Chemical composition of the red bed layer in DSDP Hole 38-336

Clay minerals were studied in samples from the Eocene red bed layer of DSDP Hole 336. It is shown that composition and distribution of clay minerals have zoning, which is usually typical for the terrestrial crust of chemical weathering of basic rocks.

Rare earth and other element contents and speciations in samples from Core AKO26-35, Pacific Ocean, Southwest Basin

Ferromanganese micro- and macronodules in eupelagic clays at Site AKO26-35 in the Southwest Pacific Basin were studied in order to check REE distribution during ferromanganese ore formation in non-productive zones of the Pacific Ocean. Host sediments and their labile fraction, ferromanganese micronodules (in size fractions 50-100, 100-250, 250-500, and >500 ?m) from eupelagic clays (horizons 37-10, 105-110, 165-175, and 189-190 cm), and buried ferromanganese micronodules (horizons 64-68, 158-159, and 165-166 cm) were under study. Based on partition analysis data anomalous REE enrichment in eupelagic clays from Site AKO26-35 is related to accumulation of rare earth elements in iron hydroxophosphates. Concentration of Ce generally bound with manganese oxyhydroxides is governed by oxidation of Mn and Ce in ocean surface waters. Micronodules (with Mn/Fe from 0.7 to 1.6) inherit compositional features of the labile fraction of bottom sediments. Concentrations of Ce, Co, and Th depend on micronodule sizes. Enrichment of micronodules in hydrogenic or hydrothermal matter is governed by their sizes and by a dominant source of suspended oxyhydroxide material. The study of buried ferromanganese micronodules revealed general regularities in compositional evolution of oxyhydroxide matrices of ferromanganese micro- and macronodules. Compositional variation of micro- and macronodules relative to the labile fraction of sediments in the Pacific non-productive zone dramatically differs from the pattern in bioproductive zones where micronodule compositions in coarser fractions are similar to those in associated macronodules and labile fractions of host sediments due to more intense suboxidative diagenesis.

(Table 5) Quaternary paleoproductivity of organic carbon in oceans based on DSDP cores

By analogy with the present-day ocean, primary productivity of paleoceans can be reconstructed using calculations based on content of organic carbon in sediments and their accumulation rates. Results of calculations based on published data show that primary productivity of organic carbon, mass of phosphorus involved in the process, and content of phosphorus in ocean waters were relatively stable during Cenozoic and Late Mesozoic. Prior to precipitation on the seafloor together with biogenic detritus, dissolved phosphorus could repeatedly be involved in the biogeochemical cycle. Therefore, only less than 0.1% of phosphorus is retained in bottom sediments. Bulk phosphorus accumulation rate in ocean sediments is partly consistent with calculated primary productivity. Some epochs of phosphate accumulation also coincide with maxima of primary productivity and minima of the fossilization coefficient of organic carbon. The latter fact can testify to episodes of acceleration of organic matter mineralization and release of phosphorus from sediments leading to increase in the phosphorus reserve in paleoceans and phosphate accumulation in some places.

Rare earth and other element contents in surface layer bottom sediments and ferromanganese nodules along the Transatlantic profile

Behavior of rare earth elements (REE) and Th is studied along the Transatlantic transect at 22°N. It is shown that both REE and Th contents relative to Al (the most lithogenic element) increase toward the pelagic region. The increasing trend becomes more complicated due to variations in content of biogenic calcium carbonate that acts as a diluting component in sediments. REE composition varies symmetrically relative to the Mid-Atlantic Ridge (MAR) emphasizing weak hydrothermal influence on sediments of the ridge axis, although the well-known criteria for hydrothermal contribution, such as Al/(Al+Mn+Fe) and (Fe+Mn)/Ti, do not reach critical values. Variations in REE content and composition allowed to distinguish the following five sediment zones in the transect: (I) terrigenous sediments of the Nares abyssal plain; (II) pelagic sediments of the North American Basin; (III) carbonate ooze of the MAR axis; (IV) pelagic sediments of the Canary Basin; and (V) terrigenous clay and calcareous mud of the African continental slope and slope base. Ferromanganese nodules of the hydrogenous type with extremely high Ce (up to 1801 ppm) and Th (up to 138 ppm) contents occur in pelagic sediments. It is ascertained that P, REE, and Th contents depend on Fe content in Atlantic sediments. Therefore, one can suggest that only minor amount of phosphorus is bound with bone debris. Low concentration of bone debris phosphorus is a result of relatively high sedimentation rates in the Atlantic Ocean, as compared with those in pelagic regions of the Pacific Ocean.

