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Magmatic oxygen fugacity (fO2) is a fundamental property to understanding the long-term evolution of the Earth's atmosphere and the formation of magmatic-hydrothermal mineral deposits. Classically, the magmatic fO2 is estimated using mineral chemistry, such as Fe-Ti oxides, zircon, and hornblende. These methods, however, are only valid within certain limits and/or require a significant amount of a priori knowledge. In this contribution, a new oxybarometer, constructed by data-driven machine learning algorithms using trace elements in zircon and their corresponding independent fO2 constraints, is provided. Seven different algorithms are initially trained and then validated on a data set that was never utilized in the training processes. Results suggest that the oxybarometer constructed by the extremely randomized trees model has the best performance, with the largest R2 value (0.91 ± 0.01), smallest RMSE (0.45 ± 0.03), and low propagated analytical error (~0.10 log units). Feature importance analysis demonstrates that U, Ti, Th, Ce, and Eu in zircon are the key trace elements that preserve fO2 information. This newly developed oxybarometer has been applied in diverse systems, including arc magmas and mid-ocean ridge basalts, fertile and barren porphyry systems, and global S-type detrital zircon, which provide fO2 constraints that are consistent with other independent methods, suggesting that it has wide applicability. To improve accessibility, the oxybarometer was developed into a software application aimed at enabling more consistent and reliable fO2 determinations in magmatic systems, promoting further research. [ABSTRACT FROM AUTHOR]

At an energy flux imbalance of about 1 W m−2, the ocean stores 90% of the heat accumulating by global warming. However, neither the causes of this nor the responsible geophysical processes are sufficiently well understood. More detailed investigations of the different phenomena contributing to the oceanic energy balance are warranted. Here, the role of low-level marine clouds in the air–sea interaction is analysed. TEOS-10, the International Thermodynamic Equation of State of Seawater—2010, is exploited for a rigorous thermodynamic description of the climatic trends in the lifted condensation level (LCL) of the marine troposphere. Rising sea surface temperature (SST) at a constant relative humidity (RH) is elevating marine clouds, cooling the cloud base, and reducing downward thermal radiation. This LCL feedback effect is negative and counteracts ocean warming. At the current global mean SST of about 292 K, the net radiative heat flux from the ocean surface to the LCL cloud base is estimated to be 24 W m−2. Per degree of SST increase, this net flux is expected to be enhanced by almost 0.5 W m−2. The climatic LCL feedback effect is relevant for the ocean's energy balance and may be rigorously thermodynamically modelled in terms of TEOS-10 equations. LCL height may serve as a remotely measured, sensitive estimate for the sea surface's relative fugacity, or conventional relative humidity. [ABSTRACT FROM AUTHOR]

Aggregates of ilmenite with varying amounts of rutile, ferropseudobrookite, and pseudorutile in suevites from the Ries impact structure have been analyzed by light microscopy, analytical scanning electron microscopy, electron microprobe analysis, and Raman spectroscopy to constrain their formation conditions. The tens to hundreds of micrometer aggregates comprise isometric ilmenite grains up to 15 μm in diameter that form a foam structure (i.e., smoothly curved grain boundaries and 120° angles at triple junctions). Grains with foam structure show no internal misorientations, indicating a post-impact formation. In contrast, ilmenite grains with internal misorientation occurring in the core of the aggregates are interpreted as shocked remnant ilmenite originating from the target gneisses. They can contain twin lamellae that share a common {11 2 0} plane with the host, and the c-axis is oriented at an angle of 109° to that of the host. Similarly, the new grains with foam structure display up to three orientation domains, sharing one common {11 2 0} plane for each pair of domains and c-axes at angles of 109° and 99°, respectively. This systematic orientation relationship likely reflects a cubic supersymmetry resulting from the transformation of the initial ilmenite upon shock (>16 GPa) to a transient perovskite-type high-pressure phase (liuite), subsequent retrograde transformation to the polymorph wangdaodeite, and then back-transformation to ilmenite. Whereas, the new grains with foam structure formed from complete transformation, the twin domains in the shocked ilmenite are interpreted to represent only partial transformation. Ferropseudobrookite occurs mostly near the rim of the aggregates. An intergrowth of ferropseudobrookite, ilmenite, and rutile, as well as magnetite or rarely armalcolite occurs at contact with the (devitrified) matrix. The presence of ferropseudobrookite indicates high temperature (>1140 °C) and reducing conditions. The surrounding matrix provided Mg2+ to form the ferropseudobrookite-armalcolite solid solution. Rutile can occur within the aggregates and/or along the ilmenite boundaries; it is interpreted to have formed together with iron during the decomposition of ilmenite at lower temperatures (850–1050 °C). We suggest magnetite in the rims formed by electrochemical gradients driven by the presence of a reducing agent, where Fe2+ within ilmenite diffused toward the rim. Subsequent cooling under oxidizing conditions led to the formation of magnetite from the iron-enriched rim as well as pseudorutile around ilmenite grains. Our study demonstrates that the specific crystallographic relationships of ilmenite grains with foam structure indicate a back-transformation from high (shock) pressures >16 GPa; moreover, the presence of associated Fe-Ti-oxides helps indicate local temperature and oxygen fugacity conditions. [ABSTRACT FROM AUTHOR]

Copper mineralization in the Pulang (PL) porphyry deposit, Langdu (LD) porphyry-skarn deposit and Songnuo (SN) porphyry prospect in northwestern Yunnan, China, is closely related to the emplacement of quartz monzonite porphyries. The chemical compositions of biotite and apatite from those porphyries were analyzed to calculate the halogen fugacity and to constrain mineralized and barren porphyries. Our data show that biotites from the PL deposit have higher MgO, SiO2, TiO2 and F contents than those from the LD deposit or SN prospect. Compared to those in the LD deposit and SN prospect, the Mg (atoms per formula unit (apfu)) and AlVI (apfu) value in biotite is greater, and the F content is greater and the SO3 and Ce2O3/Y2O3 ratio in apatite are lower in the PL deposit. Ti-biotite thermometry and apatite-biotite geothermometry show that the crystallization temperature of biotite from the PL deposit is higher than that from the SN prospect or LD deposit. The results suggest that oxygen fugacity, magmatic sulfur, and H2O contents cannot be used to efficiently distinguish the PL deposit from the LD deposit and SN prospect. However, the halogen chemistry of biotite from the PL deposit is distinctly different from that of the LD deposit or SN prospect according to the lower IV (F), indicating that mineralized quartz monzonite porphyries in the PL deposit formed during the late magmatic stage, which is in contrast to those in the LD deposit and SN prospect. The mineralized porphyries display a remarkable negative linear relationship (r = − 0.96) with the log (f HF/f HCl) and log (f H2O/f HF) ratio, which can be used to distinguish the mineralized and barren porphyries. Compared with other typical porphyry Cu systems, there is a remarkable positive linear relationship between IV (Cl) and log (f H2O/f HCl). In addition, the linear slope and intercept for log (f H2O/f HCl) ratios and the IV (Cl) of biotite from the potassic and phyllic alteration zones are significantly greater than those from other porphyries. [ABSTRACT FROM AUTHOR]

The study assessed the uniformity of the metallurgical process carried out during the period of Roman influence in Poland. The age of the investigated material was confirmed based on an analysis of the 12C/14C isotope ratio in the charcoal found in slag. The comparison was based on four Holy Cross Mountains (Poland) locations. The evaluation included smelting temperature, viscosity of the metallurgical melt, oxidation–reduction conditions, and slag cooling rate determined based on geochemical (XRF) and mineralogical (XRD, SEM, EPMA) analyses. Despite the distance between individual sampling sites, the conditions in which smelting was carried out were similar for all samples. The liquidus temperature of the analyzed slags was in the range of 1150–1200 °C. Oxidation–reduction conditions were determined through thermodynamic calculations using SLAG software. In the temperature range of 1150–1200 °C, the oxygen fugacity had to be below logP O2 = − 13.20 to − 12.53 atm to reduce iron oxides to metallic iron. The viscosity of the metallurgical melt was calculated and ranged from 0.15 to 1.02 Pa s, indicating a low viscosity. The slag cooling rate determined based on olivine morphology was in the range of > 5 to 300 °C/h. Smelting parameters were compared with other locations in Poland, and similar results were obtained for slags from Masovia and Tarchlice. In the case of one site (Opole), despite the higher maximum value of liquidus temperature, it was indicated that the process could have taken place in similar conditions, and the differences resulted from contamination of the slag with material from the furnace/pit walls. [ABSTRACT FROM AUTHOR]

Modeling the behavior of trace elements during lunar magma ocean solidification is important to further our understanding of the chemical evolution of the Moon. Lunar magma ocean evolution models rely on consistent datasets on how trace elements partition between a lunar silicate melt and coexisting minerals at different pressures, temperatures, and redox conditions. Here we report new experimental trace element partition coefficients (D) between clinopyroxene (cpx), pigeonite, orthopyroxene, plagioclase, olivine (ol), and silicate melt at conditions relevant for the lunar magma ocean. The data include Dcpx−melt at ambient and high pressures (1.5 GPa and 1310 °C), and partition coefficients at ambient pressure for pig, opx, ol, and pl. Overall, clinopyroxene is a phase that may control the fractionation of key geochemical trace element ratios, such as Lu/Hf and Sm/Nd, during the evolution of the lunar magma ocean. We explore the impact of the new silicate Dmineral−melt on the trace element evolution of the lunar magma ocean and we find that accessory phosphate minerals, such as apatite or whitlockite are of critical importance to explain the observed trace element and isotopic signature of the KREEP reservoir on the Moon. The new partition coefficients were applied to calculate the trace element evolution of the residual melts of the crystallizing lunar magma ocean and we propose a new trace element composition for the urKREEP reservoir. The new data will be useful for future thermo-chemical models in order to adequately predict the duration of the lunar magma ocean and the age of the Moon. [ABSTRACT FROM AUTHOR]

