The Dir meta-volcanic sequence: Calcalkaline magmatism in the Kohiatan Arc terrane, northern Pakistan
Abstract
A variably deformed and metamorphosed NE-SW trending belt of Dir metavolcanic sequence is exposed within the north-western portion of the Kohistan arc terrane. The sequence is mainly composed of massive and sheared volcanics and pyroclastic breccia. The petrochemical indices suggest that they are dominantly basaltic-andesite and andesite with subordinate basalt, dacite and rhyolite in composition.
Whole rock major element compositions define a calc-alkaline trend: CaO, FeO, MgO, TiO2, A12O3, V, Cr, Ni, and Sc all decrease with increasing silica, whereas alkalis, Rb, Ba, and Y increase. Mafic to intermediate volcanic rocks show calc-alkaline affinities on petrotectonic diagrams. Chondrite-normalized REE Patterns are LREE-enriched. Dacites and rhyolites have the lowest La/Lu ratios and highest Eu/Eu* ratios, reflecting the dominant role of plagioclase fractionation in their formation. MORB-normalized spider diagrams show progressive enrichment of the low-field strength incompatible elements (Cc, La, Ba, Rb, K) and a distinct negative Nb anomaly; patterns typical of subduction related magmas.
It is suggested that the high-Mg basalt of the Dir area is primitive in nature and could be the representative of the primary magnesian liquid formed by the partial melting of mantle wedge at the base of the Kohistan arc terrane. This liquid may have fractionated the other members of the sequence especially low magnesia basalt and basaltic-andesite.
References
Bard, J. P., 1983. Metamorphism of an obducted island arc; example of the Kohistan Sequence (Pakistan) in Himalayan collided range. Earth. Planet. Sci. Lett., 65, 113-144.
Borphy, J. G., 1986. The Cold Bay volcanic center, Aleutian volcanic arc. Contrib. Mineral. Petrol., 93, 368-380.
Borphy, J. G. & Marsh, B. D., 1986. On the origin of high-alumina arc basalt and the mechanics of melt extraction. Jour. Petrol., 27, 763-789.
Cann, J. R., 1970. Rb, Sr, Y, Zr and Nb in some ocean floor basaltic rocks. Earth. Planet. Sci. Lett„ 10, 7-11.
Cornad, W.R. & Kay, R.W., 1984. Ultramafic and mafic inclusions from Adak island: crystallization history and implications of primary magmas and crustal evolution in the Aleutian arc. Jour. Petrol., 25, 245-266.
Coward, M. P., Windley, B. F., Broughton, R. D., Luff, I. W., Petterson, M. G., Pudsey, C. J., Rex, D. C. & Khan, M. A., 1986. Collision tectonic in the NW Himalayas. In: Collision Tectonics (M. P. Coward & A. C. Ries, eds.). Geol. Soc. London. Spec. Pub., 19, 203-209.
Crawford, A. J., Greene, H. G. & Exon, N., 1987. Geology petrology and geochemistry of submarine volcanoes around Epi Island (Vanatu). In: Geology and offshore resources of Pacific island arcs. The New Hebrides region: Circum-pacific (H. G. Greene & F. Wong, eds.). Earth and Science Series.
Crock, J. G. & Lichte F. E., 1982. Determination of rare earth elements in geological materials by inductively coupled argon plasma/atomic emission spectrometry. Anal. Chem., 54, 1329-1332.
Feild, D. & Elliott, R.B., 1974. The chemistry of gabbro/ampibolite transitions in South Norway. Contrib. Mineral. Petrol., 38, 71-79.
Fletcher, C. J. N., 1985. Copper mineralization in the Kohistan Complex, near Dir and Drosh, North-west Frontier Province. Brit. Geol. Surv., 1-65.
Fujii. T. & Scarf, C. M., 1985. Composition of liquids coexisting with spinel lherzolite at 10 Kbar and the genesis of MORBS. Contrib. Mineral. Petrol., 90, 18-28.
Gelinas, L., Mellinger, M. & Trudel, P., 1982. Archean mafic metavolcanics from the Rouyn-No-rauda district, Abititi greenstone belt, Quebec, l. Mobility of the major elements. Canad. Jour. Earth. sci., 19, 2258-2275.
