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Francis Albarède - One of the best experts on this subject based on the ideXlab platform.
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copper Isotope Fractionation between aqueous compounds relevant to low temperature geochemistry and biology
Geochimica et Cosmochimica Acta, 2013Co-Authors: Toshiyuki Fujii, Frédéric Moynier, Keisuke Nemoto, Francis AlbarèdeAbstract:Abstract Isotope Fractionation between the common Cu species present in solution (Cu+, Cu2+, hydroxide, chloride, sulfide, carbonate, oxalate, and ascorbate) has been investigated using both ab initio methods and experimental solvent extraction techniques. In order to establish unambiguously the existence of equilibrium Isotope Fractionation (as opposed to kinetic Isotope Fractionation), we first performed laboratory-scale liquid–liquid distribution experiments. Upon exchange between HCl medium and a macrocyclic complex, the 65Cu/63Cu ratio fractionated by −1.06‰ to −0.39‰. The acidity dependence of the Fractionation was appropriately explained by ligand exchange reactions between hydrated H2O and Cl− via intramolecular vibrations. The magnitude of the Cu Isotope Fractionation among important Cu ligands was also estimated by ab initio methods. The magnitude of the nuclear field shift effect to the Cu Isotope Fractionation represents only ∼3% of the mass-dependent Fractionation. The theoretical estimation was expanded to chlorides, hydroxides, sulfides, sulfates, and carbonates under different conditions of pH. Copper Isotope Fractionation of up to 2‰ is expected for different forms of Cu present in seawater and for different sediments (carbonates, hydroxides, and sulfides). We found that Cu in dissolved carbonates and sulfates is isotopically much heavier (+0.6‰) than free Cu. Isotope Fractionation of Cu in hydroxide is minimal. The relevance of these new results to the understanding of metabolic processes was also discussed. Copper is an essential element used by a large number of proteins for electron transfer. Further theoretical estimates of δ65Cu in hydrated Cu(I) and Cu(II) ions, Cu(II) ascorbates, and Cu(II) oxalate predict Cu Isotope Fractionation during the breakdown of ascorbate into oxalate and account for the isotopically heavy Cu found in animal kidneys.
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The origin of Zn Isotope Fractionation in sulfides
Geochimica et Cosmochimica Acta, 2011Co-Authors: Toshiyuki Fujii, Frédéric Moynier, Marie-laure Pons, Francis AlbarèdeAbstract:Isotope Fractionation of Zn between aqueous sulfide, chloride, and carbonate species (Zn(2+), Zn(HS)2, Zn(HS)(3)(-), Zn(HS)(4)(2-), ZnS(HS)(-), ZnCl(+), ZnCl(2), ZnHCO(3)(+), and ZnCO(3)) was investigated using ab initio methods. Only little Fractionation is found between the sulfide species, whereas carbonates are up to 1 parts per thousand heavier than the parent solution. At pH > 3 and under atmospheric-like CO(2) pressures, Isotope Fractionation of Zn sulfides precipitated from sulfidic solutions is affected by aqueous sulfide species and the delta(66)Zn of sulfides reflect these in the parent solutions. Under high P(CO2) conditions, carbonate species become abundant. In high PCO(2) conditions of hydrothermal solutions, Zn precipitated as sulfides is isotopically nearly unfractionated with respect to a low-pH parent fluid. In contrast, negative delta(66)Zn down to at least -0.6 parts per thousand can be expected in sulfides precipitated from solutions with pH > 9. Zinc Isotopes in sulfides and rocks therefore represent a potential indicator of mid to high pH in ancient hydrothermal fluids.
