H2O Content Research Articles

Barometers Behaving Badly II: a Critical Evaluation of Cpx-Only and Cpx-Liq Thermobarometry in Variably-Hydrous Arc Magmas

ABSTRACT The chemistry of erupted clinopyroxene crystals (±equilibrium liquids) have been widely used to deduce the pressures and temperatures of magma storage in volcanic arcs. However, the large number of different equations parameterizing the relationship between mineral and melt compositions and intensive variables such as pressure and temperature yield vastly different results, with implications for our interpretation of magma storage conditions. We use a new test dataset composed of the average Clinopyroxene-Liquid (Cpx-Liq) compositions from N = 543 variably hydrous experiments at crustal conditions (1 bar to 17 kbar) to assess the performance of different thermobarometers and identify the most accurate and precise expressions for application to subduction zone magmas. First, we assess different equilibrium tests, finding that comparing the measured and predicted Enstatite-Ferrosillite and KD (using Fet in both phases) are the most useful tests in arc magmas, whereas CaTs, CaTi and Jd tests have limited utility. We then apply further quality filters based on cation sums (3.95–4.05), number of analyses (N > 5) and the presence of reported H2O data in the quenched experimental glass (hereafter ‘liquid’) to obtain a filtered dataset (N = 214). We use this filtered dataset to compare calculated versus experimental pressures and temperatures for different combinations of thermobarometers. A number of Cpx-Liq thermometers perform very well when liquid H2O contents are known, although the Cpx composition contributes little to the calculated temperature relative to the liquid composition. Most Cpx-only thermometers perform very badly, greatly overestimating temperatures for hydrous experiments. These two findings demonstrate that the Cpx chemistry alone holds very little temperature information in hydrous systems. Most Cpx-Liq and Cpx-only barometers show similar performance to one another (mostly yielding root mean square errors [RMSEs] of 2–3.5 kbar), although the best Cpx-only barometers currently outperform the best Cpx-Liq barometers. We also assess the sensitivity of different equations to melt H2O contents, which are poorly constrained in many natural systems. Overall, this work demonstrates that Cpx-based barometry on individual Cpx only provides sufficient resolution to distinguish broad storage regions in continental arcs (e.g. upper, mid, lower crust). Significant averaging of Cpx compositions from experiments reported at similar pressures can reduce RMSEs to ~1.3–1.9 kbar. We hope our findings motivate the substantial amount of experimental and analytical work that is required to obtain precise and accurate estimates of magma storage depths from Cpx ± Liq equilibrium in volcanic arcs.

Revealing the link between A-type granites and hottest melts from residual metasedimentary crust

Abstract Among S-, I-, and A-type granites, the latter are the most debated in terms of origin, and metasedimentary crust is usually discarded as a potential source. Here we tackle this issue by adopting an in-source perspective, rather than focusing on the final product (granite), documenting the occurrence of pristine melt inclusions (MIs) in garnet from residual metapelitic ultrahigh-temperature (UHT) granulite from East Antarctica. Coexistence of sapphirine + quartz, phase equilibria calculations, and Zr-in-rutile thermometry indicate that MIs trapped UHT melts formed at peak conditions (930–1000 °C) from a residual metapelitic source. MIs are granitic with weakly peraluminous to weakly peralkaline affinity, ferroan character, high alkali contents, high K/Na and Ga/Al, and low Ca, Ba, Sr, and H2O concentrations. These features and geochemical modeling indicate that MIs represent primary melts for high-SiO2 A-type granites. Therefore, MIs reveal the missing link between A-type granites and the hottest metasedimentary crust. Voluminous amounts of slightly peraluminous, high-SiO2 A-type granites can be produced in large, residual UHT terranes such as those of eastern Gondwana. Our results provide a wider view of processes responsible for granite formation and show that a larger variety of granites must be considered in models of the effects of UHT anatexis on crustal differentiation.