Chemical composition of ferromanganese nodules from the Black Sea

Ferruginate shells and tubular worm burrows from the oxygenated zone of the Black Sea (Kalamit Bay and Danube River mouth) are studied by transmission and scanning electron microscopy combined with analyses of elemental composition. Iron and manganese oxyhydroxide nodules considered here are enriched in phosphorus. They contain variable amounts of terrigenous and biogenic material derived from host sediments. Oxyhydroxides are mainly characterized by colloform structure, whereas globular and crystalline structures are less common. The dominating iron phase is represented by ferroxyhite and protoferroxyhite, whereas the manganese phase is composed of Fe-free vernadite. Concentrations of Mn, As, and Mo are 12-18 times higher relative to sediments, while concentrations of Fe, P, Ni, and Co increase 5-7 times during nodule formation.

(Table S2, page 46-47) Manganese nodule sampling station data

Legacy product - no abstract available

14C ages, grain size distribution and foraminifer abundance of sediments from the Barents Sea shelf

The origin of friable sediments blanketing the Barents Sea shelf is considered. It is shown that their characteristic seismoacoustic record patterns reflect low degree of diagenetic transformations and indicates continuous sedimentation. According to traditional views, this single sedimentary complex also includes diamicton, and the section is interpreted as a three-unit structure: diamicton, which is considered a till; the overlying friable sediments accumulated under different conditions of deglaciation in glaciomarine settings; and the postglacial marine sediments. It is demonstrated that such views are inconsistent with geomorphologic features (datings by physical methods included) indicating a prolonged hiatus that separates epochs of the diamicton accumulation and formation of friable sediments. The analysis revealed that the composition, vertical succession, and lateral distribution of different lithological types of friable sediments are related to the regular spatiotemporal replacements of different facies settings in the transgressing Arctic sea rather than by the glacial process. This inference is confirmed by the composition of foraminiferal assemblages.

Noble metals and associated trace elements in sulfides from the active TAG mound, ODP Site 158-957

Primary sulfides from cores of ODP Holes 158-957M, 158-957C, and 158-957H on the active TAG hydrothermal mound (Mid-Atlantic Ridge, 26°08'N) have been studied for concentrations of several chemical elements. Based on 262 microprobe analyses it has been found that the sulfides have extremely heterogeneous distribution of noble metals (Au, Ag, Pt, and Pd) and several associated elements (Hg, Co, and Se). Noble metals are arranged in the following order in terms of decreasing abundance, i.e. concentration level above detection limits (the number of analyses containing a specific element is given in parentheses): Au (65), Ag (46), Pt (21), and Pd (traces). The associated trace elements have the following series: Co (202), Hg (132), and Se (49). The main carriers of "invisible" portion of the noble metals are represented by pyrite (Au, Hg), marcasite and pyrite (Ag, Co), sphalerite and chalcopyrite (Pt, Pd), and chalcopyrite (Se). Noble metal distribution in sulfides reveals a lateral zonality: maximal concentrations and abundance of Au in chalcopyrite (or Pt and Ag in chalcopyrite and pyrite) increase from the periphery (Hole 957H) to the center (holes 957C and 957M) of the hydrothermal mound, while Au distribution in pyrite displays a reversed pattern. Co concentration increases with depth. Vertical zonality in distribution of the elements mentioned above and their response to evolution of ore genesis are under discussion in the paper.