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the origin of zn Isotope Fractionation in sulfides
Geochimica et Cosmochimica Acta, 2011Co-Authors: Toshiyuki Fujii, Frédéric Moynier, Marie-laure Pons, Francis AlbarèdeAbstract:Abstract Isotope Fractionation of Zn between aqueous sulfide, chloride, and carbonate species (Zn 2+ , Zn(HS) 2 , Zn ( HS ) 3 - , Zn ( HS ) 4 2 - , ZnS(HS) − , ZnCl + , ZnCl 2 , ZnHCO 3 + , and ZnCO 3 ) was investigated using ab initio methods. Only little Fractionation is found between the sulfide species, whereas carbonates are up to 1‰ heavier than the parent solution. At pH > 3 and under atmospheric-like CO 2 pressures, Isotope Fractionation of Zn sulfides precipitated from sulfidic solutions is affected by aqueous sulfide species and the δ 66 Zn of sulfides reflect these in the parent solutions. Under high P CO 2 conditions, carbonate species become abundant. In high P CO 2 conditions of hydrothermal solutions, Zn precipitated as sulfides is isotopically nearly unfractionated with respect to a low-pH parent fluid. In contrast, negative δ 66 Zn down to at least −0.6‰ can be expected in sulfides precipitated from solutions with pH > 9. Zinc Isotopes in sulfides and rocks therefore represent a potential indicator of mid to high pH in ancient hydrothermal fluids.
Donald E Canfield - One of the best experts on this subject based on the ideXlab platform.
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Isotope Fractionation by natural populations of sulfate-reducing bacteria
Geochimica et Cosmochimica Acta, 2001Co-Authors: Donald E CanfieldAbstract:Abstract Isotope Fractionation during sulfate reduction was explored for natural populations of sulfate-reducing bacteria. High Fractionations of 30‰ to 40‰ were produced when the natural population metabolized with indigenous organic substrate at environmental temperatures of 15°C to 25°C. Fractionations were unaffected by changes in sulfate concentration between 2 mM and 28 mM. After the natural substrate was exhausted, the sulfate-reducing bacterial population metabolized, in turn, with acetate, ethanol, and lactate. The high Fractionations encountered with natural substrate were only reproduced when the amended substrate was supplied at concentrations limiting the activity of the sulfate-reducing population. Higher, nonlimiting concentrations of amended substrate produced lower Fractionations of 16‰ to 21% at 25°C. The natural sulfate-reducing population, therefore, probably experienced substrate limitation while utilizing the natural substrate. At the low temperature of 5°C Fractionations with amended substrate ranged from 8‰ to 14‰ and were lower than expected based on the normal relationship between rates of sulfate reduction and the extent of Isotope Fractionation. The processes likely acting to control the magnitude of Isotope Fractionation are discussed.
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SULFUR Isotope Fractionation DURING BACTERIAL REDUCTION AND DISPROPORTIONATION OF THIOSULFATE AND SULFITE
Geochimica et Cosmochimica Acta, 1998Co-Authors: Kirsten Silvia Habicht, Donald E Canfield, Jörg RethmeierAbstract:In bacterial cultures we measured sulfur Isotope Fractionation during transformations of thiosulfate (S2O32−) and sulfite (SO32−), pathways which may be of considerable importance in the cycling of sulfur in marine sediments and euxinic waters. We documented Isotope Fractionations during the reduction and disproportionation of S2O32− and SO32− by bacterial enrichments and pure bacterial cultures from marine and freshwater environments. We also measured the Isotope Fractionation associated with the anoxygenic phototrophic oxidation of H2S to S2O32− by cyanobacteria. Except for SO32− reduction, Isotope Fractionations for these processes have not been previously reported. During the dissimilatory reduction of SO32−, H2S was depleted in 34S by 6‰, and during the reduction of S2O32− to H2S, depletions were between 7‰ and 11‰. The largest observed Isotope Fractionation was associated with the bacterial disproportionation of SO32− which caused a 34S depletion in H2S of 20–37‰ and a 34S enrichment in sulfate of 7–12‰. During the bacterial disproportionation of S2O32−, Isotope Fractionations between the outer sulfane sulfur and H2S and between the inner sulfonate sulfur and SO42− were
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sulfur Isotope Fractionation during bacterial reduction and disproportionation of thiosulfate and sulfite