The flavored superconformal Schur index of N = 4 U(N) SYM has finite N corrections encoded in its giant graviton expansion in terms of D3 branes wrapped in AdS5 × S5. The key element of this decomposition is the non-trivial index of the theory living on the wrapped brane system. A remarkable feature of the Schur limit is that the brane index is an analytic continuation of the flavored index of N = 4 U(n) SYM, where n is the total brane wrapping number. We exploit recent exact results about the Schur index of N = 4 U(N) SYM to evaluate the closed form of the brane indices appearing in the giant graviton expansion. Away from the unflavored limit, they are characterized by quasimodular forms providing exact information at all orders in the index universal fugacity. As an application of these results, we present novel exact expressions for the giant graviton expansion of the unflavored Schur index in a class of four dimensional N = 2 theories with equal central charges a = c, i.e. the non-Lagrangian theories Γ ̂ SU N with Γ = E6, E7, E8. [ABSTRACT FROM AUTHOR]

The surface of Venus is in contact with a hot (~470 °C), high pressure (92 bars), and caustic (CO2 with S, but little H2O) atmosphere, which should cause progressive alteration of the crust in the form of sulfate and iron-oxide coatings; however, the exact rate of alteration and mineral species are not well constrained. Different experimental approaches, each with its own limitations, are currently being used to constrain mineralogy and alteration rates. One note is that no experimental approach has been able to fully replicate the necessary conditions and sustain them for a significant length of time. Furthermore, geochemical modeling studies can also constrain surface alteration mineralogy, again with different assumptions and limitations. Here, we review recent geochemical modeling and experimental studies to constrain the state of the art for alteration mineralogy, rate of alteration, open questions about the surface mineralogy of Venus, and what can be constrained before the fleet of missions arrives later this decade. Combining the new results confirms that basalt on the surface of Venus should react quickly and form coatings of sulfates and iron-oxides; however, the mineralogy and rate of alteration are dependent on physical properties of the protolith (including bulk composition, mineralogy, and crystallinity), as well as atmospheric composition, and surface temperature. Importantly, the geochemical modeling results show that the mineralogy is largely controlled by atmospheric oxygen fugacity, which is not well constrained for the near-surface environment on Venus. Therefore, alteration experiments run over a range of oxygen and sulfur fugacities are needed across a wide range of Venus analog materials with varying mineralogy and crystallinity. [ABSTRACT FROM AUTHOR]

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]

We consider the refined Schur superconformal index of 4d N = 4 U(N) SYM and the first term of its giant-graviton expansion, first predicted in arXiv:2001.11667 using indirect superconformal algebra considerations and analytic continuation of fugacities. This correction is the leading non-perturbative correction to the index at large N and we reproduce it from the semiclassical partition function of quantum D3 brane wrapped on S1 × S3 in a twisted modification of the AdS5 × S5 string background, depending on the index R-symmetry fugacity. Our calculation does not exploit directly supersymmetry. It is based on the determination of the partition function of the various bosonic and fermionic fluctuations on the wrapped brane whose action is conformal with specific constant holonomies along thermal cycle. We show how those partition functions may be obtained by adapting the operator counting method of Cardy to the twisted background. [ABSTRACT FROM AUTHOR]

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

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]

Despite over 400 occurrences of kimberlites and related rocks in India, mantle-derived xenoliths are known only from a few occurrences. This paucity of mantle-derived xenoliths in Indian kimberlites has hampered investigations of the subcontinental lithospheric mantle (SCLM). Using a valuable selection of the rare xenolith inventory, we here report Fe3+/ΣFe measurements for garnets using the electron microprobe (EPMA) flank method, targeting six mantle eclogite xenoliths (KL2 pipe) and fourteen peridotitic garnet xenocrysts (P9 and P10 hypabyssal intrusions) from the Wajrakarur kimberlite field (WKF) on the Eastern Dharwar craton (EDC). These data provide some of the first direct constraints on the oxygen fugacity (fO2) of the lithospheric mantle beneath the Indian subcontinent. The measured Fe3+/ΣFe ratios vary between 0.02 and 0.05 (± 0.01) for the eclogite xenoliths and between 0.02 and 0.10 (± 0.01) for the peridotitic garnets. Calculated ΔlogfO2 values for the KL2 eclogites show a wide range from FMQ-3.9 to FMQ-0.9 (± 0.6), straddling the boundary between the diamond and carbonate stability fields. In terms of redox compositions, it appears that the KL2 eclogites are able to host diamond, which is consistent with the diamondiferous nature of this particular WKF locality and the presence of eclogitic garnet inclusions in diamonds from the nearby TK4 kimberlite body. The peridotitic garnet xenocrysts from the P9 and P10 kimberlite bodies, which were entrained between ~ 125 and 170 km depth, reveal ΔlogfO2 values between FMQ-4.5 and FMQ-2.6 (± 0.9). Garnet xenocrysts with 'normal' REE patterns exhibit higher Fe3+/ΣFe ratios compared to garnets with 'sinusoidal' REE patterns. Importantly, the Fe3+/ΣFe ratios of garnet xenocrysts with 'normal' REE patterns (~ 125–160 km depth) correlate with metasomatic Ti–Y–Zr–V enrichment, which suggests metasomatism-driven oxidation of the cratonic mantle at mid-lithospheric depths. Such melt-related mantle metasomatism was probably diamond-destructive within the otherwise diamond-fertile lithospheric keel. The observed wide range of ΔlogfO2 values for the Dharwar cratonic mantle lithosphere allows for stabilization of various metasomatic phases (e.g., amphiboles, micas, carbonates) that may have formed (or concentrated in) distinctly different metasome assemblages within the continental root that underpins Peninsular India. Changing the relative contributions from such highly diverse volatile-rich metasomes may explain the spatiotemporal association of kimberlites and various diamond-bearing potassic magma types such as orangeites, ultramafic lamprophyres and lamproites, a scenario that is influenced by the redox composition of the Dharwar craton root. [ABSTRACT FROM AUTHOR]

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]

This article reports a protocol on the application of Amp-TB2 (single-amphibole thermobarometry) based on detailed electron-microprobe analyses performed on homogeneous natural standards and synthetic glasses, and amphibole crystals (mostly phenocrysts) of volcanic products erupted by the Bezymianny volcano during its activity through time. The application of this protocol is facilitated by a new version of the model (Amp-TB2.1.xlsx) including an equation to identify heterogeneous domains (disequilibrium; not suitable for thermobarometric constraints) and homogenous (equilibrium) zones within amphibole crystals, which can be used to quantify the physicochemical parameters (i.e., pressure, P; temperature, T; volatile content in the melt, H2Omelt; oxygen fugacity, fO2) of "steady-state" magmatic crystallization. Application examples of the protocol, showing detailed core–rim microprobe data and physicochemical parameter variations in representative amphibole phenocrysts of the Bezymianny are also reported. The depth (and P) estimated by Amp-TB2.1 for this volcano are compared to seismic tomography results. Amp-TB2.1 results mainly show (1) that the Bezymianny is characterized by a very dynamic feeding system where the magma is stored at shallow crustal levels before recent activity periods characterized by climatic events and (2) that the pre-eruptive depth of magma storage generally increases with the age of the investigated products. [ABSTRACT FROM AUTHOR]