Numerical research on ammonia-coal co-firing in a 1050 MW coal-fired utility boiler under ultra-low load: Effects of ammonia ratio and air staging condition

Co-firing ammonia (NH3) with coal for thermal power generation is a promising strategy for achieving global carbon neutrality. However, the drawbacks of NH3 combustion (e.g., narrow flammability limits, low theoretical flame temperature, high NOX emissions, etc.) can negatively impact the performance of coal-fired boilers, particularly for large-scale ones operating under ultra-low loads. As such, this study was conducted to investigate the ultra-low-load combustion characteristics of a 1050 MW coal-fired boiler when employing NH3-coal co-firing technology. Three-dimensional numerical simulations of ten combustion scenarios were performed to examine the effects of the NH3 co-firing ratio (ranging from 0% to 80%, by calorie) and air staging condition (Separated Over Fire Air (SOFA) ratio ranging from 4% to 24%) on temperature, gas species distributions, and emissions. Results show that as the NH3 co-firing ratio increases to 80%, the in-furnace average gas temperature decreases by 100 ∼ 200 K. The oxidation of NH3 takes precedence over the reduction of NO with NH3, leading to a surge in NO emissions· NH3 slip can be prevented at ultra-low loads due to the rapid consumption of NH3 near coal burners. Meanwhile, CO2 emissions reduce to 20% of that observed in pure coal firing. The increased H2O content in flue gas promotes coal burnout through the water–gas reaction, while the high H2O emissions may potentially cause low-temperature corrosion. At a SOFA ratio of 16%, a relatively large high-temperature region is achieved in the furnace, indicating more stable combustion under ultra-low loads. Excessively small or large SOFA ratios can reduce combustion intensity in the primary combustion zone while contributing to lower NO emissions.

Optimal Placement of Heat Exchangers in a Carbon Capture-Based Ventilation System

Achieving acceptable air quality levels in indoor spaces by regulating the concentrations of H2O and CO2 is important for occupant health. Conventional techniques rely on supplying dehumidified outdoor air to dilute these species to within their healthy ranges. Typically, the outdoor air dehumidification is conducted using vapor compression cooling either as standalone systems or integrated with desiccant dehumidifiers. These methods are known to be energy intensive, especially in hot and humid climates. Ventilation systems using indoor air with adsorption-based CO2 capture are thus proposed. These systems use adsorbent packed beds to dehumidify and decarbonize the indoor air before it is sensibly cooled and supplied to the space. For energy efficient operation of these systems, heat recovery units are necessary. In this work, heat and mass balance models were developed and used to determine the optimal placement location of the heat recovery units. It was found that a heat exchanger preceding the decarbonization bed increased the MOFs capacity, resulting in 33 % lower mass requirements. This was accompanied by a reduction in the thermal and electrical energy consumption by 43.5 % and 25 %, respectively, with respect to the configuration where the heat exchanger was placed after both air treatment systems.

Key Factors Controlling Biotite–Silicate Melt Nb and Ta Partitioning: Implications for Nb−Ta Enrichment and Fractionation in Granites

AbstractBiotite–melt Nb and Ta partition coefficients (DNb and DTa) are crucial for understanding Nb−Ta enrichment and fractionation in rare metal granites (RMGs). However, the key factor(s) affecting biotite–melt DNb, DTa, and DNb/DTa values remain unclear. To elucidate the physicochemical factors that control the partition coefficients, we performed piston−cylinder experiments at 0.5−1.0 GPa and 850−1000°C with H2O‐added (4−10 wt.%) mixtures of granitic and biotitic glasses as starting materials. Two series of experiments (graphite‐buffered and unbuffered fO2 conditions) were conducted with calculated fO2 values ranging from ∼FMQ–1.5 to ∼FMQ+4. Under these experimental conditions, biotite–melt DNb, DTa, and DNb/DTa values are 0.30–2.63, 0.24−1.02, and 1.01−2.15, respectively. Biotite–melt DNb, DTa, and DNb/DTa values increase with decreasing melt NBO/T value (non‐bridging oxygens per tetrahedron), melt H2O content, and biotite Mg#T value [molar 100 × MgO/(MgO + FeOT)]. In addition, DNb and DTa exhibit good correlations with DTi, suggesting that DNb and DTa are predictable via DTi values. With our and literature data, we used multiple linear regressions to obtain empirical expressions of DNb and DTa as functions of the three parameters. By applying the empirical models to granite differentiation process, we found that ∼99% crystallization of biotite ± muscovite‐bearing assemblages results in an enrichment in magma Ta contents by >10 times with a decrease in Nb/Ta values from 10−13 to ∼1, which reproduces the Ta–Nb/Ta features of most RMGs. However, additional processes, such as columbite‐group mineral precipitation, may be required to account for the extremely low Nb/Ta values (<1) of some RMGs.

