Petrology, Geochemistry and Petrogenesis of Early Precambrian Mafic Dyke Swarm from Dondi-Bhanupratappur-Keshkal Area, Central Bastar Craton, India

Abstract

Different generations of Precambrian mafic dyke swarms are well documented in different parts of the Archaean Bastar craton. Mafic dykes reported from southern part of the Bastar craton is well studied but those exposed in central part have limited petrological and geochemical information. This paper presents petrological and geochemical characteristics of mafic dykes exposed around Dondi, Bhanupratappur and Keshkal areas in the central Bastar craton. These mafic dykes trend in NW–SE and intrude Archaean granite/granite-gneiss and metamorphic rocks of Bengpal and Bailadila Groups. Petrographically most of the dykes show metamorphic textures and amphibolites facies mineral assemblage but few samples retain original igneous texture and mineralogy which classifies them as metabasites and metadolerites, respectively. Geochemically these rocks show either sub-alkaline thoeliitic basaltic or basaltic andesitic nature. Further, they show variation from high-iron tholeiites to high-magnesium tholeiites. Due to the post-magmatic alteration major oxides do not show pronounced crystallization trends but trace elements, particularly high-field strength elements (HFSE), indeed display good crystallization trends. This suggests a possible co-genetic relationship between the studied samples. Ni-Zr modeling suggests that ~25% melting of a depleted mantle source followed by 30–40% fractional crystallization fed the mafic dykes of present study.