المؤلفون: Shi, Tengda^1,2 (AUTHOR), Li, Ruijing^1,2 (AUTHOR), Fu, Jie^2,3 (AUTHOR), Hou, Chao^3,4 (AUTHOR), Gao, Hui² (AUTHOR), Cheng, Guanjie^1,2 (AUTHOR), Zhang, Haibo² (AUTHOR), Jin, Shuaichen² (AUTHOR), Kong, Liang¹ (AUTHOR), Na, Guangshui^1,5 (AUTHOR) nags@hntou.edu.cn

المصدر: Journal of Environmental Sciences (Elsevier). Mar2024, Vol. 137, p347-357. 11p.

مصطلحات موضوعية: FUGACITY, OCEAN, ANTARCTIC exploration, SCIENTIFIC expeditions, ESTERS, ARTIFICIAL seawater

مستخلص: • TCEP and TCPP were dominant in the seawater and atmosphere from the northwest Pacific to the Southern Ocean. • Dry and wet deposition were two main processes influenced the air-seawater transport of OPEs in the Ross Sea. • Ross Sea has played the role of a "sink" of OPEs in summer. Eleven organophosphate esters (OPEs) in the air and seawater were investigated from the northwestern Pacific Ocean to the Southern Ocean during the 2018 Chinese 34th Antarctic Scientific Expedition. The concentration of total OPEs ranged from 164.82 to 3501.79 pg/m3 in air and from 4.54 to 70.09 ng/L in seawater. Two halogenated OPEs, tri(chloropropyl) phosphate (TCPP) and tri (2-chloroethyl) phosphate (TCEP), were generally more abundant than the non-halogenated OPEs. A level III fugacity model was developed to simulate the transfer and fate of seven OPEs in the air and seawater regions of the central Ross Sea. The model results indicate that OPEs are transferred from the air to the seawater in the central Ross Sea in summer, during which the Ross Sea acts as a final OPE sink. Dry and wet deposition dominated the processes involving OPE transfer to seawater. The OPE degradation process was also found to be more pervasive in the atmosphere than in the seawater region. These findings highlights the importance of long-range transport of OPEs and their air–seawater interface behavior in the Antarctic. [ABSTRACT FROM AUTHOR]

: Copyright of Journal of Environmental Sciences (Elsevier) is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

المؤلفون: Chen, Jun-Feng^1,2 (AUTHOR), Zhao, Yu-Yan Sara^1,3,4 (AUTHOR) zhaoyuyan@cdut.edu.cn, Shu, Qiao^1,4 (AUTHOR), Zhou, Sheng-Hua^1,5 (AUTHOR), Du, Wei^1,4 (AUTHOR), Yang, Jing⁶ (AUTHOR)

المصدر: Geochimica et Cosmochimica Acta. Jun2024, Vol. 375, p90-105. 16p.

مصطلحات موضوعية: *OLIVINE, *FUGACITY, *TRACE elements, *ISOTOPE separation, *OXYGEN, *METEORITES, *MORAINES

