Abstract <p>The siliceous sediments of the Indian Ocean hosts one of the richest deposits of polymetallic nodules, and their growth is intimately associated with these sediments. They are comprised of only ~10% coarse fraction (&gt;63 µm grain size), which are mainly composed of radiolarian tests, glass shards, micronodules and other detrital materials, making a difference of ~23% SiO₂ and 14.5% TiO₂ content between the bulk sediment and finer fraction. Rest of the major element oxides are found to be enriched in the finer fraction with maximum difference of ~300% in Na₂O. Most of the trace elements are enriched in the bulk sediment than their finer counterparts except Cu and Zn, which also come from the dissolution of radiolarian tests. Considerable amounts of Ni, Cu, Co, V, Y and REEs are also contributed in the bulk sediment via micronodules. Principal Component Analysis reveal the close association between Al₂O₃ and Fe₂O₃ in the sieved sediment indicating the role of clay fraction incorporating these metals, which can be both terrestrial and authigenic. Thus, although the coarse fractions comprise very small proportion of the bulk sediment, nevertheless it plays a crucial role in metal enrichment of the authigenic deposits in this area.</p> Research highlights <p><UnorderedList Mark="Bullet"> <ItemContent> <p>Coarse fraction of siliceous sediments is ~10% of total grain size population.</p> </ItemContent> <ItemContent> <p>They have very high concentrations of SiO₂, FeO, CuO, ZnO, etc.</p> </ItemContent> <ItemContent> <p>They contribute significantly in the total metal content of the bulk sediment.</p> </ItemContent> </UnorderedList></p>