Here we report the composition of biotite from the peraluminous Devonian South Mountain Batholith (SMB) of southwestern Nova Scotia (Canada), the largest intrusive body within the Appalachian orogen. The batholith was emplaced in two phases: an early (379–375 Ma) granodiorite-monzogranite suite (Stage 1) and a later (375–372 Ma) more-evolved monzogranite-leucogranite suite (Stage 2). Biotite analyses (major and minor elements) were obtained on 55 unmineralized samples representing 11 plutons. Regardless of the stage of pluton emplacement, biotite is commonly interstitial to alkali feldspar, quartz and plagioclase, indicating similar timing of biotite saturation. This suggests that biotite chemistry records conditions at similar extents of magma evolution for the chosen suite of samples. Biotite compositions are Fe-rich, with Fe/(Fe+Mg) ranging from 0.6 to 0.98, and Al-rich, with IVAl ranging from 2.2 to 2.9 atoms per formula unit (apfu; 22 oxygen basis), the latter reflecting the coexistence of other Al-rich phases, such as muscovite, garnet, aluminosilicates, and cordierite. Biotite anion sites are dominated by OH (>3 apfu), followed by F (~0.3 apfu) and Cl (≤0.02 apfu), with a general trend of decreasing OH, increasing F and a marked decrease in Cl, with increasing differentiation. Pressure (P) is estimated from the Al content of biotite to be between 280–430 MPa, consistent with a range of 240 to <470 MPa derived from phase equilibria and fluid inclusion microthermometry combined with mineral thermobarometry. Temperature (T) calculated from the Ti content of biotite ranges from 603–722 °C. Comparison of P-T estimates with water-saturated granite phase relations suggest minimum water contents of 6–7 wt% for the SMB magmas. The redox state of the SMB was estimated by comparing biotite Fe#-Ti relations with compositions calculated using the MELTS thermodynamic model, as experiments have shown that biotite Fe# increases with decreasing fO2 at a given extent of crystallization. Results of MELTS modeling for the most primitive magmas of the SMB sample suite indicate that the observed biotite Fe#-Ti variation is consistent with crystallization at FMQ to FMQ-1, with more oxidizing conditions suggested for the most strongly differentiated samples. To constrain the origin of the biotite anion site variation, a quantitative model using biotite-melt exchange coefficients (KD) derived from existing experimental data was used to track the change in biotite OH-F-Cl abundances as a function of crystallization, with or without an extant magmatic vapor phase (MVP). The model reproduces the relative OH, F, and Cl abundances in biotite, and suggests that SMB crystallization occurred in the presence of a MVP. The relatively reduced redox state of the SMB, similar to other peraluminous granitoid occurrences worldwide, aligns with other measures of fO2 for the SMB, including the occurrence of primary ilmenite. The observed correspondence between the estimated fO2 and that imposed by graphite-gas equilibrium suggests a role for reduced carbon in the generation and evolution of the SMB. This is consistent with evidence for SMB interaction with graphite-bearing felsic granulites of the underthrust Avalon terrane, and assimilation of carbonaceous and sulfidic metasediments during pluton ascent and emplacement. Reducing conditions and development of a MVP have implications for granophile element concentration processes in the SMB magmatic system. Low fO2 during crystallization affects the mineral/melt partitioning and solubility of the redox-sensitive elements Sn, W, U, and Mo, serving to suppress early SnO2 precipitation, and cause both an increase in W/Mo and an overall buildup of all four elements in evolving SMB liquids. Available experimental data indicate that reducing conditions also shifts DMVP/melt to favor partitioning into the melt phase. Therefore, early vapor exsolution under reducing conditions also lessens the extraction efficiency of these redox-sensitive elements to the MVP, further underscoring the role of extensive crystallization as an important metal enrichment process. [ABSTRACT FROM AUTHOR]

In the solar system, oldhamite (CaS) is generally considered to be formed by the condensation of solar nebula gas. Enstatite chondrites, one of the most important repositories of oldhamite, are believed to be representative of the material that formed Earth. Thus, the formation mechanism and the evolution process of oldhamite are of great significance to the deep understanding of the solar nebula, meteorites, the origin of Earth, and the C–O–S–Ca cycles of Earth. Until now, oldhamite has not been reported to occur in mantle rock. However, here we show the formation of oldhamite through the reaction between sulfide-bearing orthopyroxenite and molten CaCO3 at 1.5 GPa/1510 K, 0.5 GPa/1320 K, and 0.3 GPa/1273 K. Importantly, this reaction occurs at oxygen fugacities within the range of upper-mantle conditions, six orders of magnitude higher than that of the solar nebula mechanism. Oldhamite is easily oxidized to CaSO4 or hydrolysed to produce calcium hydroxide. Low oxygen fugacity of magma, extremely low oxygen content of the atmosphere, and the lack of a large amount of liquid water on the celestial body's surface are necessary for the widespread existence of oldhamite on the surface of a celestial body otherwise, anhydrite or gypsum will exist in large quantities. Oldhamites may exist in the upper mantle beneath mid-ocean ridges. Additionally, oldhamites may have been a contributing factor to the early Earth's atmospheric hypoxia environment, and the transient existence of oldhamites during the interaction between reducing sulfur-bearing magma and carbonate could have had an impact on the changes in atmospheric composition during the Permian–Triassic Boundary. [ABSTRACT FROM AUTHOR]

The Triassic Paleo-Tethyan magmatic belt in the East Kunlun Orogen (EKO) hosts a small number of porphyry-skarn deposits. The controls of these deposits, especially those in the eastern EKO, are poorly understood. In this contribution, we report new petrological, zircon U-Th-Pb-Hf isotopic, whole-rock elemental with Sr-Nd isotopic, and mineral chemistry data of the Delong quartz diorite and mafic enclaves to constrain their petrogenesis and metal fertility. The quartz diorite and mafic enclaves are emplaced in the Late Triassic (ca. 234 Ma). They are medium-K, metaluminous, enriched in large-ion lithophile elements (e.g., Rb, Ba, Th) and light rare earth elements (e.g., La, Ce, Nd), and relatively depleted in high field strength elements (e.g., Nb, Ta, Ti, P) and heavy rare earth elements (e.g., Gd, Er, Tm, Yb). The quartz diorite show similar (87Sr/86Sr)i (0.712584~0.713172) and more depleted εNd(t) (−6.4~−5.7) and εHf(t) (−2.3~+2.6) to those of mafic enclaves ((87Sr/86Sr)i = 0.712463~0.713093; εNd(t) = −6.4~−6.0; εHf(t) = −9.4~−4.8). Geochemical compositions of zircon, amphibole, and biotite yield high water content (5.3 wt.%~6.9 wt.% and 6.1 wt.%~7.3 wt.% based on amphibole, respectively) and high redox state for both the quartz diorite and mafic enclaves. These data, together with petrography, indicate the Delong intrusion was formed by mingling of magmas from enriched mantle and lower continental crust with juvenile materials. The oxidized and water-rich features of these magmas denote they have potential for porphyry Cu (±Au ± Mo) deposits, as do some Triassic magmatic rocks in the eastern EKO that show similar geochemical and petrographic characteristics with the Delong intrusion. [ABSTRACT FROM AUTHOR]

Arc magmatism is fundamental to the generation of new continental or island arc crust. However, the mechanisms that add to the chemical complexity of natural calc-alkaline magmas ranging from basaltic to rhyolitic compositions are debated. Differentiation mechanisms currently discussed include magma mixing, assimilation, crustal melting, or (fractional) crystallisation. In this contribution, the differentiation of arc magmas by decompression-driven crystallisation is investigated. We performed a set of equilibrium crystallisation experiments at variable crustal pressures (200–800 MPa) on a hydrous high-Al basalt (3.5 wt.% of H2O in the starting material) with run temperatures varying from near-liquidus conditions (1110 °C) to 900 °C. Oxygen fugacity was buffered at moderately oxidising conditions close to the NNO equilibrium. Combining these novel experiments with previous polybaric fractional crystallisation experiments (Marxer et al., Contrib Mineral Petrol 177:3, 2022) we demonstrate the effects of pressure on the crystallisation behaviour of calc-alkaline magmas with respect to liquid and cumulate lines of descent, mineral chemistry, and phase proportions. Decompression shifts the olivine-clinopyroxene cotectic curve towards melt compositions with higher normative clinopyroxene and enlarges the stability field of plagioclase. This exerts a key control on the alumina saturation index of residual liquids. We argue that near-adiabatic (or near-isothermal) decompression accompanied by dissolution of clinopyroxene entrained during residual melt extraction in the lower crust keeps arc magmas metaluminous during crystallisation-driven differentiation thereby closely reproducing the compositional spread observed for natural arc rocks. [ABSTRACT FROM AUTHOR]

The Zhaheba ophiolite is an ocean relic of the Zhaheba-Aermantai oceanic slab, a branch of the early Paleozoic Paleo-Asian Ocean. The peridotites consist mainly of harzburgite, lherzolite and minor dunite, chromitite. This study describes the whole-rock geochemistry and mineral chemistry of the Zhaheba peridotite and chromitite for the purpose of constraining their tectonic environment and genesis. The major oxides and the trace element concentrations of the peridotites are comparable with abyssal peridotite, but fall outside the field of SSZ (suprasubduction zone) peridotite and the fore-arc peridotite. The massive chromites belong to the high-Cr group, with an average Cr# (Cr/(Cr + Al)) atomic ratio) value of chromian spinel of 0.77, whereas the average Mg# value is 0.60. The disseminated chromites give a lower concentration of Cr2O3 (38.96–42.15 wt.%, average 40.35 wt.%) and lower Cr# values (0.50–0.56, average 0.53), but slightly higher contents of MgO (13.23 wt.%) and Mg# (0.61) than the massive chromites. In the diagrams of Cr#-Mg#, NiO-Cr# and TiO2-Cr#, the massive chromites fall in the field of boninite, and the disseminated chromite in the peridotite plot fall in the field of abyssal peridotite and mid-oceanic ridge basalt (MORB). The massive chromitites, with high-Cr, display a boninite affinity, whereas the disseminated chromite plot in the high-Al and abyssal peridotite type field may be generated by the extension of the Zhaheba ocean in the MOR environment then experienced deep subduction and exhumation. The calculated degrees of partial melting for the massive chromites are 21%−22%, and for the disseminated chromites in peridotites the degrees are 17%−18%. The calculated values of fO2 for the massive chromites range from −1.44 to +0.20, and the values for the disseminated chromites range from −0.32 to +0.18. The inferred parental melt composition for massive chromitite falls in the field of boninite in an arc setting, whereas the disseminated chromite in peridotites are in the field of a MORB setting. This indicates that the parental magmas of the former were more refractory than the latter. A two-stage evolution model for the chromites was proposed, in which disseminated chromites were first formed in an MOR environment and then modified by later-stage melts and fluids, and formed massive chromites were formed in an SSZ setting during intra-oceanic subduction. [ABSTRACT FROM AUTHOR]