مستخلص: Shergottite meteorites, classified as depleted, intermediate, or enriched based on incompatible trace elements and specific radiogenic isotope compositions (Sr, Nd, and Hf isotope ratios), point to multiple Martian mantle source regions. The oxygen fugacity (f O 2) of these mantle regions, determined from early crystallizing minerals using the olivine-pyroxene-spinel oxybarometer, appears to correlate with incompatible trace element enrichment and isotope compositions. However, values derived from the vanadium-in-olivine oxybarometer challenge this correlation, hinting at potential biases in oxybarometry or complexities in the redox conditions of the Martian mantle. By analyzing the intermediate shergottite Northwest Africa (NWA) 11043 with various oxybarometers, this study deduced its origin from a reduced mantle source, with an average f O 2 value of −0.77 ± 0.35 relative to the iron-wüstite (IW) buffer. Notably, these values coincide with those of depleted shergottites, which represent the depleted Martian mantle region. This redox similarity between intermediate and depleted shergottites contrasts with earlier notions that postulated intermediate shergottites as a mix of depleted and enriched mantle derivatives. Moreover, intermediate shergottites such as NWA 11043, Elephant Moraine (EETA) 79001A, and Allan Hills (ALH) 77005 display 176Hf/177Hf values akin to those of depleted shergottites, suggesting that intermediate mantle components can be separated from the depleted mantle source at approximately 2.2 Ga based on model age calculations. Therefore, there presents a consistent redox state between mantle magma sources of both intermediate and depleted shergottites since the Hesperian period, while enriched shergottites lean toward more oxidized conditions past source formation. This study prompts a reassessment of conventional theories, emphasizing the nuanced redox evolution of the Martian mantle across distinct mantle source regions and underscoring the complexity of the redox evolution of the Martian mantle. The emergence of chemically diverse mantle reservoirs might predominantly arise from early magma ocean differentiation processes, albeit with inherent oxidation nuances. The differences in f O 2 observed between intermediate and depleted shergottites underscore the need for more in-depth studies to decipher Martian mantle differentiation and evolution. [ABSTRACT FROM AUTHOR]

المؤلفون: Chau, Thi‐Tuyet‐Trang¹ (AUTHOR) thi.tuyet.trang.chau@gmail.com, Chevallier, Frédéric¹ (AUTHOR), Gehlen, Marion¹ (AUTHOR)

المصدر: Geophysical Research Letters. 4/28/2024, Vol. 51 Issue 8, p1-9. 9p.

مصطلحات موضوعية: *FUGACITY, *HEAT waves (Meteorology), *MARINE heatwaves, *SURFACE analysis, *OCEAN, *OCEAN-atmosphere interaction, LA Nina

مستخلص: The Surface Ocean CO2 Atlas (SOCAT) of CO2 fugacity (fCO2) observations is a key resource supporting annual assessments of CO2 uptake by the ocean and its side effects on the marine ecosystem. SOCAT data are usually released with a lag of up to 1.5 years which hampers timely quantification of recent variations of carbon fluxes between the Earth System components, not only with the ocean. This study uses a statistical ensemble approach to analyze fCO2 with a latency of one month only based on the previous SOCAT release and a series of predictors. Results indicate a modest degradation in a retrospective prediction test for 2021–2022. The generated fCO2 and fluxes for January–August 2023 show a progressive reduction in the Equatorial Pacific source following the La Niña retreat. A breaking‐record decrease in the northeastern Atlantic CO2 sink has been diagnosed on account of the marine heatwave event in June 2023. Plain Language Summary: There is a growing need to monitor carbon emissions and removals over the globe in near real time in order to correctly interpret changes in CO2 concentrations as they unfold. For the oceans, the best information comes from measurements of the surface ocean CO2 fugacity (fCO2) by the international marine carbon research community. So far, this data is mostly available 6 to 18 months behind real time after collection, qualification, harmonization, and processing. Here, we show that a set of biological, chemical, and physical predictors available in near real time, allows the information contained in the "old" fCO2 measurements to be transferred over time. Based on a statistical technique, we combine all these data sources to estimate global monthly maps of fCO2 and of CO2 fluxes at the air‐sea interface within one month behind real time and with good accuracy. Key Points: We demonstrate the capacity of statistical models to generate global maps of fCO2 and air‐sea flux with a latency reduced to one monthA decrease in the CO2 source for January to August 2023 diagnosed in the tropical Pacific coheres with the retreat of the La Niña eventAn unusual northeastern Atlantic sink reduction diagnosed for June 2023 is linked to record heat and exceptionally low winds [ABSTRACT FROM AUTHOR]

المؤلفون: Simakin, A. G.¹ (AUTHOR) simakin@iem.ac.ru, Shaposhnikova, O. Yu.¹ (AUTHOR), Devyatova, V. N.¹ (AUTHOR), Isaenko, S. I.² (AUTHOR), Eremin, D. D.³ (AUTHOR)

المصدر: Doklady Earth Sciences. Mar2024, Vol. 515 Issue 1, p423-429. 7p.

