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41.
42.
Effect of water on the fluorine and chlorine partitioning behavior between olivine and silicate melt
Bastian?JoachimEmail authorView authors OrcID profile André?Stechern Thomas?Ludwig Jürgen?Konzett Alison?Pawley Lorraine?Ruzié-Hamilton Patricia?L.?Clay Ray?Burgess Christopher?J.?Ballentine 《Contributions to Mineralogy and Petrology》2017,172(4):15
Halogens show a range from moderate (F) to highly (Cl, Br, I) volatile and incompatible behavior, which makes them excellent tracers for volatile transport processes in the Earth’s mantle. Experimentally determined fluorine and chlorine partitioning data between mantle minerals and silicate melt enable us to estimate Mid Ocean Ridge Basalt (MORB) and Ocean Island Basalt (OIB) source region concentrations for these elements. This study investigates the effect of varying small amounts of water on the fluorine and chlorine partitioning behavior at 1280?°C and 0.3 GPa between olivine and silicate melt in the Fe-free CMAS+F–Cl–Br–I–H2O model system. Results show that, within the uncertainty of the analyses, water has no effect on the chlorine partitioning behavior for bulk water contents ranging from 0.03 (2) wt% H2O (DCl ol/melt = 1.6?±?0.9 × 10?4) to 0.33 (6) wt% H2O (DCl ol/melt = 2.2?±?1.1 × 10?4). Consequently, with the effect of pressure being negligible in the uppermost mantle (Joachim et al. Chem Geol 416:65–78, 2015), temperature is the only parameter that needs to be considered for the determination of chlorine partition coefficients between olivine and melt at least in the simplified iron-free CMAS+F–Cl–Br–I–H2O system. In contrast, the fluorine partition coefficient increases linearly in this range and may be described at 1280?°C and 0.3 GPa with (R 2?=?0.99): \(D_{F}^{\text{ol/melt}}\ =\ 3.6\pm 0.4\ \times \ {{10}^{-3}}\ \times \ {{X}_{{{\text{H}}_{\text{2}}}\text{O}}}\left( \text{wt }\!\!\%\!\!\text{ } \right)\ +\ 6\ \pm \ 0.4\times \,{{10}^{-4}}\). The observed fluorine partitioning behavior supports the theory suggested by Crépisson et al. (Earth Planet Sci Lett 390:287–295, 2014) that fluorine and water are incorporated as clumped OH/F defects in the olivine structure. Results of this study further suggest that fluorine concentration estimates in OIB source regions are at least 10% lower than previously expected (Joachim et al. Chem Geol 416:65–78, 2015), implying that consideration of the effect of water on the fluorine partitioning behavior between Earth’s mantle minerals and silicate melt is vital for a correct estimation of fluorine abundances in OIB source regions. Estimates for MORB source fluorine concentrations as well as chlorine abundances in both mantle source regions are within uncertainty not affected by the presence of water. 相似文献
43.
Regional governance to address climate change is being constituted in New Zealand through domestic policy measures and international discourses. We examine climate change responses in two regions: Marlborough and Waikato. Informants expressed a desire for more transparent government policy; that planning for climate change makes good business sense for farmers and other businesses; that technology is sought to increase productivity and decrease environmental impact; and research networks build capacity for local action, linking sectors and organisations. Often conflicting, these responses to climate change were informed by a mix of discourses shaping New Zealand, including participatory democracy, the knowledge economy and sustainable development. 相似文献
44.
Alison R. Pawley Nicholas J. Chinnery Simon M. Clark Michael J. Walter 《Contributions to Mineralogy and Petrology》2011,162(6):1279-1289
The 10-Å phase (TAP) is a hydrous magnesium silicate that forms from the reaction of talc with H2O at high pressures. Its high-pressure, low-temperature stability means that it could be a storage site for H2O in subduction zones. We have determined the position of the TAP dehydration reaction, TAP = enstatite + coesite + H2O, in phase-equilibrium experiments from 5.0 to 7.1 GPa. Because previous studies had suggested that the composition of TAP is a function of synthesis duration, we used a TAP sample that was synthesised for 392 h. Over the pressure interval of our experiments, the dehydration reaction is isothermal, occurring at a temperature of ~690°C. It is coincident, within experimental uncertainty, with the position of the dehydration reaction of TAP synthesised in short experiments (up to 46 h). Above 7.5 GPa, TAP breaks down to enstatite + stishovite + H2O. This reaction has a negative dP/dT and terminates at an invariant point involving the 3.65-Å phase at ~9.5 GPa, 500°C. The zero volume change implied by the isothermal reaction TAP = enstatite + coesite + H2O was used to calculate the interlayer H2O content of TAP along the reaction. A best-fit H2O content of 1 H2O pfu was obtained. This H2O content is independent of TAP synthesis conditions, suggesting that variations in previously measured H2O contents of TAP occur during quenching and decompression of the samples. The stability of TAP in the Earth is probably limited to cold subduction zones, but in these, it could persist to 300 km depth. 相似文献
45.
