Effects of melt composition on Fe3+/Fe2+ in silicate melts: a step to model ferric/ferrous ratio in multicomponent systems     

Alexander Borisov  Harald Behrens  Francois Holtz 《Contributions to Mineralogy and Petrology》2015,169(2):1-12

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The effect of Cl on Pt solubility in haplobasaltic melt: Implications for micronugget formation and evidence for fluid transport of PGEs     

F.A. Blaine  R.L. Linnen  F. Holtz 《Geochimica et cosmochimica acta》2011,75(24):7792-7805

Platinum solubility was determined in a haplobasaltic, diopside-anorthite melt at 1523 K and 0.2 GPa as a function of oxygen fugacity and chlorine content. Synthetic glass powder of an An₄₂Di₅₈ composition was sealed in a platinum or platinum-iridium alloy capsule and equilibrated with a solid CaCl₂ and MgCl₂ chlorine source, water and the noble-metal capsule. All experiments were run in an internally-heated pressure-vessel equipped with a rapid-quench device with oxygen fugacity controlled by the water content and intrinsic hydrogen fugacity of the autoclave (MnO-Mn₃O₄). Resultant glasses were analyzed by isotope dilution ICP-MS and LA-ICP-MS to determine the solubility and distribution of Pt and assess potential Cl-complexation of Pt in the melt.Experiments with run durations longer than 96 h show Pt solubilities consistent with solubilities determined for the equivalent Cl-free diopside-anorthite system, under the same P-T conditions. These results indicate that chlorine has no discernable effect on Pt solubility and there is no evidence of Pt-Cl complexing in the silicate melt from 0.6 to 2.75 wt% Cl (saturation).However, products from short run duration experiments (<96 h) contain Pt concentrations which are orders of magnitude higher than those of the Pt-free starting glass and of the experimental products of the longer run duration experiments. These anomalously high levels are most pronounced in the shortest experiments and Pt concentration decreases with increasing run duration. It is suggested that this excess platinum is dissolved within the Cl-bearing fluid during the heating stages of the experiment and is left behind as the fluid dissolves into the melt leaving small amounts of Pt as “micronuggets”, increasing the bulk Pt concentration. With increasing run duration the platinum appears to migrate out of the melt, back to the capsule walls, decreasing the amount of Pt contained within the glass. This behavior offers compelling evidence that Cl-bearing fluids have the capacity to transport significant amounts of Pt under magmatic conditions.Mass balance calculations on the excess amount of Pt in the glass (above inherent solubility) in short duration experiments lead to an estimation of Pt concentration in the Cl-bearing fluid ranging from tens to a few hundred ppm, versus ppb levels in the melt. The correspondingly high estimated apparent partition coefficients of 10³-10⁴ suggest that Cl-bearing fluids can be highly efficient at enriching and transporting platinum in mafic magmatic-hydrothermal ore-forming systems. These values strongly contrast with recent experimental results in felsic systems, highlighting the potential importance of melt composition on partitioning, the need for composition specific partitioning experiments, as well as a detailed understanding of Pt distribution in experimental products.  相似文献   

A synoptic decomposition of rainfall over the Cape south coast of South Africa     

Christien J. Engelbrecht  Willem A. Landman  Francois A. Engelbrecht  Johan Malherbe 《Climate Dynamics》2015,44(9-10):2589-2607

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Experimental constraints on the origin of pahoehoe “cicirara” lavas at Mt. Etna Volcano (Sicily,Italy)     

F. Vetere  S. Mollo  P. P. Giacomoni  G. Iezzi  M. Coltorti  C. Ferlito  F. Holtz  D. Perugini  P. Scarlato 《Bulletin of Volcanology》2015,77(5):1-18

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Twentieth century precipitation trends in the upper Mzingwane sub-catchment of the northern Limpopo basin,Zimbabwe     

Maviza  Auther  Grab  Stefan  Engelbrecht  Francois 《Theoretical and Applied Climatology》2022,149(1-2):309-325

Theoretical and Applied Climatology - This study evaluates precipitation trends in the upper Mzingwane sub-catchment (UMS) of Zimbabwe using ten World Meteorological Organization (WMO)’s...  相似文献   

The Loyalty—New Hebrides Arc collision: Effects on the Loyalty Ridge and basin system,Southwest Pacific (first results of the ZoNéCo programme)     

Yves Lafoy  Francois Missegue  Dominique Cluzel  Raymond Le Suave 《Marine Geophysical Researches》1996,18(2-4):337-356

