Zircon U-Pb ages and Hf isotopes of I-type granite from western Arunachal Himalaya, NE India: Implications for the continental arc magmatism in the Palaeoproterozoic supercontinent Columbia

We present integrated in situ zircon U-Pb and Hf isotope data, along with whole-rock and mineral chemistry data for the Salari granite of western Arunachal Himalaya to constrain its emplacement age, origin, and geodynamic evolution. The investigated Salari granites are high Fe2O3, CaO, and Nb, and low SiO2 and Rb/Sr ratio with fractionated rare earth element patterns ((Ce/Yb)(N) = 9.90-20.24) and minor negative Eu anomaly (Eu/Eu* = 0.69-0.94). They are metaluminous (molar A/CNK = 0.93-1.07) and have relatively similar FeOt/MgO ratio in biotite (1.58-1.60) to Mg-biotite, indicating their affinity with I-type granites. The enrichment of large-ion lithophile elements with highly depleted negative Nb anomalies is consistent with their origin in a subduction-related environment. Our zircon U-Pb ages suggest that the magmatic emplacement of the Salari granite took place between 1,791 and 1,768 Ma. The zircon grains have mostly negative epsilon(Hf)(t) values up to -5.5 and yield crustal Hf model ages from 2.4 to 2.8 Ga, suggesting the occurrence of a major crustal growth event in the Neoarchean and re-melting of the crust during the Palaeoproterozoic. Our new results, that is, zircon U-Pb age and Hf isotope data, in conjunction with the field observations and petro-mineralogical and geochemical characteristics, suggest that the Salari granite of eastern Himalaya was produced by partial melting of older metabasaltic/metatonalitic rocks in a continental arc setting of the supercontinent Columbia during the Palaeoproterozoic.

Automated summary

The Salari granite in the western Arunachal Himalaya was formed by partial melting of older metavolcanic/metatonalitic rocks in a continental arc setting of the supercontinent Columbia during the Palaeoproterozoic. The magmatic emplacement of the Salari granite took place between 1,791 and 1,768 Ma, with characteristics of metaluminous I-type granite.