The effect of coating concentration of curcumin: H2O on copper winding characteristics

Each coil of copper produces a magnetic field and the total field inside the solenoid will be the sum of the fields caused by each coil of current. If the solenoid coils are very closely spaced, the internal field will be essentially parallel to the axis except at the very ends. To find out the magnitude of the magnetic field inside the solenoid, you can use Ampere’s law, namely B=μo∙N∙I, where B is the magnetic field strength (T), µo is air permeability (4×10‒7 T m/A), N is the number of turns and I is an electric current. The value of B depends on the number of turns per unit length, N, and current I. The field is independent of the position inside the solenoid, so the value of B is uniform. This only applies to infinite solenoids, but is a good approximation for actual points that are not near the ends of the solenoid. The research object is 4 identical copper coils with a length of 3 cm, a coil diameter of 2 cm, a cross section of 1.5 mm2 with an inductance value of 2.17 µH. Before coating curcumin on the copper winding, the initial value of the magnetic field strength was 2.54 µTesla. After the coating process of curcumin:H2O concentration, the value of the magnetic field strength increased. The method used was immersing 4 copper coils with an inductance value of 2.17 µH in curcumin:H2O concentration in a 100 ml volume measuring cup, with the respective concentrations: (20 %:80 %), (40 %:60 %), (60 %:40 %), (80 %:20 %) in a certain time. Then the copper coil conductor is supplied with a 5-volt DC voltage source. Then the value of the magnetic field strength (B) and electric current is measured, the results are compared with the system before immersing the copper coil. The measurement results showed that the values of electric current and magnetic field strength increased after curcumin coating compared to before treatment. To see the bonding performance of curcumin and copper, the FTIR test and simulation of the curcumin: copper bond were carried out using Avogadro software. In the IR test, there is a strong absorption of aromatic C-C from 1,650 cm-1 to 1,500 cm-1. Whereas in the simulation, the bond between copper and curcumin produces a bond energy of 164.532 kJ/mol or equivalent to 171.12×10-2 eV

Effects of H2O–CO2 Fluids, Temperature, and Peridotite Fertility on Partial Melting in Mantle Wedges and Generation of Primary Arc Basalts

Abstract Many lines of evidence from high P–T experiments, thermodynamic models, and natural observations suggest that slab-derived aqueous fluids, which flux mantle wedges contain variable amounts of dissolved carbon. However, constraints on the effects of H2O–CO2 fluids on mantle melting, particularly at mantle wedge P–T conditions, are limited. Here, we present new piston cylinder experiments on fertile and depleted peridotite compositions with 3.5 wt.% H2O and XCO2 [= molar CO2 / (CO2 + H2O)] of 0.04–0.17. Experiments were performed at 2–3 GPa and 1350°C to assess how temperature, peridotite fertility, and XCO2 of slab-derived fluid affects partial melting in mantle wedges. All experiments produce olivine + orthopyroxene +7 to 41 wt.% partial melt. Our new data, along with previous lower temperature data, show that as mantle wedge temperature increases, primary melts become richer in SiO2, FeO*, and MgO and poorer CaO, Al2O3, and alkalis when influenced by H2O–CO2 fluids. At constant P–T and bulk H2O content, the extent of melting in the mantle wedge is largely controlled by peridotite fertility and XCO2 of slab-fluid. High XCO2 depleted compositions generate ~7 wt.% melt, whereas, at identical P–T, low XCO2 fertile compositions generate ~30 to 40 wt.% melt. Additionally, peridotite fertility and XCO2 have significant effects on peridotite partial melt compositions. At a constant P–T–XCO2, fertile peridotites generate melts richer in CaO and Al2O3 and poorer in SiO2, MgO + FeO, and alkalis. Similar to previous experimental studies, at a constant P–T fertility condition, as XCO2 increases, SiO2 and CaO of melts systematically decrease and increase, respectively. Such distinctive effects of oxidized form of dissolved carbon on peridotite partial melt compositions are not observed if the carbon-bearing fluid is reduced, such as CH4-bearing. Considering the large effect of XCO2 on melt SiO2 and CaO concentrations and the relatively oxidized nature of arc magmas, we compare the SiO2/CaO of our experimental melts and melts from previous peridotite + H2O ± CO2 studies to the SiO2/CaO systematics of primitive arc basalts and ultra-calcic, silica-undersaturated arc melt inclusions. From this comparison, we demonstrate that across most P–T–fertility conditions predicted for mantle wedges, partial melts from bulk compositions with XCO2 ≥ 0.11 have lower SiO2/CaO than all primitive arc melts found globally, even when correcting for olivine fractionation, whereas partial melts from bulk compositions with XCO2 = 0.04 overlap the lower end of the SiO2/CaO field defined by natural data. These results suggest that the upper XCO2 limit of slab-fluids influencing primary arc magma formation is 0.04 < XCO2 < 0.11, and this upper limit is likely to apply globally. Lastly, we show that the anomalous SiO2/CaO and CaO/Al2O3 signatures observed in ultra-calcic arc melt inclusions can be reproduced by partial melting of either CO2-bearing hydrous fertile and depleted peridotites with 0 < XCO2 < 0.11 at 2–3 GPa, or from nominally CO2-free hydrous fertile peridotites at P > 3 GPa.

