|
|
 |
|||||||||||||||||
|
|||||||||||||||||
 |
|||||||||||||||||
| JOURNAL HOME | HELP | CONTACT PUBLISHER | SUBSCRIBE | ARCHIVE | SEARCH | TABLE OF CONTENTS |
1 Department of Earth Sciences, Oxford University, Parks Road, Oxford OX1 3PR, UK
2 Department of Geology, University of Leicester, and Natural Environment Research Council Isotope Geosciences Laboratory, British Geological Survey, Keyworth, Nottingham NG12 5GG, UK
3 Natural Environment Research Council Isotope Geosciences Laboratory, British Geological Survey, Keyworth, Nottingham NG12 5GG, UK
U-Pb dating of metamorphic and igneous rocks from the Hunza Valley and Baltoro regions of the Karakoram Mountains in northern Pakistan addresses the thermal and magmatic evolution of the thickened Asian plate crust before, during, and after the collision of the Kohistan arc and the Indian plate. Crustal thickening and high- temperature, sillimanite-grade metamorphism in the southern Karakoram Mountains followed the collision and accretion of the Kohistan arc during the Late Cretaceous. U-Pb ages of metamorphic monazites from sillimanite gneisses in the Hunza Valley are 63.3 ± 0.4 Ma, ca. 50–52 Ma, and 44.0 ± 2.0 Ma, and monazites from a kyanite-grade schist from the Baltoro region are 28.0 ± 0.5 Ma. Metamorphic monazites from a highly graphitic garnet + staurolite schist from the Hunza Valley yield a crystallization age of 16.0 ± 1.0 Ma. Sillimanite gneisses from the Dassu dome have magmatic zircons of 1855 ± 11 Ma, reflecting a Proterozoic continental crustal source, and metamorphic monazites of 5.4 ± 0.2 Ma. Magmatism was also sporadic; early granodiorite, monzogranite, and leucogranite dikes yield zircon, monazite, and uraninite ages of 50–52 Ma and 35.0 ± 1.0 Ma. Widespread lower crustal melting during the latest Oligocene–early Miocene culminated with emplacement of the Baltoro Plutonic Unit in the Karakoram batholith that cuts deformation fabrics in the high-grade gneisses to the south. The youngest magmatic phase dated is the 9.3 ± 0.2 Ma Sumayar leucogranite pluton. On the basis of detailed structural field studies combined with U-Pb geochronology, sillimanite-grade metamorphism was either a protracted event lasting as long as 20 m.y. (64–44 Ma) or peaked at different times within the lower crust following collision of first, the Kohistan arc, and later, the Indian plate. We also present evidence for southward propagation of peak metamorphism and postmetamorphic thrusting and folding of isograds within the past 5 m.y. Detailed geochronology shows that deformation, metamorphism, and magmatism in the middle and lower crust of the south Asian margin has been occurring within the Karakoram metamorphic complex for more than 60 m.y. Similar processes may also have affected the unplumbed depths of the south Tibetan crust.
Key Words: Karakoram • Pakistan • tectonics • uranium-lead geochronology
This article has been cited by other articles:
|
|
 |
|
  M.J. Streule, R.J. Phillips, M.P. Searle, D.J. Waters, and M.S.A. Horstwood Evolution and chronology of the Pangong Metamorphic Complex adjacent to the Karakoram Fault, Ladakh: constraints from thermobarometry, metamorphic modelling and U-Pb geochronology Journal of the Geological Society, September 1, 2009; 166(5): 919 - 932. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 B. Dhuime, D. Bosch, C. J. Garrido, J.-L. Bodinier, O. Bruguier, S. S. Hussain, and H. Dawood Geochemical Architecture of the Lower- to Middle-crustal Section of a Paleo-island Arc (Kohistan Complex, Jijal-Kamila Area, Northern Pakistan): Implications for the Evolution of an Oceanic Subduction Zone J. Petrology, March 19, 2009; (2009) egp010v1. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. D. Khan, D. J. Walker, S. A. Hall, K. C. Burke, M. T. Shah, and L. Stockli Did the Kohistan-Ladakh island arc collide first with India? Geological Society of America Bulletin, March 1, 2009; 121(3-4): 366 - 384. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G. Maheo, J. Blichert-Toft, C. Pin, S. Guillot, and A. Pecher Partial Melting of Mantle and Crustal Sources beneath South Karakorum, Pakistan: Implications for the Miocene Geodynamic Evolution of the India-Asia Convergence Zone J. Petrology, March 1, 2009; 50(3): 427 - 449. