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Age and isotopic constraints on magmatism along the Karakoram-Kohistan Suture Zone, NW Pakistan: evidence for subduction and continued convergence after India-Asia collision

Heuberger, Stefan ; Schaltegger, Urs ; Burg, Jean-Pierre ; Villa, Igor ; Frank, Martin ; Dawood, Hamid ; Hussain, Shahid ; Zanchi, Andrea

In: Swiss Journal of Geosciences, 2007, vol. 100, no. 1, p. 85-107

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    Titel
    • Age and isotopic constraints on magmatism along the Karakoram-Kohistan Suture Zone, NW Pakistan: evidence for subduction and continued convergence after India-Asia collision
    Autor
    • Heuberger, Stefan. Institute of Geology, ETH-and University of Zürich, Sonneggstrasse 5, 8092, Zürich, Switzerland
    • Schaltegger, Urs. Département de Minéralogie, Université de Genève, rue des Maraers 13, 1205, Genève, Switzerland
    • Burg, Jean-Pierre. Institute of Geology, ETH-and University of Zürich, Sonneggstrasse 5, 8092, Zürich, Switzerland
    • Villa, Igor. Institut für Geologie, University of Bern, Baltzerstrasse 1, 3012, Bern, Switzerland
    • Frank, Martin. Institute of Isotope Geology and Mineral Resources, ETH Zürich, Sonneggstr. 5, 8092, Zürich, Switzerland
    • Dawood, Hamid. Pakistan Museum of Natural History, Garden Avenue, Shakarparian, 44000, Islamabad, Pakistan
    • Hussain, Shahid. Pakistan Museum of Natural History, Garden Avenue, Shakarparian, 44000, Islamabad, Pakistan
    • Zanchi, Andrea. Dipartimento di Scienze Geologiche e Geotecnologie, Università di Milano Bicocca, 20126, Milano, Italy
    Dokumententyp
    • Postprint
    Sprache
    • Englisch
    Veröffentlicht in
    • Swiss Journal of Geosciences, 2007, vol. 100, no. 1, p. 85-107. Birkhäuser-Verlag; www.birkhäuser.ch
    Andere elektronische Ausgabe
    OAI-PMH-ID
    • oai:doc.rero.ch:320515
    Summary
    Abstract.: Detailed geological mapping in the Drosh-Shishi area in southern Chitral (NW Pakistan) was combined with high-precision U-Pb dating on zircons to constrain the timing of magmatism and associated deformation/metamorphic events related to the Kohistan-Karakoram convergence and collision. Our new ages indicate that the Mesozoic to Tertiary magmatic history of this region is influenced by long-lived melt generation above an active subduction zone. Dated intrusive rocks range in age from 130 to 39 million years, indicating that subduction-related magmatism continued after the Kohistan-Karakoram and the India-Asia collisions. Initial hafnium isotope ratios were measured on the dated zircons to constrain the type of melt source of the dated plutons. The data reveal the different nature of partly coeval magmatism in these units, i.e. continental arc magmatism in the Karakoram (ca. 130-104 Ma) and arc magmatism magmatism on the Kohistan side (112-39 Ma). Intrusions within the suture zone can be clearly traced to be Karakoram-derived on the basis of initial Hf isotopic compositions. Granite dykes crosscutting the Kohistan units have sampled an underlying, old continental basement of Gondwana affinity. The geochronological evidence presented in this paper is consistent with Cretaceous subduction beneath the Karakoram Terrane. The related calc-alkaline magmatism seems to have stopped at about 100 Ma. Granite dykes on the Kohistan side show that the magmatic and tectonic history of the Karakoram-Kohistan Suture Zone continued to the Eocene. This long tectono-metamorphic and magmatic activity in the arc plates was likely due to complex and few million year long interplays between subduction and thrusting events in the forearc, within-arc and back-arc regions between two active subduction zones