The Tora Tigga Ultramafic Complex, southern Dir district
Abstract
The ultramafic rocks of Tora Tigga near Munda are emplaced in amphibolites of the Kohistan tectonic zone along the Main Mantle Thrust. The amphibolites are represented by metamorphosed gabbros and lo rites of the Chilas layered complex, and garnet-bearing mafic to intermediate plutons. The ultramafites include dunites and a variety of peridotites, pyroxenites, and hornblendite. The hornblendites are the most abundant of these, are coarse-grained to pegmatite, and contain deformed felsic dykes and veins. The origin of the olivine- and pyroxene ulltramafites is not clear; they might be alpine-type or, more probably, cumulates of the Chilas complex and related to the metamorphosed gabbros and norites. Field relations and textural features suggest that the hornblendites have formed by metasomatism of the various rocks in the area.
References
Ahmed, Z., 1978. Petrology of the Taghma area, Swat district, N.W.F.P. Pakistan. Geol. Bull. Univ. Punjab, 15, 25-29.
Andrews-Speed, C.P. & Brookfield, ME., 1982. Middle Paleozoic to Cenozoic geology and tectonic evolution of northwestern Himalaya. Tectonophysics 82, 253-275.
Arbab, M.S H. & Khan, R.N., 1973. Geology of Dir and northern part of Timurgara quadrangle, N.W.F.P., Pakistan. Geol. Surv. Pak. Inf. Re1. 49.
Bard, J.P., 1983. Metamorphic evolution of an obducted island arc: Example of Kohistan sequence (Pakistan) in the Himalayan collided range, (this volume).
Bard, J.P., Maluski, H., Matte, Ph., and Proust, F., 1980. The Kohistan sequence: Crust and mantle of an obducted island arc. Geol. Bull. Univ. Peshawar (Spec. Issue) 13, 87-94.
Bishop, A.C. & French, W.J., 1982. Nature and origin of meladiorite layers in northern Gurnsey, Channel Islands. Min. Mag. 46, 301-321.
Bowes, D.R. & McArthur, A.C., 1976. Nature and genesis of appinite suite. Krystalinikum 12, 31-46.
Butt, K.A., Chaudhry, M.N. and Ashraf, M., 1780. An interpretation of petrotectonic assemblage west of W. Himalayan syntaxis in Dir district: and adjoining areas in northern Pakistan. Geol. Bull. Univ. Peshawar (Spec. Issue) 13, 79-86.
Chaudhry, M.N., Kausar, A.B. and Lodhi, S.A.K., 1974. Geology of Timurgara Lal Qila area, Dir district N.W.F.P. Geol. Bull. Punjab Univ. 1i, 53-74.
Coleman, R.G., 1971. Plate tectonic emplacement of upper mantle peridotites along continental edges. J. Geophys. Res. 76, 1212-1222.
Cotrell, A.H., 1948. "Effect of solute atoms on the behaviour of dislocations" in Report of a conference on strength of solids. Phys. Soc. London, 30-38.
Coward, M.P., Jan, M.Q., Rex, D., Tarney, J., Thirlwall, M. & Windley, B.F., 1982. Geo-tectonic framework of the Himalaya of N. Pakistan. J. Geol. Soc. Lond. 139, 299-308.
Deer, W.A., 1950. The diorites and associated rocks of the Glen Tilt Complex, Perthshire-11. Diorites and appinites. Geol. Mag. 87, 181-195.
Griffin, W.L. & Heier, K.S., 1973. Petrological implications of some corona structures. Lithos 6, 315-335.
Harker, A., 1932. Metamorphism: A study of the transformation of rock-masses. Methuen & Co. Ltd., London.
Jackson, E.D., 1961. Primary textures and mineral association in the ultramafic zone of the Stillwater Complex, Montana. US. Geol. Surv. Prof. Paper 358, 111-132.
Jackson, E.D., & Thayer, T.P., 1972. Some criteria for distinguishing between stratiform, concentric and alpine peridotite-gabbro complexes. Proc. 24th Int. Geol. Cong. Montreal 2, 289-296.
Jan, M.Q., 1977. The Mineralogy, Geochemistry and Petrology of Swat Kohistan, NW Pakistan. Unpub. PhD. Thesis, Univ. London.
Jan, M.Q., 1979. Petrography of pyroxene granulites from northern Swat and Kohistan. Geol. Bull. Univ. Peshawar (Spec. Issue) 11, 65-87.
Jan, M.Q., 1980. Petrology of the obducted mafic and ultramafic metamorphites from the southern part of the Kohistan island arc sequence. Geol. Bull. Univ. Peshawar (Spec. Issue) 13, 95-108.
