Multistage Neoarchean magma genesis in the Bundelkhand Craton, India: Evidence from whole-rock elemental and Nd isotopic study of mafic magmatic enclaves and granitoids

Abstract

Using field, petrography and geochemistry (elemental and Nd isotopic compositions), an integrated study has been carried out on the Neoarchean lithologies comprising mafic magmatic enclaves (MMEs) and undeformed granitoids of the Bundelkhand Craton (Central India) to understand their genesis and crustal evolution. Based on the degree of mingling/mixing with the host granitoids, the MMEs are classified into three types as E-1, E-2 and E-3 types. The E-1 type MMEs represent the early fragments formed by fractional crystallization of mafic/ultramafic magma. The E-2 type MMEs formed due to restricted mingling and rapid crystallization of a hot mafic magma that interacted with felsic granitoid magma. The E-3 type MMEs show compositional similarity with its felsic host and are proposed to have formed by magma mixing process. The MMEs underwent varying degrees of isotopic equilibration with the host granitoids. The E-1 and E-2 type MMEs were resulted from depleted mantle-wedge and the E-3 type MMEs formed from a metasomatized mantle-wedge during subduction. Underplating of basaltic magma probably played a key role in the crustal formation and also provided heat for large scale melting of the crustal rocks giving rise to granitic magma. Such tectono-magmatic events also produced mafic magmas that variably interacted with the granitic magma and played a significant role in the generation of huge Bundelkhand granitoid massif during the Neoarchean.