Magma chamber processes and geodynamic implications of the Pithora pluton, Bastar Craton, Central India

Abstract

The interaction between the coeval mafic and felsic magmas result in mixing, mingling, and chemical exchanges between both the end‐member magmas. We document the features relevant to the magma chamber processes and quantify the extent of mixing by means of detailed field, petrographic, mineral, and whole‐rock geochemistry from one of the less known granitic plutons from the Pithora region that forms part of the Kanker granite, Bastar Craton. The study area is composed of granite, granodiorite (mixed zone), and quartz diorite microgranular enclaves (MEs). The occurrence of syn‐plutonic mafic dykes, cuspate contact, magmatic flow textures, and hybridization suggest the coeval emplacement of end‐member magmas. Petrographic evidence such as disequilibrium textures such as resorption, quartz ocelli, and spikes in plagioclase, acicular apatites, and mafic clots are formed by magma mixing. Plagioclase from MEs and the mixed region exhibit disequilibrium textures such as normal, reverse, and oscillatory zoning suggestive of magma mixing. Whole‐rock geochemical data indicates the metaluminous to peraluminous host granites and metaluminous ME. The broadly linear trend of geochemical variation diagrams for these granitoids and MEs showcase the hybridization of two end‐member magmas. The mineral chemistry of the biotites and hornblende show subduction affinity, being further constrained by whole‐rock trace elemental systematics. The granitoids of Pithora region were formed in a subduction setting where large‐scale mantle‐ and crustal‐derived magmas were generated and subsequently mixed at crustal emplacement level.