The Jiaodong Peninsula is closely related to Mesozoic granites in terms of spatial and temporal aspects. However, the specific association between the genesis of gold mineralization and these granites remains unclear. It is also ambiguous why Laoshan-type granites, which are similar to Mesozoic granites, are not gold mineralized. In this study, we analyzed the Laoshan granites and compiled Mesozoic magmatic rock data (Linglong, Guojialing, and Weideshan suites) of the Jiaodong Peninsula. We performed whole-rock major and trace elements, LA–ICP–MS zircon U–Pb geochronology and geochemistry analyses. Our zircon U–Pb data denote that the Laoshan granite was emplaced during the 118 ± 1 Ma. The Laoshan granite is characterized by high SiO2 content (76.03–80.28 wt.%), high TFe2O3/MgO (11.1–27.1) and Ga/Al (3.0–3.5) ratios, high zircon saturation temperature (809–850 °C), and negative Eu (Eu/Eu* = 0.05–0.08) anomalies, showing A-type granite characteristics. Furthermore, the Laoshan granite is identified as an A1-type granite with low Ba (33.1–42.0 ppm) and Sr (14.1–21.0 ppm) contents. It was formed in an extensional tectonic environment induced by the subducting slab roll-back of the Paleo-Pacific Plate, mainly from the partial melting of lower crustal materials, mixed with a small amount of mantle components. Zircon trace elements indicate that the Laoshan suite had relatively high oxygen fugacity and temperature (ΔFMQ = + 2.43 to + 4.22, T-Ti in zircon (mean) = 796 °C) compared to the pre-mineralization and contemporaneous mineralization magma. We propose that oxidized adakitic magma (Weideshan suite) may contribute to the enrichment and mineralization of gold. Although Laoshan-type granite also has a high oxygen fugacity, its location is distant from the ore-controlling faults, which ultimately hinders the formation of gold mineralization. From the Jurassic to the Cretaceous, the tectonic and geochemical properties of magmatic rocks in the Jiaodong Peninsula have changed, and gold deposits are formed in such a transitional process (compression to extension, reduction to oxidation). [ABSTRACT FROM AUTHOR]

Volatile element abundance is a crucial factor triggering mineralization and controlling the enrichment of molybdenum in porphyry deposits. The Chalukou deposit is the largest porphyry Mo deposit in NE China, with an average grade of 0.087% Mo. In this contribution, we present petrology, bulk geochemistry, zircon U–Pb geochronology and Lu–Hf isotopes, and apatite geochemistry for the Chalukou deposit. The intrusive rocks include pre‐mineralization monzogranite, syn‐mineralization quartz porphyry, fine‐grained porphyry and granite porphyry, and post‐mineralization monzogranite and feldspar porphyry. These granitoids are metaluminous to peraluminous, and belong to alkali‐calcic to calc‐alkalic series. Zircon εHf(t) values of granitoids range from +0.2 to +5.7 with corresponding Hf crustal model ages of 805–1170 Ma, indicating a Mesoproterozoic juvenile crustal source modified by mantle‐derived magma. They are characterized by logf(O2) of −16.1 to −9.4, with an average of −12.5, ΔFMQ of +0.8 to +7.9, with an average of +4.5, showing a relatively high oxidation state for the syn‐mineralization magma. The apatites in quartz porphyry have the highest F contents, ranging from 3.61 to 4.62 wt%. At Chalukou, F‐rich magma is conducive to the convection of magma and promotes the efficient separation of differentiation magma, making the magmatic‐hydrothermal fluid circulate many times, eventually resulting in the accumulation of ore‐forming materials on the top of the magma chamber and gradually aggravating mineral enrichment processes. [ABSTRACT FROM AUTHOR]

Porphyry Mo deposits are the most important type of Mo resource. They result from a high oxygen fugacity of the parent magma, which acts as an effective indicator for evaluating the mineralization. In the ore-forming system of porphyry Mo deposits, sulfur exists mainly as sulfate in highly oxidized magma but as sulfide in ores. What triggers the reduction in the mineralization system that leads to sulfide precipitation has not yet been determined. Most of the previous studies have focused on the origin and evolution of the ore-forming parent magma, and the effects of reductive surrounding rocks on porphyry mineralization have been ignored. In this study, a comprehensive geological–geochemical investigation and review have been performed on the typical porphyry Mo deposits, the Nannihu-Sandaozhuang, Yuchiling, and Shapingou deposits in China, and the Mt. Emmons deposits in America. Black carbonaceous sedimentary layers commonly surround porphyry Mo ores, which are widely altered and discolored during mineralization. CH4 is commonly present in fluid inclusions in the main mineralization stage, and the δ13CV-PDB values of calcite and fluid inclusions from the altered surrounding rocks and ore minerals are generally low and significantly different from those of marine sedimentary carbonate rocks, indicating that the involvement of reductive components from carbonaceous surrounding rocks might be key to the redox state transformation leading to mineral precipitation. On the other hand, the CH4 produced by the thermal decomposition of organic matter or carbonaceous reaction with H2O can diffuse into the ore-forming system along the structural fractures and reduce the SO42− in the ore-forming hydrothermal fluids to form sulfide precipitation without direct contact between the intrusion and the carbonaceous surrounding rocks. Moreover, the CH4 content controls the location of the orebody formation with the high content producing orebodies mainly in the porphyry intrusion, while the low CH4 content results in the orebodies mainly occurring at the contact zone between the porphyry and carbonaceous surrounding rocks. Compared to the magmatic stage of mineralization, the involvement of reductive components in the carbonaceous surrounding rocks during the hydrothermal stage is more favorable for forming giant/large Mo deposits. The highly oxidized porphyry with reductive carbonaceous surrounding rocks or Fe-rich volcanic rocks offers a new indicator for efficiently evaluating porphyry Mo mineralization. [ABSTRACT FROM AUTHOR]

The recently discovered 460 Gaodi porphyry Mo-Cu deposit is a sub-economic deposit characterized by low Mo-Cu grades, dispersed mineralization, and separated Mo- and Cu-ore bodies. This study aims to elucidate the factors underlying this type of sub-economic mineralization. Electron-microprobe analyses of biotite from ore-related granite porphyry yielded Ti-in-biotite crystallization temperatures of 677–734 °C (an average of 719 °C) and biotite phenocryst crystallization depths of 6.0 to 12.9 km. LA-ICP-MS analyses of zircons from the same sample revealed average zircon Ce4+/Ce3+ ratios of 299.7 and elevated zircon lg(ƒO2) ratios, with an average ΔFMQ of +6.6 ± 1.9. These discoveries suggest that the magma responsible for ore formation boasts a high degree of oxidation, yet also possesses a magma chamber located at a significant depth within the upper crust. This implies an extensive exsolving depth for fluids. Furthermore, our microthermometry analysis of fluid inclusions reveals that a portion of the fluid experiences considerable conductive cooling as it ascends along the conduit, owing to the depth of fluid exsolution. This process results in the ore fluids remaining in the liquid-only region without undergoing boiling, which is conducive to the enrichment of metals. We emphasize the fact that fluid-exsolving depth plays a critical role in determining the metal grades and economic value of a porphyry deposit by regulating the P-T evolution path of the ore fluids [ABSTRACT FROM AUTHOR]

Partition coefficients for rare earth elements (REEs) between apatite and basaltic melt were determined as a function of oxygen fugacity (fO2; iron-wüstite to hematite-magnetite buffers) at 1 bar and between 1110 and 1175 °C. Apatite-melt partitioning data for REE3+ (La, Sm, Gd, Lu) show near constant values at all experimental conditions, while bulk Eu becomes more incompatible (with an increasing negative anomaly) with decreasing fO2. Experiments define three apatite calibrations that can theoretically be used as redox sensors. The first, a XANES calibration that directly measures Eu valence in apatite, requires saturation at similar temperature-composition conditions to experiments and is defined by: ( Eu 3 + ∑ Eu ) Apatite = 1 1 + 10 − 0.10 ± 0.01 × log (f o 2 ) − 1.63 ± 0.16 . The second technique involves analysis of Sm, Eu, and Gd in both apatite and coexisting basaltic melt (glass), and is defined by: ( Eu Eu ∗ ) D Sm×Gd = 1 1 + 10 − 0.15 ± 0.03 × log (f o 2 ) − 2.46 ± 0.41 . The third technique is based on the lattice strain model and also requires analysis of REE in both apatite and basalt. This calibration is defined by ( Eu Eu ∗ ) D lattice strain = 1 1 + 10 − 0.20 ± 0.03 × log (f o 2 ) − 3.03 ± 0.42 . The Eu valence-state partitioning techniques based on (Sm × Gd) and lattice strain are virtually indistinguishable, such that either methodology is valid. Application of any of these calibrations is best carried out in systems where both apatite and coexisting glass are present and in direct contact with one another. In holocrystalline rocks, whole rock analyses can be used as a guide to melt composition, but considerations and corrections must be made to either the lattice strain or Sm × Gd techniques to ensure that the effect of plagioclase crystallization either prior to or during apatite growth can be removed. Similarly, if the melt source has an inherited either a positive or negative Eu anomaly, appropriate corrections must also be made to lattice strain or (Sm × Gd) techniques that are based on whole rock analyses. This being the case, if apatite is primary and saturates from the parent melt early during the crystallization sequence, these corrections may be minimal. The partition coefficients for the REE between apatite and melt range from a maximum DEu3+ = 1.67 ± 0.25 (as determined by lattice strain) to DLu3+ = 0.69 ± 0.10. The REE partition coefficient pattern, as observed in the Onuma diagram, is in a fortuitous situation where the most compatible REE (Eu3+) is also the polyvalent element used to monitor fO2. These experiments provide a quantitative means of assessing Eu anomalies in apatite and how they be used to constrain the oxygen fugacity of silicate melts. [ABSTRACT FROM AUTHOR]