Performance of high-frequency spark discharge for efficient NOx production with tunable selectivity

Plasma-based NOx synthesis from ambient air is a promising sustainable technology for producing value-added chemicals, such as nitrogen fertilizer and medication. The relatively low efficiency and product selectivity are major concerns that hinder the commercialization of this technology. Despite advancements in reducing energy costs, limited attention has been paid to improving and controlling selectivity, which significantly contributes to the overall cost. Thus, the present study aimed to gain insights into the efficient pathways and key factors for highly selective NOx synthesis in a recently developed high-frequency spark discharge (HFSD) reactor. The thorough investigations conducted proved that the higher energy efficiency of HFSD is due to higher vibrational and rotational excitations and their efficient utilization. However, the significant impact of higher temperatures on reactions led to poor selectivity of NO and NO2. Therefore, the role of influential factors, such as O2 and H2O contents, as well as residence time, on reactions, were analyzed and optimized. It is found that controlling the oxygen content remarkably improved product selectivity but negatively affected the energy cost. Moreover, water vapor triggered the so-called extended Zeldovich mechanism, which was evident in N2/H2O, affecting NOx formation and selectivity. Interestingly, tuning the gas flow rate effectively controlled selectivity without sacrificing the energy cost. A high NO selectivity of 95% was achieved at an energy cost of 2.1 MJ/mol when a relatively high flow rate of 4 L/min was used.

Fluid migration along deep‐crustal shear zone: A case study of the Rhenosterkoppies Greenstone Belt in the northern Kaapvaal Craton, South Africa