Geochimica et Cosmochimica Acta, 1998Co-Authors: Kirsten Silvia Habicht, Donald E Canfield, Jörg RethmeierAbstract:In bacterial cultures we measured sulfur Isotope Fractionation during transformations of thiosulfate (S2O32−) and sulfite (SO32−), pathways which may be of considerable importance in the cycling of sulfur in marine sediments and euxinic waters. We documented Isotope Fractionations during the reduction and disproportionation of S2O32− and SO32− by bacterial enrichments and pure bacterial cultures from marine and freshwater environments. We also measured the Isotope Fractionation associated with the anoxygenic phototrophic oxidation of H2S to S2O32− by cyanobacteria. Except for SO32− reduction, Isotope Fractionations for these processes have not been previously reported. During the dissimilatory reduction of SO32−, H2S was depleted in 34S by 6‰, and during the reduction of S2O32− to H2S, depletions were between 7‰ and 11‰. The largest observed Isotope Fractionation was associated with the bacterial disproportionation of SO32− which caused a 34S depletion in H2S of 20–37‰ and a 34S enrichment in sulfate of 7–12‰. During the bacterial disproportionation of S2O32−, Isotope Fractionations between the outer sulfane sulfur and H2S and between the inner sulfonate sulfur and SO42− were <4‰. We observed Isotope exchange between the two sulfur atoms of S2O32− leading to a depletion of34S in H2S by up to 12‰ with a comparable enrichment of 34S in SO42−. No Isotope Fractionation was associated with the anoxygenic phototrophic oxidation of H2S to S2O32−. The depletion of 34S into H2S during the bacterial reduction and disproportionation of S2O32− and SO32− may, in addition to sulfate reduction and the bacterial disproportionation of elemental sulfur, contribute to the generation of 34S-depleted sedimentary sulfides.
Yongbing Li - One of the best experts on this subject based on the ideXlab platform.
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Equilibrium lithium Isotope Fractionation in Li-bearing minerals
Geochimica et Cosmochimica Acta, 2018Co-Authors: Yongbing Li, Yiwen Ju, Zhiming YangAbstract:Abstract Lithium Isotopes are important geochemical tracers for many geological processes. Knowledge of Li Isotope Fractionation factors is essential for understanding the behavior of Li Isotopes. On the basis of density functional perturbation theory (DFPT), we calculate Li Isotope Fractionation parameters of α-eucryptite (LiAlSiO4), β-eucryptite (LiAlSiO4), lithiophilite (LiMnPO4), montebrasite (LiAlPO4OH), petalite (LiAlSi4O10), bikitaite [Li2(Al2Si4O12)·2H2O], spodumene (LiAlSi2O6), lithiophosphate (Li3PO4) and amblygonite (LiAlPO4F). The reduced partition function ratios of 7Li/6Li (103 ln β7-6) for these minerals decrease in the order petalite > lithiophosphate > bikitaite > α-eucryptite > β-eucryptite > montebrasite > amblygonite > lithiophilite > spodumene, agreeing with the observations on granitic pegmatites. Li Isotope Fractionations in these Li-rich minerals have a notable linear correlation with the average Li O bond lengths, and are significantly influenced by Li coordination number. Furthermore, we calculate Li Isotope Fractionation factors of Li-bearing forsterite (Mg2SiO4) and diopside (CaMgSi2O6). It is found that forsterite is enriched in heavy Li relative to diopside, and both minerals’ 103 ln β7-6 values depend on Li contents. These results allow for better understanding Li Isotope Fractionations in natural systems and provide a theoretical basis for Li Isotope applications to understand geological processes.
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equilibrium nickel Isotope Fractionation in nickel sulfide minerals
Geochimica et Cosmochimica Acta, 2018Co-Authors: Yongbing Li, Yiwen JuAbstract:Abstract Nickel is an important element on Earth, and a major element in the Earth's core, and plays important roles in many geological and biological systems. As an important sink of Ni, Ni sulfides are closely concerned with Ni migration in magma systems and the genesis and evolution of magmatic sulfide deposits. Ni Isotopes of Ni sulfides may be a powerful geochemical tracer in magmatic processes and evolution of magmatic sulfide deposits. However Ni Isotope Fractionation factors of sulfides remain poorly known, which makes the applications of Ni Isotopes to geological problems associated with sulfides difficult. In this study, the first-principles methods are used to compute Ni Isotope Fractionation parameters of polydymite (Ni3S4), heazlewoodite (Ni3S2), millerite (NiS), godlevskite (Ni9S8) and vaesite (NiS2). The reduced partition function ratios of 60Ni/58Ni ( 10 3 ln β 60 – 58 ) for these minerals decrease in the order of polydymite > heazlewoodite > millerite > godlevskite > vaesite. Ni Isotope Fractionations in these Ni sulfides show an approximately linear dependence on the average Ni S bond lengths, and have a significant negative correlation with the average Ni Ni bond lengths. Furthermore, a change in Fe/Ni ratio can also lead to Ni Isotope Fractionation, and with substitution Fe for Ni, the reduced partition function ratios of 60Ni/58Ni decrease.
