Geology of the drainage divide between Kohistan and Kaghan, N. Pakistan
Abstract
This paper describes the geology of an area of about 1200 krn2 in the upper Kaghan valley. The area is traversed by Main Mantle Thrust, which juxtaposes the southeastern part of the Kohistan terrane in tectonic contact with the higher Himalayas of the Indian plate. The Indian-plate sequence in the study area comprises a basement of granitic gneisses (both ortho- and paragneisses) followed by the Domel unit (calcareous schists/paragneisses, garnetiferrous marbles, calc silicates and amphibolites) and the Parla Sapat unit (graphitic quartz-mica to garnet staurolite schists). These rocks are in tectonic contact with the mafic-ultramafic rocks of the Sapat complex along the Main Mantle Thrust. The Sapat complex underplates metabasalts of the Kamila amphibolite belt (i.e., Niat metavolcanic unit) and comprises ultramafic cumulates (dunites, peridotites and pyroxenites) at the base, layered gabbros in the middle and isotropic gabbros in the upper levels. The complex is folded through two phases of folding and metamorphosed under greenschist/lower amphibolite facies. The restored thickness of the complex approaches in excess of 2 kms.
The Main Mantle Thrust was mapped at several new locations during this study. Our observations show that the MMT at the base of the Sapat complex is younger than the melange/ olistostorm preserved in the upper parts of the Parla Sapat unit. The thrust cuts upsection laterally, and to the east of Babusar, occurs at the base of the Niat metavolcanic unit.
References
Ahmad, S., 1981. Preliminary account of the occurrence of Ni-sulfides in serpentinites of Sohch area, Kaghan valley, District Mansehra, N.W.F.P., Pakistan. Geol. Bull. Univ. Punjab., 16, 172.
Ahmed, Z. & Chaudhry, M. N., 1978. Geology of the Babusar area, Diamir district, Gilgit, Pakistan. Geol. Bull. Punjab Univ., 12, 67-78.
That, M. l. & Le Fort, P., 1992. Sm-Nd age and Petrogenesis of Rampur metavolcanic rocks, NW Himalayas: Late Archaean relics in the Himalayas Belt. Precamb. Res., 56, 191-210.
Chamberlain, C. P., Zeitler, P. K. & Erickson, E., 1991. Constraints on the tectonic evolution of the northwestern Himalaya from geochronologic and petrologic studies of Babusar Pass, Pakistan. Jour. Geol., 99, 829-849.
Chaudhry, M. N. & Ghazanfar, M., 1987. Geology, structure and geomorphology of Upper Kaghan valley, NW Himalaya, Pakistan. Geol. Bull. Punjab Univ., 22, 13-57.
Chaudhry, M. N., Ghazanfar, M. & Qayyum, M., 1986. Metamorphism at the Indo-Pak plate margin, Kaghan valley, District Mansehra, Pakistan. Geol. Bull. Punjab Univ., 21, 62-86.
DiPietro, J. A., Pogue, K. R., Lawrence, R. D, Baig, M. S., Hussain, A. & Ahmad, I., 1993. Stratigraphy south of the Main Mantle Thrust, Lower Swat, Pakistan. In: Himalayan Tectonics (PJ. Treloar & M.P. Searle, eds.). Geol. Soc. London, Spec. Pub., 74, 207-220.
Gansser, A., 1964. Geology of the Himalayas. Wiley Interscience, London.
Gansser, A., 1979. Reconnaissance visit to the ophiolites in Baluchistan and the Himalayas. In: Geodynamics of Pakistan. (A Farah & K. A. DeJong, eds.). Geol. Surv. Pak., Quetta, 193-213.
Ghazanfar, M., Chaudhry, M. N. & Hussain, M., 1991. Geology and petrotectonicsofsoutheast Kohistan, northwest Himalaya, Pakistan. Kashmir Jour. Geol. 8 & 9, 67-97.
