Thesis

Geochemical signature of Himalayan gneiss domes : implications for channel flow

The Leo Pargil, Renbu, and Yalashangbo gneiss domes are among the western and eastern most in the chain of north Himalayan gneiss domes. The processes of gneiss dome formation are still debated, but there is a growing consensus that they result from the diapiric rise of pooled melt from a mid-crustal, ductile channel. Under the channel flow model, the ductile channel is exhumed towards the southern Himalayan range front and is exposed as the Greater Himalayan Sequence (GHS). Gneiss domes should have a petrogenetic relationship to the GHS if the channel flow theory is correct. Geochemical investigation of gneiss domes can therefore help to determine their provenance and mode of origin. U-Pb dating, REE analyses, and Pb isotope data of these three gneiss domes suggest that they have a shared parent material, and that this parent material is most likely derived from the GHS. Results from this study are therefore consistent with the channel flow model, and strengthen arguments in favor of channel flow in the Himalayas along the length of the orogen.

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