COMPARATIVE STUDY OF THE AGE AND PROVENANCE OF DETRITAL MINERALS FROM SANGDANLIN, SOUTHERN TIBET AND LADAKH, NW INDIA: IMPLICATIONS FOR THE INDIA-ASIA COLLISION

The Indus-Yarlung Tsangpo suture zone (IYTSZ) records one of the largest orogenic events since Paleozoic times, the India-Asia collision. It contains remnants of what was once a >4000 km wide ocean, Neotethys, which lay between Gondwana India and Eurasia. Numerous studies over the last half-century have focused on determining the age of this collision, with estimates ranging from 70 Ma (Yin and Harrison, 2000) to ~35 Ma (Aitchison et al., 2007). Evidence of the collision in north-west India can be found in the Indus Group, which records the transition from a fore-arc environment in early Paleocene times to an post-collisional basin in Miocene times (Garzanti and Van Haver, 1988). In southern Tibet, at Sangdanlin, the Paleocene-Eocene Zeba Group contains the deep-water sequences of the Sangdanlin Formation and the flyschoid sediments of the Zheya Formation (Ding, 2003). An understanding of both stratigraphic relationships and likely depositional environments is crucial when assessing estimates of the timing of the India-Asia collision. Two widely used and robust methods employed to investigate these relationships are detrital zircon geochronology and chrome spinel petrogenesis. These methodologies can elucidate the major sources of sediment as well as the minimum age of deposition, where other chronostratigraphic methods are unfeasible. The dominant populations and potential source regions for detrital zircon and spinel grains from two important areas along the IYTSZ will be identified and compared. Their implications with respect to the timing of the India-Asia collision will also be discussed. References: Aitchison, J.C., Ali, J.R., and Davis, A.M., 2007, When and where did India and Asia collide?: Journal of Geophysical Research, v. 112, p. B05423, doi:10.1029/2006JB004706. Ding, L., 2003, Paleocene deep-water sediments and radiolarian faunas: Implications for evolution of Yarlung-Zangbo foreland basin, southern Tibet: Science in China Series D - Earth Sciences, v. 46, p. 84-96. Garzanti, E., and Van Haver, T., 1988, The Indus clastics: forearc basin sedimentation in the Ladakh Himalaya (India): Sedimentary Geology, v. 59, p. 237-249. Yin, A., and Harrison, T.M., 2000, Geologic Evolution of the Himalayan-Tibetan Orogen: Annual Review of Earth and Planetary Sciences, v. 28, p. 211-280.