HR: 0830h
AN: T21D-0478    [PDF]
TI: Geochronological, Geochemical and Structural Constraints on the Initiation and Evolution of the Karakoram Fault, Ladakh, Northwest India
AU: * Phillips, R J
EM: richardp@earth.ox.ac.uk
AF: University of Oxford, Department of Earth Sciences, Parks Road, Oxford, OX4 3PR United Kingdom
AU: Parrish, R R
EM: rrp@nigl.nerc.ac.uk
AF: NERC Isotope Geosciences Laboratory, BGS Keyworth, Nottingham, NG12 5GG United Kingdom
AU: Searle, M P
EM: mikes@earth.ox.ac.uk
AF: University of Oxford, Department of Earth Sciences, Parks Road, Oxford, OX4 3PR United Kingdom
AB: The significance and role of major strike-slip faults during continental deformation is a major source of debate among geologists and geophysicists. In the last thirty years two end-member views of deformation have evolved, each offering a profoundly different philosophy of continental tectonics. While one end-member view suggests that regional deformation is distributed through a continuously deforming upper mantle with an overlying brittle carapace (e.g. England and Houseman, 1986), the other interprets deformation as constrained by slip on major discontinuities at the lithospheric scale (e.g. Armijo et al., 1986; Peltzer et al., 1989). A significant factor in this discussion is the role of strike-slip faults in Asia and in particular that of the Karakoram Fault (KF). The KF, a c.800 km dextral strike-slip fault, which bounds the southwestern margin of Tibet, is suggested to be one of the main faults that controls the eastward extrusion of the deforming Asian lithosphere (Molnar \& Tapponnier 1975). As each end-member model for continental deformation differs in the significance that it attaches to the extrusion hypothesis, it is vital that an accurate geological offset and a precise age for KF initiation are established because these parameters constrain the extent of the extrusion. The initiation and evolution of the KF can therefore provide important data with which to test models for continental deformation. In this paper, the authors examine the strain history of the KF in detail and compare its evolution to other strike-slip faults in the region. We present new U-Pb ID-TIMS data on 15 samples constrained by 70 mineral ages, coupled with new geochemical data and micro- and macro-structural analysis in the Ladakh region. We will discuss the temporal, spatial and geochemical relationship between Karakoram Batholith (KKB) and the Eastern Karakoram Batholith (EKB) and suggest a mode of initiation for the KF and describe its evolution. End-member models of deformation are then discussed in relation to the initiation and evolution of the KF in light of this new dataset. References cited: Armijo, R., P. Tapponnier, J.L. Mercier \& T. Han. Quaternary extension in southern Tibet: Field observations and tectonic implications. J. Geophys. Res., 91, 13,803-13,872, 1986. England, P.C. \& G.A. Houseman. Finite strain calculations of continental deformation, 2. Applications to the India-Asia plate collision. J. Geophys. Res., 91, 3664-3676, 1986. Molner, P. \& P. Tapponnier. Cenozoic tectonics of Asia, effects of continental collision. Science, 189, 419-426, 1975. Peltzer, G., P. Tapponnier, \& R. Armijo. Magnitude of Late Quaternary left-lateral displacements along the north edge of Tibet. Science, 246, 1285-1289, 1989.
DE: 8110 Continental tectonics--general (0905)
DE: 8155 Plate motions--general
SC: Tectonophysics [T]
MN: 2003 Fall Meeting