مصطلحات موضوعية: *PLATINUM group, *FUGACITY, *CHROMITE, *CHLORINE, *FLUIDS

مستخلص: At high PT parameters of cumulates of ultramafic–mafic intrusions and low oxygen fugacity (below QFM buffer), Pt in the form of a carbonyl complex is dissolved in a CO2-bearing fluid. The high solubility of Pt chloride in brines with NaCl, which is related to the formation of low-sulfide deposits of platinum group elements, is attained only at high oxygen fugacity (above the QFM buffer). It is suggested that native platinum at low oxygen fugacity in low-Н2О СО–СО2 (Н2О) fluid can also transit into a cation-soluble form due to the reaction of chloration. The experimental data are provided for the interaction of NaCl with magnetite and chromite (accessory minerals of ultramafic–mafic intrusions) at Р = 200 MPa, Т = 950°С, and fO2 fugacity (fCl2), which is only 3–4 orders of magnitude lower than fCl2 in Pt–PtCl2 equilibrium and 2.5–3.0 orders of magnitude higher than in 1 M HCl aqueous fluid at the same Р‒Т–fO2 parameters. [ABSTRACT FROM AUTHOR]

المؤلفون: Hughes, Ery C.^1,2 (AUTHOR) e.hughes@gns.cri.nz, Liggins, Philippa³ (AUTHOR), Saper, Lee^2,4 (AUTHOR), M. Stolper, Edward² (AUTHOR)

المصدر: American Mineralogist. Mar2024, Vol. 109 Issue 3, p422-438. 17p.

مصطلحات موضوعية: *FUGACITY, *MAGMAS, *SULFUR, *OXYGEN, *SATURATION vapor pressure, *MERCURY vapor, *ISLAND arcs

مستخلص: Geobarometers are commonly used to determine the pressure (and hence depth) of magmatic bodies. For instance, at equilibrium, the concentration of dissolved volatiles in a vapor-saturated melt can be used as a barometer: this is the pressure of vapor-saturation P s a t v . Most determinations of P s a t v assume that melt and vapor contain only oxidized C-O-H species. However, sulfur is the third most abundant volatile element in magmas, and oxygen fugacity f O 2 exerts a strong influence on the speciation of the melt and vapor. To explore how S and f O 2 afect calculations of P s a t v , we model a Hawaiian tholeiite that contains both reduced and oxidized C-O-H-S species in the melt and vapor. We find that excluding reduced CO-H species in the system can result in significant underestimations of P s a t v under reducing conditions (ΔFMQ < 0). The efect of S on P s a t v is small except in the vicinity of the "sulfur solubility minimum" (SSmin; 0 < ΔFMQ < +2), where excluding S-bearing species can result in underestimates of P s a t v . The implications of these results depend on the volatile concentration of the system being investigated, its fO2, and the melt composition and temperature. Our results suggest there will be little impact on P s a t v calculated for mid-ocean ridge basalts because their f O 2 is above where reduced C-O-H species become important in the melt and vapor and yet below the SSmin. However, the f O 2 of ocean island and arc basalts are close enough to the SSmin and their S concentrations high enough to influence P s a t v . However, high-CO2 and high-H2O concentrations are predicted to reduce the efect of the SSmin. Hence, P s a t v calculated for shallowly trapped melt inclusions and matrix glass are more afected by the SSmin than deeply trapped melt inclusions. Lunar and martian magmas are typically more reduced than terrestrial magmas, and therefore accurate P s a t v calculations for them require the inclusion of reduced C-O-H species. [ABSTRACT FROM AUTHOR]

المؤلفون: Eker Sanli, Gizem¹ (AUTHOR), Erkul, Seyma Nur¹ (AUTHOR), Tasdemir, Yücel¹ (AUTHOR) tasdemir@uludag.edu.tr

المصدر: Polycyclic Aromatic Compounds. 2024, Vol. 44 Issue 2, p1019-1036. 18p.

