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James M Brenan - One of the best experts on this subject based on the ideXlab platform.

  • the solubility of pd and au in hydrous intermediate Silicate Melts the effect of oxygen fugacity and the addition of cl and s
    Geochimica et Cosmochimica Acta, 2018
    Co-Authors: Neal A Sullivan, Zoltan Zajacz, James M Brenan
    Abstract:

    Abstract The solubilities of Pd and Au in a hydrous trachyandesitic Melt were experimentally determined at 1000 °C and 200 MPa at oxygen fugacity (ƒO 2 ) from 0.45 log units below to 6.55 log units above the Ni-NiO buffer (NNO). The effect of adding metal-binding ligands (i.e. Cl and S) to the Silicate Melt was also studied. The solubility of Au increases from 0.15 ± 0.1 to 3.85 ± 1.48 ppm in Cl- and S-free Melts with ƒO 2 increasing from NNO−0.45 to NNO+6.55 with a slope that suggests that it is present in 1+ oxidation state over the entire studied ƒO 2 range. On the other hand, Pd solubility, shows a more moderate increase with ƒO 2 , especially in the lower half of the studied range, increasing from 2.66 ± 0.25 ppm at NNO−0.45 to only 3.62 ± 0.38 ppm at NNO+1.72 in Cl- and S-free Melts. Overall, the variation in Pd solubility as a function of ƒO 2 indicates Pd being dissolved in the Silicate Melt in both zero and 1+ oxidation state, with the former being dominant below NNO+4.5. At NNO−0.45 to +3.48, the addition of 3170–4060 ppm Cl to the Silicate Melt increased the solubility of Au by an average factor of 1.5, in comparison to Cl-free Melts. However, at NNO+6.55, Au solubility increased by a factor of 2.5. The addition of Cl had a negligible effect on the solubility of Pd except for a large increase (factor of 2.4) at NNO+6.55. At reducing conditions (NNO−0.45), the addition of 170 ppm S to the Silicate Melt increased the solubility of Au by a factor of ∼4 but did not change the solubility of Pd in comparison to S-free Melts. The observation that Pd is dominantly present as Pd 0 at NNO

  • se te fractionation by sulfide Silicate Melt partitioning implications for the composition of mantle derived magmas and their Melting residues
    Earth and Planetary Science Letters, 2015
    Co-Authors: James M Brenan
    Abstract:

    Abstract Partitioning of Se and Te has been measured between coexisting sulfide liquid, monosulfide solid solution (MSS) and Silicate Melt at 0.9–1.5 GPa, 1200–1300 °C, fO 2 controlled near the fayalite–magnetite–quartz buffer (FMQ-1.2 to -1.6) and 3–22 wt% FeO in the Silicate Melt. Both elements are highly compatible in the sulfide phase relative to Silicate liquid (D sulfide phase/Silicate liquid > 600), with the identity of the sulfide dictating the sense of Se–Te fractionation. Whereas the measured D Te / D Se is ∼5–9 for sulfide liquid/Silicate liquid partitioning, MSS/Silicate Melt partitioning fractionates Te from Se in the opposite sense, with D Te / D Se of ∼0.5–0.8. At fixed fO 2 , D SulLiq/SilLiq values for both Se and Te decrease ∼8-fold over the range in Silicate Melt FeO content investigated. The relative values of D SulLiq/SilLiq for Cu to Se increase with increasing FeO in the Silicate Melt, such that D Cu exceeds D Se only for Melts with >11 wt% FeO. Hence the standard belief that D Cu > D Se as indicative of sulfide removal should be carefully assessed in the context of the FeO content of the magmas involved. Assuming a chondritic mantle Se/Te, predicted MSS and sulfide liquid compositions are generally in accord with natural mantle sulfides, in terms of their designation as MSS or sulfide liquid, based on independent criteria. However, additional variability is likely due to Te redistribution in accessory platinum group minerals (PGM), or that some sulfides are metasomatic. Calculations show that the Se/Te ratio of Silicate Melt derived from a sulfide liquid-saturated mantle is significantly higher, and more variable, than for Silicate Melt in equilibrium with residual MSS; modest sulfide liquid removal at low pressure, however, likely obscures the Se/Te fractionation imposed by the source sulfide phase. Models indicate that the composition of MORB is consistent with Melts produced from sulfide-bearing sources with chondritic Se/Te, and source sulfur contents higher than estimates for depleted mantle. The calculated composition of sulfide-saturated Melting residues show relatively little deviation in Se/Te if MSS is residual, but a sharp drop in this ratio for sulfide liquid control. Although the data are scattered, a portion of the peridotite array near the primitive mantle composition is consistent with model trends, and suggests control by residual MSS.

  • the solubility of platinum in Silicate Melt under reducing conditions results from experiments without metal inclusions
    Geochimica et Cosmochimica Acta, 2014
    Co-Authors: Neil R Bennett, James M Brenan, Kenneth T Koga
    Abstract:

    Abstract The solubility of Pt in Silicate Melt was investigated at conditions of 2073–2573 K, 2 GPa and ∼IW −1.5 to +3.5. These are the first measurements of Pt solubility under conditions more reducing than the iron-wustite buffer (IW) which are demonstrably free from contamination by metal-inclusions. Pt solubility increases with increasing temperature and decreasing oxygen fugacity. The ability of carbon to enhance Pt solubility under reducing conditions ( 3500 K. Under these conditions however, the estimated Pt/Os ratio is ∼40,000 times higher than that estimated for the PUM ( Brandon et al., 2006 ). Instead, the PUM composition is generated most readily by metal–Silicate equilibrium at more modest temperatures (∼3100 K), followed by a late accretion of chondritic material subsequent to core formation.