Gill, J. B., 1981. Orogenic Andesites and plate tectonics. Springer Berlin Heidelberg, New York. 390p.
Gust, D. A. & Perfit, M. R., 1987. Phase relation of high-Mg basalt from the Aleutian island arc: implication for primary island arc basalt. Contrib. Mineral. Petrol., 97, 7-18.
Hamidullah, S., Islam, F. & Farooq, M., 1992. Petrology and geochemistry of the western part of Kalam-Dir igneous complex, Kohistan arc, northern Pakistan. In: Geology and geodynamic evolution of the Himalayan collision zone (K. Sharma, ed.). Physics and Chemistry Of the Earth, 17, 31-46.
Hanson, G. N., 1980. Rare earth elements in petrogenetic studies of igneous systems: Annual Rev. Earth Planet. Sci. Lett., 8, 371-406.
Hole, M. J., Saundes, A. J., Marriner, G. F. & Tarney, J., 1984 Subduction of pelagic sediments; implication for the origin of Ce-anomalous basalts from Mariana Islands. Jour. Geol. Soc. Load. 453472.
Irvine, T. N. & Barager, W. R. A., 1971. A guide to the chemical classification of the common volcanic rocks. Canad. Jour. Sci., 8, 523-548.
Jakes, P. & Gill, J. B., 1970. Rare earth element and the island arc tholeiite series. Earth Planet. Sci. Lett., 9, 17-28.
Kakar, S. K., Mian, S. B. & Khan, J., 1971. The geology of Jandul valley, western Dir. Geol. Bull. Univ. Peshawar, 6, 54-73.
Khan, M. A., 1979. Geology of the Baraul Valley, Dir. Geol. Bull. Univ. Peshawar, 11, 153-162.
Majid, M. & Paracha, F. A., 1980. Calc-alkaline magmatism at the destructive plate margin in Kohistan Pakistan. Geol. Bull. Univ. Peshawar, 13, 109-120.
Majid, M., Shah, M. T., Latif, A, Aurangzeb, & Kamal, M., 1981. Major elements abundance in the Kalam lavas. Geol. Bull. Univ. Peshawar, 14, 45-62.
Marsh, B. D., 1979. Island arc development: some observations, experiments and speculations. Jour. Geol., 87, 687-713.
Marsh, B. D., 1979. Island arc development: some observations, experiments, and speculation. Jour. Geol., 87, 687-714.
Masuada, A., 1968. Geochemistry of Lanthanides in basalts of central Japan. Earth Planet. Sci. Lett., 4, 284-292.
Miyashiro, A., 1974. Volcanic rock series in island arc and active continental margins. Amer. Jour. sci., 274, 321-355.
Myers, J. D., 1988. Possible petrogenetic relations between low and high-MgO Aleutian basalts. Geol. Soc. Amer. Bull. 100, 1040-1053.
Myers, J. D., Frost, C. & Angevine C. L., 1986. A test of a quartz eclogite source for parent Aleutian magma: a mass balance approach. Jour. Geol., 94, 811-828.
Nakamura, K., 1974. Determination of REE, Ba, Fe, Mg, Na and K in carbonaceous and ordinary chondrites. Geoch. et. Cosmoch. Acta., 38, 757-775.
Osborn, E. E, 1962. Reaction series for subalkaline igneous rocks based on different oxygen pressure conditions. Amer. Minerals, 47, 211-216.
Pearce. J. A., 1975. Basalt geochemistry used to investigate past tectonic environments on Cyprus. Tectonophysics, 25, 41-67.
Pearce, J. A., 1983. Role of the sub-continental lithosphere in magma genesis at active continental margins. In: Continental Basalt and Mantle Xenoliths (C. J. Hawkesworth & M.J. Norry, eds.). Shiva, Nantwich, 230-249.
Pearce, J. A. & Cann, J. R., 1973. Tectonic setting of basic volcanic rocks determined using trace element analyses. Earth Planet. Sci. Lett., 19, 290-300.
