Geology of the Kohistan-Ladakh arc and its relation to the main Himalayan belt
Abstract
A significant part of the Himalayan orogeny is characterized by its lateral continuity of the dominant structural features. In the eastern part of the orogen the continuity of the structural features and also of the main lithological units is less clear as the presence of the Kohistan Ladakh paleo-arc complicates the structural relationships. Classically, the batholithic units of the Kohistan-Ladakh arc are grouped and correlated with the Gandese batholith and jointly referred to as the Trans-Himalayan batholith formed in a Andean-type continental margin. We present new field observations, which constrains the location of the Shyok Suture zone in the Ladakh area, and new structural, geochemical and geochronological data from the Kohistan-Ladakh batholith. Our new data questions the assumption that solid-state deformation observed in the Kohistan batholith is related to the closure of the Shyok suture zone. The temporal relationship of deformed and undeformed plutonic rocks however, has been used to constrain the collision of the Kohistan-Ladakh arc and the Karakoram. Accordingly, the collision based on the geochronological data is essentially unconstrained. New extensive geochemical data from the Kohistan and Ladakh batholith compared to the available data from the Cretaceous-Eocene Gangdese batholith and the Karakoram batholith indicates that the Kohistan-Ladakh batholith is significantly less enriched in the incompatible trace element composition and has less radiogenic isotopic composition than the Karakoram and Gangdese batholith. Therefore, we speculate that the Kohistan-Ladakh arc largely evolved as an oceanic arc sequence and was not part of the Cretaceous southern Asian continental margin system. Instead it represent an “autonomous” arc system unrelated to the Trans-Himalayan batholith. If our speculation is correct the Shyok Suture zone has no lateral equivalent east of the Karakoram fault zone but is the northern “branch” of the Indus-Tsangpo suture zone.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2009
- Bibcode:
- 2009AGUFM.T41D..02J
- Keywords:
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- 1100 GEOCHRONOLOGY