Petrology of a Hornblende-Rich Pegmatite and Host Amphibolites near Matta, Upper Swat.
Abstract
The 500x30m pegmatite near Matta consists of hornblende+ epidote+- garnet lithology and hornblendite, with a small proportion of leucocratic, deformed dykes and veins. J t is hosted by epidote amphibolites derived from gabbroic rocks md belonging to the southern amphibolite belt of the Kohistan zone. The hornblende-epidote lithology of the pegmatite is chemically identical to the amphibolites and is, therefore, neither a younger intrusion in nor a metasomatic product of the amphibolites. The coarse-grained fabric of the pegmatite may have developed locally in response to a higher concentration of fluid phase, mainly water but some fluorine. The hornblendite, which is coarser grained (with zip to 35cm long crystals) and may cut the hornblende-epidote lithology, may be a product of meramorphic differentiation or, more likely, metasomatism. The ampbhibolites are tholeiitic in affinity and probably represent the Tethyan oceanic crust.
References
Arndt, N.T., Naldrett, A. J. & Pyke, D.R., 1977. Komatiite and iron-rich tholeiitic lavas of Munro Township, Northeast Ontario. J. Petrol. 18, 319-369.
Banaras, M. & Ghani, A., 1983. Petrography of the Tora Tigga Complex, Munda area, Dir District, Unpub. M.Sc. thesis, Univ. Peshawar.
Bard, J.P., 1983. Metamorphic evolution of an abducted island arc: Example of the Kohistan sequence (Pakistan) in the Himalayan collided range. Geol. Bull. Univ. Peshawar 16, (this volume).
Barth, T.F.W., 1962. Theoretical Petrology. 2nd Ed. Wiley, New York.
Bass, M.N., Moberly, R., Dhodes, J.M., Shih, C. & Church, S.E., 1973. Volcanic rocks cored in the central Pacific. Initial Reports D.S.D.P. 17, 429-503.
Butt, K.A., 1983. Tectonic environments favorable for Ni and Pt group element sulphide deposits in Northern Pakistan. Proc. 2nd Nat. Sem. Dev. Min. Res. Peshawar, Pakistan, 1-11.
Butt, K.A., Chaudhry, M.N.& Ashraf, M., 1980. An interpretation of petro-tectonic assemblage west of western Himalayan Syntaxis in Dir District and adjoining areas in Northern Pakistan. Geol. Bull. Univ. Peshawar 13, 79-86.
Coward, M.P., Jan, M.Q., Rex, D., Tarney, J., Thirlwall, M. & Windley, B.F., 1982. Geotectonic framework of the Himalaya of N. Pakistan. J. Geol. Soc. London 139, 299-308.
Deer, WA., Howie, R.A. & Zussman, J., 1962. Rock-forming Minerals, Vol. I. Ortho and Ring Silicates. Longman, London.
Enami, M. & Banno, S., 1980. Zoisite-clinozoisite relations in low- to medium grade high pressure metamorphic rocks and their implications. Min. Mag. 43, 1005-1013.
Hallberg, J.A. & Williams, D.A.C., 1972. Archaean mafic and ultramafic rock associations in the eastern Goldfields region, Western Australia. Earth Planet. Sci. Lett. 15, 191-200.
Jan, M.Q., 1977. The mineralogy, geochemistry, and petrology of Swat-Kohistan, NW Pakistan. Unpub. Ph.D. thesis. Univ. London.
Jan, M.Q., 1979a. Petrography of the amphibolites of Swat and Kohistan. Geol. Bull. Univ. Peshawar 11, 51-64.
Jan, M.Q., 1979b. Petrography of the pyroxene granulites from northern Swat and Kohistan. Geol. Bull. Univ. Peshawar 11, 65-87.
Jan, M.Q., 1982. Chemical changes accompanying the ganulite to amphibolite transition in Swat, NW Pakistan. In 'Contemporary Geoscientific Researches in Himalaya, 2,' (A.K. Sinha ed.), 49-52.
Jan, M.Q., & Kempe, D.R.C., 1973. The petrology of the basic and intermediate rocks of Upper Swat, Pakistan Geol. Mag. 110, 285-300.
Jan, M.Q., & Howie, R.A., 1982. Hornblendic amphiboles from basic and intermediate rocks of Swat-Kohistan, northwest Pakistan. Am. Mineral, 67, 1155-1178.
Jan, M.Q., Banaras, M., Ghani, A. & Asif, M., 1983. The Tora Tigga ultramafic complex, southern Dir district. Geol. Bull. Univ. Peshawar 16, 11-29.
Laurent, R., Delaloye, M., Vuagnat, M. & Wagner, J.J., 1979. Composition of parental basaltic magma in ophiolites. In 'Ophiolites' (A. Panayiotou, ed.), Proc. Int. Ophiolite Sympo. Geol. Sum. Dept., Ministry of Agr. & Nat. Res., Repub. Cyprus, 172-181.
Leake, B.E., 1972. The mineralogical modification of the chemistry of metamorphic rocks. Geol. Mag. 109, 331-337.
Leake, B.E., 1978. Nomenclature of amphiboles. Min. Mag. 42, 533-563.
Naldrett, AJ., & Cabri, L.J., 1976. Ultramafic and related mafic rocks. Their classification and genesis with special reference to concentration of nickel sulphides and Pt group elements. Econ. Geol. 71, 1131-1158.
Nesbitt, R.W. & Sun, S.S., 1976. Geochemistry of Archaean Spinifex-textured peridotites and Magnesian and low-magnesian tholeiites. Earth Planet. Sci. Lett. 3 1, 433-453.
Nesbitt, R.W. & Purvis, A.C., 1979. Komatiites: Geochemistry and genesis, Canadian Mineral, 17, 165-186.
Niggli, P., 1954. Rocks and Mineral Deposits. Freeman, San Francisco.
Pearce, J.A., 1975. Basalt geochemistry used to investigate past tectonic environments on Cyprus. Tectonophysics 25, 41-67.
Shams, F.A., 1975. The petrology of the Thak Valley Igneous Complex, Gilgit Agency, Northern Paltistan. Acad. Naz. Lincei, Ser. 8, 59, 454-464.
Tahirkheli, R.A.K. & Jan, M.Q., (eds.), 1979. Geology of Kohistan, Karakoram Himalaya, Northern Pakistan. Geol. Bu11. Univ. Peshawar 11.
