Geochemical studies of hybrid granite from Madugulapalli area, Eastern Dharwar Craton, Southern India: Implications for crustal mixing.

Magma produced by melting of continental crust and mantle at the Archean-Proterozoic boundary are compositionally variable and chemical compositions provide evidence for the mixing of two sources. Understanding the composition of hybrid magma is essential for determining the comparative influence of crust and mantle sources during orogenesis. The hybrid granites are less documented in Indian cratons, especially less in Dharwar Craton. Here we present petrographic and whole-rock geochemical data of Madgulapalli granitic rocks situated in the NE part of the Eastern Dharwar Craton (EDC), to elucidate their petrogenesis and role in crust formation. The Madugulapalli granites (MPG) are composed chiefly of plagioclase, quartz, and alkali feldspar with associated biotite showing alteration and inter-granular textures. Geochemically, they are metaluminous to peraluminous in nature with calc-alkaline hybrid granite. The hybrid granites exhibit both negative and positive europium anomalies; the lower Rb/Sr, Rb, Sr, and higher Sr/Y, (Dy/Yb)N ratios suggest that the interaction of older rocks with residual garnet source melted at high pressures. We hypothesize that hybrid granites are formed by interaction (e.g., metasomatism, mingling, or mixing) between parental magmas and pre-existing rocks with the influence of sanukitoid melts (heat source) in a subduction environment. The genesis of the hybrid granites demonstrates the mixing coupled with differentiation in the petrogeny's residue system in a syn-collision setting followed by continental crust stability in EDC during the Neoarchean period. [ABSTRACT FROM AUTHOR]