Zircon U-Pb geochronology and Hf isotopic compositions of Palaeoproterozoic meta-granitoids in the Lesser Himalaya, Nepal: Tectonostratigraphic implications

The Lesser Himalayan Belt in the northern margin of Indian Shield preserves abundant sedimentary and magmatic records related to the assembly and breakup of the Columbia supercontinent. However, the Palaeoproterozoic tectonic history of the northern margin of the Indian Shield and its position in the Columbia supercontinent are still controversial. Based on detailed geological investigations in the Dailekh area of western Nepal, we conducted zircon U-Pb dating and Lu-Hf isotopic analysis for meta-granitoids that intruded into the Lesser Himalayan Crystalline and Metasediments. The Dungeshworl granitic augen gneiss, meta-monzogranite, and tonalitic gneiss yielded crystallization ages of 1,829 +/- 12 Ma, 1,856 +/- 11 Ma, and 1,852 +/- 11 Ma respectively, which demonstrate that the deposition limits of both the Lesser Himalayan Crystalline and Metasediments are the Palaeoproterozoic. Zircon epsilon(Hf)(t) values of these meta-granitoids range from -3.99 to +0.18, with corresponding depleted mantle two-stage model (T-DM2) ages of 2.41-2.62 Ga, indicating that they formed by reworking of Neoarchean to Palaeoproterozoic crust. Synthesizing existing geochronological, petrochemical, and zircon Lu-Hf isotopic data for metamorphic sedimentary and igneous rocks from the entire Lesser Himalayan Belt, we suggest that the Palaeoproterozoic magmatism in the northern margin of Indian Shield may be formed within subduction-related tectonics responded to the assembly of Columbia supercontinent.