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Possible constraints on anatectic melt residence times from accessory mineral dissolution rates: an example from Himalayan leucogranites

Published online by Cambridge University Press:  05 July 2018

Michael Ayres ,
Nigel Harris  and
Derek Vance
Michael Ayres
Affiliation:
Department of Earth Sciences, The Open University, Milton Keynes MK7 6AA, UK
Nigel Harris
Affiliation:
Department of Earth Sciences, The Open University, Milton Keynes MK7 6AA, UK
Derek Vance
Affiliation:
Institut für Isotopengeologie, ETH-Zentrum, 8092 Zürich, Switzerland
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Abstract

The concentrations of LREE and Zr in a granitic melt formed by anatexis of a metapelitic protolith will be buffered by the stability of monazite and zircon respectively. The rate at which equilibrium is reached between dissolving monazite and zircon and a static melt is limited by the rate at which Zr and LREE can diffuse away from dissolution sites. If melt extraction rates exceed the rates at which the LREE and Zr in the melt become homogenized by diffusion, extracted melts will be undersaturated with respect to these elements. Evidence from accessory phase thermometry suggests that for many Himalayan leucogranites generated by crustal anatexis, the melts equilibrated with restitic monazite and zircon prior to extraction. In contrast, discordant temperatures determined from accessory phase thermometry suggest that tourmaline leucogranites from the Zanskar region of NW India did not equilibrate prior to extraction. Quantitative interpretation of this discordance assumes that the melt was static prior to extraction, and that accessory phase inheritance was minimal. Modelling of the time-dependant homogenization process suggests that tourmaline leucogranites generated at 700°C probably remained in contact with restitic monazite in the protolith for less than 7 ka and certainly less than 50 ka. Such rapid extraction rates suggest that deformation-driven mechanisms were important in removing these melts from their source.

Keywords

anatexismelt residence timeleucogranitesHimalayas
Type
Petrology
Information
Mineralogical Magazine , Volume 61 , Issue 404 , February 1997 , pp. 29 - 36
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1997