  • re os fractionation by sulfide Melt Silicate Melt partitioning a new spin
    Chemical Geology, 2008
    Co-Authors: James M Brenan
    Abstract:

    Abstract Experiments have been done to assess the role of residual sulfide (Melt and crystalline monosulfide solid solution, or MSS) in controlling the behavior of rhenium and osmium during basalt petrogenesis. In order to facilitate efficient separation of the sulfide and Silicate phases, sulfide Melt–Silicate Melt partitioning experiments were done at 1200 °C, 105 Pa and high gravitational acceleration using a furnace mounted in a centrifuge. Additional (static) high pressure experiments (1.5 GPa; 1200, 1250 °C) were performed to measure both sulfide–Silicate and MSS–sulfide partitioning. Results from high pressure experiments show that MSS–sulfide Melt partitioning does not significantly fractionate Re from Os, so the behavior of these elements during mantle Melting will not be sensitive to the identity of the residual sulfide phase. In contrast, most experiments produced minimum values of Dsulfide/Silicate, Os/Dsulfide/Silicate, Re > 1, with some values > 150, which is the requisite minimum to produce the observed Re/Os fractionation in mantle-derived magmas. Dsulfide/Silicate for Re varies over a wide range, from > 20,000 to ∼ 20, depending on the fO2 − fS2 conditions imposed on an experiment, and defines two coherent groupings, based on fS2, described by the expressions: log Dsulfide/Silicate = − 6.95(± 0.20) + 2.39(± 0.04) {1/2 log fS2 − 1/2 log fO2} (ΔFMQP > 1.5) log Dsulfide/Silicate = − 7.79(± 0.44) + 2.90(± 0.11) {1/2 log fS2 − 1/2 log fO2} (ΔFMQP  in which ΔFMQP is the difference between the log fS2 of the sample and that of the fayalite–magnetite–quartz–pyrrhotite buffer at the same temperature. Values of Dsulfide/Silicate for Re which apply to a specific igneous system can be predicted using the results of this study, combined with estimates of the prevailing fO2 and fS2. By this approach, Dsulfide/Silicate determined from the rhenium content of coexisting sulfide globules and Silicate glass for MORB (FAMOUS locality) is similar to predicted values, whereas Dsulfide/Silicate measured for Loihi is somewhat lower than expected. Generally speaking, values of Dsulfide/Silicate for Re of ∼ 400–800 are expected for Melting of oceanic basalt sources, with deviations in bulk partitioning of Re corresponding to the effect of fO2 on mineral–Melt partition coefficients, or by changes in modal sulfide content. Using the experimental partitioning data, along with reasonable estimates of source sulfur content and degree of Melting, the Re–Yb systematics for MORB can be reproduced from a depleted mantle composition provided magmas undergo extensive fractional crystallization and/or magma mixing.

  • an experimental study of the solubility and partitioning of iridium osmium and gold between olivine and Silicate Melt
    Earth and Planetary Science Letters, 2005
    Co-Authors: James M Brenan, William F. Mcdonough, R D Ash
    Abstract:

    We have performed metal solubility and olivine-Melt partitioning experiments to understand the behaviour of iridium, osmium and gold during crust-mantle differentiation. All experiments were performed metal-saturated, with molten gold added to suppress nugget formation. Coexisting olivine and iron-bearing basalt glass produced in experiments at 1 bar (10 5 Pa), 1260- 1350 8C and fO2 of FMQ+0.6 to +5.4 were analysed by laser ablation ICPMS. Olivine-Melt partition coefficients (Ds) for Ir increase from ~0.4 at FMQ+5.4 to ~2 at FMQ+2.5, with the latter value being consistent with the behaviour of Ir in lavas that have evolved by olivine fractionation. The increase in DIr with decreasing fO2 is consistent with an increase in the relative proportion of Ir 2+ in the Melt, as it has an estimated ionic radius close to the bstrain-freeQ value for octahedral coordination in olivine. Gold is highly incompatible in olivine (D=1� 2 � 10 � 3 or less), consistent with its relatively large ionic radius in the Au 1+ oxidation state. This, together with our previous measurements of olivine-Melt partitioning for Pt, Pd, Ru and Rh, indicates that olivine-equilibrated Melts will have depletions in Ir, Rh and Ru relative to Pt, Pd and Au, consistent with that measured in primitive, sulfur-poor magmas. Our data provide an upper bound on Os solubility in Silicate Melt of 10 ppb at FMQ+0.6, even though Os partition coefficients could not be measured. The solubility of Os, Ru and Ir in Silicate Melt is comparable to the concentrations of these elements in primitive, sulfur-poor magmas, suggesting they could be metal-saturated. D 2005 Elsevier B.V. All rights reserved.

Andreas Audetat - One of the best experts on this subject based on the ideXlab platform.

  • chalcophile element partitioning between cu rich sulfide phases and Silicate Melt and implications for the formation of earth s continental crust
    Geochimica et Cosmochimica Acta, 2021
    Co-Authors: Andreas Audetat, Zhiwei Liu, Fangyue Wang
    Abstract:

