Geochemistry and K-Ar dates of the Mazagan granodiorite at V30-225, VA79-96KD and DSDP Hole 79-544A, off Moroccan coast

Gneissic granodiorite was recovered by drilling at the base of the Mazagan escarpment, 100 km west of the Casablanca, Morocco, at 4000 m water depth. Coarse, predeformative muscovite yielded dates of -515 Ma, fine-grained muscovite of -455 Ma, biotite -360 and 335 Ma, and feldspar -315 Ma. These dates are tentatively correlated with the microscopic results. We assume a minimum age of middle Cambrian for the granodiorite, an Ordovician deformation and mylonitization, and a Late Carboniferous overprint under upper greenschist facies conditions.

Grain size and chemical compositions of bottom sediments from the Amur Bay

Composition of clay minerals in the <0.001 mm size fraction from the uppermost layer of bottom sediments in the northern Amur Bay was determined by X-ray powder diffraction analysis, and enrichment of 33 elements in the <0.001 mm and <0.01 mm size fractions of surface sediments from a number of sites at the marginal filter of the Razdol'naya River were studied by ICP-MS. Fe, U, and chalcophile elements occur in the highest concentrations in sediments from all sampling sites within the filter. The bottom sediments are not enriched in trace, alkali, and alkaline earth elements. Maximum concentrations of chemical elements were found in deposits from the brackish part of the marginal filter, perhaps, because of formation of Fe and Mn (Al) hydroxides. Bottom sediments at the boundary between the brackish and marine parts of the filter contain the lowest concentrations of the examined elements.

Annual variations in composition of the North Dvina River water

New data on elemental composition of particulate matter from the North Dvina River are presented. In May (period of snowmelt flood) it is similar to the upper layer of the continental crust due to active erosion of crust material in the catchment area. In August (summer low water period) impact of biogenic components increases and elevated concentrations of Cd, Sb, Mn, Zn, Pb, and Cu are observed. At other seasons no significant increase in heavy and rare earth element concentrations is observed.

Inorganic and organic geochemistry and sediment descriptions at DSDP Hole 93-603B

About one hundred samples of sediments and rocks recovered in Hole 603B were analyzed for type, abundance, and isotopic composition of organic matter, using a combination of Rock-Eval pyrolysis, C-H-N-S elemental analysis, and isotope-ratio mass spectrometry. Concentrations of major, minor, and trace inorganic elements were determined with a combination of X-ray fluorescence and induction-coupled plasma spectrometry. The oldest strata recovered in Hole 603B (lithologic Unit V) consist of interbedded light-colored limestones and marlstones, and black calcareous claystones of Neocomian age. The inorganic and organic geochemical results suggest a very terrigenous aspect to the black claystones. The organic geochemical results indicate that the limestones and marlstones contain a mixture of highly degraded marine and terrestrial organic matter. Comparison of the Neocomian carbonates at Site 603 with those on the other side of the North Atlantic, off Northwest Africa at Site 367, shows that the organic matter at Site 367 contains more marine organic matter, as indicated by higher pyrolysis hydrogen indices and lighter values of d13C. Comparison of inorganic geochemical results for the carbonate lithologies at Site 603 with those for carbonate lithologies at Site 367 suggests that the Site 603 carbonates may contain clastic material from both North American and African sources. The black claystones at Site 603, on the other hand, probably were derived almost entirely from North American clastic sources. Lithologic Unit IV overlying the Neocomian carbonates, consists of interbedded red, green, and black claystones. The black claystones at Site 603 contain more than ten times the organic carbon concentration of the interbedded green claystones. The average concentration of organic carbon in the black claystones (2.8%), however, is low relative to most mid-Cretaceous black claystones and shales in the Atlantic, particularly those found off Northwest Africa. The geochemical data all suggest that the organic matter in the black claystones is more abundant but generally more degraded than the organic matter in the green claystones, and that it was derived mainly from terrestrial sources and deposited in oxygenated bottom waters. The increased percentage of black claystone beds in the upper Cenomanian section, and the presence of more hydrogen-rich organic matter in this part of the section, probably resulted from the increased production and accumulation of marine organic matter that is represented worldwide near the Cenomanian/Turonian boundary in deep-sea and land sections. A few upper Cenomanian black claystone samples that have hydrogen indices > 150 also contain particularly high concentrations of V and Zn. Most samples of black claystone, however, are not particularly metal-rich compared with other black claystones and shales. Compared with red claystones from lithologic Unit IV, the green and black claystones are enriched in many trace transition elements, especially V, Zn, Cu, Co, and Pb. The main difference between the "carbonaceous" claystones of lithologic Unit IV and "variegated" or "multicolored" claystones of the overlying Upper Cretaceous to lower Tertiary Unit III is the absence of black claystone beds. As observed at several other sites (105 and 386), the multicolored claystones at Site 603 are somewhat enriched in several trace transition elements-especially Cu, Ni, and Cr-relative to most deep-sea clays. The multicolored claystones are not enriched in Fe and Mn, and therefore are not "metalliferous" sediments in the sense of those found at several locations in the eastern Pacific. The source of the slightly elevated concentrations of transition metals in the multicolored claystones probably is upward advection and diffusion of metals from the black claystones of the underlying Hatteras Formation. The red, orange, and green claystone beds of lithologic Unit II (Eocene), like those of Unit III, really represent a continuation of deposition of multicolored claystone that began after the deposition of the Neocomian carbonates. The color of the few black beds that occur within this unit results from high concentrations of manganese oxide rather than high concentrations of organic matter.

