwal Himalaya. Himalayan Geology 11, 360–72.Google Scholar
Baski, A. K. 1982. A Note on the calculation of errors in conventional K–Ar dating. Chemical Geology 35, 267–72.Google Scholar
Blenkinsop, T. G. 1988. Definition of low-grade metamorphic zones using illite crystallinity. Journal of Metamorphic Geology 6, 623–36.CrossRefGoogle Scholar
Dewey, J. F., Shackleton, R. M., Chang, Chengfa, & Sun, Yiyin. 1988. The tectonic evolution of the Tibetan Plateau. Philosophical Transactions of the Royal Society of London A327, 379–413.Google Scholar
England, P. C., & Molnar, P., 1993. Cause and effect among thrusts and normal faulting, anatectic melting, and exhumation in the Himalaya. In Himalayan Tectonics (eds Treloar, P. J. and Searle, M. P.), pp. 401–11. Special Publication of the Geological Society of London no. 74.Google Scholar
Fettes, D. J., Graham, C. M., Sassi, F. P., & Scolari, A., 1976. The basal spacing series variation across the Caledonides. Scottish Journal of Geology 12, 227–36.CrossRefGoogle Scholar
Frey, M., 1987. Low Temperature Metamorphism. Glasgow & London: Blackie, 350 pp.Google Scholar
Glasmann, J. R., 1987. Comments on ‘The evolution of illite to muscovite: mineralogical and isotopic data from the Glarus Alps, Switzerland.’ Contributions to Mineralogy and Petrology 96, 72–4.CrossRefGoogle Scholar
Guidotti, C. V., & Sassi, F. P., 1976. Muscovite as a petrogenetic indicator mineral in metamorphosed pelites and semipelites. Neues Jahrbuch für Mineralogie Abhandlungen 127, 97–142.Google Scholar
Halliday, A. N., 1977. K–Ar dating of mineralisation episodes – a discussion. Economic Geology 72, 870–1.CrossRefGoogle Scholar
Halliday, A. N., & Mitchell, F. G., 1983. K–Ar ages of clay concentrates from Irish orebodies and their bearing on the timing of mineralisation. Transactions of the Royal Society of Edinburgh: Earth Sciences 74, 1–14.CrossRefGoogle Scholar
Hamilton, P. J., Kelley, S., & Fallick, A. E., 1989. K–Ar dating of illite in hydrocarbon reservoirs. Clay Minerals 24, 215–31.CrossRefGoogle Scholar
Harland, W. B., Armstrong, R. L., Llewellyn, P. G., Cox, A. V., Craig, L. E., Smith, A. G., & Smith, D. G., 1989. A Geologic Time Scale. Cambridge University Press, 263 pp.Google Scholar
Harrison, T. M., & McDougall, I., 1980. Investigation of an intrusive contact in NW Nelson, New Zealand. Thermal, chronological and isotopic constraints. Geochimica Cosmochimica Acta 44, 1985–2003.CrossRefGoogle Scholar
Hubbard, M. S., & Harrison, T. M., 1988. 40Ar/39Ar constraints on deformation and metamorphism in the MCT zone and the Tibetan slab, eastern Himalaya. Tectonics 8, 865–80.CrossRefGoogle Scholar
Hunziker, J. C., Frey, M., Clauer, N., Dallmeyer, R. D., Friedrichsen, H., Flehmig, W., Hochstrasser, K., Roggwiler, P., & Schwander, H., 1986. The evolution of illite to muscovite: mineralogical and isotopic data from the Glarus Alps, Switzerland. Contributions to Mineralogy and Petrology 92, 157–80.CrossRefGoogle Scholar
Hunziker, J. C., Frey, M., Clauer, N., Dallmeyer, R. D., 1987. Reply to comments on the evolution of illite to muscovite by J. R. Glasmann. Contributions to Mineralogy and Petrology 96, 75–7.CrossRefGoogle Scholar
Johnson, M. R. W., 1986. The structural evolution of the Kumaun Lesser Himalaya. In Current Trends in Geology. IX. Himalayan thrust and associated rocks (ed. Saklani, P. S.), pp. 27–39. New Delhi: Today & Tomorrow’s Publishers.Google Scholar
Johnson, M. R. W., & Oliver, G. J. H., 1990. Pre-collisional and post-collisional thermal events in the Himalaya. Geology 18, 753–6.2.3.CO;2>CrossRefGoogle Scholar
Kelley, S., & Bluck, B. J., 1989. Detrital mineral ages from the Southern Uplands using 40Ar–39Ar laser probe. Journal of the Geological Society, London 146, 401–3.CrossRefGoogle Scholar
Kemp, A. E. S., Oliver, G. J. H., & Baldwin, J. R., 1985. Low-grade metamorphism and accretionary tectonics: Southern Uplands terrain, Scotland. Mineralogical Magazine 49, 335–44.CrossRefGoogle Scholar
Kisch, H. J., 1987. Correlation between indicators of very low-grade metamorphism. In Low Temperature Metamorphism (ed. M., Frey), pp. 227–303. London, Glasgow: Blackie.Google Scholar
Kisch, H. J., 1991. Illite crystallinity – recommendations on sample preparation, X-ray diffraction settings, and interlaboratory samples. Journal of Metamorphic Petrology 9, 665–70.CrossRefGoogle Scholar
Kübler, B., 1967. La cristallinité de l'illite et les zones tout à fait supérieures du métamorphisme. In Etages Tectoniques, pp. 105–21. A la Baconnére, Neuchâtel (Suisse).Google Scholar