    Abstract To constrain the behavior of chalcophile (sulfide-loving) elements during arc magmatic differentiation and to understand the formation conditions of Earth’s continental crust, the partition coefficients (D) of Mn, Co, Cu, Zn, As, Se, Mo, Ag, Cd, Sn, Sb, Te, Re, Au, Pb, and Bi between monosulfide-solid-solution (MSS), Cu-rich sulfide liquid (SL; containing 11–45 wt.% Cu), and hydrous Silicate Melt (SM) of basaltic to dacitic compositions were determined at 1000–1200 °C, 0.5–1.0 GPa, and fO2 1–1.5 log units above the fayalite–magnetite–quartz (FMQ) buffer. The D SL / S M values are 16–160 for Co, 1100–8400 for Cu, 50–220 for Se, 1200–5900 for Ag, 50–1800 for Cd, 700–3300 for Te, 15–510 for Re, 5700–90,000 for Au, 20–440 for Pb, and 140–3300 for Bi. The D SL / S M values for Mn, Zn, As, Mo, Sn, and Sb are below 1–40. The D MSS / S M values are 55–260 for Co, 530–1700 for Cu, 74–110 for Se, 30–110 for Ag, 4–40 for Cd, 15–70 for Te, 200–5900 for Re, and 140–270 for Au. The D MSS / S M values for Mn, Zn, As, Mo, Sn, Sb, Pb, and Bi are below 1–3. The D SL / S M of Au increase with increasing Cu content of the sulfide liquid, but the D SL / S M of the other elements little affected by the Cu concentration in the sulfide liquid. Because of their distinct dissolution mechanisms in the Silicate Melt, the D SL / S M and D MSS / S M of Mn, Co, Zn, Cd, Sn, and Pb are mainly controlled by the Silicate Melt FeOtot content ([FeOtot]); the D SL / S M and D MSS / S M for Re, Mo, As, Sb, and Bi are mainly controlled by [FeOtot] and fO2; the D SL / S M and D MSS / S M for Cu, Ag, and Au are mainly controlled by [FeOtot] and the content of reduced sulfur in the Silicate Melt; and the D SL / S M and D MSS / S M for Se and Te are mainly controlled by fO2. Using all available D SL / S M and D MSS / S M data, a partitioning model was developed for predicting D SL / S M and D MSS / S M of chalcophile elements as a multi-function of temperature, pressure, fO2, and Silicate Melt and sulfide compositions. Sulfide phase relations suggest that the sulfides precipitating from arc magmas containing >100 µg/g Cu in the Silicate Melt occur as Cu-rich sulfide liquid, whereas the sulfides precipitating from arc magmas containing 30–70 µg/g Cu in the Silicate Melt occur as mixed MSS and Cu-rich sulfide liquid. Modeling the Cu evolution trends of global arc magmas illustrates that the precipitating sulfides are dominantly MSS in continental arcs with a crustal thickness of >30 km, with the proportion of sulfide liquid being less than 20%; whereas, in island arcs with a crustal thickness of

  • effects of temperature Silicate Melt composition and oxygen fugacity on the partitioning of v mn co ni cu zn as mo ag sn sb w au pb and bi between sulfide phases and Silicate Melt
    Geochimica et Cosmochimica Acta, 2015
    Co-Authors: Yuan Li, Andreas Audetat
    Abstract:

    In order to assess the role of sulfide in controlling the ore metal budgets and fractionation during magmatic genesis and differentiation, the partition coefficients (D) of V, Mn, Co, Ni, Cu, Zn, As, Mo, Ag, Sn, Sb, W, Au, Pb, and Bi between sulfide liquid (SL), monosulfide solid solution (MSS), and basaltic to rhyolitic Melts (SM) were determined at 900–1200 °C, 0.5–1.5 GPa, and oxygen fugacity (fO2) ranging from ∼FMQ−2 to FMQ+3, in a piston-cylinder apparatus. The DSL/SMDSL/SM values range from 0.4 to 2 for V, 0.5 to 3 for Mn, 80 to 580 for Co, 2300 to 18,000 for Ni, 800 to 4600 for Cu, 1 to 11 for Zn, 20 to 180 for As, 4 to 230 for Mo, 450 to 1600 for Ag, 5 to 24 for Sn, 10 to 80 for Sb, 0.03 to 0.16 for W, 2000 to 29,000 for Au, 24 to 170 for Pb, and 830 to 11,000 for Bi; whereas the DMSS/SMDMSS/SM values range from 0.04 to 10 for V, 0.5 to 10 for Mn, 70 to 2500 for Co, 650 to 18,000 for Ni, 280 to 42,000 for Cu, 0.1 to 80 for Zn, 0.2 to 30 for As, 1 to 820 for Mo, 20 to 500 for Ag, 0.2 to 220 for Sn, 0.1 to 40 for Sb, 0.01 to 24 for W, 10 to 2000 for Au, 0.03 to 6 for Pb, and 1 to 350 for Bi. Both DMSS/SMDMSS/SM and DSL/SMDSL/SM values generally increase with decreasing temperature or decreasing FeOtot content in Silicate Melt, except for Mo, DMSS/SMDMSS/SM and DSL/SMDSL/SM of which show a clear decrease with decreasing temperature. At given temperature and FeOtot content, high oxygen fugacity appears to lead to a significant decrease in DMSS/SMDMSS/SM of Au, Bi, Mo, and potentially As. The partitioning data obtained experimentally in this study and previous studies were fitted to an empirical equation that expresses the DMSS/SMDMSS/SM and/or DSL/SMDSL/SM of a given element as a function of temperature, oxygen fugacity, and FeOtot content of the Silicate Melt: log(DSL/SMorDMSS/SM=d+a·10,000/T+b·(ΔFMQ)+c·log(FeOMelt)in which T is temperature in K, FeOMelt denotes wt% FeOtot in Silicate Melt, and ΔFMQ denotes log fO2 relative to the fayalite–magnetite–quartz (FMQ) oxygen buffer. The application of this equation to natural samples of basaltic to rhyolitic composition yields DMSS/SMDMSS/SM and DSL/SMDSL/SM values that agree with the measured values within ±0.5 log units for most of the elements, indicating the validity of the application of this equation to natural systems. Our partitioning data imply that sulfide liquid saturation in low-temperature intermediate to felsic Melts causes a strong depletion in Cu, Au, Bi, and potentially Ag in the Silicate Melt, whereas MSS saturation may cause a depletion in Cu and potentially Au. Other elements including W, Zn, As, Mo, Sn, Sb, and Pb are much less or not affected by the saturation of sulfide liquid or MSS. These results place important constrains on the potential of magmas in forming porphyry-type ore deposits and the origin of the observed variability in metal ratios in porphyry-type ore deposits.

