Composition of surface layer bottom sediments from the Kem' River estuary, White Sea

Based on grain-size, mineralogical and chemical analyses of samples collected in cruises of R/V Ekolog (Institute of Northern Water Problems, Karelian Research Centre of RAS, Petrozavodsk) in 2001 and 2003 regularities of chemical element distribution in surface layer bottom sediments of the Kem' River Estuary in the White Sea were studied. For some toxic elements labile and refractory forms were determined. Correlation analysis was carried out and ratios Me/Al were calculated as proxies of terrigenous contribution. Distribution of such elements as Fe, Mn, Zn, Cr, Ti was revealed to be influenced by natural factors, mainly by grain size composition of bottom sediments. These metals have a tendency for accumulation in fine-grained sediments with elevated organic carbon contents. Distribution of Ni is different from one of Fe, Mn, Zn, Cr, Ti. An assumption was made that these distinctions were caused by anthropogenic influence.

Chemistry on manganese nodules from the Pacific Ocean

Three manganese nodules from the Pacific Ocean have been analysed for 35 elements by using mainly spectrophotometric and spectrographic methods. Cu, Co, Ni, Zn, and Pb were found in amounts approaching 1 %, which far exceeds their average concentrations in igneous rocks. On the other hand, elements having readily hydrolysable ions, such as Ga, Sc, Zr, Y, La and Ti, are present only in amounts comparable with their concentrations in igneous rocks. Sb, Bit Be, and Cr were not detected. The hydrochloric acid-insoluble fraction of nodules is practically free of the heavy metals that are characteristic of the acid-soluble fraction; it consists principally of clay minerals, together with lesser amounts of quartz, apatite, biotite and sodium and potassium felspars.

Authigenic carbonate of ODP SIte 104-643

Different generations of complex authigenic carbonates formed in siliceous muds (lithologic Unit IV) and hemipelagic clays (lithologic Unit V) of ODP Site 643, Leg 104 Norwegian Sea. The dominant phase in Unit IV is an early diagenetic Mn, Fe-calcite with a strong negative d13C ( -14 to -16 per mil) signature, and slightly negative d180 values. The strong negative d13C results from extensive incorporation of 12C-enriched CO2 derived from bacterial degradation of marine organic matter into early Mn, Fe - calcite cements. Concomitant framboidal pyrite precipitation and abundant SEM microtextures showing excellent preservation of delicate structures of fragile diatom valves by outpourings with early Mn-calcites strongly support their shallow burial formation before the onset of compaction. Later generations of authigenic mineralizations in lithologic Unit IV include minor amounts of a second generation of calcite with platy crystals, possibly precipitated along with opal-A dissolution, and finally opal-CT crystallization in deeper seated environments overgrowing earlier precipitates with films and lepispheres. The last mineralization is collophane (fluor apatite) forming amorphous aggregates and tiny hexagonal crystals. Authigenic mineral assemblages in lithologic Unit V consist of rhodochrosites, transitional rhodochrosite/manganosiderites, and apatite. A negative d13C ( -7.1 to -15.6 per mil) and a fluctuating d18O signal indicates that the micritic to sparitic rhodochrosites, transitional rhodochrosites/manganosiderites were formed at various burial depths. CO2 resulted from organic matter degradation in the lowermost sulfate reduction zone and from biogenic methane generation in the lowermost sediments, resulting in variable and negative d13C signals. The change in carbonate mineralogy reflects major compositional differences compared to sediments in Unit IV. Most prominent is an increase in altered ash as a primary sediment component and a sudden decrease of siliceous microfossils. Upward diffusion of cations, lowered salinities in pore waters, and elevated temperatures provide diagenetic environments favoring increased remobilization processes.

Oxygen isotope values from biogenic apatie (conodont elements and fish teeth) from the Lower Triassic Mianwali Formation (Salt Range, Pakistan)

Recovery from the end-Permian mass extinction is frequently described as delayed, with complex ecological communities typically not found in the fossil record until the Middle Triassic epoch. However, the taxonomic diversity of a number of marine groups, ranging from ammonoids to benthic foraminifera, peaked rapidly in the Early Triassic. These variations in biodiversity occur amidst pronounced excursions in the carbon isotope record, which are compatible with episodes of massive CO2 outgassing from the Siberian Large Igneous Province. Here we present a high-resolution Early Triassic temperature record based on the oxygen isotope composition of pristine apatite from fossil conodonts. Our reconstruction shows that the beginning of the Smithian substage of the Early Triassic was marked by a cooler climate, followed by an interval of warmth lasting until the Spathian substage boundary. Cooler conditions resumed in the Spathian. We find the greatest increases in taxonomic diversity during the cooler phases of the early Smithian and early Spathian. In contrast, a period of extreme warmth in the middle and late Smithian was associated with floral ecological change and high faunal taxonomic turnover in the ocean. We suggest that climate upheaval and carbon-cycle perturbations due to volcanic outgassing were important drivers of Early Triassic biotic recovery.

Geochemistry and provenance of basaltic clasts within volcaniclastic debris flows at DSDP Site 89-585

Pebble-sized basaltic and glassy clasts were extracted from seamount-derived volcaniclastic debris flows and analyzed for various trace elements, including the rare earths, to determine their genetic relationships and provenance. All the clasts were originally derived from relatively shallow submarine lava flows prior to sedimentary reworking, and have undergone minor low-grade alteration. They are classified into three petrographic groups (A, B, and C) characterized by different phenocryst assemblages and variable abundances and ratios of incompatible elements. Group A (clast from Hole 585) is a hyaloclastite fragment which is olivine-normative and distinct from the other clasts, with incompatibleelement ratios characteristic of transitional or alkali basalts. Groups B and C (clasts from Hole 585A) are quartz-normative, variably plagioclase-clinopyroxene-olivine phyric tholeiites, all with essentially similar ratios of highly incompatible elements and patterns of enrichment in light rare earth elements (chrondrite-normalized). Variation within Groups B and C was governed by low-pressure fractionation of the observed phenocryst phases, whereas the most primitive compositions of each group may be related by variable partial melting of a common source. The clasts have intraplate chemical characteristics, although relative to oceanic hot-spot-related volcanics (e.g., Hawaiian tholeiites) they are marginally depleted in most incompatible elements. The source region was enriched in all incompatible elements, compared with a depleted mid-ocean-ridge basalt source.