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First-principles study of sulfur Isotope Fractionation in pyrite-type disulfides
American Mineralogist, 2014Co-Authors: Yongbing LiAbstract:The sulfides are an important group of minerals. As a geochemical tracer, the sulfur Isotope Fractionation in sulfides can be used to analyze the ore-forming process and the ore-forming material source. Fe, Co, Ni, and Mn are the first row transition metals, and pyrite (FeS 2 ), cattierite (CoS 2 ), vaesite (NiS 2 ), and hauerite (MnS 2 ) crystallize in the pyrite-type structure. However, there are few studies on the sulfur Isotope Fractionation in these disulfides. So studying the Isotope Fractionation between them provides the opportunity to examine the various members of a structural group in which only the metal atom is changed, thereby providing information that permits a systematic development of concepts regarding sulfur Isotope Fractionation in transition-metal disulfides. In the present paper, the sulfur Isotope Fractionation parameters for pyrite, cattierite, vaesite, and hauerite with the pyrite-type structure have been calculated using first-principles methods based on density functional theory in the temperature range of 0–1000 °C. The structure parameters of these four minerals and the vibration frequencies of pyrite are in good agreement with previous experimental values. The metal-sulfur distance increases in the order FeS 2 , CoS 2 , NiS 2 , and MnS 2 , the sulfur-sulfur distance decreases in the order FeS 2 , CoS 2 , MnS 2 , and NiS 2 , these two sequences agree with the experimental results. Our calculations show that the order of heavy Isotope enrichment is pyrite > cattierite > vaesite > hauerite. It seems that the sulfur Isotope Fractionation in disulfides depends mainly on the metal-sulfur bonds.
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Calculation of sulfur Isotope Fractionation in sulfides
Geochimica et Cosmochimica Acta, 2006Co-Authors: Yongbing LiAbstract:Abstract The increment method has been successfully applied to calculate thermodynamic Isotope Fractionation factors of oxygen in silicates, oxides, carbonates, and sulfates. In this paper, we modified the increment method to calculate thermodynamic Isotope Fractionation factors of sulfur in sulfides, based on chemical features of sulfur–metal bonds and crystal features of sulfide minerals. To approximate the bond strength of sulfides, a new constant, known as the Madelung constant, was introduced. The increment method was then extended to calculate the reduced partition function ratios of sphalerite, chalcopyrite, galena, pyrrhotite, greenockite, bornite, cubanite, sulvanite, and violarite, as well as the Isotope Fractionation factors between them over the temperature range from 0 to 1000 °C. The order of 34 S enrichment in these nine minerals is pyrrhotite > greenockite > sphalerite > chalcopyrite > cubanite > sulvanite > bornite > violarite > galena. Our improved method constitutes another model for calculating the thermodynamic Isotope Fractionation factors of sulfur in sulfides of geochemical interest.
Frédéric Moynier - One of the best experts on this subject based on the ideXlab platform.