Silicate vapors play a key role in planetary evolution, especially dominating early stages of rocky planet formation through outgassed magma ocean atmospheres. Our open-source thermodynamic modeling software "VapoRock" combines the MELTS liquid model with gas-species properties from multiple thermochemistry tables. VapoRock calculates the partial pressures of 34 gaseous species in equilibrium with magmatic liquid in the system Si–Mg–Fe–Al–Ca–Na–K–Ti–Cr–O at desired temperatures and oxygen fugacities (f O2, or partial pressure of O2). Comparison with experiments shows that pressures and melt-oxide activities (which vary over many orders of magnitude) are reproduced to within a factor of ∼3, consistent with measurement uncertainties. We also benchmark the model against a wide selection of igneous rock compositions including bulk silicate Earth, predicting elemental vapor abundances that are comparable to (Na, Ca, and Al) or more realistic than (K, Si, Mg, Fe, and Ti) those of the closed-source MAGMA code (with maximum deviations by factors of 10–300 for K and Si). Vapor abundances depend critically on the activities of liquid components. The MELTS model underpinning VapoRock was calibrated and extensively tested on natural igneous liquids. In contrast, MAGMA's liquid model assumes ideal mixtures of a limited set of chemically simplified pseudospecies, which only roughly approximates the nonideal compositional interactions typical of many-component natural silicate melts. Finally, we explore how relative abundances of SiO and SiO2 provide a spectroscopically measurable proxy for oxygen fugacity in devolatilized exoplanetary atmospheres, potentially constraining f O2 in outgassed exoplanetary mantles. [ABSTRACT FROM AUTHOR]

The magmatic process within upper crust encompasses various contents such as the transition between magmatic and hydrothermal systems and changes in oxygen fugacity (ƒO2), which ultimately play key roles in the formation of porphyry Cu deposits (PCDs). However, tracing these magmatic processes, especially in porphyry systems, is not an easy task. This study reported the detailed process of magmatic fluid exsolution and systematical variation of magmatic ƒO2 within the upper crust of a Tongchang–Chang'anchong porphyry Cu deposit, based on detailed investigations of mineral crystallization sequences and compositional features of the minerals in the fertile porphyries. Results indicate that the fertile porphyries show a high initial ƒO2, with ΔFMQ ≥ +3.0 (ΔFMQ is the deviation of logƒO2 from the fayalite–magnetite–quartz (FMQ) buffer). The magmatic ƒO2 (ΔFMQ) continued to decrease to ~+2 until fluid exsolution occurred at ~790 °C due to wall-rock contamination. The magmatic fluid exsolution process caused a temporary increase in the ƒO2 (to ΔFMQ = ~+3.4). The high magmatic ƒO2 during this process (790–750 °C) resulted in a higher content of ore-forming materials in the exsolved magmatic fluid. When the temperature dropped below 750 °C, the magmatic ƒO2 began to continuously decrease and eventually reached ΔFMQ = ~+0.6. The lower magmatic ƒO2 hindered the further migration of ore-forming materials through the exsolved fluid during this process (< 750 °C). Results of this study indicate that the initial magma during the upper crustal magmatic process of PCDs generally has a high ƒO2, and the contamination of reduced components can significantly decrease the magmatic ƒO2. The early magmatic fluid exsolution process can maintain a high magmatic ƒO2 condition, thereby efficiently extracting ore-forming minerals and producing ore-forming fluids, which is the key to the formation of PCDs. The latter continuous decrease in magmatic ƒO2 during the fluid exsolution process may be the reason preventing the Tongchang–Chang'anchong porphyry Cu deposit to form a giant PCD. [ABSTRACT FROM AUTHOR]

The Fule deposit is a typical Cd-, Ge- and Ga-enriched Pb-Zn deposit located in the southeast of the Sichuan–Yunnan–Guizhou Pb-Zn polymetallic ore province in China. Zoned, euhedral cubic and pentagonal dodecahedral and anhedral pyrites were observed, and they are thought to comprise two generations. First generation pyrite (Py1) is homogeneous and entirely confined to a crystal core, whereas second generation pyrite (Py2) forms bright and irregular rims around the former. Second generation pyrite also occurs as a cubic and pentagonal dodecahedral crystal in/near the ore body or as an anhedral crystal generally closed to the surrounding rock. The content of S, Fe, Co, and Ni in Py1 are from 52.49 to 53.40%, 41.91 to 44.85%, 0.19 to 0.50% and 0.76 to 1.55%, respectively. The values of Co/Ni, Cu/Ni and Zn/Ni are from 0.22 to 0.42, 0.02 to 0.08 and 0.43 to 1.49, respectively, showing that the Py1 was formed in the sedimentary diagenetic stage. However, the contents of S, Fe, Co, and Ni in Py2 are in the range from 51.67 to 54.60%, 45.01 to 46.52%, 0.03 to 0.07% and 0.01 to 0.16%, respectively. The Co/Ni, Cu/Ni and Zn/Ni values of Py2 are from 0.40 to 12.33, 0.14 to 13.70 and 0.04 to 74.75, respectively, which is characterized by hydrothermal pyrite (mineralization stage). The different δ34S values of the Py1 (−34.9 to −32.3‰) and the Py2 (9.7 to 20.5‰) indicate that there are at least two different sources of sulfur in the Fule deposit. The sulfur in Py1 was derived from the bacterial sulfate reduction (BSR), whereas the sulfur in the ore-forming fluids (Py2) was derived from the thermochemical sulfate reduction (TSR). The main reasons for the different morphologies of pyrite in the regular spatial distribution in the Fule deposit are temperature and sulfur fugacity. [ABSTRACT FROM AUTHOR]

To investigate the effect of carbon-bearing phases on the release of fluids in subducted serpentinites, we performed high-pressure multi-anvil experiments on representative ophicarbonate assemblages over a pressure range from 2.5 GPa to 5 GPa and from 450 °C to 900 °C, across the antigorite-out reaction. Parallel experiments were performed on carbonate-free serpentinites. In all experiments, we monitored and/or controlled the oxygen fugacity. The addition of 20 wt. % CaCO3 to a serpentinite assemblage at 2.5 GPa is found to decrease the onset of the serpentine dehydration by over 100 °C, in comparison to carbonate-free assemblages. Similarly, the final disappearance of serpentine is also affected by the presence of CaCO3. For a bulk CaCO3 content of 20 wt. %, this causes a decrease in maximum stability of antigorite by 50 °C. For a bulk CaCO3 content exceeding 25 wt. %, this difference can be as high as 100 °C in warm and 150 °C in cold subduction zones, causing antigorite to be completely dehydrated at 500 °C. This results from the reaction of CaCO3 with serpentine to form clinopyroxene and Mg-rich carbonates. This reaction, however, causes no discernible decrease in the proportion of carbonate, indicating that the amount of released carbon is insignificant. Whilst CaCO3, therefore, influences serpentine stability, there is no significant effect of hydrous phases on the carbonate stability. On the other hand, a MgCO3-bearing system shows no significant effects on the serpentinite stability field. Further experiments and oxygen fugacity calculations indicate that graphite is not stable in typical magnetite-bearing serpentinites. The reduction of carbonates to graphite would require oxygen fugacities that are 1–2 log units below those of magnetite-bearing serpentinites. This confirms earlier studies and indicates that reduction of carbonates can only occur through the infiltration of external H2-rich fluids. [ABSTRACT FROM AUTHOR]

The Maletoyvayam high-sulfidation (HS) epithermal Au-Ag deposit is one of the numerous hydrothermal deposits of the Kamchatka volcanogenic belt, consisting of two main associations: Au-rich (Ag-free) and Ag-bearing. The first one derived from acidic solutions, whereas the second assemblage crystallized from moderately dilute solutions, with both occurring at high oxygen fugacity. The Au-rich association contains the most atypical gold chalcogenides of the Au-Se-Te-S system, which are characterized by Se-S and Te-Se substitutions, e.g., a complete series from maletoyvayamite to tolstykhite Au3(Se,S)4Te6; a series of auroselenide Au(Se1.00–0.64S0.36–0.00); a combined series of gachingite Au(Te,Se) and unnamed Au(Se,Te): Au(Te0.80–0.40Se0.20–0.60). Meanwhile, in the second Ag-bearing assemblage, sulfides of the Au-Ag type prevails, e.g., petrovskaite AuAgS, miargyrite (Ag,Au)(Sb,As)S2, uytenbogaardtite Ag3AuS2, fischesserite Ag3AuSe2 with Au-Ag substitution, and tolstykhite. The Se/S ratio, of the second association, decreases while increasing the Ag concentration in the ore-forming system, including Au-Ag substitutions. The Au content in miargyrite (Au,Ag)SbS3 reaches up to 0.48 apfu, suggesting the existence of a new mineral phase of composition AgAuSb2S6. Au oxide complexes, in both associations, are represented by either a mixture of redeposited gold and Fe-Sb oxide or a homogeneous (Au,Sb,Fe)2O3 composition. These oxides are formed by replacement of calaverite. The ore mineralization of this HS deposit is considered unique due to the special conditions of the ore-forming environment, such as acidic solutions, high oxygen fugacity, and log fSe2 above −5.7; all contributed to the formation of AuSe phases. [ABSTRACT FROM AUTHOR]

