Nature and Provenance of Heavy Mineral Distribution at Krishna River Delta, East Coast of India

Abstract

The present study deals with four sedimentary cores viz. Turumella (120m), Inturu (160m), Ponnapalli (110m) and Nizampatnam (150m) which were recovered from the Krishna delta. Total heavy minerals wt% varies from 0.32 to 7.00 (av. 2.44%) in the study area. The major heavy minerals were noticed in four studied cores i.e. opaques (Ilmenite + magnetite), pyriboles (pyroxenes + amphiboles), garnet, zircon, monazite, rutile and other heavy minerals (epidote, kyanite, tourmaline, etc.). Heavy mineral substance in Krishna river sediments forced by basement rocks, drainage basin and weathering conditions of the river environment. The occurrence of different lithological units in the drainage basins is contributing sediments, mainly opaques (Ilmenite + magnetite) and pyriboles (Amphibole + pyroxenes) from Deccan traps as well as Archean provenance which covered more than 55% of drainage basin. The red garnets (almandine), prismatic sillimanites and rounded zircons are derived from khondalites (metapeletic rocks) and pink garnets, elongated zircons and ortho- pyroxenes are derived from charnockites of Eastern Ghat Granulite Belt (EGGB). The fresh appearance of heavy minerals indicates short residence time in depositional environment without any chemical dissolution effect. The rounded and sub rounded grains of magnetite and ilmenite indicate long distance of transportation and/or reworked nature. The sub angular grains of magnetite and ilmenite indicate that they might have been derived from nearby sources, i.e. mainly an Eastern Ghat Group of rocks. The prismatic characteristic of the sillimanite mineral grains also suggests that their derivation is from khondalitic rocks. Opaques are from Deccan traps as well as Archean provenance. Garnets, sillimanites and zircons are derived from khondalites (metapeletic rocks) and charnockites of Eastern Ghat Granulite Belt.