Heavy Mineral Placer Sand Deposits of Kontiagarh Area, Ganjam District, Orissa, India

摘要

The Kontiagarh placer deposit in the Ganjam district, Orissa, India extends in northeast direction having a width of 700-1000 m. A total of 187 samples were collected meterwise from 55 bore holes in a grid pattern from beach, frontal, intermediate and back dunes covering an area of approximately 1 km~2. Light minerals decrease in size from the beach to the back dunes, whereas the size distribution of heavy minerals in the beach and dunes is more or less uniform. The average heavy mineral content in the beach and dunes vary from 9.38 percent to 24.20 percent. The heavy minerals are ilmenite, garnet, sillimanite, rutile, monazite, and zircon with trace amounts of magnetite, hornblende, diopside, sphene, tourmaline, and epidote. Heavy minerals are mostly less than 350 urn in size, with a peak distribution in the range between 180 and 125 um. Ilmenite shows exsolution intergrowth with hematite. Mineral chemistry of ilmenite, hematite, leucoxene, magnetite, monazite and sillimanite are examined by EPMA. Leucoxene is lower in Fe and higher in Ti, Al, Cr and V than ilmenite. The litho-units of the Precambrian Eastern Ghats Mobile Belt, comprising primarily khondalite, charnockite, calc-silicate granulite and gneiss, are the source of heavy minerals for this deposit. The bulk sample has 7.30 percent ilmenite, 5.24 percent sillimanite, 9.16 percent garnet, 0.18 percent rutile, 0.14 percent monazite, 0.06 percent zircon and 0.52 percent other heavy minerals. The deposit has good potential for economic exploitation of ilmenite, rutile, sillimanite, monazite, zircon and garnet.