Perfit, M. R., Gust, D. A, Bence, A. E., Arculus, R. J. & Taylor, S. R., 1980. Chemical characteristics of island-arc basalts: implications for mantle sources: Chem. Geol., 30, 227-256.
Pudsey, C. J., 1986. The northern suture, Pakistan; margin of the Cretaceous island arc: Geol. Mag., 123, 405-423.
Rabi, F., and Khattah, N., 1983. Petrography and geochemistry of diorites and volcanics from northern Dir. Unpubl. M.Sc. thesis, Peshawar University.
Ramsey, W. R. N., Crawford, A. J. & Foden, J. D., 1984. Field setting, mineralogy, chemistry and genesis of arc picrite. New Georgia, Solomon Islan. Contrib. Mineral. Petrol., 88, 386-402.
Saunders, A. D., Tarney, J. & Weaver, S. D., 1980. Transverse variation across the Antarctic Peninsula: implications for the genesis of calc-alkaline magmas. Earth. Planet. Sci. Lett., 46, 344-360.
Shah, M. T., 1991. Geochemistry, Mineralogy and petrology of the sulfide mineralization and associated rocks in the area around Besham and Dir, northern Pakistan. Unpubl. Ph.D. thesis, Univ. of South Carolina, Columbia, U.S.A.
Shah, M. T. & Shervais, J. W., 1991. Petro-chemical evolution of the Dir metavolcanic sequence, Kohistan arc terrane, northern Pakistan. Geol. Soc. Amer. Abst., 23, A391p.
Shah, M. T., Shervais, J. W. & Ikramuddin, M., 1990. Geochemistry of metavolcanics and associated Cu-mineralization in the Dir area of Kohistan island arc, N. Pakistan. Geol. Soc. Amer. Abst., 22. A363p.
Sullivan, M., Windley, A. D, Saunders, A. D., Haynes, J. R. & Rex., D C., 1992. A palaeogeographic reconstruction of the Dir group: evidence for magmatic arc migration within Kohistan, N. Pakistan. In: Himalayan Tectonics (P.J. Treloar, & M.P. seari, eds.). Geol. soc. spec. Publ. 74, 139-160.
Tahirkheli, R. A., Mattauer, M., Proust, F., & Tapponnier, P., 1979. The India-Eurasia suture zone in northern Pakistan; synthesis and interpretation of recent data at plate scale. In: Geodynamic of Pakistan. (A. Farah & K. DeJong eds.). Geol. Surv. Pakistan, 125-130.
Tatsumi, Y., Sakuyama, M., Fukuyama, H. & Kushiro, I., 1983. Generation of arc basalt magmas and thermal structure of the mantle wedge in subduction zone. Jour. Geophys. Res., 88, 5815-5825.
Treloar, P. J., Rex, D. C, Guise, P. G., Coward, M. P., Searle, M. P., Windley, B. F., Petterson, M. G., Jan, M. Q. & Luff, I. W., 1989. K-Ar and Al-Ar geochronology of the Himalayan collision in NW Pakistan: constraints on the timing of suturing, deformation, metamorphism and uplift. Tectonics, 8, 881-909.
Vance, R. K. & Condie K. C., 1987. Geochemistry of foot-wall alteration associated with the early proterozoic united Verde massive sulfide deposits, Jerome Arizona. Econ. Geol., 82, 571-586.
Whitford, D. Korsch, M. J., Parrit, P. M. & Craven, S. J., 1988. Rare earth element mobility around the volcanogenic polymetallic massive sulfide deposit at Que river, Tasmania, Australia. Chem. Geol., 68, 105-119.
Winchester, J. A. & Floyd, P. A., 1976. Geochemical magma type discrimination: application to altered and metamorphosed basic igneous rocks. Earth Planet. Sci. Lett., 28, 459-469.
Wood, D. A., Tarney, J., Varet, J., Saunders, A. D., Bougault, H., Joron, J. L., Treuil, M. & Cann, J. R., 1979. Geochemistry of basalt drilled in the north Atlantic by IPOD leg 49: implication for mantle heterogeneity. Earth Planet. Sci. Lett., 42, 77-97.