In the sector of San Jose, Macanal, and Tabaquen, in eastern Colombia, granitic rocks cut by pegmatite dikes and quartz veins appear with the presence of magnetite, ilmenite, and ilmenorutile. Using magnetic petrology and geochemistry concepts and methods, the main objective is to determine if these types of rocks are genetically related and how the fluid chemically evolves during its crystallization and cooling. This work was conducted in three stages. Petrography and opaque metallography for identifying the occurrence, paragenesis, and secondary processes that transform the oxides. In a second stage and utilizing an Electron Probe Microanalyzer (EPMA), 214 quantitative analyses (WDS) and four compositional maps for magnetite, ilmenite, and ilmenorutile were performed, measuring the oxides FeO, TiO2, V2O3, MgO, MnO, Nb2O5, Ta2O5, Al2O3, Ga2O3, NiO, CaO, Cr2O3, SnO, and WO3. Since magnetite and ilmenite are favorable geothermometers that also allow the calculation of oxygen fugacity, the ILMAT program was used to calculate these values. In closing, integrate the data with the magnetic susceptibility values. The results determine crystallization temperatures between 358-414 °C for the granitic-host rock and 402-499 °C for pegmatites dykes, in a system where oxygen fugacity increases, the Mn2+ is enriched in the ilmenite, and magnetite preserves a low content of trace elements thorough the evolution of the fluid. Taken together with the martitization and exsolution of hematite and rutile within ilmenite found in the petrography, these results allow us to conclude that an oxide-silicate re-equilibration process controls the evolution of this magmatic-hydrothermal fluid with a KUIlB cooling trend-type reaction. Based on the Al + Mn vs. Ti + V ratio, the signature of the magnetite is like the Lucky Friday mine's signature studied by Nadoll. However, the analysis of the 95th percentile shows a different concentration of trace elements in the magnetite of both sectors. Therefore, a new field of discrimination is proposed for this environment of anorogenic pegmatites of the NYF family. Finally, the magnetic susceptibility is controlled only by the abundance of magnetite in each type of rock. The granitic host rocks have the highest susceptibility values, followed by pegmatites and quartz veins with the lowest. [ABSTRACT FROM AUTHOR]

Adopted by the Intergovernmental Oceanographic Commission (IOC) of UNESCO in 2010 and the International Union of Geodesy and Geophysics (IUGG) in 2011, the Thermodynamic Equation of Seawater 2010 (TEOS-10) is the current geophysical standard for the thermodynamic properties of humid air, seawater and ice. TEOS-10 equations for evaporation and sublimation enthalpies are derived mathematically from the thermodynamic potential of a »sea air« model, denoting a multi-phase equilibrium composite of the geophysical aqueous mixtures. To estimating evaporation rates from the ocean, Dalton equations in various versions are implemented in numerical climate models. Some of those equations appear to be biased on climatic time scales if compared with proper thermodynamic driving forces. Such equations may lead to a spurious amplification of the hydrological cycle and an implied effect of cooling oceans. As an unbiased alternative, Dalton equations are proposed in terms of TEOS-10 relative fugacity (RF) or its conventional relative humidity (RH) approximations. With respect to RH uncertainties or trends, the substantial sensitivity of the evaporation flux may be estimated to be as much as 5 W m−2 per 1 %rh. Within a maximum error of only 0.04 %rh, sea-surface RF may be approximated in terms of dew-point or frost-point temperatures using a simple formula. [ABSTRACT FROM AUTHOR]

Control of oxygen fugacity during high-temperature phase equilibrium experiments is required to simulate the conditions that exist in natural systems. At high pressures, oxygen fugacity may be imposed using solid buffer equilibria via the classic "double capsule" technique. This design becomes untenable, however, at temperatures above the melting points of commonly used noble metal capsule materials and/or where buffer assemblages may alloy with the capsule or contaminate the sample. Here we introduce and test a modified double capsule approach that includes a solid metal-oxide buffer in close proximity to but separate from the sample of interest. Buffers used include (in order of most oxidized to reduced) Ni-NiO, Co-CoO, W-WO3, Fe-FeO, Mo-MoO2, Cr-Cr2O3, V-V2O3, Ta-Ta2O5, and Nb-NbO. At a fixed temperature, these buffers span a wide range—up to 10 log fO2 units. To demonstrate the buffering capacity of this double capsule approach, secondary redox equilibria and V-doped CaO-MgO-Al2O3-SiO2 system glasses were studied in experiments using the double capsule geometry. The secondary equilibria provide an independent verification of the oxygen fugacity established in the double capsule environment. The glasses proved difficult to interpret, and our results provide guidance to future efforts to utilize the glass oxybarometer at reducing conditions. Application of this modified double capsule technique to studies of V valence in MgAl2O4 spinels led to the recognition of several factors that will affect V valence in this system: temperature of equilibration, duration of experiment, and spinel bulk composition. We have synthesized V-bearing MgAl2O4 spinel at the reduced conditions of the Cr-Cr2O3, (IW-3.51), Ta-Ta2O5, (IW-5.37), and Nb-NbO buffers (IW-5.44). This spinel exhibits a very small V3+ pre-edge peak consistent with its reduced nature. The absence of evidence for V2+ suggests that MgAl2O4 spinel excludes V2+ due to the preference of V for octahedral sites. This finding is supported by DFT calculations for spinels of variable composition, and in agreement with some other indirect evidence for preference for V3+ in aluminous spinels (Bosi et al. 2016,; Paque et al. 2013,). [ABSTRACT FROM AUTHOR]

The liquid line of descent from trachyte to pantellerite is controlled primarily by fractional crystallization of alkali feldspar, with whole-rock compositions following a fractionation path along the 'thermal valley' in the peralkaline haplogranite system Qz-Ab-Or-Ac-Ns and terminating at a minimum on the feldspar-quartz cotectic. Although whole-rock compositions for different pantelleritic suites follow nearly identical paths in a Qz-Ab-Or projection that terminate near the experimental minimum (Qz40.5Or34.5Ab25 at 100 MPa, projected from Ac-Ns), matrix glass from samples with near-minimum compositions record extreme differentiation and form a 'cotectic delta' beyond the terminus of the 'thermal valley'. Although each glass trend shows a continuing increase in Zr to >3000 μg/g, the most evolved compositions in each suite differ in peralkalinity (mol [Na + K] / Al) and in the proportions of FeOT, Qz, Ab, Or, and other components, which are related to subtle variations in the mafic phases controlled mainly by differences in oxygen fugacity (f O2) and pressure (P). To determine the controls over mafic mineral crystallization in pantelleritic magmas and the various paths these suites take beyond the apparent (whole-rock) minimum, amphibole-phyric suites from the ~159 ka Cala dell'Altura and Cala Gadir volcanic centres and the ~8–10 ka Cuddia Mida volcanic centre on Pantelleria have been analyzed and compared with each other and with the well-characterized and amphibole-free, compositionally zoned Green Tuff, the ~46 ka caldera-forming ignimbrite of the Cinque Denti caldera. Differences between the extended fractionation trends may be ultimately attributed to variations in oxygen fugacity, depth of emplacement, and water saturation. Shallower (lower pressure) magma reservoirs such as the one for the Green Tuff are water-saturated and undergo degassing, which leads to an increase in relative oxygen fugacity. Deeper (higher pressure) magma reservoirs remain water-undersaturated and retain water in the melt, which both maintains lower relative oxygen fugacities and enables the crystallization of amphibole. Amphibole formation appears to require melt water contents >4 wt%, low oxygen fugacity (<ΔNNO-1.5), and low temperatures (<700°C), although fluorine may stabilize it at higher temperatures in some rocks. [ABSTRACT FROM AUTHOR]

This study uses simulations to explore the energy distributions involved in the adsorption of methane gas in shales. Molecular mechanics calculations were carried out using the Forcite module in BIOVIA material studio software. The critical challenge in molecular-scale simulations remains the need to improve the description of the gas adsorption prior to up-scaling to a realistic scenario. Resolving this challenge requires the implementation of multi-scale techniques that employ atomistic/molecular-level results as input. Thus, it is pertinent that the appropriate molecular data on CH4 gas interaction with shale is obtained. This study provides empirical data on CH4 sorption/adsorption in shale at the molecular level to confirm the CH4 storage potential of shales. The effect of pressure on the CH4 sorption/adsorption was also investigated. A vital aspect of this study is elucidating the energy distribution and dominant energy that controls CH4 sorption/adsorption to serve as a basis for the exploitation of CH4 in productive shales. Following the intensive simulation exercise, the average total energy of CH4 sorption varied from approximately -30 to -120 kcal/mol with increase in pressure from 500 to 2500 psi, suggesting increasing thermodynamic stability. The results indicated that van der Waals energy is the major sorption energy with values ranging from 60 to -250 kcal/mol as the sorption pressure increased, while electrostatic energy recorded the least contribution. The total adsorption energy increased from -5 to -16 kcal/mol for reservoir pressure range of 1-15 MPa. This energy distribution data confirmed the possibility of CH4 adsorption on shale under reservoir pressure conditions. [ABSTRACT FROM AUTHOR]

