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Masaru Yoshida, Gondwna Institute for Geology and Environment (Japan)
Bishal Nath Upreti, Department of Geology, Trichandra Campus, Tribhuvan University (Nepal)
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The Himalayan Orogen is composed of several major geotectonic belts with the Higher Himalayan Gneiss (HHG) belt as the central high-grade belt, which is covered by a Palaeozoic-Mesozoic belt composed of the Tibetan-Tethys Sedimentary Sequence. The deposition of original sediments of the HHG is considered to have taken place during ca 800 Ma and 500 Ma (DeCelles et al., 2000, Science, 288, 497-499). Detrital zircon ages and Sm-Nd isotopic data of the Higher Himalayan Gneisses so far published suggest that the original sediments of the HHG might have received material mostly from the Circum-East Antarctic Orogen (CEAO) including Western Australia and East Antarctica (Yoshida and Upreti, 2006, Gondwana Research, 10, 346-356., and references therein), and that the original material of the Tibethan-Tethys Sedimentary Sequence was derived mostly from the HHG and partly from the CEAO and only small amount on the western area from the Arabian Nubian Shield (Upreti et al., 2005, Abstract. The 1st International Conference on the "Geology of Tethys).
The provenances of rocks from the major two geologic units of the Himalayan Orogen are in contradiction to recent ideas of isolated India-Enderby Land crust on the globe during the Neoproterozoic (e.g., Pisarevsky et al, 2003, Geol. Soc., London, Special Pub. No. 206, 35-55), and support the juxtaposition of the Indian Craton with the CEAO during the Neoproterozoic and with the Arabian Nubian Shield after ca 500 Ma. The juxtaposition of India with the CEAO during the Neoproterozoic strongly supports the assembly of East Gondwana as well as of East Antarctica during the Grenvillian Circum-East Antarctic Orogeny (e.g., Yoshida et al., 2003, Geol. Soc, London, Special Pub. No. 206, 57-75.).
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