Deep-sea red clay

The sediments in the deep sea consist of only few basic types which in their manifold combinations are suited for the description of a varied facial pattern (Table 1.4). The characteristic pelagic deep-sea sediment far from coastal areas is deep-sea red clay, an extremely fine-grained (median < 1 pm) red-brown clay sediment which covers the oceanic deep-sea basins below the Calcite Compensation Depth (CCD). More than 90 % is composed of clay minerals, other hydrogenous minerals, like zeolite, iron-manganese precipitates and volcanic debris. Snch sediment composition demonstrates an anthigenic origin. The... 

The hemipelagic sediments are basically made of the same components as the deep-sea red clay... 

The latter group comprises the components of the deep-sea red clay and the terrigenous silici-clastics. On the basis of experiences made in the Deep Sea Drilling Project, Dean et al. (1985) have... 

Basically, it can be stated that the sedimentation rate decreases with increasing distance from a sediment source, may this either be a continent or an area of high biogenic productivity. The highest rates of terrigenous mud formation are recorded on the shelf off river mouth s and on the continental slope, where sedimentation rates can amount up to several meters per one thousand years. Distinctly lower values are observed at detritus-starved continental margins, for example of Antarctica. The lowest sedimentation rates ever recorded lie between 1 and 3 mm ky. and are connected to deep-sea red clay in the offshore deep-sea basins (Table 1.7), especially in the central Pacific Ocean. 

A more widespread process consists of the hydrogenous formation of clay at the sediment-seawater interface, in deep-sea environments characterized by water depths > 4000 m, insignificant terrigenous supply, and very low sedimentation rate (South Pacific basins. The sediments mostly consist of reddish-brown oozes rich in Fe and Mn oxides (i.e., deep sea red clay ). There iron-rich smectites of the nontronite group may form in significant proportions, probably due to long-term low temperature interactions between (1) metal... 

Reference materials that represent the primary deep-sea and coastal depositional environments and biological materials would solve many of the problems that radiochemists face in analysis of sediments from these settings. Radiochemists require reference materials comprising the primary end member sediment and biological types (calcium carbonate, opal, and red clay from the deep-sea and carbonate-rich, silicate-rich, and clay mineral-rich sediments from coastal environments and representative biological materials). Additional sediment reference material from a river delta would be valuable to test the release of radionuclides that occurs as riverine particles contact seawater. 

The absence of sepiolite and palygorskite from sediments and sedimentary rocks in other parts of the world is most likely due to a lack of attention on the part of researchers who have looked at clay mineral suites in the past. This can be explained in part by the similarity of the respective major low-angle peaks which can be confused with montmorillonite (12 8 sepiolite-one water layer montmorillonite) and illite (10.5 8 palygorskite-slightly "expanded" illite). A priori there is no reason why these minerals should be particular to French sedimentary rocks except that workers from this country have been particularly alert to their presence. This opinion is reinforced by the now-frequent reports of sepiolite and, to a lesser extent, palygorskite in sea sediments of the Atlantic shelf and ridge, Mediterranean, Red Sea and Pacific deep sea (see JOIDES reports—National Science Foundation Publications). 

Murray J. W. and Kuivila K. M. (1990) Organic matter diagenesis in the northeast Pacific transition from aerobic red clay to suboxic hemipelagic sediments. Deep-Sea Res. 37, 59-80. 

The process of enrichment of trace metals in these non-biologically produced sediments is probably adsorption to the surface of iron and manganese oxides that form on virtually all particle surfaces in the ocean. This is also the process that forms manganese nodules in vast areas of deep-ocean sediments. Manganese nodules actually accrete on the sea floor at a rate of approximately 1 mm per million years, primarily in areas where there is little accumulation of CaCOs and opal-rich sediments, e.g. the vast red clay provinces of the North Pacific Ocean. Manganese nodules are enriched in the same metals that are found authigenically in the sediments (Table 12.4) to such an extreme... 

Table 1.7 Sedimentation rates of red clay in various deep-sea basins of the world ocean (data from various sources, e.g. Berger 1974, Gross 1987).

Deep-sea sediments cover more than 50% of the earth s surface and consist of carbonates, red clay and siliceous ooze (cf. Chap. 1). On average, red clay covers about 31% of the world s ocean basins but its abundance is much higher in the Pacific (49%) than in the Atlantic (26%) and Indian (25%) Oceans (Glasby 1991). Carbonates act as a diluent for the transition elements in deep-sea sediments because of the low contents of these elements in them and the composition of deep-sea sediments is therefore often presented on a carbonate-free basis. 

Radiometric dating has revealed wide variations (by four orders of magnitude) for the growth rates of marine manganese deposits Co-rich Mn cmsts (0.8 mm Ma Puteanus and Halbach 1988), deep-sea manganese nodules on red clay substrates (1-2 mm Ma Hu and Ku 1984), deep-sea manganese nodules on siliceous ooze substrates (3 -8 mm Ma" Hu and Ku... 

Deep-sea or red clay covers the deep ocean basins below CCD. Calcareous sediments cover topographic highs like ocean ridges above CCD. Siliceous sediments occur in the Southern Ocean around Antarctica, along the equator in the Indian and Pacific oceans. Terrigenous sediments drape the continental margins. 

Kato et al. (2011) found vast amounts of deep sea mud in the Pacific Ocean. The muds are generally metalliferous sediment, zeolitic clay, and pelagic " red clay. Thicknesses vary from a few meters to 70 m. They occur up to 50 m below the sea floor. These deposits occur in the eastern South Pacific and central North Pacific. They contain 1000-2300 ppm total REY (REE + Y). In the eastern South Pacific (5°-20° S, 90°-150° W), the REY-rich mud has high REY contents, 1000-2230 ppm total REY and 200 30 ppm total HREE. REY contents of the mud are comparable to or greater than those of the southern China ion-absorption-lype deposits (where EREY = 500-2000 ppm EHREE = 50-200 ppm) notably, the HREEs are in general nearly twice as abundant as in the Chinese deposits (Kato et al. 2011). 

Singer, A. StofFers, P. (1987) Mineralogy of a hydrothermal sequence in a core from the Atlantis 11 Deep, Red Sea. Clay Min. 22 251-267... 

Mat. Sci. Materials in Electronics 3 201-205 Taitel-Goldman, N. Singer, A. (2001) High-re-solution transmission electron microscopy study of newly formed sediments in the Atlantis 11 Deep, Red Sea. Clays Clay Min. 

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