The unique properties of polyvinyl alcohol (PVA) and polysulfone (PSf), such as good membrane-forming ability and adjustable structure, provide a great opportunity for CO2-separation membrane development. This work focuses on the fabrication of PVA/PSf composite membranes for CO2/N2 separations. The membranes prepared by coating a 7.5 wt% PVA on top of PSf substrate showed a relatively thin selective layer of 1.7 µm with an enhanced CO2/N2 selectivity of 78, which is a ca. 200% increase compared to the pure PSf membranes. The CO2/N2 selectivity decreases at a rapid rate with the increase of feed pressure from 1.8 to 5 bar, while the CO2 permeance shows a slight reduction, which is caused by the weakening of coupling transportation between water and CO2 molecules, as well as membrane compaction at higher pressures. Increasing operating temperature from 22 °C to 50 °C leads to a slight decrease in CO2 permeance, but a significant reduction in the CO2/N2 selectivity from 78 to 27.1. Moreover, the mass transfer coefficient of gas molecules is expected to increase at a higher velocity, which leads to the increase of CO2 permeance at higher feed flow rates. It was concluded that the CO2 separation performance of the prepared membranes was significantly dependent on the membrane operating parameters, and process design and optimization are crucial to bringing CO2-separation membranes for industrial applications in post-combustion carbon capture. [ABSTRACT FROM AUTHOR]

Water in natural gas can result in various operational problems, which may lead to equipment failure and plant shutdown. Knowing the amount of water capable of condensing from natural gas is essential. Many methods have been developed for ascertaining the amount of this condensable water (water content) from many gas mixtures. However, when hydrates are present, available methods for estimating the amount of condensable water are scarce and very limited in the open literature. The reliability of the data has always been a cause for concern due to the tendency for the inaccuracy of the results. In this study, two semi-empirical methods for ascertaining the amount of condensable water in natural gas with and without hydrates were used to test the reliability of the water content data of four different published natural gas-hydrate systems, including methane and propane gas mixture, raw/unprocessed, binary (methane + water), and synthetic natural gas. The results showed that only the data set for the methane and propane gas mixture was a reliable gas-hydrate equilibrium system, while the synthetic gas mixture needed further validation. Therefore, the methodology in this study can be used as a quick and simple means for ascertaining the reliability of water content data of natural gas-hydrate systems. [ABSTRACT FROM AUTHOR]

While noble metals often occur as minor components in host minerals in various ore deposits, little theoretical assessment exists to predict the occurrence of these metals. Here, we probe the fundamental controls responsible for the occurrence of trace elements in host minerals through first-principles calculations. We apply the theoretical model to understanding the debated issues concerning the occurrence of gold (Au) in pyrite, in which the valence of Au is ascribed to either positive or negative values. Our results indicate that (1) both positive and negative valent Au may occur in pyrite and (2) higher sulfur fugacity and lower temperature lead to more Au+ occupying Fe sites in pyrite. These findings suggest that chemical states and speciation of the Au in host pyrite are ultimately controlled by temperature and sulfur fugacity, providing insight into the formation conditions of ore deposits and facilitating strategy design for beneficiation. [ABSTRACT FROM AUTHOR]

Weathering crusts after granites are the most important source of heavy rare-earth elements (HREE) worldwide. Although HREE in these deposits is known to be inherited from parental rocks, the origin of HREE enrichment and the reasons why it is rare outside of China remains unclear. Here, we report the occurrence of variably organized nanoparticles of Ce-poor (<0.2 wt%), Nd-Y-rich bastnäsite-(La), and associated cerianite in parental granites from a HREE deposit, South China. The mineral contains high-HREE abundances (up to 13 wt% Y2O3). Synchrotron radiation-induced X‑ray diffraction and high-resolution transmission electron microscopy analyses suggest that the mineral grew as disordered nanocrystals and (nearly) coaligned nanoparticle aggregations, thus supporting "nonclassical" crystallization mechanisms by particle attachment under hydrothermal conditions. The nanocrystalline Ce-poor, Nd-Y-rich bastnäsite-(La) precipitated at rapidly decreasing temperature related to the influx of externally derived fluids, which caused CO2-H2O immiscibility and REE supersaturation. This interpretation is supported by petrographic data and microthermometric analysis of fluid inclusions in quartz. Unusually high fO2 resulted in Ce oxidation and decoupling from trivalent lanthanides, producing polycrystalline mineralization. [ABSTRACT FROM AUTHOR]

Osorno volcano (41°06'S, 72°20'W) is a composite stratovolcano of the Central Southern Volcanic Zone of the Chilean Andes. It is the southernmost member of a NE–SW trending alignment of volcanic edifices including La Picada and Puntiagudo volcanoes and the Cordón Cenizos chain. According to contemporary descriptions recorded by Charles Darwin in 1835, two eruptive events occurred: the first during January–February, and the second during November–December 1835 and January 1836. The volcano erupted basaltic andesite lavas and tephra fall deposits (52.4 to 52.9 SiO2 wt. %), which contain phenocrysts of olivine, plagioclase, clinopyroxene, and spinel. The compositions of these phenocryst phases, together with those of olivine-hosted melt inclusions, allowed us to constrain intensive parameters for the pre-eruptive magmas. These varied from 1060°C to 1140°C, with an oxygen fugacity buffer of ~ΔQFM +1.1, dissolved water concentrations of up to 5.6 wt. % (average of ~4.2 wt. %) and maximum pressures equivalent to ~7-km depth. Textural relations, such as crystal accumulations and clots, zoning in crystals and other indications of disequilibrium, lead us to infer the involvement of a crystal mush, rich in individual crystals and clots of crystals, which underwent a degree of disaggregation and entrainment into the transiting magma prior to eruption. Comparison of trace element abundances, including rare earth elements, fluid-mobile elements, and relatively fluid-immobile elements, combined with 87Sr/86Sr and 143Nd/144Nd isotope ratios, allows us to consider variations in slab-derived fluid input and the minor role of crustal contamination on the Osorno eruptive products and those from neighboring volcanic systems. Our results suggest both a greater contribution from slab-derived fluid and a higher degree of partial melting in the systems supplying stratovolcanoes (Osorno, Calbuco, and La Picada) relative to those supplying small eruptive centers built over the major regional Liquiñe-Ofqui Fault Zone. [ABSTRACT FROM AUTHOR]

We present a conceptually simple method to perform high-temperature experiments in a one-atmosphere box furnace that has a negligible cost of materials. The experimental setup consists of two commercially available materials and can be customized to sample or furnace size with few limitations. Furthermore, the design allows easy extraction of samples in one piece, making them eligible for textural analysis. The setup comprises a graphite capsule and a fireclay shell, the latter of which acts as a heat-resistant protective shield. Containers must be individually hand-crafted, but each can hold multiple samples. The setup can be reliably used in temperature conditions below the heat tolerance limit of the commercial fireclay, commonly ~1400 °C. Moreover, the graphite capsule buffers the oxygen fugacity to strongly reducing conditions during the experiment. The main advantage of our method lies in the utilization of easily accessible and low-cost materials that provides a widely applicable experimental setup easily used at larger scales. The method was developed during an experimental study of magmatic crystal-liquid suspensions and was reliable for experiments lasting for up to 36 h. [ABSTRACT FROM AUTHOR]

A set of 1-atm gas-mixing experiments (n = 31) was run using Re wire loops at low-oxygen fugacity (ƒO2, within one half-log unit of the Fe–FeO buffer) and temperatures of 1175–1400 °C to explore the compositional dependence of the Fe2+–Mg olivine–liquid exchange coefficient, K D , Fe 2 + - Mg ol / liq , under conditions where corrections for liquid Fe3+ are small. The bulk compositions used for these experiments include a picrite, a high-alumina basalt, and a suite of three MORB compositions with variable Fe/Mg. The K D , Fe 2 + - Mg ol / liq values from the n = 14 experiments run on pre-saturated Re wire loops were fit to a regular solution model that relates K D , Fe 2 + - Mg ol / liq to temperature, melt composition, and olivine composition. Fe2+–Mg exchange in the experiments is well-described using two parameters: the SiO2 content of the liquid and the coexisting olivine composition. Combining our experiments with a literature compilation of low-pressure, low-ƒO2 experiments (largely on non-terrestrial bulk compositions) produced a combined data set spanning a broad region of composition space (e.g., liquid TiO2 and Na2O + K2O contents up to 18.4 wt% and 8.4 wt%, respectively). Fitting this expanded experimental database required two additional liquid compositional terms: Ti, and a Si-(Na + K) cross-term. Because the Fe3+ content of all of the experimental liquids is low, the compositional variation seen in K D , Fe 2 + - Mg ol / liq is effectively independent of the compositional effects on liquid Fe3+/Fe2+ ratios. Given olivine–liquid Mg or Fe2+ partition coefficient information, it is possible to eliminate the explicit dependence of K D , Fe 2 + - Mg ol / liq on olivine composition, enabling a simple iterative approach for calculating the composition of coexisting olivine given only the bulk composition (and Fe3+/Fe2+ ratio) of an olivine-saturated liquid. [ABSTRACT FROM AUTHOR]

