Summary of Abstract Submission

Abstract Submission No. IO50-11-0012PresentationPoster

EFFECT OF COARSE FRACTIONS (>63μ) ON THE GEOCHEMICAL COMPOSITION OF SILICEOUS SEDIMENTS FROM CENTRAL INDIAN BASIN (CIB), INDIAN OCEAN

Simontini Sensarma*1, Ranadip Banerjee1, Subir Mukhopadhay2

1 National Institute of Oceanography, India
2 Jadavpur University, India

ABSTRACT :

This study attempts to understand the effect of coarse fraction (CF) in the siliceous sediments from 20 locations of Central Indian Ocean Basin (CIB). CIB siliceous sediments contained ≤10% CF (>63) on avg and were silty clay in nature. The CF content of the samples were mainly radiolarian tests (>90%), glass shards (5-8%), micronodules (1-3%) and rock/mineral fragments (~1%). The glass shards were usually transparent but some were translucent with orangish/brownish tints. They were mostly angular without any abrasion or rounded edges indicating their possible in situ origin. The micronodules were botryoidal in shape and some were attached with the radiolarian tests. Palagonite crystals were ubiquitous with other mineral/rock fragments. Geochemical investigation revealed that Si and Ti were higher in the bulk sediment than their sieved counterparts, indicating their source to be mainly from biogenic silica, glass shards and rock fragments. In fact biogenic silica was >50% on avg of the total silica concentrations in all the samples. Fe and Mn showed no distinct trend after sieving. However, both showed excellent correlation with Ni, Cu, Co, V, Sr, Y and REEs in the bulk sediments, which became insignificant after sieving, suggesting the possible association of these elements with the micronodules. REE concentration decreased in the sediment after sieving, although the distribution pattern remained same. Thus although the CF of the studied samples constituted very less proportion of the bulk sediment, nevertheless, it played an important role in trace metal and REE enrichment of the sediments.