Composition of Holocene lithificates at the slopes of the Untersee Mountain Valley, East Antarctica

It was found out that the lower parts of slopes of the Untersee mountain valley (East Antarctica) were locally covered with lithificates (both carbonate-free and carbonate-poor). They occur in three modes: crusts, films, and impregnates. All of them cover Late Pleistocene moraine material and consist of mixture of lacustrine sedimentary material and filling material of moraines. A mechanism of their genesis is offered.

Chemical composition of sediments from DSDP Legs 45 and 71

Results of mineralogical and geochemical investigations of post-Middle Jurassic deposits of the Atlantic Ocean are based on materials of the Deep Sea Drilling Project. Comparative characteristics of primary matter for ''black shales'' are given. Exhalative origin of heavy metal accumulation in near-axial sedimentary deeps of the Mid-Atlantic Ridge (23°N) are shown. History of post-Middle Jurassic sedimentation is considered on the base of clay mineral-, clastic component-, trace and rare- chemical element studies.

Composition of standard reference samples of Fe-Mn nodules and bottom sediments

The first series of Soviet standard reference samples of composition of ore materials and ocean pelagic sediments has been created. It includes iron-manganese nodules (SDO-4, SDO-5 and SDO-6), ore crusts (SDO-7) diatomaceous ooze (SDO-8), and deep-sea red clays (SDO-9). The standards are intended to serve as a metrologic basis for physical, physicochemical and chemical analyses of iron-manganese minerals and ocean sediments. The standards are provided with certified analyses of rock-forming components and certain trace elements. Certified characteristics are based on statistical analysis of data obtained from an inter-laboratory experiment involving analysis of the standard reference samples by a variety of methods.

Phosphate d18O pore-water profiles of sediment core GeoB11807-2 and GeoB11804-4

Phosphorus cycling in the ocean is influenced by biological and geochemical processes that are reflected in the oxygen isotope signature of dissolved inorganic phosphate (Pi). Extending the Pi oxygen isotope record from the water column into the seabed is difficult due to low Pi concentrations and small amounts of marine porewaters available for analysis. We obtained porewater profiles of Pi oxygen isotopes using a refined protocol based on the original micro-extraction designed by Colman (2002). This refined and customized method allows the conversion of ultra-low quantities (0.5 - 1 µmol) of porewater Pi to silver phosphate (Ag3PO4) for routine analysis by mass spectrometry. A combination of magnesium hydroxide co-precipitation with ion exchange resin treatment steps is used to remove dissolved organic matter, anions, and cations from the sample before precipitating Ag3PO4. Samples as low as 200 µg were analyzed in a continuous flow isotope ratio mass spectrometer setup. Tests with external and laboratory internal standards validated the preservation of the original phosphate oxygen isotope signature (d18OP) during micro extraction. Porewater data on d18OP has been obtained from two sediment cores of the Moroccan margin. The d18OP values are in a range of +19.49 to +27.30 per mill. We apply a simple isotope mass balance model to disentangle processes contributing to benthic P cycling and find evidence for Pi regeneration outbalancing microbial demand in the upper sediment layers. This highlights the great potential of using d18OP to study microbial processes in the subseafloor and at the sediment water interface.

Seafloor hydrothermal activity in sediment core MV0502-15JC

A large diameter piston core containing 8.35 m of metalliferous sediment has been recovered from a small abyssal valley in the remote Southwest Pacific Basin (31°42.194'S, 143°30.331'W; 5082 m water depth), providing unique insight into hydrothermal activity and eolian sedimentation there since the early Oligocene. A combination of fish-teeth Sr-isotope stratigraphy and INAA geochemical data reveals an exponentially decreasing hydrothermal flux 31 Ma to the present. Although hydrothermal sedimentation related to seafloor spreading explains this trend, a complex history of late Eocene/early Oligocene ridge jumps, propagating rifts and plate tectonic reorganization of South Pacific seafloor could have also played a role. A possible hiatus in deposition, as recorded by changes in core composition just below 2 m depth, is beyond the resolution of the fish teeth Sr isotope dating method employed here; however, the timing of this interval may be coincident with extinction of the Pacific-Farallon Ridge at ~20 Ma. A low flux eolian component accumulating at this site shows an increase relative to the hydrothermal component above 2 m depth, consistent with dust-generating continental sources far to the west (Australia/New Zealand). This is the first long-term paleoceanographic record obtained from within the South Pacific "bare zone" (Rea et al., 2006), an anomalous region where Pacific seafloor has largely escaped sediment accumulation since the Late Cretaceous.

Chemical composition of Fe-Mn nodules and crusts from the Pacific Ocean

The book is devoted to study of diagenetic changes of organic matter and mineral part of sediments and interstitial waters of the Pacific Ocean due to physical-chemical and microbiological processes. Microbiological studies deal with different groups of bacteria. Regularities of quantitative distribution and the role of microorganisms in geochemical processes are under consideration. Geochemical studies highlight redox processes of the early stages of sediment diagenesis, alterations of interstitial waters, regularities of variations in chemical composition of iron-manganese nodules.

Composition and sorption capacity of oceanic and marine ferromanganese nodules

Experimental data obtained show that oceanic and marine ferromanganese nodules and crusts are natural ion-exchangers. Exchange capacity of oceanic ferromanganese aggregates is much higher than that of shallow-water marine ones, whereas reactivities of exchange cations (Na, K, Ca, and Mg) are almost equal in both.