The Zuluhong quartz-vein-type polymetallic deposit, located in the Alatau area of Western Tianshan, China, is a particular and typical tungsten deposit associated with copper. This paper presents major and trace element analyses of magmatic and altered (i.e, chloritized) biotite from the deposit, in order to identify the source of the magmas and characterize the mineralization physical-chemical condition. Magmatic biotite is Fe-rich and has high Rb/Ba ratios (0.27–9.14), indicative of extensive differentiation of granite. Moreover, magmatic biotite has total rare earth element (∑REE) contents that are 5–10% of the whole-rock contents, shows slight light REE depletion, and negative Ce anomalies. Magmatic biotite is enriched in some large-ion lithophile elements (LILE; e.g., Rb and K) and depleted in some high-field-strength elements (HFSE; e.g., Th and Nb). These geochemical features, coupled with geological evidence, indicate that the Zuluhong intrusion is a highly fractionated I-type granite derived from lower crustal melting. During ore formation, magmatic biotite was partially to totally altered to chlorite due to interaction with ore-forming fluids. The temperature and oxygen fugacity decreased during alteration. The mineralization in the Zuluhong polymetallic deposit can be divided into at least two stages. In the early stage, quartz-vein-type wolframite mineralization formed from Si- and volatile-rich fluids that were derived from fractionated granitic magma. In the later stage, W–Cu ores formed as metal sulfides were dominated by chalcopyrite. The later ore-forming fluids experienced a decrease in temperature and oxygen fugacity as they reacted (i.e, chloritization and lesser silicification) with reducing wall rocks around the contact zone of the intrusion. [ABSTRACT FROM AUTHOR]

As part of the work the high-pressure sorptomat - a novel apparatus for sorption tests under conditions of high gas pressure was developed. The sorption measurement is carried out using the volumetric method, and the precise gas flow pressure regulator is used in the device to ensure isobaric conditions and regulate the sorption pressure in the range of 0-10 MPa. The uniqueness and high precision of sorption measurements with the constructed apparatus are ensured by the parallel use of many pressure sensors with a wide measurement range as well as high precision of measurement - due to the use of precise pressure sensors. The obtained results showed, i.a. that the time of reaching the isobaric conditions of the measurement is about 6-7 seconds and it is so short that it can be considered a quasi-step initiation of sorption processes. Moreover, the results of the measurement pressure stabilization tests, during the CO2 sorption test on activated carbon, have shown that the built-in pressure regulator works correctly and ensures isobaric sorption measurement conditions with the precision of pressure stabilization of ±1% of the measurement pressure. The maximum range of sorption measurement using the high-pressure sorptomat is 0-86 400 cm3/g, and the maximum measurement uncertainty is ±2% of the measured value. The activated carbon sample used for the tests was characterized by a high sorption capacity, reaching 104.4 cm³/g at a CO2 pressure of 1.0 MPa. [ABSTRACT FROM AUTHOR]

In this study, we use Cr-spinel as an efficient indicator to evaluate the oxygen fugacity evolution of the Xiarihamu Ni-Cu deposit and the Shitoukengde non-mineralized intrusion. Oxygen fugacity is calculated using an olivine-spinel oxybarometer, with spinel Fe3+/ΣFe ratios determined by a secondary standard calibration method using an electron microprobe. Cr-spinel Fe3+/ΣFe ratios of the Xiarihamu Ni-Cu deposit vary from 0.32 ± 0.09 to 0.12 ± 0.01, corresponding to magma fO2 values ranging from ΔQFM+2.2 ± 1.0 to ΔQFM-0.6 ± 0.2. By contrast, those of the Shitoukengde mafic-ultramafic intrusion increase from 0.07 ± 0.02 to 0.23 ± 0.04, corresponding to magma fO2 varying from ΔQFM-1.3 ± 0.3 to ΔQFM+1.0 ± 0.5. A positive correlation between fO2 and Cr-spinel Fe3+/ΣFe ratios suggests that the Cr-spinel Fe3+/ΣFe ratios can be used as an indicator for magma fO2. The high fO2 (QFM+2.2) of the harzburgite in the Xiarihamu Ni-Cu deposit suggests that the most primitive magma was characterized by relatively oxidized conditions, and then became reduced during magmatic evolution, causing S saturation and sulfide segregation to form the Xiarihamu Ni-Cu deposit. The evolution trend of the magma fO2 can be reasonably explained by metasomatism in mantle source by subduction-related fluid and addition of external reduced sulfur from country gneisses (1.08–1.14 wt% S) during crustal processes. Conversely, the primitive magma of the Shitoukengde intrusion was reduced and gradually became oxidized (from QFM-1.3 to QFM+1.0) during crystallization. Fractional crystallization of large amounts of Cr-spinel can reasonably explain the increasing magma fO2 during magmatic evolution, which would hamper sulfide precipitation in the Shitoukengde intrusion. We propose that the temporal evolution of oxygen fugacity of the mantle-derived magma can be used as one of the indicators for evaluating metallogenic potential of Ni-Cu sulfide deposits and the reduction processes from mantle source to shallow crust play an important role in the genesis of magmatic Ni-Cu sulfide deposits. [ABSTRACT FROM AUTHOR]

The North Qilian orogenic belt is a typical area of "cold" subduction of the early Paleozoic oceanic plate, forming a series of high pressure and low temperature metamorphic rock assemblages. Among them, eclogite is a kind of protolith, which is basaltic or gabbro high pressure metamorphic rock, mainly composed of garnet and chlorite which are two kinds of minerals. Eclogites record the entire history of subduction zone metamorphism and later exhumation. Due to the crystal habit and the developed joints, the strength of the pyroxene in the matrix is weak, so it is subjected to the main strain during deformation, whereas garnet tends to show only passive rotational deformation. This paper presents some new results in petrology and tectonic geophysics of eclogite block-like and planar eclogite. The massive and facial eclogite rocks contain eclogite facies mineral assemblages, and the peak temperature and pressure conditions are t = 450 ~ 520 °C and P = 1.9 ~ 2.3 GPa, which are consistent with the adjacent eclogite. Combined with the characteristics of in situ Lu-Hf isotopes, Ce4+/Ce3+ ratios of zircons, relative oxygen fugacity, and absolute oxygen fugacity, it is shown that the oxygen fugacity of the granodiorite porphyry (BL023, BLO31, DB048) of the folio chemical and massive eclogite deposits are all located in MH (magnetite-hematite) buffer zone. Through the calculation results of absolute oxygen fugacity of rock mass, it can be seen that the absolute oxygen fugacity of ore-bearing rock mass is significantly higher than that of non-ore-bearing rock mass. This paper systematically summarizes the research progress of the microscopic and ultrastructural deformation of eclogite minerals in high-pressure metamorphic zones, and discusses the changes of mineral composition, oxygen fugidity, and fabric of eclogite deformation characteristics during the recovery of subduction and reentry. [ABSTRACT FROM AUTHOR]

Ilmenite-, magnetite- and clinopyroxene−melt trace element partition coefficients were investigated experimentally as a function of oxygen fugacity and melt composition in a range of synthetic ferrobasaltic bulk compositions. The experiments were performed at a constant temperature (1080 °C) and pressure (1 atm) over a range of oxygen fugacity (fO2) conditions from ca. 2 log units below to ca. 2 log units above the FMQ buffer. The partitioning behaviour of the divalent cations Zn, Mn, Co and Ni are found to be controlled by the degree of polymerisation of the coexisting melt; the partitioning behaviour of rare earth elements, Y and Sc can be explained well by the lattice strain model and the partitioning of the high-field strength elements Zr, Hf, Ta and Nb is influenced by the TiO2 content of the melt. Vanadium partitioning is strongly influenced by oxygen fugacity and a series of linear regression equations are presented to express the dependence of the mineral−melt partitioning behaviour of the multivalent cation V on oxygen fugacity. Furthermore, calibration of the partitioning of vanadium between magnetite–ilmenite pairs as an oxybarometer is proposed and applied to a ferrobasaltic layered intrusion—the Skaergaard intrusion—to provide an estimate of oxygen fugacity. [ABSTRACT FROM AUTHOR]

Motivated by recent studies of supersymmetric black holes, we revisit the phase diagram of AdS black holes, whether BPS or not, with particular emphasis on the role of rotation. We develop BPS thermodynamics systematically and, in many explicit examples, we study its striking similarities with more familiar AdS black holes, as well as some differences. We highlight an important fugacity that preserves BPS saturation but is not captured by the supersymmetric index. [ABSTRACT FROM AUTHOR]

A membrane-based enthalpy exchanger is a device used for heat and humidity recovery in ventilated buildings. The energy-saving potential of such a device is dependent on the parameters responsible for heat and moisture recovery. The trend is toward composite membranes, which are custom produced, and their parameters can be adjusted for a given application; therefore, the diffusion and sorption characteristics of such membranes are unknown. In order to obtain the values of the water vapor diffusivity of three investigated handmade membranes, a serial resistance model using a Field and Laboratory Emission Cell (FLEC) is proposed. Experiments were conducted to identify the resistance in each step of the moisture transfer process to extract the moisture diffusivity in the membranes. The calculated moisture diffusivities in the membranes were 8.99 × 10−12 (m2/s) for the membranes from cellulose acetate, 1.9 × 10−10 (m2/s) for the microporous PE/PUR membranes, and 1.53 × 10−11 (m2/s) for the PET/PUR microfibrous membranes. The obtained membrane diffusivities were then used in the proposed effectiveness-NTU-based model of an exchanger with a cross-flow arrangement to predict performance under various operating conditions. The results show that the highest latent effectiveness was found for the exchanger core made from the PE/PUR membrane and the lowest was for the one with the PE/PUR membrane core. [ABSTRACT FROM AUTHOR]