Radionuclide concentrations, ratios, and derived ages of massive sulfides from ODP Leg 139 and Leg 169 sites

Massive sulfide samples from the Bent Hill area were analyzed for 230Th/234U and 231Pa/235U disequilibria. Apparent ages calculated from these ratios are between 8.2 and >300 ka. Concordant ages were found for only three samples that originate near the surface from the clastic sulfide zone and suggest "true" ages of between 8.5 and 16.0 ka (mean of 230Th and 231Pa ages). The uranium vs. depth distribution in the Bent Hill Massive Sulfide deposit suggests an open system for uranium for the deeper part of the deposit, which was probably caused by extensive recrystallization processes inhibiting true age determinations.

Pore water geochemistry of ODP Hole 169-1037B and Site 196-1038

Data were presented to compare pore fluids from Sites 1037 and 1038 in the Escanaba Trough, Gorda Ridge. Site 1037 constitutes the reference site, and Site 1038 is the hydrothermally affected site. The program was undertaken for two purposes: (1) to make a detailed analysis of the halide chemistry of these two sites, with the specific aim of discerning any potential differences in the generation of dissolved halides as a result of sediment diagenesis in these drill sites and (2) to investigate the geochemistry of Ba2+ and Mn2+ at these two sites to discover potential hydrothermal effects reflected in the concentration-depth distributions of these elements.

Pore water geochemistry of Håkon Mosby mud volcano sediments measured at station PS74/169-1_PUC-15 (Z1-S1, new flow surface)

Pore water and turnover rates were determined for surface sediment cores obtained in 2009 and 2010. The pore water was extracted with Rhizons (Rhizon CSS: length 5 cm, pore diameter 0.15 µm; Rhizosphere Research Products, Wageningen, Netherlands) in 1 cm-resolution and immediately fixed in 5% zinc acetate (ZnAc) solution for sulfate, and sulfide analyses. The samples were diluted, filtered and the concentrations measured with non-suppressed anion exchange chromatography (Waters IC-Pak anion exchange column, waters 430 conductivity detector). The total sulfide concentrations (H2S + HS- + S**2-) were determined using the diamine complexation method (doi:10.4319/lo.1969.14.3.0454). Samples for dissolved inorganic carbon (DIC) and alkalinity measurements were preserved by adding 2 µl saturated mercury chloride (HgCl2) solution and stored headspace-free in gas-tight glass vials. DIC and alkalinity were measured using the flow injection method (detector VWR scientific model 1054) (doi:10.4319/lo.1992.37.5.1113). Dissolved sulfide was eliminated prior to the DIC measurement by adding 0.5 M molybdate solution (doi:10.4319/lo.1995.40.5.1011). Nutrient subsamples (10 - 15 ml) were stored at - 20 °C prior to concentration measurements with a Skalar Continuous-Flow Analyzer (doi:10.1002/9783527613984).