Provenance study of siliciclastic sediments, Jhura Dome, Kachchh, Gujarat

Abstract

Provenance of the siliciclastic rocks of Patcham and Chari Formations (Bathonian to Oxfordian) has been ascertained by means of heavy mineral studies. The study shows abundance of transparent heavies like garnet, zircon, tourmaline, staurolite, rutile, hornblende, andalusite, kyanite, anatase and epidote, in decreasing order, and constitute 26.47 percent of total heavies. The opaque group is represented mainly by goethite and limonite, which constitute 73.45 per cent. The statistical data of heavies reveals that garnet, zircon and tourmaline are more or less uniform throughout the stratigraphic column and constitute 43.92 per cent, 22.27 per cent and 19.99 per cent respectively. The average percentage of staurolite and rutile is 5.40 and 4.52. The percentage of anatase, kyanite, hornblende, andalusite and epidote is very less. On the basis of distribution pattern of heavy minerals in stratigraphic column, heavies are grouped into two distinct assemblages i.e. (i) garnet-staurolite-hornblende-kyanite-epidote assemblage, (ii) prismatic and rounded to subrounded grains of zircon-tourmaline-rutile assemblage. The presence of heavy mineral assemblages in the stratigraphic column r eveals that the sediments of Patcham and Chari Formations have been derived mainly from two lithologically different Precambrian terrains; one is dominated by metamorphic rocks and the other is igneous (acid and basic), besides a little contribution of sedimentary source. Source rocks were situated close to basin of deposition in the northeast and east i.e. Aravalli range and north and northwest dominated by granite-syenite suite belonging to Nagar-Parkar Massif. The variable ZTR index indicates manifestation of relief and climatic change in the source area. © Geol. Soc. India.