The north‐dipping Hout River Shear Zone (HRSZ), which marks the boundary between the high‐grade Limpopo Complex in its hanging wall and the low‐grade granite‐greenstone terrane of the Kaapvaal Craton in South Africa in its footwall, is a deep‐crustal shear zone that controlled emplacement of hot Limpopo Complex granulites over and against low‐grade granite‐greenstones during exhumation at ~2.72–2.62 Ga. This major shear zone controlled migration of large volumes of hydrous fluids released during devolatilization of underthrusted greenstones that infiltrated into hot overlying granulites, establishing a retrograde anthophyllite‐in isograd and associated zone of retrograde rehydrated granulite that bounds the Limpopo Complex in the south. Here, we report new petrological data based on mineral equilibrium modelling of amphibolites from the Rhenosterkoppies Greenstone Belt (RGB) located in the immediate footwall of the HRSZ and discuss evidence that these rocks also interacted with high‐temperature fluids that infiltrated along the HRSZ. This study provides an important perspective of the interaction of hot granulites with underthrusted relatively cold greenschist‐facies rocks along the steeply north‐dipping section of the HRSZ, and shows that evidence for such interaction is restricted to a relatively narrow zone in the footwall of the HRSZ termed a hot‐iron‐zone. The peak mineral assemblage of a garnet‐free amphibolite from the RGB (magnesio‐hornblende + plagioclase + quartz + clinopyroxene + titanite + ilmenite) yielded the peak P–T condition of 7–8 kbar and 640–680°C with H2O content of 3.5–3.8 mol%. Clinopyroxene is replaced by actinolite + quartz and epidote + quartz symplectites by a post‐peak hydration event at <5 kbar and <590°C caused by elevated H2O content in the rock (>4.0 mol%), possibly related to fluid infiltration along the HRSZ. Mineral equilibria in a garnet‐bearing amphibolite records a prograde path from 5 to 7 kbar and 540–630°C to the peak conditions at 7.6–8.7 kbar and 620–650°C. A clockwise P–T path suggesting rapid compression and decompression has been inferred for the amphibolites from the RGB, possibly because of pressure increase related to overthrusting of the high‐grade terrane (Southern Marginal Zone of the Limpopo Complex) onto the low‐grade granite‐greenstone terrane, followed by rapid exhumation. The quantity of H2O associated with the amphibolite‐facies metamorphism in the RGB was elevated from the peak stage (M(H2O) = 3.5–3.8 mol%) to the retrograde stage (M(H2O) = 4.0–4.5 mol%) of metamorphism in the RGB, possibly suggesting fluid infiltration not only from internal sources but also from external sources. The results of this study indicate that a H2O‐bearing fluid, which infiltrated along the HRSZ, affected both the footwall and the hanging wall sections of the shear zone, although the effect on the footwall section was limited.

A laser absorption sensor for fuel slip monitoring in high-humidity flue gases from ammonia combustion

Ammonia has been recently recognized as a promising carbon-free fuel to help decarbone both the power and industrial heating sectors. However, fuel slip during ammonia combustion is of high concern because of the high toxicity of the chemical, motivating the development of sensitive sensors for real-time monitoring of ammonia emission in combustion flue gases. In this work, a near-infrared absorption spectroscopic sensor was developed for trace ammonia (NH3) measurements in high-humidity flue gas environments with water vapor (H2O) mole fractions up to 40%. The focus on high humidity is motivated by the facct that ammonia combustion generally leads to flues gases with notably higher water vapor concentations as compared to conventional hydrocarbons. The sensor used a distributed feedback laser to target the NH3 absorption line near 6612.73 cm−1. Proof-of-concept tests were conducted in a high-temperature multi-pass cell with a controlled temperature of 500 K and pressure of 1 atm. A custom-designed variable humidity generator was used to provide a reference NH3/N2 mixture with a controlled H2O mole fraction (10%–40%) to simulate ammonia combustion flue gases. Direct absorption spectroscopy and wavelength modulation spectroscopy were both used to ensure a relatively large dynamic range. H2O-induced broadening effects on the measured absorption profile were quantified. The developed sensor was firstly validated against NH3/N2 mixtures with different H2O concentrations, with a lower detection limit of 76 ppb achieved. Real-time measurements of NH3 slip in the flue gases from CH4/NH3/air flames and CH4/NH3 co-firing industrial furnace were performed as a demonstration of the sensor for time-resolved ammonia monitoring with sufficient accuracy, sensitivity, and time response.

Determining the impact of magma water contents on porphyry Cu fertility: Constraints from hydrous and nominally anhydrous mineral analyses

Most large-scale porphyry-style mineralization is genetically associated with oxidized, sulfur-rich, and hydrous magmas, the sources of which were enriched in mantle-derived or juvenile crust−derived materials. Geochemical indices for these features can distinguish fertile magmas and barren magmas. However, fertile magmas that generate different-sized porphyry deposits are usually geochemically indistinguishable, and the factors controlling the size of porphyry mineralization are poorly understood. Here, we used zircon H2O contents and the compositions of apatite hosted in zircon, phenocrysts, and groundmass to compare the water contents and volatile evolution of fertile magmas in the Yulong ore belt, Tibet, which generated giant-, large-, and medium-sized porphyry deposits. We found that these porphyries have comparable major- and trace-element and zircon Hf-O isotope compositions, with high oxygen fugacity and sulfur contents. A negative correlation between [see PDF for equation] versus [see PDF for equation] of apatites suggests that the magmas consistently achieved H2O saturation before zircon crystallization, and zircon hydroxyl contents reveal that the water contents of the melt positively correlate with the size of the deposits, consistent with larger deposits achieving H2O saturation at deeper crustal levels. The deeper H2O saturation also caused larger amounts of Cl extraction, as indicated by the trends of increasing [see PDF for equation] and decreasing [see PDF for equation] with larger deposit sizes. These data sets can be reconciled by magmas forming larger deposits having higher H2O contents and suggest that the H2O content is a key control on their fertility. Our study highlights the utility of integrated hydrous and nominally anhydrous mineral analyses for constraining enigmatic magmatic volatile processes in magmatic ore-forming systems.