  • partitioning of v mn co ni cu zn as mo ag sn sb w au pb and bi between sulfide phases and hydrous basanite Melt at upper mantle conditions
    Earth and Planetary Science Letters, 2012
    Co-Authors: Yuan Li, Andreas Audetat
    Abstract:

    The partitioning of 15 major to trace metals between monosulfide solid solution (MSS), sulfide liquid (SL) and mafic Silicate Melt (SM) was determined in piston-cylinder experiments performed at 1175– 1300 1C, 1.5–3.0 GPa and oxygen fugacities ranging from 3.1 log units below to 1.0 log units above the quartz–fayalite–magnetite fO2 buffer, which conditions are representative of partial Melting in the upper mantle in different tectonic settings. The Silicate Melt was produced by partial Melting of a natural, amphibole-rich mantle source rock, resulting in hydrous (B5 wt% H2O) basanitic Melts similar to low-degree partial Melts of metasomatized mantle, whereas the major element composition of the starting sulfide (B52 wt% Fe; 39 wt% S; 7 wt% Ni; 2 wt% Cu) was similar to the average composition of sulfides in this environment. SL/SM partition coefficients are high (Z 100) for Au, Ni, Cu, Ag, Bi, intermediate (1–100) for Co, Pb, Sn, Sb (7 As, Mo), and low (r 1) for the remaining elements. MSS/SM partition coefficients are generally lower than SL/SM partition coefficients and are high (Z 100) for Ni, Cu, Au, intermediate (1–100) for Co, Ag (7Bi, Mo), and low (r 1) for the remaining elements. Most sulfide–Silicate Melt partition coefficients vary as a function of fO2, with Mo, Bi, As (7 W) varying by a factor 4 10 over the investigated fO2 range, Sb, Ag, Sn (7 V) varying by a factor of 3–10, and Pb, Cu, Ni, Co, Au, Zn, Mn varying by a factor of 3–10. The partitioning data were used to model the behavior of Cu, Au, Ag, and Bi during partial Melting of upper mantle and during fractional crystallization of primitive MORB and arc magmas. Sulfide phase relationships and comparison of the modeling results with reported Cu, Au, Ag, and Bi concentrations from MORB and arc magmas suggest that: (i) MSS is the dominant sulfide in the source region of arc magmas, and thus that Au/Cu ratios in the Silicate Melt and residual sulfides may decrease with increasing degree of partial Melting, (ii) both MSS and sulfide liquid are precipitated during fractional crystallization of MORB, and (iii) fractional crystallization of arc magmas is strongly dominated by MSS. & 2012 Published by Elsevier B.V.

Yuan Li - One of the best experts on this subject based on the ideXlab platform.

  • effects of temperature Silicate Melt composition and oxygen fugacity on the partitioning of v mn co ni cu zn as mo ag sn sb w au pb and bi between sulfide phases and Silicate Melt
    Geochimica et Cosmochimica Acta, 2015
    Co-Authors: Yuan Li, Andreas Audetat
    Abstract:

    In order to assess the role of sulfide in controlling the ore metal budgets and fractionation during magmatic genesis and differentiation, the partition coefficients (D) of V, Mn, Co, Ni, Cu, Zn, As, Mo, Ag, Sn, Sb, W, Au, Pb, and Bi between sulfide liquid (SL), monosulfide solid solution (MSS), and basaltic to rhyolitic Melts (SM) were determined at 900–1200 °C, 0.5–1.5 GPa, and oxygen fugacity (fO2) ranging from ∼FMQ−2 to FMQ+3, in a piston-cylinder apparatus. The DSL/SMDSL/SM values range from 0.4 to 2 for V, 0.5 to 3 for Mn, 80 to 580 for Co, 2300 to 18,000 for Ni, 800 to 4600 for Cu, 1 to 11 for Zn, 20 to 180 for As, 4 to 230 for Mo, 450 to 1600 for Ag, 5 to 24 for Sn, 10 to 80 for Sb, 0.03 to 0.16 for W, 2000 to 29,000 for Au, 24 to 170 for Pb, and 830 to 11,000 for Bi; whereas the DMSS/SMDMSS/SM values range from 0.04 to 10 for V, 0.5 to 10 for Mn, 70 to 2500 for Co, 650 to 18,000 for Ni, 280 to 42,000 for Cu, 0.1 to 80 for Zn, 0.2 to 30 for As, 1 to 820 for Mo, 20 to 500 for Ag, 0.2 to 220 for Sn, 0.1 to 40 for Sb, 0.01 to 24 for W, 10 to 2000 for Au, 0.03 to 6 for Pb, and 1 to 350 for Bi. Both DMSS/SMDMSS/SM and DSL/SMDSL/SM values generally increase with decreasing temperature or decreasing FeOtot content in Silicate Melt, except for Mo, DMSS/SMDMSS/SM and DSL/SMDSL/SM of which show a clear decrease with decreasing temperature. At given temperature and FeOtot content, high oxygen fugacity appears to lead to a significant decrease in DMSS/SMDMSS/SM of Au, Bi, Mo, and potentially As. The partitioning data obtained experimentally in this study and previous studies were fitted to an empirical equation that expresses the DMSS/SMDMSS/SM and/or DSL/SMDSL/SM of a given element as a function of temperature, oxygen fugacity, and FeOtot content of the Silicate Melt: log(DSL/SMorDMSS/SM=d+a·10,000/T+b·(ΔFMQ)+c·log(FeOMelt)in which T is temperature in K, FeOMelt denotes wt% FeOtot in Silicate Melt, and ΔFMQ denotes log fO2 relative to the fayalite–magnetite–quartz (FMQ) oxygen buffer. The application of this equation to natural samples of basaltic to rhyolitic composition yields DMSS/SMDMSS/SM and DSL/SMDSL/SM values that agree with the measured values within ±0.5 log units for most of the elements, indicating the validity of the application of this equation to natural systems. Our partitioning data imply that sulfide liquid saturation in low-temperature intermediate to felsic Melts causes a strong depletion in Cu, Au, Bi, and potentially Ag in the Silicate Melt, whereas MSS saturation may cause a depletion in Cu and potentially Au. Other elements including W, Zn, As, Mo, Sn, Sb, and Pb are much less or not affected by the saturation of sulfide liquid or MSS. These results place important constrains on the potential of magmas in forming porphyry-type ore deposits and the origin of the observed variability in metal ratios in porphyry-type ore deposits.