Macintyre, R. M., & Hamilton, P. J., 1984. Isotope geochemistry of lavas from sites 553 and 555. In Initial Reports of the Deep Sea Drilling Project, vol. 18 (eds Roberts, D. G. and D., Schnitker), pp. 775–81. Washington: US Government Printing Office.Google Scholar
Merriman, R. J., & Roberts, B., 1985. A survey of white mica crystallinity and polytypes in pelitic rocks of Snowdonia and Llyn, N., Wales. Mineralogical Magazine 49, 305–19.CrossRefGoogle Scholar
Metcalfe, R. P., 1993. Pressure, Temperature, and time constraints on metamorphism across the Main Central Thrust zone and the High Himalaya Slab in the Garhwal Himalaya. In Himalayan Tectonics (eds Treloar, P. J. and Searle, M. P.), pp. 485–509. Special Publication of the Geological Society of London no. 74.Google Scholar
Miller, W. M., Fallick, A. E., Leake, B. E., Macintyre, R. M., & Jenkin, G. R. T., 1991. Fluid disturbed hornblende K–Ar ages from the Dalradian rocks of Connemara, Western Ireland. Journal of the Geological Society, London 148, 985–92.CrossRefGoogle Scholar
Morrison, C. W. K., & Oliver, G. J. H., 1993. A study of illite crystallinity and fluid inclusions in the Kathmandu Klippe and the Main Central Thrust zone, Nepal. In Himalayan Tectonics (eds Treloar, P. J. and Searle, M. P.), pp. 525–40. Special Publication of the Geological Society of London no. 74.Google Scholar
Oliver, G. J. H., & Kelley, S., 1993. 40Ar–39Ar fusion ages from the Polish Sudetes: Variscan tectonothermal reworking of Caledonian protoliths. Neues Jahresbuch Geologie Palaeontologie Monatshefte 1993, 321–34.CrossRefGoogle Scholar
Padan, A., Kisch, H. J., & Shargam, R., 1982. Use of lattice parameter b0 of dioctahedral illite/muscovite for the characterisation of P/T gradients of incipient metamorphism. Contributions to Mineralogy and Petrology 79, 85–95.CrossRefGoogle Scholar
Rice, A. N. H., Bevins, R. E., Robinson, D., & Roberts, D., 1989. Evolution of low-grade metamorphic zones in the Caledonides of Finnmark, North Norway. In The Caledonide Geology of Scandinavia (ed. Gayer, R. A.), pp. 172–92. London: Graham & Trottman.Google Scholar
Roberts, B., Morrison, C. W. K., & Hirons, S., 1990. Low grade metamorphism of the Manx Group, Isle of Man: a comparative study of white mica ‘crystallinity’ techniques. Journal of the Geological Society of London 147, 271–8.CrossRefGoogle Scholar
Sassi, F. P., & Scolari, A., 1974. The b0value of the potassic white micas as a barometric indicator in low-grade metamorphism of pelitic schists. Contributions to Mineralogy and Petrology 45, 143–52.CrossRefGoogle Scholar
Searle, M. P., Windley, B. F., Coward, M. P., Cooper, D. J. W., Rex, A. J., Rex, D. C., Tingdong, L., Xuchang, X., Jan, M. Q., Thakur, V. C., & Kumar, S., 1987. The closing of Tethys and the tectonics of the Himalaya. Geological Society of America Bulletin 96, 679–701.Google Scholar
Searle, M. P., Metcalfe, R. P., Rex, A. J., & Norry, M. J., 1993. Field relations, petrogenesis and emplacement of the Bhagirathi leucogranite, Garhwal Himalaya. In Himalayan Tectonics (eds Treloar, P. J. and Searle, M. P.), pp. 485–509. Special Publication of the Geological Society of London no. 74.Google Scholar
Sibson, R., 1977. Fault Rocks and fault mechanisms. Journal of the Geological Society, London 133, 191–213.CrossRefGoogle Scholar
Singh, I. B., & Rai, V., 1983. Fauna and biogenic structures in Krol–Tal succession (Vendian-Early Cambrian), Lesser Himalaya: their biostratigraphic and palaeontological significance. Journal of the Palaeontological Society of India 28, 67–90.Google Scholar
Srivastava, P., & Mitra, G., 1994. Thrust geometries and deep structure of the outer and lesser Himalaya, Kumaun and Garhwal (India): Implications for evolution of the Himalayan fold-and-thrust belt. Tectonics 13, 89–109.CrossRefGoogle Scholar
Steiger, R. H., & Jäger, E., 1977. Subcommission on Geochronology: convention on the use of decay constants in geo- and cosmochronology. Earth and Planetary Science Letters 36, 359–62.CrossRefGoogle Scholar
Stöckxin, J., 1980. Geology of Nepal and its regional Framework. Journal of the Geological Society, London 137, 1–34.CrossRefGoogle Scholar
Valdiya, K. S., 1980. Geology of Kumaun Lesser Himalaya. Wadia Institute of Himalayan Geology. Dehra Dun: Himachal Times Press, 291 pp.Google Scholar
Weber, K., 1972. Notes on determination of illite crystallinity. Neues Jahrbuch Mineral Monatshefte 1972, 267–72.Google Scholar