Insights into the evolution of the Hindu Kush-Kohistan-Karakoram from modern river sand detrital geo- and thermochronological studies

Zhuang, G. and Najman, Y. and Tian, Y. and Carter, Andrew and Gemignani, L. and Wijbrans, J. and Jan, Q. and Khan, A. (2018) Insights into the evolution of the Hindu Kush-Kohistan-Karakoram from modern river sand detrital geo- and thermochronological studies. Journal of the Geological Society 175 (6), pp. 934-948. ISSN 0016-7649.

Abstract

The Hindu Kush-Kohistan-Karakoram region is critical to understanding the long-term accretion history of the south Asian margin pre- and post-India-Asia collision and the impact of these collisions on the development of high topography. However, knowledge about this region remains incomplete due to sparse studies. Here, we present a study comprising detrital zircon U-Pb geochronology, detrital muscovite 40Ar/39Ar thermochronology, and numerical modeling on 40Ar/39Ar dates. The study identifies zircon U-Pb age peaks at 200 Ma, 110–130 Ma, 60–80 Ma, and 28–40 Ma, supporting the polyphase collisions and crustal growth in the south Asian margin. Modeling study reveals fast cooling/erosion at 115–129 Ma, 69–71 Ma, 27–35 Ma, and <8 Ma, which are synchronous with collision related crustal growth, indicating the significant impact of accretion both prior to and post India-Asia collision. This study, along with studies in eastern Karakoram, reveals along-strike variations in erosion and exhumation with young (since late Miocene) intense erosion focusing on the east-central Karakoram. We suggest that this east-west spatial variation in exhumation may have been associated with more intense crustal shortening, and thus the greater crustal thickness, topographic relief and altitude observed in the eastern, compared to western, Karakoram.

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