Amorphous Iron Oxide Precipitates in Sediments Cored during Leg 5, Deep Sea Drilling Project

Iron-Rich Sediments Cored during Leg 8 of the Deep Sea Drilling Project

“…The biogenic material is dominantly calcareous nannoplankton. This association is identical to that of basal sediments from east Pacific drill Sites 37, 38, and 39 of Leg 5 documented by von der Borch and Rex (1970). The material is also similar to iron and manganese oxide-rich sediments described by Bostrom and Peterson (1966), , and Bostrom, Peterson, Joensuu and Fisher (1969) from crestal areas of active mid-ocean ridges, particularly the East Pacific Rise.…”

“…The iron-manganese sediments of Leg 5, for example (von der Borch and Rex, 1970), contain up to 27.8 per cent iron, an as yet undetermined amount of manganese, and abundant amorphous material that may be in part silica. It is possible that a banding of iron oxide-rich layers and silica-rich layers could be produced either diagenetically or by subsequent metamorphism of these deposits to produce a banded iron formation which would resemble some of the ancient deposits both in mineralogy and lithologic association.…”

The hydrothermal alteration of oceanic basalts by seawater

“…von der Borch and Rex, 1970;von der Borch ct al, 1971;Cook, 1971;Cronan et al 1972;Cronan, 1973Cronan, , 1974Horowitz and Cronan, 1976). These represent ancient hydrothermal deposits that were precipitated at the ridge crest and have moved to their present positions as a result of sea-floor spreading, suggesting that hydrothermal circulation at the mid-ocean ridges has been a geologically continuous process.…”

“…The concept of sea-floor spreading requires that these sediments move away from the ridge and are gradually overlain by pelagic sediments. This leads to the formation of a metal-enriched basal sediment layer which has been sampled in several areas of the ocean by the Deep Sea Drilling Project (von der Borch and Rex, 1970;von der Borch et al, 1971;Cronan et al, 1972;Cronan, 1973;Horowitz and Cronan, 1976). A few examples of the chemical composition of these sediments are listed in Table 4-1.…”

Lithology, colour, mineralogy, and geochemistry of marine sediments from the Southwestern Pacific and Samoan Basins

“…This is an abbreviation fOF "red-brown semi-opaque oxides", a term applied by Yeats et al (1976) to disseminated grains and globules of amorphous iron oxides. These were previously recognised microscopically by von der Borch & Rex (1970) and Cronan & Garrett (1973). Sediments of the Southwest Pacific contain as much as 10% or more RSO, appearing as reddishbrown speckles in a brown clay matrix on smear slides.…”