The ZoNéCo 1 and 2 cruises of Ifremer's Research Vessel L'Atalante, collected new swath bathymetry and geophysical data over the southern and northern segments of the basins and ridges forming the Loyalty system. Between the two surveyed areas, previous studies found evidence for the resistance of the Loyalty Ridge to subduction beneath the New Hebrides trench near 22°S–169°E. On the subducted plate, except for seismicity related to the downbending of the Australian plate, recorded shallow seismicity is sparse within the Loyalty system (Ridge and Basin) where reliable focal mechanism solutions are almost absent.Swath bathymetry, seismic reflection and magnetic data acquired during the ZoNéCo 1 and 2 cruises revealed a transverse asymmetric morphology in the Loyalty system, and an along-strike horst and graben structure on the discontinuous Loyalty Ridge. South of 23°50S and at 20°S, the two WSW-ENE-trending fault systems, respectively, sinistral and dextral, that crosscut the southern and northern segments of the Loyalty system, are interpreted as due to the early effects of collision with the New Hebrides Arc. A NNW-SSE trend, evident along the whole Loyalty system and on the island of New Caledonia, is interpreted as an inherited structural trend that may have been reactivated through flexure of the Australian lithospheric plate at the subduction zone.Overall then, the morphology, structure and evolution of the southern and northern segments of the Loyalty system probably result from the combined effects of the Australian plate lithospheric bulge, the active Loyalty-New Hebrides collision and the overthrust of the New Caledonian ophiolite.  相似文献   

A field comparison of two methods for the determination of copper complexation: Bacterial bioassay and fixed-potential amperometry     

Janet G. Hering  William G. Sunda  Randolph L. Ferguson  Francois M.M. Morel 《Marine Chemistry》1987,20(4)

Complexation of copper added to seawater was determined by bacterial bioassay and fixedpotential amperometry. Consistent results were obtained by these two fundamentally different methods. The results of this study support the validity of both techniques and the field applicability of fixed-potential amperometry.The intercomparison studies were performed on samples collected at the N.Y.C. sewage sludge dumpsite and in relatively unpolluted coastal waters. In this limited study, the calculated free cupric ion concentrations at ambient total copper concentrations were similar at both sites.  相似文献   

Waves of agitation inside anchovy schools observed with multibeam sonar: a way to transmit information in response to predation   总被引：2，自引：0，他引：2  

Gerlotto  Francois; Bertrand  Sophie; Bez  Nicolas; Gutierrez  Mariano 《ICES Journal of Marine Science》2006,63(8):1405-1417

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Particulate barium fluxes and export production in the northwestern Mediterranean   总被引：1，自引：0，他引：1  

Erika Sternberg  Catherine Jeandel  Juan-Carlos Miquel  Beat Gasser  Marc Souhaut  Roseanna Arraes-Mescoff  Roger Francois 《Marine Chemistry》2007,105(3-4):281-295

Biogenic barium, mostly in the barite (BaSO₄) form, has been proposed as a tracer for export production in the ocean. Here we report on biogenic barium (Ba_xs) and particulate organic carbon (POC) fluxes from sediment traps deployed at the DYFAMED site in the Northwestern Mediterranean Sea. Ba_xs fluxes display average values of 37 ± 45 and 50 ± 58 μg/m²/d at 200 and 1000 m respectively, and are linearly correlated to POC fluxes (mean values of 7.9 ± 9.3 and 6.8 ± 6.8 mg C/m²/d at 200 and 1000 m). Export production estimates, calculated using published Ba_xs- or POC-based algorithms, all fall below or close to the lower limit of potential export values proposed in the literature. This work clearly demonstrates the usefulness of Ba_xs as a tracer of oceanic export production in the Northwestern Mediterranean Sea. However, development of a quantitative export production proxy requires a clear understanding of the underlying cause(s) for the observed spatial variations in the relationship between Ba_xs and POC fluxes. The present study confirms that the processes leading to barite formation differ between margin and open-ocean sites and probably account for much of the regional variability in the POC/Ba_xs ratio.  相似文献   

Correction to: Ferric/ferrous ratio in silicate melts: a new model for 1 atm data with special emphasis on the effects of melt composition     

Alexander?BorisovEmail authorView author&#;s OrcID profile  Harald?Behrens  Francois?Holtz 《Contributions to Mineralogy and Petrology》2018,173(12):107

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