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Compositional and pressure controls on calcium and magnesium Isotope Fractionation in magmatic systems
Geochimica et Cosmochimica Acta, 2020Co-Authors: Chunfei Chen, Frédéric Moynier, Jin Xiang Huang, Zaicong Wang, Yongsheng Liu, Stephen Foley, Wei DaiAbstract:Stable Isotope Fractionation in magmatic systems depends on equilibrium Isotope Fractionation between different phases. However, current equilibrium stable Isotope theory mostly assumes ideal crystal structures and simple chemical compositions, but it is unclear how the pressure and complex compositional variations in natural microscopic mineral structures affect inter-mineral stable Isotope Fractionation and thus control stable Isotope Fractionation in macroscopic magmatic systems. Here, we calculate the Casingle bondO and Mgsingle bondO bond lengths controlled by pressure and compositional variations of coexisting garnet (Grt) and clinopyroxene (Cpx) in the Roberts Victor eclogites from the Kaapvaal Craton and use these data as a proof of concept to interpret their inter-mineral Ca and Mg isotopic compositions (Δ44/40CaGrt-Cpx and Δ26MgGrt-Cpx). Our results show that the Casingle bondO difference between Grt and Cpx (ΔCasingle bondOGrt-Cpx) shows a significant increase with CaO content from 3.4 to 13.6 wt.% in Grt and with pressure from 2.9 to 6.9 GPa. ΔCasingle bondOGrt-Cpx has an excellent negative correlation with inter-mineral Ca Isotope Fractionation corrected for temperature effect (Δ44/40CaGrt-Cpx × T2/106), indicating that inter-mineral Ca Isotope Fractionation is controlled by pressure and compositional variations of the Grt through effects on the bond lengths. Inter-mineral Mg Isotope Fractionation corrected for temperature effect (Δ26MgGrt-Cpx × T2/106) in these eclogites shows a negative correlation with pressure but no obvious correlations with the mineral compositions, suggesting the dominant role of pressure effect in addition to temperature. The Mgsingle bondO bond length of Grt increases by about 0.02 Å with increasing CaO content in Grt of these eclogites, implying a mild compositional effect on inter-mineral Mg Isotope Fractionation. The results suggest that pressure and compositional variations in minerals control the equilibrium stable Isotope Fractionation between minerals. Utilizing the Ca Isotope Fractionation factor controlled by crystal chemistry of garnet, our modelling indicates that partial melting of eclogite in the mantle could not significantly fractionate Ca Isotopes and, therefore, that low δ44/40Ca values in previously reported basalts cannot be attributed to the involvement of eclogite in their sources. This suggests that crystal chemistry exerts major controls on Isotope Fractionation in magmatic systems in addition to temperature.
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Compositional and pressure controls on calcium and magnesium Isotope Fractionation in magmatic systems
Geochimica et Cosmochimica Acta, 2020Co-Authors: Chunfei Chen, Frédéric Moynier, Jin Xiang Huang, Stephen F. Foley, Zaicong Wang, Yongsheng Liu, Wei DaiAbstract:Abstract Stable Isotope Fractionation in magmatic systems depends on equilibrium Isotope Fractionation between different phases. However, current equilibrium stable Isotope theory mostly assumes ideal crystal structures and simple chemical compositions, but it is unclear how the pressure and complex compositional variations in natural microscopic mineral structures affect inter-mineral stable Isotope Fractionation and thus control stable Isotope Fractionation in macroscopic magmatic systems. Here, we calculate the Ca O and Mg O bond lengths controlled by pressure and compositional variations of coexisting garnet (Grt) and clinopyroxene (Cpx) in the Roberts Victor eclogites from the Kaapvaal Craton and use these data as a proof of concept to interpret their inter-mineral Ca and Mg isotopic compositions (Δ44/40CaGrt-Cpx and Δ26MgGrt-Cpx). Our results show that the Ca O difference between Grt and Cpx (ΔCa OGrt-Cpx) shows a significant increase with CaO content from 3.4 to 13.6 wt.% in Grt and with pressure from 2.9 to 6.9 GPa. ΔCa OGrt-Cpx has an excellent negative correlation with inter-mineral Ca Isotope Fractionation corrected for temperature effect (Δ44/40CaGrt-Cpx × T2/106), indicating that inter-mineral Ca Isotope Fractionation is controlled by pressure and compositional variations of the Grt through effects on the bond lengths. Inter-mineral Mg Isotope Fractionation corrected for temperature effect (Δ26MgGrt-Cpx × T2/106) in these eclogites shows a negative correlation with pressure but no obvious correlations with the mineral compositions, suggesting the dominant role of pressure effect in addition to temperature. The Mg O bond length of Grt increases by about 0.02 A with increasing CaO content in Grt of these eclogites, implying a mild compositional effect on inter-mineral Mg Isotope Fractionation. The results suggest that pressure and compositional variations in minerals control the equilibrium stable Isotope Fractionation between minerals. Utilizing the Ca Isotope Fractionation factor controlled by crystal chemistry of garnet, our modelling indicates that partial melting of eclogite in the mantle could not significantly fractionate Ca Isotopes and, therefore, that low δ44/40Ca values in previously reported basalts cannot be attributed to the involvement of eclogite in their sources. This suggests that crystal chemistry exerts major controls on Isotope Fractionation in magmatic systems in addition to temperature.