مصطلحات موضوعية: *SPATIO-temporal variation, *FUGACITY, *SPRING, *AUTUMN, *AIR sampling, *SOIL air

مصطلحات جغرافية: BURSA (Turkey)

مستخلص: This study investigated the spatiotemporal variations in the occurrence of polychlorinated biphenyl (PCB) congeners both in soil and ambient air. Soil and air samples were taken simultaneously for three seasons (spring, summer, and autumn) from industrial, urban, and semi-rural areas in Bursa, Turkey. Light and medium PCB homologous groups were dominant in all samples.Total PCB (∑25 PCBs) concentrations in the air were 0.12 ± 0.13, 0.06 ± 0.07, and 0.08 ± 0.11 ng/m3 and in soil were 4.01.±2.38, 5.44 ± 3.14, and 3.66 ± 1.56 ng/g DM for summer, spring, and winter, respectively. Moreover, the samples were taken from different sites to determine the spatial fluctuations. The average ∑25 PCBs in the air were 0.22 ± 0.06, 0.03 ± 0.01, and 0.03 ± 0.02 ng/m3 and in soil were 7.08 ± 1.84, 2.98 ± 0.52, and 3.06 ± 0.70 ng/g DM for industrial, urban and semi-rural sites, respectively. Maximum air and soil PCB concentrations were determined in the industrial region. The spatiotemporal changes in the fugacity fractions and net fluxes were also examined. The direction of the PCB movement was assessed and the results indicated that soil was a diffusive source for PCBs. The calculated fugacity fractions (ff) were above 0.7 while average flux values were calculated as 0.65 ± 0.33 ng/m2-d, 0.21 ± 0.19 ng/m2-d, and 0.26 ± 0.27 ng/m2-day for industrial, urban and semi-rural regions, respectively. [ABSTRACT FROM AUTHOR]

المؤلفون: Leuthold, J.^1,2 (AUTHOR), Blundy, J.³ (AUTHOR) jonathan.blundy@earth.ox.ac.uk, Ulmer, P.¹ (AUTHOR)

المصدر: Contributions to Mineralogy & Petrology. Dec2023, Vol. 178 Issue 12, p1-26. 26p.

مصطلحات موضوعية: *TRACE elements, *FUGACITY, *X-ray absorption near edge structure, *CHEMICAL speciation, *PLAGIOCLASE, *VANADIUM, *MAGNESIUM

