Vanadium-titanium carbide inclusion in graphite from hydrothermal ejecta at 13°N, east pacific rise

An inclusion of vanadium-titanium carbide has been found in oceanic hydrothermal graphite by scanning electron microscopy; its composition was determined by electron microprobe. This represents a new find in the system TiC-VC, to which belongs khamrabaevite (Ti, V)C. The conditions of formation of the V-Ti carbide, corresponding to the iron-magnetite buffer, could be encountered during the serpentinization of basalt.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Graphite crystals in hydrothermal vents

Most studies of the hydrothermal input at active ocean ridges have concentrated on elements present in solution rather than particulate matter. During the exploratory cruises Clipperton1,2 and Geocyatherm 3, we moored and recovered sediment traps close to hydrothermal vents associated with the 13°N East Pacific Rise (EPR) with the aim of studying the particulate flux. The first trap was moored about 300 m east of the axis of the central valley, the second was located directly in the central valley at about 200 m from active vents. Both traps were 50 m above the sea floor and well under the depth of expansion of the hydrothermal plume1. We report here that, in addition to the expected sulphides, we recovered crystals of graphite with antimonide overgrowths. This graphite is considered to be of hydrothermal origin; it can readily be distinguished from continentally-derived carbonaceous particles. The flux of hydrothermal graphite is estimated to be about 1.7 nmol cm-2 yr-1. © 1984 Nature Publishing Group.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Les spinelles de fer et de fer-zinc trouves dans des trappes a sediments amarrees pres d'events hydrothermaux oceanique.

Fe- and Fe/Zn-spinels found in sediment traps moored near active hydrothermal vents located on the East Pacific Rise at 13oN are described. Their chemical composition differs from that of spinels from eruptive rocks, chimney walls and pelagic sediments (Mn nodules), particularly in their Zn content (ZnO 0-33.1%; mean value 5.43%), and is explained by high-T reactions occurring in the oceanic crust.-R.A.H.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Vanadiferous minerals from the Nereus Deep, Red Sea

The chemical analysis by EMP/EDS of 140 samples in cores from six Red Sea troughs and basins has led to the discovery in the Nereus Deep of high vanadium concentrations (up to 1.3% V2O3) in several bulk samples, and to the isolation of a major magnetite phase. This vanado-magnetite, remarkable for its high content of vanadium (mean = 1.45% V2O3) and its lack of titanium is frequently zoned, the V-content decreasing toward the outer zones. Oxides with up to 42% V2O3, have also been found. Since the origin of the magnetite is clearly authigenic, its high vanadium and low titanium concentrations are traced back to the differential hydrothermal leaching of Fe-Ti-oxides which occur profusely in basic eruptive rock clasts, actually present in some of the overlying seams. -AuthorsSCOPUS: NotDefined.jFLWNAinfo:eu-repo/semantics/publishe

Nankai Trough, Japan Trench and Kuril Trench: geochemistry of Fluids sampled by submersible "Nautile"

Deep-water samples collected during the Kaiko project are often associated with biological communities located on geological structures favorable to fluid venting. The evidence of fluid venting are the temperature anomalies, the decrease in sulfate concentrations, the content in methane and the low C1 (C2 + C3) ratio of light hydrocarbons. Because of large dilution by ambiant seawater during sampling it is difficult to compute the composition of the advected end-member pore fluid. Part of this fluid should originate in the "petroleum window", i.e. at temperature about 60°C. Modeling the upward flow of water, taking into account the anomalies of temperature measured on the seafloor and the geochemical anomalies, leads to non-steady-state advection of the pore fluid. The occurrence of a deep component in the fluid has implications for the geological and tectonic models of the subduction zones off Japan. © 1987.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Stable (S, C, O) and radiogenic (Sr, Pb) isotope geochimistry of the Frasnian barite mineralization of Chaudfontaine (Belgium)

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Stable (S, C, O) and radiogenic (Sr, Pb) isotopes geochemistry of the barite Frasnian mineralization of Chaudfontaine (Belgium)

Joint Meeting EUG IV - EGS XII, Strasbourg, April, 1987.info:eu-repo/semantics/publishe

Isotope geochemistry (S, C, O, Sr, Pb) of the Chaudfontaine mineralization (Belgium)

Investigations on S, C, O, Sr, and Pb isotopes in ores, gangue, and country rocks of the Chaudfontaine ore deposit confirm that interbedded barite and white sparry calcites are cogenetic. They emphasize the marine origin of S and the nonmarine origin of the metals. They underline the important role played by the bacterial reduction at the site of deposition. Hypotheses concerning the source of the metals and the nature of the brines involved in their transportation are briefly discussed. © 1989 Springer-Verlag.info:eu-repo/semantics/publishe