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copper Isotope Fractionation between aqueous compounds relevant to low temperature geochemistry and biology
Geochimica et Cosmochimica Acta, 2013Co-Authors: Toshiyuki Fujii, Frédéric Moynier, Keisuke Nemoto, Francis AlbarèdeAbstract:Abstract Isotope Fractionation between the common Cu species present in solution (Cu+, Cu2+, hydroxide, chloride, sulfide, carbonate, oxalate, and ascorbate) has been investigated using both ab initio methods and experimental solvent extraction techniques. In order to establish unambiguously the existence of equilibrium Isotope Fractionation (as opposed to kinetic Isotope Fractionation), we first performed laboratory-scale liquid–liquid distribution experiments. Upon exchange between HCl medium and a macrocyclic complex, the 65Cu/63Cu ratio fractionated by −1.06‰ to −0.39‰. The acidity dependence of the Fractionation was appropriately explained by ligand exchange reactions between hydrated H2O and Cl− via intramolecular vibrations. The magnitude of the Cu Isotope Fractionation among important Cu ligands was also estimated by ab initio methods. The magnitude of the nuclear field shift effect to the Cu Isotope Fractionation represents only ∼3% of the mass-dependent Fractionation. The theoretical estimation was expanded to chlorides, hydroxides, sulfides, sulfates, and carbonates under different conditions of pH. Copper Isotope Fractionation of up to 2‰ is expected for different forms of Cu present in seawater and for different sediments (carbonates, hydroxides, and sulfides). We found that Cu in dissolved carbonates and sulfates is isotopically much heavier (+0.6‰) than free Cu. Isotope Fractionation of Cu in hydroxide is minimal. The relevance of these new results to the understanding of metabolic processes was also discussed. Copper is an essential element used by a large number of proteins for electron transfer. Further theoretical estimates of δ65Cu in hydrated Cu(I) and Cu(II) ions, Cu(II) ascorbates, and Cu(II) oxalate predict Cu Isotope Fractionation during the breakdown of ascorbate into oxalate and account for the isotopically heavy Cu found in animal kidneys.
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Nuclear field shift effect in Isotope Fractionation of thallium
Journal of Radioanalytical and Nuclear Chemistry, 2012Co-Authors: Toshiyuki Fujii, Frédéric Moynier, Arnaud Agranier, Emmanuel Ponzevera, Akihiro Uehara, Hajimu YamanaAbstract:Environmental transport of Tl is affected by redox reaction between Tl(I) and Tl(III) and ligand exchange reactions of them. In order to deepen the knowledge of Tl chemistry, we investigated Fractionation of Tl stable Isotopes ( 203 Tl and 205 Tl) in a chemical exchange system. Tl Isotopes were fractionated in a liquid- liquid extraction system, in which aqueous and organic phases are hydrochloric acid solution and dichloroethane including a crown ether, respectively. After purification by ion-exchange chemistry, the Isotope ratio of 205 Tl/ 203 Tl in equilibrated aqueous phase was measured precisely by multiple-collector-inductively-coupled-plasma-mass- spectrometry. A large Isotope Fractionation (1 % was found. Electronic structures of possible Tl species (hydra- ted Tl ? ,T l 3? , and Tl chlorides) were calculated by ab initio methods, and the Isotope Fractionation factor was theoret- ically obtained. The Isotope Fractionation via intramolec- ular vibrations was calculated to be much smaller than the experimental result. The Isotope Fractionation via isotopic change in nuclear volume, named the nuclear field shift effect, was calculated to be (1 % in Tl(I)-Tl(III) redox systems and/or ligand exchange systems of Tl(III). The nuclear field shift effect was found to be the major origin of Tl Isotope Fractionation.