مستخلص: Along with temperature, pressure and melt chemistry, magmatic oxygen fugacity (fO2) has an important influence on liquid and solid differentiation trends and melt structure. To explore the effect of redox conditions on mineral stability and mineral-melt partitioning in basaltic systems we performed equilibrium, one-atmosphere experiments on a picrite at 1200–1110 °C with fO2 ranging from NNO-4 log units to air. Clinopyroxene crystallizes from 1180 °C to near-solidus, along with plagioclase, olivine and spinel. Olivine Mg# increases with increasing fO2, eventually reacting to pigeonite. Spinel is absent under strongly reducing conditions. Mineral-melt partition coefficients (D) of redox-sensitive elements (Cr, Eu, V, Fe) vary systematically with fO2 and, in some cases, temperature (e.g. DCr in clinopyroxene). Clinopyroxene sector zoning is common; sectors along a- and b-axes have higher AlIV, AlVI, Cr and Ti and lower Mg than c-axis sectors. In terms of coupled substitutions, clinopyroxene CaTs (MgSi = AlVIAlIV) prevails under oxidized conditions (≥ NNO), where Fe3+ balances the charge, but is limited under reduced conditions. Overall, AlIV is maximised under high temperature, oxidizing conditions and in slowly grown (a–b) sectors. High AlIV facilitates incorporation of REE (REEAlIV = CaSi), but DREE (except DEu) show no systematic dependence on fO2 across the experimental suite. In sector zoned clinopyroxenes enrichment in REE3+ in Al-rich sectors is quantitatively consistent with the greater availability of suitably-charged M2 lattice sites and the electrostatic energy penalty required to insert REE3+ onto unsuitably-charged M2 sites. By combining our experimental results with published data, we explore the potential for trace element oxybarometry. We show that olivine-melt DV, clinopyroxene-melt DV/DSc and plagioclase-melt DEu/DSr all have potential as oxybarometers and we present expressions for these as a function of fO2 relative to NNO. The crystal chemical sensitivity of heterovalent cation incorporation into clinopyroxene and the melt compositional sensitivity of the Eu2+–Eu3+ redox potential limit the use of clinopyroxene-melt and plagioclase-melt, however, olivine-melt DV affords considerable precision and accuracy as an oxybarometer that is independent of temperature, and crystal and melt composition. Variation of DV and DV/DSc with fO2 for olivine and clinopyroxene contains information on redox speciation of V in coexisting melt. By comparing the redox speciation constraints from partitioning to data from Fe-free synthetic systems and XANES spectroscopy of quenched glasses, we show that homogenous equilibria involving Fe and V species modify V speciation on quench, leading to a net overall reduction in the average vanadium valence. Mineral-melt partitioning of polyvalent species can be a useful probe of redox speciation in Fe-bearing systems that is unaffected by quench effects. [ABSTRACT FROM AUTHOR]

المؤلفون: Eberhard, Lisa¹ (AUTHOR) l.eberhard@uu.nl, Frost, Daniel J¹ (AUTHOR), McCammon, Catherine A¹ (AUTHOR), Dolejš, David² (AUTHOR), Connolly, James A D³ (AUTHOR)

المصدر: Journal of Petrology. Oct2023, Vol. 64 Issue 10, p1-18. 18p.

مصطلحات موضوعية: *FUGACITY, *ANTIGORITE, *SUBDUCTION zones, *MAGNETITE, *MOSSBAUER spectroscopy, *OCEANIC crust

مستخلص: Serpentinites play an important role in the delivery of water into subduction zones. In addition, serpentinites also contain ferric Fe and can transport significant redox potential. We present high-pressure and high-temperature experiments and Mössbauer spectroscopy measurements on natural lizardite and antigorite samples equilibrated at various oxygen fugacities in order to quantify the relationship between the oxygen fugacity f (O2) and the Fe3+/Fetot ratio in these two phases. In antigorite, Fe3+ partitions into the octahedral site and is charge balanced by tetrahedral Al. In lizardite, tetrahedral Fe3+ is observed only at low temperature as well as under high f (O2), whereas Fe3+ prefers the octahedral site at temperatures exceeding 500 °C and at 3 to 5 GPa. Although metastable, lizardite remains in redox equilibrium in our experiments at conditions above the lizardite to antigorite phase transformation at 300 °C and demonstrates a similar stability to antigorite. The Al concentration of lizardite is found to be temperature dependent, and it was possible to reequilibrate the Fe3+/Fetot ratio of lizardite from 0.1 to 0.9 by using redox buffers such as Fe metal, graphite, graphite–calcite, Re–ReO2 and Ru–RuO2. Our experiments on antigorite demonstrate that antigorite does not adjust its Al concentration on experimental time scales. Since Fe3+ is charge balanced by Al, it was also not possible to manipulate the Fe3+/Fetot ratio of antigorite. The coexisting phases, however, show chemical equilibration with this antigorite composition. We have retrieved the standard Gibbs energy for Fe3+- and Al-endmembers of antigorite and lizardite and calculated the metamorphic evolution of subducting serpentinites. The lizardite to antigorite transformation does not cause a decrease in the bulk Fe3+/Fetot ratio under f (O2) buffered conditions, in contrast to observations from some natural settings, but does result in the formation of additional magnetite due to antigorite having a lower Fe3+/Fetot ratio than lizardite at equilibrium. If the f (O2) of antigorite serpentinite is buffered during subduction, such as due to the presence of graphite and carbonate, the bulk Fe3+/Fetot ratio decreases progressively. On the other hand, in a closed system where the bulk serpentinite Fe3+/Fetot ratio remains constant, the f (O2) increases during subduction. In this scenario, the f (O2) of an antigorite serpentinite with a typical Fe3+/Fetot ratio of 0.4 increases from the fayalite–magnetite–quartz to the hematite–magnetite f (O2) buffer during dehydration. These f (O2) results confirm earlier inferences that fluids produced by antigorite dehydration may not contain sufficient oxidised sulphur species to oxidise the mantle wedge. Sufficiently high levels of f (O2) to mobilise oxidised sulphur species may be reached upon antigorite dehydration, however, if closed system behaviour maintains a high bulk redox potential across the lizardite to antigorite phase transformation. Alternatively, oxidation of the mantle wedge might be achieved by oxidising agents from sources in subducted oceanic crust and sediments. [ABSTRACT FROM AUTHOR]

