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Title

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

Authors
Heuberger, Stefan
Burg, Jean-Pierre
Villa, Igor Maria
Frank, Martin
Dawood, Hamid
Hussain, Shahid
Zanchi, Andrea
Published in Swiss Journal of Geosciences. 2007, vol. 100, no. 1, p. 85-107
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 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
Keywords Suture zoneCollisionArc magmatismGeochronologyKarakoramKohistan
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Article (Published version) (1.7 MB) - document accessible for UNIGE members only Limited access to UNIGE
Other version: http://link.springer.com/10.1007/s00015-007-1203-7
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Research group Isotope Geochemistry, Geochronology and Thermochronology
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HEUBERGER, Stefan et al. Age and isotopic constraints on magmatism along the Karakoram-Kohistan Suture Zone, NW Pakistan: Evidence for subduction and continued convergence after India-Asia collision. In: Swiss Journal of Geosciences, 2007, vol. 100, n° 1, p. 85-107. https://archive-ouverte.unige.ch/unige:28484

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Deposited on : 2013-06-10

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