The Central Crystalline Precambrian Peraluminous Granites of the Western Part of Bhutan Himalaya

The quartzo-feldspathic protoliths associated with the Central Crystalline gneisses of the western Bhutan-eastern Sikkim Himalayan segment are of peraluminous adamellite, granite (s.s.) and trondhjemite compositions. Peraluminous granite melt of first event is generated coeval to the kyanite or sillimanite grade metamorphism and it has syntectonically intruded a metapelite-quartzite sequence. These granites, along with the mctasedimentaries. have undergone partial melting under amphibolite facies conditions resulting in the generation of the peraluminous granite melt of second generation. which has syn- to late-tectonically intruded the pelitic sehist-quartzite-peraluminous gneiss assemblage. Approximately 20 Ma old post-tectonic peraluminous granites (s.s.) of the third event have intruded the Central Crystalline. The Central Crystalline adamellite-granite-trondhjemite suite is of 'non-minimum' melt compositions in contrast to the 'minimum melts' of the ≤20 Ma old leucogranites (such as the Manaslu granite of Nepal), which show unifonn granite (s.s.) compositions.