Hot-spring waters near the Main Central thrust in the Marsyandi River of central Nepal have Sr concentrations to 115 mM with 87Sr/86Sr to 0.77. Small amounts of hydrothermal water (#1% of total river discharge) have a significant impact on the solute chemistry and the budget of radiogenic Sr in the Marsyandi. In the upper Marsyandi, river chemistry reflects carbonate weathering, with 87Sr/86Sr ...

Ž . Previous research on sea floor Fe III oxyhydroxide deposits has focused primarily on deep-sea, hydrothermal systems found along volcanically active portions of the mid-ocean ridges and on hydrogenetic deposits formed in deep basins and along continental shelves. There is, however, not much known about their formation in shallow-water settings associated with volcanic islands. The hydrotherm...

Evaluation of volcanic and hydrothermal fluxes to the surface environments is important to elucidate the geochemical cycle of sulphur and the evolution of ocean chemistry. This paper presents S/(3)He ratios of vesicles in mid-ocean ridge (MOR) basalt glass together with the ratios of high-temperature hydrothermal fluids to calculate the sulphur flux of 100 Gmol/y at MOR. The S/(3)He ratios of h...

In the austral summer of 2011 we undertook an investigation of three volcanic highs in the Central Bransfield Basin, Antarctica, in search of hydrothermal activity and associated fauna to assess changes since previous surveys and to evaluate the extent of hydrothermalism in this basin. At Hook Ridge, a submarine volcanic edifice at the eastern end of the basin, anomalies in water column redox p...

The unique geochemistry of marine shallow-water hydrothermal systems promotes the establishment of diverse microbial communities with a range of metabolic pathways. In contrast to deep-sea vents, shallow-water vents not only support chemosynthesis, but also phototrophic primary production due to the availability of light. However, comprehensive studies targeting the predominant biogeochemical p...

When its hydrothermal supply ceases, hydrothermal sulfide chimneys become inactive and commonly experience oxidative weathering on the seafloor. However, little is known about the oxidative weathering of inactive sulfide chimneys, nor about associated microbial community structures and their succession during this weathering process. In this work, an inactive sulfide chimney and a young chimney...

Palladium, platinum, and gold were analyzed for 20 interstitial water samples from Leg 125. No Pd or Pt was detected in fluids from serpentinite muds from Conical Seamount in the Mariana forearc, indicating that low-temperature seawater-peridotite interaction does not mobilize these elements into the serpentinizing fluids to levels above 0.10 parts per billion (ppb) in solution. However, Au may...

As many of the methanogens first encountered at hydrothermal vents were thermophilic to hyperthermophilic and comprised one of the lower roots of the evolutionary tree, it has been assumed that methanogenesis was one of the earliest, if not the earliest, pathway to life. It being well known that hydrothermal springs associated with serpentinization also bore abiotic methane, it had been further...

Although the rare earth element (REE) geochemistry of hydrothermal systems have intensively been investigated at mid-oceanic ridges, studies are relatively few at the converging plate zones like the Okinawa Trough. The “chimney” deposits obtained by using submersible “SHINKAI 2000” from the Iheya Ridge site, Okinawa Trough are largely composed of massive carbonates and silicates with minor amou...