المؤلفون: Imamura, Yosuke

المصدر: Progress of Theoretical & Experimental Physics: PTEP; Jun2024, Vol. 2024 Issue 6, p1-10, 10p

مصطلحات موضوعية: FUGACITY, GRAVITONS

مستخلص: We discuss giant graviton expansions for the Schur index of |${\cal N}=4$| |$U(N)$| SYM with the insertion of Wilson lines of the fundamental and antifundamental representations. We first propose a double-sum giant graviton expansion and numerically confirm that it correctly reproduces the line operator index. We also find that it reduces to a simple-sum expansion when we treat the index as a Taylor series with respect to a specific fugacity. [ABSTRACT FROM AUTHOR]

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المؤلفون: Vereshchagin, Oleg S., Khmelnitskaya, Maya O., Murashko, Mikhail N., Vapnik, Yevgeny, Zaitsev, Anatoly N., Vlasenko, Natalia S., Shilovskikh, Vladimir V., Britvin, Sergey N.

المصدر: Mineralogy & Petrology; Jun2024, Vol. 118 Issue 2, p305-319, 15p

مصطلحات موضوعية: IRON meteorites, MINERALS, CHEMICAL speciation, FUGACITY, PHOSPHIDES

مصطلحات جغرافية: JORDAN, ISRAEL

مستخلص: Mineral assemblages formed at low oxygen fugacity are commonly confined to the lithologies of extraterrestrial or deep Earth origin. The occurrences of reduced mineral phases in upper crustal rocks [formed under oxygen fugacity conditions below the iron-wüstite (IW) buffer] are rare. However, they are important for understanding the chemical drivers of natural redox processes. Here, we present detailed studies of reduced mineral assemblages, which were found in situ in superficial combustion metamorphic (CM) rocks of west-central Jordan and compare them to reduced mineral assemblages found in situ in the CM rocks of south-central Israel. The studied assemblages contain a suite of exotic phases more typical of meteorites: native iron, phosphides (schreibersite, Fe3P; allabogdanite, Fe2P; transjordanite, Ni2P; murashkoite, FeP; halamishite, Ni5P4; zuktamrurite, FeP2; polekhovskyite, MoNiP2), and sulphides (daubréelite, FeCr2S4; oldhamite, CaS; troilite, FeS), part of which (native iron, allabogdanite, halamishite, polekhovskyite, daubréelite) have not previously been discovered in the CM rocks of west-central Jordan. The mineralogical diversity of terrestrial phosphides and the occurrence of Ni- / Mo-rich phases can be explained by (1) high P, Ni, and Mo content in the sedimentary protolith, (2) transformations of primary Fe3P / Fe2P, (3) extreme disequilibrium of the processes, and (4) crystal-chemical control of Ni- / Mo- speciation. [ABSTRACT FROM AUTHOR]

: Copyright of Mineralogy & Petrology is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)