Petrogenesis of Neoproterozoic Adakite-Like Rocks in the Southwestern Part of the Western Dharwar Craton, South India

Abstract

The Elimala and Markanje Plutons in the Mangalore-Gundlupet Crustal Corridor of the southern part of the Western Dharwar Craton were investigated to elucidate their geochemistry, geochronology, and petrogenesis. Zircon geochemistry revealed high Hf concentrations (9019–10011 ppm), steep HREE enrichment, positive Ce anomalies, and negative Eu anomalies, typical of magmatic zircons derived from highly evolved melts. U–Pb dating of magmatic zircons from the Elimala Pluton yielded a Concordia age of 832 ± 4 Ma, indicating crystallization during the Neoproterozoic. Bulk-rock geochemical analyses classified the granitoids as calc-alkaline, metaluminous to weakly peraluminous, I-type granitoids. Rare earth element patterns and trace element compositions, such as high Sr/Y and low (Dy/Yb)_N ratios, indicate derivation from the partial melting of thickened lower crustal rocks within the garnet and/or amphibole stability field. The studied rocks exhibit characteristics of adakite-like granitoids, displaying affinities to high-silica adakites but with distinct compositional features that differentiate them from slab-derived melts. Their petrogenesis is attributed to low-degree partial melting of thickened lower continental crust rather than fractional crystallization or slab melting. Zircon trace element signatures and bulk-rock chemistry collectively suggest a crustal origin with minimal post-magmatic alteration, supported by low loss-on-ignition values and immobile element behavior. These findings provide new insights into the diverse lithology and crustal evolution of the southern part of the Western Dharwar Craton during the Neoproterozoic and the processes that led to the formation of adakite-like rocks.