Heavy Mineral Assemblages And Distribution Between Kooduthalai And Midalam, Southern Tamil Nadu, India

Abstract

In this work, we studied the heavy-mineral placer deposits in the sediments of the coastal stretch between Kooduthalai and Midalam, Southern Tamil Nadu. For the present assessment, we collected a total of 187 samples from six sites viz. Kooduthalai, K. Uvari, Navaladi, Thiruvembalapuram, Vattakottai and Midalam. Sediment samples were collected down to a depth of 6m.We used a hand auger and a manually-driven Conrad banka drill for sampling. The collected samples were sub-sampled for every 0.5m depth interval. Samples were weighed, sieved and separated for different heavy minerals and identified with the help of a polarizing microscope. We followed standard protocol in sample processing and identification. We estimated the quantity of geological reserve of heavy minerals for one square meter. Pink, black and greenish yellow sediment patches occur in the study area. The heavy minerals present in this region include both the opaque and non-opaque varieties, the dominant minerals being ilmenite and garnet with small amounts of zircon, rutile, sillimanite, leucoxene and monazite. The average concentration of heavy minerals varies from 62.59 to 66.54%. We find the spatial distribution of ilmenite increasing from Kooduthalai (east coast) to Midalam (west coast), whereas garnet exhibits a reverse pattern. Monazite is confined to Vattakottai and Midalam (south to west coast). The assemblages of heavy minerals are concentrated in the fine and very fine sand fractions. The formation and concentration of these deposits are governed not only by the characteristics of the host rock in the Peninsula, Western Ghats and Quaternary sedimentary deposits but also by weathering processes, geological agents and coastal hydrodynamics. The concentration of heavy minerals in this region varies from 5 to 12 tonnes per square