Timing of magmatic and metamorphic events in the Jijal complex of the Kohistan arc deduced from Sm–Nd dating of mafic granulites
Published:January 01, 2000
H. Yamamoto, E. Nakamura, 2000. "Timing of magmatic and metamorphic events in the Jijal complex of the Kohistan arc deduced from Sm–Nd dating of mafic granulites", Tectonics of the Nanga Parbat Syntaxis and the Western Himalaya, M. Asif Khan, Peter J. Treloar, Michael P. Searle, M. Qasim Jan
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Mafic to ultramafic granulites in the northeastern part of the Jijal complex include two-pyroxene granulite, garnet-clinopyroxene granulite and garnet hornblendite. Field and textural relations indicate that two-pyroxene granulite is a relict left after formation of the garnet-clinopyroxene granulite and garnet hornblendite was an originally intrusive rock which dissected the protoliths of mafic granulites. Sm-Nd mineral isochron ages of 118 ± 12 Ma, 94.0 ± 4.7 Ma and 83 ± 10 Ma were determined for two-pyroxene granulite, garnet-clinopyroxene granulite and garnet hornblendite respectively. These ages, together with previously reported chronological data, led to the following tectonic implications: (1) crystallization of the granulite protoliths predates, or is coeval with, the tectonic accretion of the Kohistan arc to the Asian continent; (2) crustal thickening related to the accretion was probably responsible for the high-pressure granulite-facies metamorphism in the Jijal complex; (3) formation of the garnet hornblendite assemblage was probably after crystallization of garnet-clinopyroxene granulite.
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Tectonics of the Nanga Parbat Syntaxis and the Western Himalaya
The western syntaxis of the Himalaya is one of the most exciting frontiers of continental tectonis studies. The region around the mountain of Nanga Parbat has some of the highest peaks, deepest valleys and highest uplift, exhumation and erosion rates known on earth. Surrounding regions include the Hindu Kush and Karakoram mountains (Asian plate), the Kohistan island arc and the Ladakh and Zanskar ranges of the western Himalaya (Indian plate). This volume includes 24 papers on all these regions as well as five new fold-out maps of the eastern Hindu Kush, the Spontang Ophiolite region of Ladakh, part of the west margin of the Indian plate, the Indus syntaxis in Pakistan and the Bouguer gravity anomalies in Pakistan.