Scientific publications

The Proterozoic granites and gneisses of the Himalayan orogen, particularly those exposed in the Lesser Himalaya, provide essential insights into the geodinamics of the northern Indian craton. Here, we investigate the Toneta granites of the Garhwal Himalaya using whole rock geochemistry, zircon U–Th–Pb geochronology, and wholerock Sm–Nd isotope systematics to constrain their petrogenesis, source characteristics, and tectonic significance. Zircon U–Th–Pb dating yields a crystallization age of 1845 ± 19 Ma, with inherited zircon cores at 3.52, 2.78, 2.62, and 2.10 Ga, indicating recycling of Paleoarchean to Paleoproterozoic crustal components. Sm–Nd isotopic data further support a significant contribution from ancient Archean crust. The granites are strongly peraluminous (A/CNK = 1.01–2.40) and characterized by high SiO₂, Al₂O₃ и K₂O contents, together with depletion in Ba, Sr, Nb, and Ti and enrichment in Rb, Th, U, and Pb, supporting their S-type affinity. Chondrite-normalized REE patterns show LREE enrichment, relative HREE depletion, and pronounced negative Eu anomalies, indicating significant feldspar involvement during partial melting and/or magmatic differentiation. The combined geochronological, geochemical, and isotopic characteristics suggest that the Toneta granites formed predominantly through partial melting of metasedimentary crust containing an Archean component. Their emplacement at ca. 1.85 Ga is interpreted to reflect crustal thickening and thermal reworking during a Paleoproterozoic convergent tectonic episode. These features are consistent with an accretionary–collisional tectonic setting associated with the assembly of the Columbia (Nuna) supercontinent at ca. 1.85 Ga. The Toneta granites thus provide important evidence for Paleoproterozoic crustal recycling and stabilization of the northern Indian continental crust.