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The origin of Zn Isotope Fractionation in sulfides
Geochimica et Cosmochimica Acta, 2011Co-Authors: Toshiyuki Fujii, Frédéric Moynier, Marie-laure Pons, Francis AlbarèdeAbstract:Isotope Fractionation of Zn between aqueous sulfide, chloride, and carbonate species (Zn(2+), Zn(HS)2, Zn(HS)(3)(-), Zn(HS)(4)(2-), ZnS(HS)(-), ZnCl(+), ZnCl(2), ZnHCO(3)(+), and ZnCO(3)) was investigated using ab initio methods. Only little Fractionation is found between the sulfide species, whereas carbonates are up to 1 parts per thousand heavier than the parent solution. At pH > 3 and under atmospheric-like CO(2) pressures, Isotope Fractionation of Zn sulfides precipitated from sulfidic solutions is affected by aqueous sulfide species and the delta(66)Zn of sulfides reflect these in the parent solutions. Under high P(CO2) conditions, carbonate species become abundant. In high PCO(2) conditions of hydrothermal solutions, Zn precipitated as sulfides is isotopically nearly unfractionated with respect to a low-pH parent fluid. In contrast, negative delta(66)Zn down to at least -0.6 parts per thousand can be expected in sulfides precipitated from solutions with pH > 9. Zinc Isotopes in sulfides and rocks therefore represent a potential indicator of mid to high pH in ancient hydrothermal fluids.
Toshiyuki Fujii - One of the best experts on this subject based on the ideXlab platform.
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copper Isotope Fractionation between aqueous compounds relevant to low temperature geochemistry and biology
Geochimica et Cosmochimica Acta, 2013Co-Authors: Toshiyuki Fujii, Frédéric Moynier, Keisuke Nemoto, Francis AlbarèdeAbstract:Abstract Isotope Fractionation between the common Cu species present in solution (Cu+, Cu2+, hydroxide, chloride, sulfide, carbonate, oxalate, and ascorbate) has been investigated using both ab initio methods and experimental solvent extraction techniques. In order to establish unambiguously the existence of equilibrium Isotope Fractionation (as opposed to kinetic Isotope Fractionation), we first performed laboratory-scale liquid–liquid distribution experiments. Upon exchange between HCl medium and a macrocyclic complex, the 65Cu/63Cu ratio fractionated by −1.06‰ to −0.39‰. The acidity dependence of the Fractionation was appropriately explained by ligand exchange reactions between hydrated H2O and Cl− via intramolecular vibrations. The magnitude of the Cu Isotope Fractionation among important Cu ligands was also estimated by ab initio methods. The magnitude of the nuclear field shift effect to the Cu Isotope Fractionation represents only ∼3% of the mass-dependent Fractionation. The theoretical estimation was expanded to chlorides, hydroxides, sulfides, sulfates, and carbonates under different conditions of pH. Copper Isotope Fractionation of up to 2‰ is expected for different forms of Cu present in seawater and for different sediments (carbonates, hydroxides, and sulfides). We found that Cu in dissolved carbonates and sulfates is isotopically much heavier (+0.6‰) than free Cu. Isotope Fractionation of Cu in hydroxide is minimal. The relevance of these new results to the understanding of metabolic processes was also discussed. Copper is an essential element used by a large number of proteins for electron transfer. Further theoretical estimates of δ65Cu in hydrated Cu(I) and Cu(II) ions, Cu(II) ascorbates, and Cu(II) oxalate predict Cu Isotope Fractionation during the breakdown of ascorbate into oxalate and account for the isotopically heavy Cu found in animal kidneys.