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References

Clemens, J.D. (1984) Water contents of silicic to intermediate magmas. Lithos, 17, 273–387.CrossRefGoogle Scholar
Clemens, J.D. and Mawer, C.K. (1992) Granitic magma transport by fracture propagation. Tectonophysics, 204, 339-60.CrossRefGoogle Scholar
Clemens, J.D. and Vielzeuf, D. (1987) Constraints on melting and magma production in the crust. Earth Planet. Sci. Lett., 86, 287–306.CrossRefGoogle Scholar
Copeland, P., Parrish, R.R. and Harrison, T.M. (1988) Identification of inherited radiogenic Pb in monazite and its implications for U-Pb systematics. Nature, 333, 760-3.Google Scholar
Copeland, P., Harrison, T.M. and Le Fort, P. (1990) Age and cooling history of the Manaslu granite: implications for the Himalayan tectonics. J. Volcanol. Geotherm. Res., 44, 33–50.CrossRefGoogle Scholar
Deniel, C., Vidal, P., Fernandez, A., Le Fort, P. and Peucat, J.-J. (1987) Isotopic study of the Manaslu granite (Himalaya, Nepal): inferences on the age and source of Himalayan leucogranites. Contrib. Mineral. Petrol., 96, 78–92.CrossRefGoogle Scholar
Ferrara, G., Lombardo, B., Tonarini, S. and Turi, B. (1991) Sr, Nd and O isotopic characterization of the Gophu La and Gumburanjun leucogranites (High Himalaya). Schweiz. Mineral. Petrogr. Mitt., 71, 35–51.Google Scholar
France-Lanord, C. and Le Fort, P. (1988) Crustal melting and granite genesis during the Himalayan collision orogenesis. Trans. R. Soc. Edin., 79, 183-95.Google Scholar
Guillot, S. and Le Fort, P. (1995) Geochemical constraints on the bimodal origin of High Himalayan leucogranites. Lithos, 35, 221-34.CrossRefGoogle Scholar
Harris, N., Ayres, M. and Massey, J. (1995) Geochemistry of granitic melts produced during the incongruent melting of muscovite; Implications for the extraction of Himalayan leucogranite magmas. J. Geophys. Res., 100, 15767-77.CrossRefGoogle Scholar
Harris, N.B.W. and Massey, J.A. (1994) Decompression and anatexis of Himalayan metapelites. Tectonics, 13, 1537-46.CrossRefGoogle Scholar
Harrison, T.M. and Watson, E.B. (1983) Kinetics of zircon dissolution and zirconium diffusion in granitic melts of variable water content. Contrib. Mineral. Petrol., 84, 66–72.CrossRefGoogle Scholar
Harrison, T.M. and Watson, E.B. (1984) The behavior of apatite during crustal anatexis: Equilibrium and kinetic considerations. Geochim. Cosmochim. Acta, 48, 1467-77.CrossRefGoogle Scholar
Holtz, F. and Johannes, W. (1995) Maximum and minimum water contents of granitic melts: implications for chemical and physical properties of ascending magmas. Lithos, 32, 149-59.CrossRefGoogle Scholar
Inger, S. and Harris, N. (1993) Geochemical constraints on leucogranite magmatism in the Langtang Valley, Nepal Himalaya. J. Petrol., 34, 345-68.CrossRefGoogle Scholar
McKenzie, D. (1985) The extraction of magma from the crust and mantle. Earth Planet. Sci. Lett., 74, 81–91.CrossRefGoogle Scholar
Montel, J.-M. (1993) A model for monazite/melt equilibrium and application to the generation of graniic magmas. Chem. Geol., 110, 127-46.CrossRefGoogle Scholar
Pichavant, M. (1987) Effects of B and H2O on liquidus phase relations in the haplogranite system at 1 kbar. Amer. Mineral., 72, 1056-70.Google Scholar
Rapp, R.P. and Watson, E.B. (1986) Monazite solubility and dissolution kinetics: implications for the thorium and light rare earth chemistry of felsic magmas. Contrib. Mineral. Petrol., 94, 304-16.CrossRefGoogle Scholar
Rutter, E.H. and Neumann, D.H.K. (1995) Experimental deformation of partially molten granites under fluid-absent conditions with implications for extraction of granite melts. J. Geophys. Res., 100, 15697-715.CrossRefGoogle Scholar
Scaillet, B., France-Lanord, C. and Le Fort, P. (1990) Badrinath-Gangotri plutons (Garhwal, India): petrological and geochemical evidence for fractionation processes in a high Himalayan leucogranite. J. Volcanol. Geotherm. Res., 44, 163-88.CrossRefGoogle Scholar
Scaillet, B., Pichavant, M. and Roux, J. (1995) Experimental crystallization of leucogranite magmas. J. Petrol., 36, 663–705.CrossRefGoogle Scholar
Watson, E.B. and Harrison, T.M. (1983) Zircon saturation revisited: temperature and composition effects in a variety of crustal magma types. Earth Planet. Sci. Lett., 64, 295–304.CrossRefGoogle Scholar
Watson, E.B., Vicenzi, E.P. and Rapp, R.P. (1989) Inclusion/host relations involving accessory minerals in high-grade metamorphic and anatectic rocks. Contrib. Mineral. Petrol., 101, 220-31.CrossRefGoogle Scholar
Watt, G.R. and Harley, S.L. (1993) Accessory phase controls on the geochemistry of crustal melts and restites produced during water-undersaturated partial melting. Contrib. Mineral. Petrol., 114, 550-66.CrossRefGoogle Scholar
Wickham, S.M. (1987) The segregation and emplacement of granitic magmas. J. Geol. Soc. London, 144, 281-97.CrossRefGoogle Scholar
Wolf, M.B. and London, D. (1994) Apatite dissolution into peraluminous haplogranitic melts: An experimental study of solubilities and mechanics. Geochim. Cosmochim. Acta, 58, 4127-45.CrossRefGoogle Scholar