Placer mineral studies before and after the tsunami were undertaken systematically along the coastal region from Tuticorin to Ovari, Tamil Nadu. Different size grades of heavy minerals show a similar trend of concentration from +70 to +200 mesh, except at +80 and +170 mesh size grades before the event. After the tsunami, a shift in the modality to a slightly coarser grade is noticed in all the beaches at stations Ovari and Manappad. An increasing trend of heavy mineral concentration was noticed after the tsunami at Tuticorin south, Tuticorin north, Manappad and Ovari. Depletion of placers in other regions is attributable to the beach configurations. At Ovari, a higher percentage of heavy minerals may be attributed to the deposition of tsunamigenic sediments towards the shore region. SEM studies show the internal surface features for different minerals. The present study has disclosed a higher concentration of garnets and zircons after the tsunami.

India has an extensive coastline of about 7,500 km long and a vast exclusive economic zone of more than 2.1 mn km², which includes the Andaman, Nicobar and Lakshadweep Islands, enriched with different types of placer minerals. Placer deposits are formed as a result of disintegration of valuable minerals from rocks and redeposition of heavy minerals at suitable places and are repositories for valuable minerals like monazite, zircon, ilmenite, garnet, and magnetite. Factors such as their easy mineability, availability of cost-effective indigenous mining technology, and better profit ratios have increased the importance of placers over the years as a major source of economic minerals. Rajamanickam (2001) has classified placers into marine placers including raised beaches, and offshore placers including ongoing and palaeo/fossil placers of both buried and exposed types. Minerals with certain inherent characteristics such as high specific gravity and chemical strength to resist the denudating action of transporting agents can be accumulated as placers. Heavy minerals are those minerals having specific gravity of more than 2.89. Angusamy and Rajamanickam (2000) have studied the distribution of heavy minerals between Kanyakumari and Mandapam. Indian resources constitute about 35% of world resources of ilmenite, 10% of rutile, 14% of zircon and 71.4% of monazite (Rajamanickam et al., 2004).

The Effect of Tsunami on the Placer Mineral Distribution in the Beaches between Tuticorin and Ovari, Tamil Nadu, India, Rajamanickam, concentration, minerals, placers, ilmenite, Manappad, monazite, economic, studies, zircon, disintegration, Angusamy, extensive, attributable, accumulated, indigenous, Kanyakumari, Lakshadweep, Mandapam, mineability, characteristics, Nicobar, palaeofossil