Low-temperature hydrothermal systems are generally dominated by Fe–Si oxyhydroxide deposits. However, the formation process and mechanism of modern oxyhydroxides at ultra-slow spreading centers remain poorly understood. This study focused on six deposits collected from different sites a typical center, Southwest Indian Ridge (SWIR). The mineralogical geochemical evidence showed significant char...

New measurements of Os, He, Sr and Nd isotopes, along with major and trace elements, are presented for basalts from the three volcanic flank zones in Iceland and from Jan Mayen Island. The Os/Os ratios in lavas with <30 ppt Os (n = 4) are elevated compared to ratios in coexisting olivine and appear to be contaminated at a shallow level. The Os/Os ratios in the remaining lavas with >30 ppt Os (n...

Various diffusion raodels can be applied to Rb-Sr systems in cooling rocks. It is argued that a closed-system diffusioncontrolled model, inw3lving local equilibrium along grain boundaries, is most appropriate for describing the exchange of Sr isotopes between minerals in a rock sample during cooling. A finite-difference numerical method is used to solve the diffusion and mass-balance equations....

Fluorite is a widespread mineral in porphyry and hydrothermal vein Mo-polymetallic deposits. Here, fluorite utilised as probe to trace the fluid source reveal evolution process Chalukou giant Mo (Pb–Zn) deposit, Northeast China, which characterised early later vein-style Zn–Pb mineralisation. A detailed rare earth element (REE) Sr–Nd isotope study of combined with Sr isotopes sphalerite conduct...

[1] The geochemical differences between individual Hawaiian shields provide clues to the magma source components in the Hawaiian plume. Lavas from Koolau (Makapuu-stage) and Kahoolawe volcanoes define the enriched, i.e., relatively high Sr/Sr and low Nd/Nd, extreme for Hawaiian shield lavas. There are, however, important geochemical differences between these shields; Kahoolawe lavas lack the re...

• Neoproterozoic metavolcanics from Wedel Jarlsberg Land and Nördenskiold Land, Svalbard trace magma-crust interaction. The crustal assimilants change geographically reflecting the depositional environment of sedimentary crust. metatuffs have mechanically assimilated shales during eruption. Late metavolcanic rocks occur along Southwest coast Svalbard. protoliths Nordenskiöld are mainly diabase,...

Investigations have been undertaken to provide constraints on the nature of geochemically active processes in the mantle and their effects on mantle evolution and magma generation. Three types of approaches have been implemented: (1) To study isotopic systematics and trace element abundances in young, mantle-derived volcanic rocks, which, because of their tectonic setting, had little or no chan...