Undressing the researcher: feminism, embodiment and sexuality at a queer bathhouse event 总被引:2,自引:0,他引:2
In this paper we examine how the researcher's body can be used as a tool for data collection in the process of ethnographic fieldwork. We focus in particular on the tensions inherent in undertaking embodied ethnographic research in the sexualized setting of a queer women's bathhouse event in Toronto, Canada. Our discussion addresses three moments within the research process: preparing our bodies to attend the bathhouse; positioning our bodies within the spaces of the bathhouse; and interacting with our bodies during the event. Through this discussion we argue that the body of the researcher is a contested site of knowledge production. 相似文献
46.
Sébastien Nomade Jean-François Pastre Alison Pereira Alexandra Courtin-Nomade Vincent Scao 《Comptes Rendus Geoscience》2017,349(2):71-80
Since the 1960s, an early explosive activity in the Mont-Dore Massif is associated with a major pyroclastic rhyolitic eruption (5–7 km3) known as the “Grande Nappe” (GN). This event, linked to the formation of a 6-km-diameter cryptic caldera named “Haute Dordogne”, was before our investigation dated by 40Ar/39Ar at 3.07 ± 0.04 Ma. Our new single-crystal laser fusion 40Ar/39Ar dates obtained on two outcrops of the GN (Rochefort-Montagne and Ludières) questioned several hypotheses made concerning this “landmark” event of the Mont-Dore Massif history. We demonstrate that: (1) the GN rhyolitic eruption has occurred much later than previously estimated (i.e. 2.77 ± 0.02–0.07 Ma full external uncertainties); (2) the correlation made between the Vendeix rhyolitic complexes (intra-caldera position) dated back to 2.74 ± 0.04 Ma and the GN is proposed; (3) xenocryst contamination could be very high (i.e. 70% for the Rochefort-Montagne GN outcrop) and explains the noticeable older age obtained previously; (4) a link between the GN eruption and the formation of a caldera is questionable; the hypothesis of a northward-oriented blast channeled eastward toward the paleo-Allier River is thus proposed. 相似文献
47.
Alison J. Smith 《Journal of Paleolimnology》1993,8(2):121-134
The modern ostracode distribution in lakes of the north-central United States shows how ostracode abundances are related to concentrations of major ions such as calcium, sulfate, and bicarbonate. These relationships are quantified for species living in lakes that range from fresh water (200 S cm-1) to saline water (17 000 S cm-1). Lakes located in the Minnesota forests have different ostracode assemblages and different water chemistry than lakes located on the prairie of North Dakota and South Dakota. These differences are attributed to differences in precipitation and rock-water interactions. Multivariate analyses of the ostracode and water chemistry data set indicate that different ostracode species are associated with different water types. For example, Limnocythere sappaensis and Heterocypris glaucus are found in bicarbonate-enriched sulfate-dominated waters, whereas Limnocythere staplini is found in bicarbonate-depleted sulfate-dominated waters. Candona ohioensis and Limnocythere itasca are found in fresh water, and Candona rawsoni is eurytopic and found in both bicarbonate-enriched and bicarbonate-depleted sulfate-dominated waters. Ostracodes can be used to identify changes in both ionic composition (solutes) and ionic concentration.This publication is the second of a series of papers presented at the Conference on Sedimentary and Paleolimnological Records of Saline Lakes. This Conference was held August 13–16, 1991 at the University of Saskatchewan, Saskatoon, Canada. Dr Evans is serving as Guest Editor for this series. 相似文献
48.
49.
50.
The availability of underwater light is a critical factor in the growth and abundance of primary producers in shallow embayments.
The goal of this study was to examine the relative importance of factors influencing light availability in this type of water
body. Many simulation models of aquatic ecosystems predict light attenuation from chlorophyll or phytoplankton stock. In the
three southern New England sites studied here, no useful relationship was found to exist between chlorophyll and KPAR (the diffuse attenuation coefficient of photosynthetically active radiation; Kirk 1994; Mobley 1994). In 40 of 53 cases,
a regression of chlorophyll versus KPAR was not statistically significant. Variation in KPAR did demonstrate a correlation to salinity, implicating a freshwater source of light attenuating material. This was true even
in a system with little freshwater inflow. Colored dissolved organic matter (CDOM) is one such terrestrial input that enters
estuaries from their watersheds and can strongly influence the availability of light to aquatic primary producers. This study
demonstrated that over 70% of the variability in the KPAR coefficient can be attributed to CDOM in the shallow estuaries studied. This illustrates the need for improved model formulations
that include CDOM in the prediction of light attenuation in shallow coastal systems. A new equation has been developed to
predict KPAR with CDOM. 相似文献