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J.A. CHAMBERS, T.W. ARGLES, M.S.A. HORSTWOOD, N.B.W. HARRIS, R.R. PARRISH, and T. AHMAD Tectonic implications of Palaeoproterozoic anatexis and Late Miocene metamorphism in the Lesser Himalayan Sequence, Sutlej Valley, NW India Journal of the Geological Society, May 1, 2008; 165(3): 725 - 737. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. C. Robinson, A. Yin, C. E. Manning, T. M. Harrison, S.-H. Zhang, and X.-F. Wang Cenozoic evolution of the eastern Pamir: Implications for strain-accommodation mechanisms at the western end of the Himalayan-Tibetan orogen Geological Society of America Bulletin, July 1, 2007; 119(7-8): 882 - 896. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
P. Kapp, P. G. DeCelles, G. E. Gehrels, M. Heizler, and L. Ding Geological records of the Lhasa-Qiangtang and Indo-Asian collisions in the Nima area of central Tibet Geological Society of America Bulletin, July 1, 2007; 119(7-8): 917 - 933. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. P. SEARLE and R. J. PHILLIPS Relationships between right-lateral shear along the Karakoram fault and metamorphism, magmatism, exhumation and uplift: evidence from the K2-Gasherbrum-Pangong ranges, north Pakistan and Ladakh Journal of the Geological Society, March 1, 2007; 164(2): 439 - 450. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. R. St-Onge, N. Wodicka, and O. Ijewliw Polymetamorphic Evolution of the Trans-Hudson Orogen, Baffin Island, Canada: Integration of Petrological, Structural and Geochronological Data J. Petrology, February 1, 2007; 48(2): 271 - 302. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. P. Searle Diagnostic features and processes in the construction and evolution of Oman-, Zagros-, Himalayan-, Karakoram-, and Tibetan-type orogenic belts Geological Society of America Memoirs, January 1, 2007; 200(0): 41 - 61. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M.P. SEARLE Role of the Red River Shear zone, Yunnan and Vietnam, in the continental extrusion of SE Asia Journal of the Geological Society, December 1, 2006; 163(6): 1025 - 1036. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
B. HACKER, P. LUFFI, V. LUTKOV, V. MINAEV, L. RATSCHBACHER, T. PLANK, M. DUCEA, A. PATINO-DOUCE, M. McWILLIAMS, and J. METCALF Near-Ultrahigh Pressure Processing of Continental Crust: Miocene Crustal Xenoliths from the Pamir J. Petrology, August 1, 2005; 46(8): 1661 - 1687. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
P. Kapp, A. Yin, T. M. Harrison, and L. Ding Cretaceous-Tertiary shortening, basin development, and volcanism in central Tibet Geological Society of America Bulletin, July 1, 2005; 117(7-8): 865 - 878. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. C. Robinson, A. Yin, C. E. Manning, T. M. Harrison, S.-H. Zhang, and X.-F. Wang Tectonic evolution of the northeastern Pamir: Constraints from the northern portion of the Cenozoic Kongur Shan extensional system, western China Geological Society of America Bulletin, July 1, 2004; 116(7-8): 953 - 973. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
Y. Najman, E. Garzanti, M. Pringle, M. Bickle, J. Stix, and I. Khan Early-Middle Miocene paleodrainage and tectonics in the Pakistan Himalaya Geological Society of America Bulletin, October 1, 2003; 115(10): 1265 - 1277. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. N. Ducea, V. Lutkov, V. T. Minaev, B. Hacker, L. Ratschbacher, P. Luffi, M. Schwab, G. E. Gehrels, M. McWilliams, J. Vervoort, et al. Building the Pamirs: The view from the underside Geology, October 1, 2003; 31(10): 849 - 852. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 R. R. Parrish, R. R. Parrish, R. R. Parrish, and S. R. Noble Zircon U-Th-Pb Geochronology by Isotope Dilution -- Thermal Ionization Mass Spectrometry (ID-TIMS) Reviews in Mineralogy and Geochemistry, January 1, 2003; 53(1): 183 - 213. [Full Text] [PDF]
|
|
|
|
 |
|
 G. Foster and R. R. Parrish Metamorphic monazite and the generation of P-T-t paths Geological Society, London, Special Publications, January 1, 2003; 220(1): 25 - 47. [Abstract] [PDF]
|
|
| JOURNAL HOME | HELP | CONTACT PUBLISHER | SUBSCRIBE | ARCHIVE | SEARCH | TABLE OF CONTENTS |
