Geochemical constraints on the petrogenesis and tectonic environment of gabbroic intrusives in the Siang Window of Eastern Himalaya,Northeast India |
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Authors: | A Krishnakanta Singh |
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Institution: | 1.Wadia Institute of Himalayan Geology,Dehradun,India |
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Abstract: | Carbonate and calcareous-quartzite of Miri-Buxa Group in the Siang Window of Eastern Himalaya intruded by mafic rocks of gabbroic affinity. These intrusive rocks are low-Ti tholeiites (Ti/Y = 379−478; Nb/La = 0.99−1.88) and characterized by enriched LILE-LREE, depleted in HFSE with minor REE fractionation (La/Yb)N = 2.72−3.35)]. Geochemical behaviour of the incompatible trace elements with the rare earth elements abundances indicates their cogenetic nature and their emplacement in a continental rift tectonic environment. The liquidus olivine temperature of these mafic rocks ranges from 1262°C to 1380°C showing a gentle decrease of Mg] with a steep increase of Fe]. These charters thus imply that the rocks are either related to the extent of common source or fractionational crystallization of plagioclase and clinopyroxene from a single batch parental magma. Petrogenetic modeling of Mg]-Fe] and REE indicates that these mafic intrusives probably derived from a mantle source similar to komatiitic composition at moderate to high degree (8%–20%) of partial melting. |
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