Aluminum-induced structure evolution and mechanical strengthening of calcium silicate hydrates: an atomistic insight

How Al3+ dissolved from supplementary cementitious materials influences the performance of cement paste is far from being fully understood, especially from an atomistic insight. Herein, Al3+ is introduced into calcium silicate hydrate (CSH, the main phase of cement paste) to evaluate its effect using atomistic simulation. Structurally, Al3+ heals defects in the silicate chains, forms cross-links between calcium aluminosilicate layers, and reduces interlayer space and H2O content. The chemical stability of interlayer H-bonds and Ca-O bonds is also improved. The diffusion of the interlayer H2O and Ca2+ is decelerated, attributed to Al-induced channel blocking and stronger interfacial adhesion with the calcium silicate layers. Mechanically, the Al-induced chain bridging enhances the load-bearing capacity of aluminosilicate chains along y direction, resulting in ∼ 57.1% and ∼ 100.4% enhancement of Young’s modulus and tensile strength. In z direction, the cross-links provide ultra-strong connections between the layers by raising Young’s modulus and strength by ∼ 4 and ∼ 6 times. This study provides profound guidance for future design of environmental-friendly cement with promising mechanical properties and durability.

Impacts of iron on ultrastructural features of NCI-H295R cell line related to steroidogenesis

The current study was intended to evaluate impacts of both iron (Fe) enrichment and overload (in the form of ferrous sulphate heptahydrate, FeSO4.7H2O) on ultrastructural characteristics of human adrenocarcinoma NCI-H295R cell line. Here, the NCI-H295R cells were treated with 0, 3.90, and 1000 µM FeSO4.7H2O, and consequently proceeded for purposes of ultrastructural studies. Micrographs taken under transmission electron microscope (TEM) were investigated from the qualitative and quantitative (unbiased stereological approaches) aspects, and obtained findings were compared among the three groups of the cells. The ultrastructural features related to the steroidogenic process were found to be similar between the untreated and both Fe-exposed cell populations, with conspicuous mitochondria with well-defined lamellar cristae (creating clusters of varying sizes in the regions of increased energy demands) and concentric whorls of smooth endoplasmic reticulum (SER) being the most noticeable characteristics. The precise estimates of the component (volume, surface) fractions of the nucleus, mitochondria, and lipid droplets (LDs), as well as of the nucleus/cytoplasm (N/C) ratio have revealed close similarities (P > 0.05) in all cell groups investigated. Nonetheless, the low concentration of FeSO4.7H2O exhibited beneficial action on ultrastructural organization of the NCI-H295R cells. In effect, these cells were distinguished by mitochondria with smoother surfaces and clearer outlines, higher density of thin, parallel lamellar cristae (deeply extending into the mitochondrial matrix), and more widespread distribution of fine SER tubules as compared to the control ones, all of them suggesting higher level of energy requirements and metabolic activity, and more intensive rate of steroidogenesis. Interestingly, no obvious ultrastructural modifications were observed in the NCI-H295R cells treated with high FeSO4.7H2O concentration. This finding can be linked to either an adaptive ultrastructural machinery of these cells to cope with the adverse effect of the element or to insufficient dose of FeSO4.7H2O (1000 µM) to induce ultrastructural signs of cytotoxicity. Purposefully, the results of the current study complement our previous paper dealing with impacts of FeSO4.7H2O on the NCI-H295R cell viability and steroidogenesis at the molecular level. Hence, they fill a knowledge gap considering structure-function coupling in this cellular model system upon the metal exposure. This integrated approach can enhance our understanding of the cellular responses to Fe enrichment and overload which can be helpful for individuals with reproductive health concerns.