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Nuclear field shift effect in Isotope Fractionation of thallium
Journal of Radioanalytical and Nuclear Chemistry, 2012Co-Authors: Toshiyuki Fujii, Frédéric Moynier, Arnaud Agranier, Emmanuel Ponzevera, Akihiro Uehara, Hajimu YamanaAbstract:Environmental transport of Tl is affected by redox reaction between Tl(I) and Tl(III) and ligand exchange reactions of them. In order to deepen the knowledge of Tl chemistry, we investigated Fractionation of Tl stable Isotopes ( 203 Tl and 205 Tl) in a chemical exchange system. Tl Isotopes were fractionated in a liquid- liquid extraction system, in which aqueous and organic phases are hydrochloric acid solution and dichloroethane including a crown ether, respectively. After purification by ion-exchange chemistry, the Isotope ratio of 205 Tl/ 203 Tl in equilibrated aqueous phase was measured precisely by multiple-collector-inductively-coupled-plasma-mass- spectrometry. A large Isotope Fractionation (1 % was found. Electronic structures of possible Tl species (hydra- ted Tl ? ,T l 3? , and Tl chlorides) were calculated by ab initio methods, and the Isotope Fractionation factor was theoret- ically obtained. The Isotope Fractionation via intramolec- ular vibrations was calculated to be much smaller than the experimental result. The Isotope Fractionation via isotopic change in nuclear volume, named the nuclear field shift effect, was calculated to be (1 % in Tl(I)-Tl(III) redox systems and/or ligand exchange systems of Tl(III). The nuclear field shift effect was found to be the major origin of Tl Isotope Fractionation.
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The origin of Zn Isotope Fractionation in sulfides
Geochimica et Cosmochimica Acta, 2011Co-Authors: Toshiyuki Fujii, Frédéric Moynier, Marie-laure Pons, Francis AlbarèdeAbstract:Isotope Fractionation of Zn between aqueous sulfide, chloride, and carbonate species (Zn(2+), Zn(HS)2, Zn(HS)(3)(-), Zn(HS)(4)(2-), ZnS(HS)(-), ZnCl(+), ZnCl(2), ZnHCO(3)(+), and ZnCO(3)) was investigated using ab initio methods. Only little Fractionation is found between the sulfide species, whereas carbonates are up to 1 parts per thousand heavier than the parent solution. At pH > 3 and under atmospheric-like CO(2) pressures, Isotope Fractionation of Zn sulfides precipitated from sulfidic solutions is affected by aqueous sulfide species and the delta(66)Zn of sulfides reflect these in the parent solutions. Under high P(CO2) conditions, carbonate species become abundant. In high PCO(2) conditions of hydrothermal solutions, Zn precipitated as sulfides is isotopically nearly unfractionated with respect to a low-pH parent fluid. In contrast, negative delta(66)Zn down to at least -0.6 parts per thousand can be expected in sulfides precipitated from solutions with pH > 9. Zinc Isotopes in sulfides and rocks therefore represent a potential indicator of mid to high pH in ancient hydrothermal fluids.
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the origin of zn Isotope Fractionation in sulfides
Geochimica et Cosmochimica Acta, 2011Co-Authors: Toshiyuki Fujii, Frédéric Moynier, Marie-laure Pons, Francis AlbarèdeAbstract:Abstract Isotope Fractionation of Zn between aqueous sulfide, chloride, and carbonate species (Zn 2+ , Zn(HS) 2 , Zn ( HS ) 3 - , Zn ( HS ) 4 2 - , ZnS(HS) − , ZnCl + , ZnCl 2 , ZnHCO 3 + , and ZnCO 3 ) was investigated using ab initio methods. Only little Fractionation is found between the sulfide species, whereas carbonates are up to 1‰ heavier than the parent solution. At pH > 3 and under atmospheric-like CO 2 pressures, Isotope Fractionation of Zn sulfides precipitated from sulfidic solutions is affected by aqueous sulfide species and the δ 66 Zn of sulfides reflect these in the parent solutions. Under high P CO 2 conditions, carbonate species become abundant. In high P CO 2 conditions of hydrothermal solutions, Zn precipitated as sulfides is isotopically nearly unfractionated with respect to a low-pH parent fluid. In contrast, negative δ 66 Zn down to at least −0.6‰ can be expected in sulfides precipitated from solutions with pH > 9. Zinc Isotopes in sulfides and rocks therefore represent a potential indicator of mid to high pH in ancient hydrothermal fluids.