Petrogenesis of S-type granites and metapelites from NW lesser Himalaya: implications for Paleozoic crustal reworking and pre-Himalayan tectonics

Abstract

The Lesser Himalaya preserves a record of Proterozoic sedimentation and metamorphism overprinted by Paleozoic felsic magmatism, providing key insights into pre-Himalayan crustal reworking along the northern Indian margin. This study presents integrated petrographic observations and whole-rock major, trace element and rare earth element (REE) geochemistry of Mesoproterozoic Salkhala Formation and the intruding Kaplas and Jamotha granites. The metapelites are characterized by elevated Al₂O₃, Th and LREE contents, together with high Al₂O₃/TiO₂ and Th/Sc ratios, indicating derivation from an evolved felsic upper continental crustal source. The Kaplas and Jamotha granites are weakly to moderately peraluminous, show S-type affinity, and exhibit pronounced negative Eu anomalies, consistent with feldspar-controlled melt evolution and derivation through partial melting of metasedimentary protoliths. Trace-element systematics and tectonic discrimination diagrams suggest post-collisional felsic magmatism related to Paleozoic tectonothermal reactivation and intracrustal anatexis. The overall geochemical coherence between granites and host metapelites supports a shared crustal source and highlights the role of sediment recycling and metamorphic–magmatic coupling in the long-term evolution of the Lesser Himalaya.