Jan, M.Q., & Asif, M. In press. Geochemistry of tonalites and quartz (diorites) of the Kohistan-Ladakh ('Transhimalayan') granitic belt in Swat, NW Pakistan. In Granites of Himalaya, Karakoram and Hindukush (F.A. Shams, ed.).
Jan, M.Q., & Howie, R.A., 1981. The mineralogy and geochemistry of the metamorphosed basic and ultrabasic rocks of the Jijal complex, Kohistan, NW Pakistan. Jour. Petrology 22, 85-126.
Jan, M.Q., & Howie, R.A., 1982. Hornblendic amphiboles from basic and intermediate rocks of Swat-Kohistan, NW Pakistan. Amer. Mineral. 67, 1155-1178.
Jan, M.Q., & Howie, R.A., In press. Some minor olivine gabbros and metamorphosed ultramafic rocks from Swat, NW Pakistan. Geol. Bull. Univ. Punjab. (Spec. Issue).
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.
Kakar, S.K., Badshah, MS. & Khan, J., 1971. The geology of the Jandul valley, western Dir. Geol. Bull, Univ. Peshawar 6, 54-73.
Key, C.H., 1977. Origin of appinitic pockets in the diorites of Jersey, Channel Islands. Min. Mag. 41, 183-192.
Khan, R.N., 1969. Geology of Timurgara quadrangle, Dir, NW Pakistan. Geol. Surv. Pak. Unpubl. Rept.
Khan, R.N. & Saleemi, B.A., 1972. Geology of Kotegram and Akhagram quadrangle, Dir district and Swat, N.W.F.P., Pakistan. Geol. Surv. Pals. Inf. Rel. 80.
Khattak, M.U.K. & Parvez, M.K., 1982. A petrographic account of the east-central part of the Chilas Complex, northern Pakistan. Unpub. M.Sc. Thesis, Univ. Peshawar.
MacKenzie, D.B., 1960. High-temperature alpine-type peridotite from Venezuela. Geol. Soc. Amer. Bull. 71, 303-318.
Moores, E.M., 1973. Geotectonic significance of ultramafic rocks. Earth Sci. Reviews 9, 241-258.
Naldrett, A. J. & Cabri, L. J., 1976. Ultramafic and related mafic rocks: Their classification and genesis with special reference to the concentration of nickel sulfides and platinum group elements Econ. Geol. 71, 1131-1158.
Nicholls, G.D., 195 1. The Glenelg-Ratagain igneous complex. Quart. J. Geol. Soc. Lond. 106, 309-344.
Nockolds, S.R., 1941. The Garabal Hill Glen Fvne igneous complex. Quart. J. Geol. Soc. Lond. 96, 451-521.
Park, C.F., Jr. & MacDiarmid, R.A., 1964. Ore Deposits. W.H. Freeman & 6. San Francisco.
Shams, F.A., 1975. The petrology of the Thank valley igneous complex, Gilgit Agency, northern Pakistan. Accd. Naz. Linccii, Ser. 8. 59, 453-464.
Spry, A. 1969. Metamorphic Textures. Pergamon Press, New York.
Sorensen, H., 1967. Metamorphic and metasomatic processes in the formation of ultramafic rocks. In "Ultramafic and Related Rocks". (P.J. Wyllie ed.), Wiley, New York, 204-211.
Tahirkheli, R.A.K., 1982. Geology of Himalaya, Karakoram and Hindukush in Pakistan. Geol. Bull. Univ. Peshawar (Spec. Issue) 15, 2-51.
Tahirkheli, R.A.K., Mattauer, M., Proust, F. & Tapponier, P., 1977. The India-Eurasia suture zone in northern Pakistan: Syi~tllesis and interpretation of recent data at
date scale. In 'Geodynamics of Pakistan' (A. Farah & K.A. DeJong eds.). Spec. Publ. Geol. Surv. Pak., Quetta, 124-130.
Thayer, T.P. & Himmelberg, G.R., 1968. Rock succession in the alpine-type mafic complex at Canyon Mountain, Oregon. 23rd Int. Geol. Cong. 1, 175-186.
Upadhyay, H.D. & Neale, E.R.W., 1979. On the tectonic regimes of ophiolite genesis. Earth and Plan. Sci. Lett. 43, 93-102.
Wyllie, P.J., 1967. Ultramafic and Related Rocks. Wiley, New York, 19-38.
Wyllie, P.J., 1969. The origin of ultramafic and ultrabasic rocks. Tectonophysics, Spec. Issue 7, 437-456.