Ghazanfar, M., Chaudhry, M. N. and Qayyum, M., 1992. The stratigraphic framework of northwest Himalaya along the Kaghan valley section, Pakistan. In: Himalayan Orogen and Global Tectonics. (A.K. Sinha, ed.). Oxford & IBH Publ. co. Pvt Ltd. Delhi.
Greco, A., Martinotti, G., Papritz, K., Ramsay, J. G. & Rey, 1989. The crystalline rocks of the Kaghan valley (NE Pakistan). Ecl. Geol. Helv., 82, 629-653.
Greco, A. and Spencer, D. A., 1993. A section through the Indian plate, Kaghan Valley, NW Pakistan. In: Himalayan Tectonics (P.J. Treloar & M.P. Searle, eds.). Geol. Soc. London, Spec. Pub., 74, 221-236.
Jan, M. Q, Khan, M. A. & Qazi, M. S., 1993. The Sapat mafic-ultramafic complex, Kohistan arc, North Pakistan. In: Himalayan Tectonics (P. J. Treloar and M. P. Searle, eds.). Geol. Soc. London Spec. Publ., 74, 113—121.
Jan, M. Q. & Windley, B. F., 1990. Chromian spinel silicate chemistry in ultramafic rocks of the Jijal complex, northwest Pakistan. Jour. Petrol., 31, 667-715.
Kazmi, A. H., Lawrence, R. D., Dawood, H., Snee, L. W. & Hussain, S., 1984. Geology of the Indus suture zone in the Mingora-Shangla area of Swat, N. Pakistan. Geol. Bull. Univ. Peshawar, 17, 127-143.
Khan, M. A., Khan, A., Qazi, M. S. & Jan, M. Q., 1994. Geology and structure of the Main Mantle Thrust (Raikot-Naransegment), south-eastern Kohistan, northern Pakistan. Geol. Bull. Punjab. Univ., 28. (in press)
Khan, M. A. & Thirwall, M. F., 1988. Babusar amphibolites: Arc tholeiites from the southern Kohistan arc, N. Pakistan. Geol. Bull. Univ. Peshawar, 21, 147-158.
Le Fort, P., Debon, F. & Sonet, J., 1980. The Lesser Himalayas Cordierite Granite Belt. Typology and age of the Pluton of Mansehra, Pakistan. Geol. Bull. Univ. Peshawar, 3, 51-61.
Miller, D. J. & Christensen, N. I., 1994. Seismic signature and geochemistry of an island arc: A multidisciplinary study of the Kohistan accreted terrane, north Pakistan. Jour. Geophys. Res., 99, B6, 11623-11642.
Miller, D. J., Loucks, R. R. & Ashraf, M., 1991. Platinum group elements mineralization in the Jijal layered mafic-ultramafic complex, Pakistani Himalayas. Econ. Geol., 86, 1093-1102.
Robertson, A. & Degnan, P., 1994. The Dras arc complex: Lithofacies and reconstruction of a Late Cretaceous oceanic volcanic arc in the Indus Suture Zone, Laddakh Himalaya. Sed. Geol., 92, 117-145.
Smith, H. A., Chamberlain, C. P. & Zeitler, P. K., 1994. Timing and location of Himalayan metamorphism within the Indian plate, northwest Himalaya, Pakistan. Jour. Geol., 102, 493-508.
Spencer, D. A., 1993. Tectonics of the Higher- and Tethyan Himalaya, Upper Kaghan valley, NW Himalaya, Pakistan: Implications of an early collision, high pressure (eclogite facies) metamorphism to the Himalayan belt. Ph. D. dissertation, Swiss Fedral Institute of Technology, Zurich.
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 Ar-Ar geochronology of the Himalayan collision in NW Pakistan: Constraints on the timing of suturing, deformation, metamorphism arid uplift. Tectonics, 8, 881-909.
Wadia, D. N., 1931. The syntaxis of the North-West Himalayas: Its rocks, tectonics and orogeny. Rec. Geol. Surv. India, 65/2, 189-220.