  • the effects of sulfur silicon water and oxygen fugacity on carbon solubility and partitioning in fe rich alloy and Silicate Melt systems at 3 gpa and 1600 c implications for core mantle differentiation and degassing of magma oceans and reduced planet
    Earth and Planetary Science Letters, 2015
    Co-Authors: Yuan Li, Rajdeep Dasgupta, Kyusei Tsuno
    Abstract:

    Abstract The partition coefficient of carbon between Fe-rich alloy Melt and Silicate Melt, D C metal / Silicate and solubility of C–O–H volatiles in reduced Silicate Melts are key parameters that need to be quantified in order to constrain the budget and origin of carbon in different planetary reservoirs and subsequent evolution of volatiles in magma oceans (MO) and Silicate mantles. In this study, three sets of graphite-saturated experiments have been performed at 3 GPa and 1600 °C to investigate the effects of oxygen fugacity ( f O 2 ), sulfur, silicon, and water on the dissolution and partitioning of carbon between Fe-rich alloy Melt and Silicate Melt. The results show that the presence of 0–5 wt% sulfur in alloy Melt does not have considerable effect on carbon solubility (∼5.6 wt%) in alloy Melt, determined by electron microprobe, whereas the presence of 0–10 wt% silicon decreases the carbon solubility from ∼5.6 wt% to 1.8 wt%. Carbon solubility (11–192 ppm) in Silicate Melt, determined by SIMS, is strongly controlled by f O 2 and the bulk water content. Decreasing log ⁡ f O 2 from IW-0.6 to IW-4.7 or increasing bulk water content from 0.07 to 0.55 wt% results in significant increase of carbon solubility in Silicate Melt. Raman and FTIR spectroscopic analyses of Silicate glasses show that the carbon species is mostly methane, which is further confirmed by the strong, positive correlation between the non-carbonate carbon and non-hydroxyl hydrogen in Silicate Melt. The D C metal / Silicate ranging from 180 to 4600 decreases with decreasing f O 2 or increasing bulk water in Silicate Melt. In addition, increasing Si in alloy Melt also decreases D C metal / Silicate . Our results demonstrate that f O 2 and bulk water contents in Silicate Melt play an important role in determining the fractionation of carbon in planetary MO. A reduced, hydrous MO may have led to a considerable fraction of carbon retained in the Silicate mantle, whereas an oxidized, dry MO may have lost almost its entire carbon into the core. If delivery of bulk Earth carbon predominantly occurred after >90% of accretion, i.e., in a relatively oxidized MO (IW-2 to IW-1), then with applicable D C metal / Silicate > 1000 , most early Earth carbon would also enter the segregating core. Finally, the predominance of methane in reduced Silicate Melt with f O 2 below IW-1 also indicates that degassing of a hydrous, solidifying MO may have created a reduced early atmosphere, and degassing from lunar and Martian mantle may have released much more methane than carbon dioxide.

  • partitioning of v mn co ni cu zn as mo ag sn sb w au pb and bi between sulfide phases and hydrous basanite Melt at upper mantle conditions
    Earth and Planetary Science Letters, 2012
    Co-Authors: Yuan Li, Andreas Audetat
    Abstract:

    The partitioning of 15 major to trace metals between monosulfide solid solution (MSS), sulfide liquid (SL) and mafic Silicate Melt (SM) was determined in piston-cylinder experiments performed at 1175– 1300 1C, 1.5–3.0 GPa and oxygen fugacities ranging from 3.1 log units below to 1.0 log units above the quartz–fayalite–magnetite fO2 buffer, which conditions are representative of partial Melting in the upper mantle in different tectonic settings. The Silicate Melt was produced by partial Melting of a natural, amphibole-rich mantle source rock, resulting in hydrous (B5 wt% H2O) basanitic Melts similar to low-degree partial Melts of metasomatized mantle, whereas the major element composition of the starting sulfide (B52 wt% Fe; 39 wt% S; 7 wt% Ni; 2 wt% Cu) was similar to the average composition of sulfides in this environment. SL/SM partition coefficients are high (Z 100) for Au, Ni, Cu, Ag, Bi, intermediate (1–100) for Co, Pb, Sn, Sb (7 As, Mo), and low (r 1) for the remaining elements. MSS/SM partition coefficients are generally lower than SL/SM partition coefficients and are high (Z 100) for Ni, Cu, Au, intermediate (1–100) for Co, Ag (7Bi, Mo), and low (r 1) for the remaining elements. Most sulfide–Silicate Melt partition coefficients vary as a function of fO2, with Mo, Bi, As (7 W) varying by a factor 4 10 over the investigated fO2 range, Sb, Ag, Sn (7 V) varying by a factor of 3–10, and Pb, Cu, Ni, Co, Au, Zn, Mn varying by a factor of 3–10. The partitioning data were used to model the behavior of Cu, Au, Ag, and Bi during partial Melting of upper mantle and during fractional crystallization of primitive MORB and arc magmas. Sulfide phase relationships and comparison of the modeling results with reported Cu, Au, Ag, and Bi concentrations from MORB and arc magmas suggest that: (i) MSS is the dominant sulfide in the source region of arc magmas, and thus that Au/Cu ratios in the Silicate Melt and residual sulfides may decrease with increasing degree of partial Melting, (ii) both MSS and sulfide liquid are precipitated during fractional crystallization of MORB, and (iii) fractional crystallization of arc magmas is strongly dominated by MSS. & 2012 Published by Elsevier B.V.

