Coastal Placer Deposits of Central Tamil Nadu, India

ABSTRACT

Placer mineral exploration has been undertaken along the beach of Central Tamil Nadu coast from Pondicherry to Vedaranyam. On the basis of the drainage network, geomorphology, and the coastal environment, the study area has been grouped into three sectors, North, Central, and South. Heavy mineral by Wt% shows a slightly higher abundance in the Northern sector, an enrichment of opaques in the Central sector from stations between Poompuhar and Karaikal, and a total depletion in the Southern sector. An abundance of heavies in the Northern sector is considered to be the result of a higher wave energy, and the cymatogenic downwarping of the basin during the present transgression. An enrichment of heavies in the Central sector from Poompuhar to Karaikal is attributable to the reworking of the beach ridges, which were submerged during the present transgression, and to the role of density sorting. A depletion of heavies in the Southern sector is accounted for by the absence of a terrigenous supply and the prevalence of wave shadow conditions throughout the year. The nature of the heavy mineral assemblage reflects the derivation of sediments principally from khondalites, granites, metamorphic rocks and paleo-sediments. Factor analysis also supplements the predominant role of a density factor in the segregation of heavy minerals in the study area. A five-stage model is proposed for the formation of placer deposits in the study region. The present study has disclosed rich concentrations of ilmenites in the central sector between Poompuhar and Karaikal that can be commercially exploited.

Keywords:

• Heavy minerals
• Beach placers
• Ilmenite
• Provenance
• Central Tamil Nadu Coast
• India

Authors thank the Department of Ocean Development, Ocean Science and Technology Cell (OSTC), Government of India for the financial support to carry out this project. We thank the authorities of Tamil University, Thanjavur, for granting necessary permission to carry out this work. We also acknowledge Prof. Vaughn Barrie of Pacific Geoscience Center, Geological Survey of Canada for critically going through this manuscript and for his invaluable suggestions. We thank Dr. A. R. Gujar, National Institute of Oceanography, Goa, India, for providing XRD analysis of ilmenites.

Notes

NM-non-magnetics; il-ilmenite; Mag-magnetite

C-Convergence; D-Divergence; I-Inept wave condition.