Characterisation of Kalalikhera felsic volcanics, Pur-Banera belt, Rajasthan: Insights from monazite–xenotime geochemistry and chemical ages

Abstract

Geological and geochemical characteristics of the litho units exposed in and around Kalalikhera area of Pur-Banera belt have confirmed the presence of felsic volcanic rock unit named Kalalikhera felsic volcanic, with characteristic features such as (i) abundance of lapilli composed of polygonal quartz and feldspar and (ii) presence of relict bipyramidal quartz. These volcanics are associated with thin bands of chert. Geochemically, the volcanics are found to be of rhyolitic composition. Development of garnet porphyroblasts along with preferred orientation of the silicate minerals of rhyolite indicates a low to medium grade metamorphism and deformation of the units. Monazite geochemistry of the volcanics indicated towards the metamorphic origin of monazites, with REE pattern show steep fractionation trend from La to Lu. The in-situ chemical age of 2192 ± 57 Ma recorded from xenotime is interpreted as indicative of the opening of the Aravalli basin with the onset of rifting leading to the formation of Kalalikhera volcanics. The estimated ages of 1784 ± 92, 1351 ± 45 and 1026 ± 57 Ma from monazite analyses are interpreted as different metamorphic events associated with (i) closure of the basin and the onset of Aravalli orogeny, (ii) further imprints of Delhi orogeny, and (iii) with late Grenvillian age imprints.