Zoltan Zajacz - One of the best experts on this subject based on the ideXlab platform.

  • the solubility of pd and au in hydrous intermediate Silicate Melts the effect of oxygen fugacity and the addition of cl and s
    Geochimica et Cosmochimica Acta, 2018
    Co-Authors: Neal A Sullivan, Zoltan Zajacz, James M Brenan
    Abstract:

    Abstract The solubilities of Pd and Au in a hydrous trachyandesitic Melt were experimentally determined at 1000 °C and 200 MPa at oxygen fugacity (ƒO 2 ) from 0.45 log units below to 6.55 log units above the Ni-NiO buffer (NNO). The effect of adding metal-binding ligands (i.e. Cl and S) to the Silicate Melt was also studied. The solubility of Au increases from 0.15 ± 0.1 to 3.85 ± 1.48 ppm in Cl- and S-free Melts with ƒO 2 increasing from NNO−0.45 to NNO+6.55 with a slope that suggests that it is present in 1+ oxidation state over the entire studied ƒO 2 range. On the other hand, Pd solubility, shows a more moderate increase with ƒO 2 , especially in the lower half of the studied range, increasing from 2.66 ± 0.25 ppm at NNO−0.45 to only 3.62 ± 0.38 ppm at NNO+1.72 in Cl- and S-free Melts. Overall, the variation in Pd solubility as a function of ƒO 2 indicates Pd being dissolved in the Silicate Melt in both zero and 1+ oxidation state, with the former being dominant below NNO+4.5. At NNO−0.45 to +3.48, the addition of 3170–4060 ppm Cl to the Silicate Melt increased the solubility of Au by an average factor of 1.5, in comparison to Cl-free Melts. However, at NNO+6.55, Au solubility increased by a factor of 2.5. The addition of Cl had a negligible effect on the solubility of Pd except for a large increase (factor of 2.4) at NNO+6.55. At reducing conditions (NNO−0.45), the addition of 170 ppm S to the Silicate Melt increased the solubility of Au by a factor of ∼4 but did not change the solubility of Pd in comparison to S-free Melts. The observation that Pd is dominantly present as Pd 0 at NNO

  • copper transport by high temperature sulfur rich magmatic vapor evidence from Silicate Melt and vapor inclusions in a basaltic andesite from the villarrica volcano chile
    Earth and Planetary Science Letters, 2009
    Co-Authors: Zoltan Zajacz, Werner E Halter
    Abstract:

    Abstract Silicate Melt inclusions have been analyzed in co-crystallized plagioclase, olivine and clinopyroxene in a typical arc-related basaltic-andesite from the Villarrica volcano (Chile). The Melt inclusions show identical compositions with respect to most major and trace elements in all host minerals. However plagioclase hosted Melt inclusions are variably enriched in Cu (up to ~ 4800 ppm) and Ag (up to ~ 950 ppb). We interpret the elevated Cu and Ag concentrations to be the result of heterogeneous entrapment of Silicate Melt with a sulfur-rich, chlorine-poor high-temperature magmatic vapor phase in which Cu and Ag were strongly compatible. This assumption is supported by the presence of individual Cu-rich vapor inclusions in some plagioclase crystals. Such a magmatic vapor phase may play a significant role in the transport of S, Cu and Ag within or between magmatic reservoirs and, consequently, in the formation of porphyry-type ore deposits.

  • diffusive reequilibration of quartz hosted Silicate Melt and fluid inclusions are all metal concentrations unmodified
    Geochimica et Cosmochimica Acta, 2009
    Co-Authors: Zoltan Zajacz, Werner E Halter, Jacob J Hanley, Christoph A Heinrich, Marcel Guillong
    Abstract:

    Abstract Experiments were conducted to determine the extent and mechanism by which the composition of quartz-hosted Silicate Melt inclusions (SMI) and aqueous fluid inclusions (FI) can undergo post-entrapment modification via diffusion. Quartz slabs containing assemblages of SMI and FI were reacted with synthetic HCl bearing and metalliferous aqueous fluids at T  = 500–720 °C and P  = 150–200 MPa. SMI from the single inclusion assemblages were analyzed by laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) and electron probe microanalysis (EPMA) before and after the experiments. Analyses revealed that rapid diffusion of the univalent cations Na + , Li + , Ag + , Cu + and H + occurred through the quartz from the surroundings, resulting in significant changes in the concentrations of these elements in the inclusions. Concentrations of other elements with an effective ionic radius larger than that of Ag + , or multiple valence states were not modified in the inclusions during the experiments. Our results warn inclusion‘‘ researchers that the interpretation of Na, Li, Cu and Ag concentrations from quartz-hosted SMI and FI should be treated critically.

