A note on geochemistry of surface sediments from Krishna-Godavari basin, East Coast of India

摘要

A closely spaced 75 surface sediments drawn from "Gas Hydrate" Project taken up by National Institute of Oceanography on aregional scale from the Krishna-Godavari Basin (Latitude 15 degrees 35' to 16 degrees 20' N; Longitude 81 degrees 40' to 82 degrees 30'E) are analysed for texture, major, and some trace and rare earth elements to understand their source and provenance. Water depth in the study area varies between 300 to 2000 m and there is a WNW-ESE trending sedimentary ridge in the southwestern part of basin. Sediments are mostly silty clay in nature. Ti - bearing minerals such as titanite and pyrophanite are evident by the strong positive correlation between Ti and Ca (r = 0.89) and Ti and Mn (r =0.67) respectively. An independent behaviour of Zr suggests occurrence of zircon mineral. The strong positive correlation among Al, Fe, Mg and K (r = 0.68 to 0.90) suggests their association with clay. The average total REE (Sigma REE 176 +/- 13 ppm) abundance is similar to that of average shale with a flat shale-normalized REE pattern suggest a terrigenous source. High concentration of Fe (6.45 +/- 0.43%), Ti (0.82 +/- 0.07%), V (192 23 ppm), Cr (128 +/- 13 ppm) and Zr (159 +/- 19 ppm) and presence of smectite as a major clay mineral suggest that Peninsular Godavari River has sediment influx from source rocks of Eastern India mainly Deccan Trap, Precambrian and Dharwar formation. Further, it confirms that the role of Ganges-Brahmaputra River sediments to the basin appears to be small compared to the Peninsular rivers.