Abstract:
Chemical analyses of 747 sediment samples collected during DSDP legs 22, 24, 26 and 27 in the Indian Ocean are reported with special attention to the composition of zeolite brown clays and the sediment-basalt contact zone. The brown clays are most enriched in the elements Li, Mg, Al, Ti, V, Mn, Fe, Co, Ni, Cu, Zn and Pb and depleted in K, Ca and Sr compared to other sediment types. The Cretaceous brown clays are lower in V, Mn, Fe, Co, Ni and Cu compared to their later counterparts. In general, however, there does not appear any substantial variation in the composition of the brown clays with geologic age. The basal sediments studied show little influence of element enrichment compared with normal pelagic clays. Exceptions are the basal sediments of Sites 213 and 215 on either side of the Ninety-east Ridge. These sediments are considered to approach the characteristics of metalliferous sediments. Comparison of the geochemistry of the pelagic deep-sea clays from the Indian, Atlantic and Pacific Oceans reveals that the average trace element composition of the Indian Ocean pelagic clays lines, in general, between those of Atlantic and Pacific Ocean clays.