  • determination of fluid Melt partition coefficients by la icpms analysis of co existing fluid and Silicate Melt inclusions controls on element partitioning
    Geochimica et Cosmochimica Acta, 2008
    Co-Authors: Zoltan Zajacz, Werner E Halter, Thomas Pettke, Marcel Guillong
    Abstract:

    Abstract Analyses of co-existing Silicate Melt and fluid inclusions, entrapped in quartz crystals in volatile saturated magmatic systems, allowed direct quantitative determination of fluid/Melt partition coefficients. Investigations of various granitic systems (peralkaline to peraluminous in composition, log fO2 = NNO−1.7 to NNO+4.5) exsolving fluids with various chlorinities (1–14 mol/kg) allowed us to assess the effect of these variables on the fluid/Melt partition coefficients (D). Partition coefficients for Pb, Zn, Ag and Fe show a nearly linear increase with the chlorinity of these fluid (DPb ∼ 6 ∗ mCl, DZn ∼ 8 ∗ mCl, DAg ∼ 4 ∗ mCl, DFe ∼ 1.4 ∗ mCl, where mCl is the molinity of Cl). This suggests that these metals are dissolved primarily as Cl-complexes and neither oxygen fugacity nor the composition of the Melt affects significantly their fluid/Melt partitioning. By contrast, partition coefficients for Mo, B, As, Sb and Bi are highest in low salinity (1–2 mol/kg Cl) fluids with maximum values of DMo ∼ 20, DB ∼ 15, DAs ∼ 13, DSb ∼ 8, DBi ∼ 15 indicating dissolution as non-chloride (e.g., hydroxy) complexes. Fluid/Melt partition coefficients of copper are highly variable, but highest between vapor like fluids and Silicate Melt (DCu ⩽ 2700), indicating an important role for ligands other than Cl. Partition coefficients for W generally increase with increasing chlorinity, but are exceptionally low in some of the studied brines which may indicate an effect of other parameters. Fluid/Melt partition coefficients of Sn show a high variability but likely increase with the chlorinity of the fluid (DSn = 0.3–42, DW = 0.8–60), and decrease with decreasing oxygen fugacity or Melt peraluminosity.

  • a quartz bearing orthopyroxene rich websterite xenolith from the pannonian basin western hungary evidence for release of quartz saturated Melts from a subducted slab
    Journal of Petrology, 2008
    Co-Authors: Eniko Bali, István János Kovács, Kalman Torok, Zoltan Zajacz, Cs. Szabó, Werner E Halter, Orlando Vaselli, Robert J Bodnar
    Abstract:

    An unusual quartz-bearing orthopyroxene-rich websterite xenolith has been found in an alkali basaltic tuff at Szigliget, Bakony-Balaton Highland Volcanic Field (BBHVF), western Hungary. Ortho- and clinopyroxenes are enriched in light rare earth elements (LREE), middle REE and Ni, and depleted in Nb, Ta, Sr and Ti compared with ortho- and clinopyroxenes occurring in either peridotite or lower crustal granulite xenoliths from the BBHVF. Both ortho- and clinopyroxenes in the xenolith contain primary and secondary Silicate Melt inclusions, and needle-shaped or rounded quartz inclusions. The Melt inclusions are rich in SiO 2 and alkalis and poor in MgO, FeO and CaO. They are strongly enriched in LREE and large ion lithophile elements, and display negative Nb, Ta and Sr anomalies, and slightly positive Pb anomalies. The xenolith is interpreted to represent a fragment of an orthopyroxene-rich body that crystallized in the upper mantle from a hybrid Melt that formed by interaction of mantle peridotite with a quartz-saturated Silicate Melt that was released from a subducted oceanic slab. Although the exact composition of the slab Melt cannot be determined, model calculations on major and trace elements suggest involvement of a metasedimentary component.

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  • the effect of tetrahedral al3 on the partitioning of water between clinopyroxene and Silicate Melt
    Earth and Planetary Science Letters, 2010
    Co-Authors: Glenn A Gaetani, J A Oleary, Erik H Hauri
    Abstract:

    Abstract This experimental study examines the influence of tetrahedrally coordinated Al 3+ ( IV Al 3+ ) on the partitioning of H + between high-Ca clinopyroxene and Silicate Melt. Experiments were carried out at 1.5 GPa and 1275 to 1350 °C on a natural high-alumina basalt and a compositionally similar synthetic basalt that is nominally alumina free. The results extend the compositional range of clinopyroxene for which partitioning has been determined experimentally to both higher and lower IV Al 3+ , thereby clarifying its role in maintaining charge neutrality during H + incorporation. Clinopyroxene-Melt partition coefficients for H + ( D H 2 O Cpx  −  Melt ) determined for the high-alumina basalt are among largest ever reported ( D H 2 O Cpx  −  Melt = 0.0228 to 0.0477), while those determined for the nominally alumina-free starting composition are the smallest ( D H 2 O Cpx  −  Melt = 0.00445 to 0.0071). Our results confirm that H + is incorporated into clinopyroxene through two independent mechanisms: (1) the creation of metal vacancies and coupled hydroxyl defects and (2) a coupled substitution involving IV Al 3+ that creates isolated hydroxyl defects. The relative importance of each of these incorporation mechanisms was quantified by formulating D H 2 O Cpx  −  Melt as the sum of a metal vacancy-related partition coefficient ( D H 2 O V Me ) and an Al-coupled substitution-related partition coefficient ( D H 2 O Al ) and fitting the resulting expression to all available experimental data. The contribution of D H 2 O V Me to D H 2 O Cpx  −  Melt is relatively constant at 0.006 ± 0.002, but is sensitive to pressure, temperature, H 2 O fugacity and pyroxene composition. The contribution of D H 2 O Al varies from ∼ 0 to 0.038 and is strongly dependent on phase composition, but insensitive to pressure and temperature. Two parameterizations of D H 2 O Cpx  −  Melt that account for the potential effects of temperature, pressure and phase composition were calibrated using our data and experimentally determined partition coefficients from the literature. The first parameterization considers only compositional effects and can be used to estimate D H 2 O Cpx  −  Melt in cases where pressure and/or temperature are unknown. This equation was used to demonstrate that the pre-eruptive H 2 O contents of arc lavas calculated on the basis of H + in clinopyroxene phenocrysts are systematically higher than those inferred from olivine-hosted Melt inclusions, so that the former provide a record that is closer to primary (undegassed) values. The second parameterization considers the effects of pressure and temperature in addition to phase composition and provides a moderately better fit to the experimental data. This equation was used to re-evaluate the influence of H 2 O on the depth at which peridotite partial Melting begins beneath oceanic spreading centers. Our calculations indicate that partial Melting begins at depths that are shallower than suggested by previous estimates. For a potential temperature of 1350 °C, peridotite containing 50, 100, 150, and 200 ppm H 2 O dissolved in nominally anhydrous minerals begins Melting at depths of 75, 79, 83, and 87 km, respectively.

