Sedimentology, geochemistry and paleomagnetic of ODP Hole 151-913B

The Eocene and Oligocene epochs (55 to 23 million years ago) comprise a critical phase in Earth history. An array of geological records (Zachos et al., 2001, doi:10.1126/science.1059412; Lear et al., 2000, doi:10.1126/science.287.5451.269; Coxall et al., 2005, doi:10.1038/nature03135; Pekar et al., 2005; doi:10.1130/B25486.1; Strand et al., 2003, doi:10.1016/S0031-0182(03)00396-1) supported by climate modelling (DeConto and Pollard, 2003, doi:10.1038/nature01290) indicates a profound shift in global climate during this interval, from a state that was largely free of polar ice caps to one in which ice sheets on Antarctica approached their modern size. However, the early glaciation history of the Northern Hemisphere is a subject of controversy (Coxall et al., 2005, doi:10.1038/nature03135; Tripati et al., 2005, doi:10.1038/nature03874; Wolf-Welling et al., 1996, doi:10.2973/odp.proc.sr.151.139.1996; Moran et al., 2006, doi:10.1038/nature04800). Here we report stratigraphically extensive ice-rafted debris, including macroscopic dropstones, in late Eocene to early Oligocene sediments from the Norwegian-Greenland Sea that were deposited between about 38 and 30 million years ago. Our data indicate sediment rafting by glacial ice, rather than sea ice, and point to East Greenland as the likely source. Records of this type from one site alone cannot be used to determine the extent of ice involved. However, our data suggest the existence of (at least) isolated glaciers on Greenland about 20 million years earlier than previously documented (Winkler et al., 2002, doi:10.1007/s005310100199), at a time when temperatures and atmospheric carbon dioxide concentrations were substantially higher.

(Table 2) Major and trace elements in black smoker particulates

We present geochemical data of black smoker particulates filtered from hydrothermal fluids with seawater-dilutions ranging from 0-99%. Results indicate the dominance of sulphide minerals (Fe, Cu, and Zn sulphides) in all samples taken at different hydrothermal sites on the Mid-Atlantic Ridge. Pronounced differences in the geochemistry of the particles between Logatchev I and 5°S hydrothermal fields could be attributed to differences in fluid chemistry. Lower metal/sulphur ratios (Me/H2S < 1) compared to Logatchev I result in a larger amount of particles precipitated per liter fluid and the occurrence of elemental sulphur at 5°S, while at Logatchev I Fe oxides occur in larger amounts. Systematic trends with dilution degree of the fluid include the precipitation of large amounts of Cu sulphides at a low dilution and a pronounced drop with increasing dilution. Moreover, Fe (sulphides or oxides) precipitation increases with dilution of the vent fluid by seawater. Geochemical reaction path modeling of hydrothermal fluid-seawater mixing and conductive cooling indicates that Cu sulphide formation at Logatchev I and 5°S mainly occurs at high temperatures and low dilution of the hydrothermal fluid by seawater. Iron precipitation is enhanced at higher fluid dilution, and the different amounts of minerals forming at 5°S and Logatchev I are thermodynamically controlled. Larger total amounts of minerals and larger amounts of sulphide precipitate during the mixing path when compared to the cooling path. Differences between model and field observations do occur and are attributable to closed system modeling, to kinetic influences and possibly to organic constituents of the hydrothermal fluids not accounted for by the model.

Geochemical analysis at ODP Site 207-1261 from the Demerara Rise in the western equatorial Atlantic

A high-resolution geochemical record of a 120 cm black shale interval deposited during the Coniacian-Santonian Oceanic Anoxic Event 3 (ODP Leg 207, Site 1261, Demerara Rise) has been constructed to provide detailed insight into rapid changes in deep ocean and sediment paleo-redox conditions. High contents of organic matter, sulfur and redox-sensitive trace metals (Cd, Mo, V, Zn), as well as continuous lamination, point to deposition under consistently oxygen-free and largely sulfidic bottom water conditions. However, rapid and cyclic changes in deep ocean redox are documented by short-term (~15-20 ka) intervals with decreased total organic carbon (TOC), S and redox-sensitive trace metal contents, and in particular pronounced phosphorus peaks (up to 2.5 wt% P) associated with elevated Fe oxide contents. Sequential iron and phosphate extractions confirm that P is dominantly bound to iron oxides and incorporated into authigenic apatite. Preservation of this Fe-P coupling in an otherwise sulfidic depositional environment (as indicated by Fe speciation and high amounts of sulfurized organic matter) may be unexpected, and provides evidence for temporarily non-sulfidic bottom waters. However, there is no evidence for deposition under oxic conditions. Instead, sulfidic conditions were punctuated by periods of anoxic, non-sulfidic bottom waters. During these periods, phosphate was effectively scavenged during precipitation of iron (oxyhydr)oxides in the upper water column, and was subsequently deposited and largely preserved at the sea floor. After ~15-25 ka, sulfidic bottom water conditions were re-established, leading to the initial precipitation of CdS, ZnS and pyrite. Subsequently, increasing concentrations of H2S in the water column led to extensive formation of sulfurized organic matter, which effectively scavenged particle-reactive Mo complexes (thiomolybdates). At Site 1261, sulfidic bottom waters lasted for ?90-100 ka, followed by another period of anoxic, non-sulfidic conditions lasting for ~15-20 ka. The observed cyclicity at the lower end of the redox scale may have been triggered by repeated incursions of more oxygenated surface- to mid-waters from the South Atlantic resulting in a lowering of the oxic-anoxic chemocline in the water column. Alternatively, sea water sulfate might have been stripped by long-lasting high rates of sulfate reduction, removing the ultimate source for HS**- production.

Preparation, physico-chemical behavior and catalytic property for ammonia oxidation of perovskite like mixed oxides La2-xSrxCuO4-lambda

A series of Sr2+ doped perovskite like oxides La2-xSrxCuO4-lambda (x = 0 similar to 1) were prepared, the structure, lattice parameters, content of Cu3+, oxygen vacancies created by Sr2+ substitution and composition of these complex oxides were studied by XRD and iodic titration method. The redox ability,active oxygen species and surface image were evaluated and analyzed with TPD, TG, XPS and SEM measurements. The catalytic activity for ammonia oxidation over these oxides was tested, and the relationship among the catalytic properties, structure, nonstoichiometric oxygen,redox ability and surface behavior were correlated and some information on the mechanism of ammonia oxidation was obtained.

Controlled growth of anodic aluminium oxide films with hexagonal array of nanometer-sized pores filled with textured copper nanowires

Anodic aluminium oxide (AAO) films exhibiting a homogeneous morphology of parallel pores perpendicular to the surface were prepared in a two-step anodization process and filled with copper by electrochemical deposition. The optimum growth conditions for the formation of freestanding AAO films with hexagonal compact array of cylindrical pores were studied by field emission scanning electron microscopy and small angle X-ray scattering. The results show well-defined periodic structures with uniform pores size distribution for films with pore diameters between 40 and 70 nm prepared using different voltages and temperatures during the second anodization step. X-ray photoelectron spectroscopy and X-ray diffraction analysis of AAO films filled with copper show the formation of nanowires with high structural order, exhibiting a preferential crystalline orientation along the (2 2 0) axis and only small fraction of copper oxides. The best results for textured Cu nanowires were obtained at a reduction potential of -300 mV. (C) 2009 Elsevier Ltd. All rights reserved.