Geochemical (Ti–Mg) characteristics of the Proterozoic mafic metavolcanic rocks of Raialo Group of Alwar sub-basin, North Delhi Fold Belt, NW India

Abstract

The Mesoproterozoic North Delhi Fold Belt (NDFB) represents the northeastern limit of the Aravalli–Delhi Fold Belt in the NW Indian craton. The mafic metavolcanic rocks from the Tehla–Pandupol region of the Raialo Group were investigated from the southern part of the Alwar sub-basin of NDFB. In this preliminary study, we present broad geochemical groupings of these rocks and attempt to decipher their petrogenesis and tectonic setting. The mafic metavolcanic rocks are gray to greenish gray, compact to foliated, and commonly occur as ground-level exposures, occasional hillocks, and along the lower flanks of quartzite ridges. Their mineralogical and textural attributes suggest variable degrees of alteration and greenschist to lower amphibolite facies metamorphism. Geochemically, these rocks can be subdivided into three broad types; low Ti –high Mg, moderate Ti –moderate Mg, and high Ti –low Mg groups. Trace element characteristics of low- and medium- Ti groups (the early phases) show a notable crustal input while the most evolved, high- Ti group seems to be generally unaffected by crustal contamination. Systematic variation in geochemical characteristics during progressive differentiation and REE characteristics define a genetic relationship between low and moderate Ti groups while high- Ti represents a distinct group, unrelated to the rest.