  • mineral Melt partitioning of trace elements during hydrous peridotite partial Melting
    Contributions to Mineralogy and Petrology, 2003
    Co-Authors: Glenn A Gaetani, Adam J R Kent, Timothy L Grove, I D Hutcheon, E M Stolper
    Abstract:

    This experimental study examines the mineral/Melt partitioning of incompatible trace elements among high-Ca clinopyroxene, garnet, and hydrous Silicate Melt at upper mantle pressure and temperature conditions. Experiments were performed at pressures of 1.2 and 1.6 GPa and temperatures of 1,185 to 1,370 °C. Experimentally produced Silicate Melts contain up to 6.3 wt% dissolved H2O, and are saturated with an upper mantle peridotite mineral assemblage of olivine+orthopyroxene+clinopyroxene+spinel or garnet. Clinopyroxene/Melt and garnet/Melt partition coefficients were measured for Li, B, K, Sr, Y, Zr, Nb, and select rare earth elements by secondary ion mass spectrometry. A comparison of our experimental results for trivalent cations (REEs and Y) with the results from calculations carried out using the Wood-Blundy partitioning model indicates that H2O dissolved in the Silicate Melt has a discernible effect on trace element partitioning. Experiments carried out at 1.2 GPa, 1,315 °C and 1.6 GPa, 1,370 °C produced clinopyroxene containing 15.0 and 13.9 wt% CaO, respectively, coexisting with Silicate Melts containing ~1–2 wt% H2O. Partition coefficients measured in these experiments are consistent with the Wood-Blundy model. However, partition coefficients determined in an experiment carried out at 1.2 GPa and 1,185 °C, which produced clinopyroxene containing 19.3 wt% CaO coexisting with a high-H2O (6.26±0.10 wt%) Silicate Melt, are significantly smaller than predicted by the Wood-Blundy model. Accounting for the depolymerized structure of the H2O-rich Melt eliminates the mismatch between experimental result and model prediction. Therefore, the increased Ca2+ content of clinopyroxene at low-temperature, hydrous conditions does not enhance compatibility to the extent indicated by results from anhydrous experiments, and models used to predict mineral/Melt partition coefficients during hydrous peridotite partial Melting in the sub-arc mantle must take into account the effects of H2O on the structure of Silicate Melts.

  • partitioning of moderately siderophile elements among olivine Silicate Melt and sulfide Melt constraints on core formation in the earth and mars
    Geochimica et Cosmochimica Acta, 1997
    Co-Authors: Glenn A Gaetani, T L Grove
    Abstract:

    This study investigates the effects of Variations in the fugacities of oxygen and sulfur on the partitioning of first series transition metals (V, Cr, Mn, Fe, Co, Ni. and Cu) and W among coexisting sulfide Melt, Silicate Melt, and olivine. Experiments were performed at 1 atm pressure, 1350 C, with the fugacities of oxygen and sulfur controlled by mixing CO2, CO, and SO2 gases. Starting compositions consisted of a CaO-MgO-Al2O3-SiO2-FeO-Na2O analog for a barred olivine chondrule from an ordinary chondrite and a synthetic komatiite. The f(sub O2)/f(sub S2), conditions ranged from log of f(sub O2) = -7.9 to - 10.6, with log of f(sub S2) values ranging from - 1.0 to -2.5. Our experimental results demonstrate that the f(sub O2)/f(sub S2) dependencies of sulfide Melt/Silicate Melt partition coefficients for the first series transition metals arc proportional to their valence states. The f(sub O2)/f(sub S2) dependencies for the partitioning of Fe, Co, Ni, and Cu are weaker than predicted on the basis of their valence states. Variations in conditions have no significant effect on olivine/Melt partitioning other than those resulting from f(sub O2)-induced changes in the valence state of a given element. The strong f(sub O2)/f(sub S2) dependence for the olivine/Silicate Melt partitioning of V is attributable to a change of valence state, from 4+ to 3+, with decreasing f(sub O2). Our experimentally determined partition coefficients are used to develop models for the segregation of sulfide and metal from the Silicate portion of the early Earth and the Shergottite parent body (Mars). We find that the influence of S is not sufficient to explain the overabundance of siderophile and chalcophile elements that remained in the mantle of the Earth following core formation. Important constraints on core formation in Mars are provided by our experimental determination of the partitioning of Cu between Silicate and sulfide Melts. When combined with existing estimates for siderophile element abundances in the Martian mantle and a mass balance constraint from Fe, the experiments allow a determination of the mass of the Martian core (approx. 17 to 22 wt% of the planet) and its S content (approx.0.4 wt%). These modeling results indicate that Mars is depleted in S, and that its core is solid.