Magmatic evolution in an open and polybaric system feeding the Miocene calcalkaline lava domes of Cixerri (SW Sardinia, Italy)

The lava domes of the Cixerri half-graben (SW Sardinia) are part of the subduction-related igneous activity that developed in Sardinia during the Upper Eocene-Middle Miocene (38–12 Ma), with calcalkaline and high-K calcalkaline affinity. The investigated rocks are porphyritic basaltic andesites and andesites, with amphibole, plagioclase and minor clinopyroxene phenocrysts included in a groundmass composed of the same phases together with feldspar, quartz and opaque oxides. 40Ar/39Ar analyses of plagioclase and amphibole separates from an andesite indicate a crystallization age of 21.31 ± 0.05 Ma. The high abundance of amphibole in the Cixerri rocks, unlike andesites from the neighboring Sardinian districts, could be explained with the high calculated oxygen fugacity (NNO+1–NNO+2) and H2O content (up to 9 wt%) in the Cixerri magmas. Bulk-rock major and trace element variations, and mass balance calculations are consistent with a magma evolution mainly driven by fractional crystallization of amphibole and plagioclase, which occurred in a polybaric plumbing system, as highlighted by the calculated pressure of amphibole crystallization (2–4 kbar and 6–9 kbar). Bulk rock isotope variations (87Sr/86Sri = 0.70701–0.70786 and 143Nd/144Ndi = 0.512328–0.512436) indicate that the magma evolution took place in open-system conditions with a low degree of crustal assimilation. The HREE flat patterns point to a magma source in the spinel stability field located in a mantle wedge depleted in incompatible elements and metasomatized by slab and sediment derived fluids and melts.

Open-system differentiation of mafic magmas before the formation of layered Fe-Ti(V) deposits in Southeast China

Mafic magmatic differentiation is an important mechanism to drive Fe-Ti enrichments in melt and final formation of layered Fe-Ti-(V) oxide deposits, but how the differentiation operates and how the state of magmatic reservoirs controls differential metallogenic potential are unclear. The Xialan magmatic complex in northern Guangdong Province is the only complex hosting layered Fe-Ti (V) deposits in Southeast China and the formation of such oxide deposits is not addressed in detail. Here, we present an integrated study of geochronology, mineral geochemistry, whole-rock major and trace elements, as well as Sr-Nd-Pb isotopes, on the mafic rocks associated with the Xialan layered Fe-Ti (V) oxide deposits. The investigated mafic rocks are cogenetic and can be classified into three types according to field and textural features: diabase, Fe-Ti rich gabbro, and Fe-Ti barren gabbro. Based on petrographic observation and major and trace element geochemistry, the gabbros and diabases represent cumulates and residual melts, respectively. However, the Fe-Ti rich gabbros show different Nd isotopes from the other rocks, which indicates an open-system differentiation for the Xialan parental magma. A two-stage evolution process for the Xialan parental magma before the final crystallization fractionation to form the oxide deposits is further proposed based on MELTs modeling results and the characters of mineral assemblages. At the early stage, the magmas started differentiation with 0.5 wt% initial H2O content and moderate oxygen fugacity (△FMQ = ca. + 0.5 – +1.5) at 5 kbar and generated Fe-Ti enriched melts. At the later stage, the Fe-Ti rich melts gradually evolved to a much higher H2O content (>3 wt%), which stabilized the Fe-Ti oxides and hornblendes. Wall-rock assimilation during the late-stage magma evolution is suggested to be the key factor to elevate the H2O contents and oxygen fugacity of the magma which finally produced the layered Fe-Ti oxides. As such, this study demonstrates that open-system differentiation of mafic magmas can play a key role in the final generation of some hornblende-bearing layered Fe-Ti oxide deposits.

The estimated water content of the Abaga basalts (Inner Mongolia, China) and compositions of the recycled materials in the source: Implication for magma genesis

The Abaga volcanic rocks are intraplate basalts that formed in the late Cenozoic period and are located in eastern central Inner Mongolia. Previous studies have discussed the genesis of the studied basalts. However, limited information about subducted recycled materials (the water content, sediments, and melts of the subducted plate), which control the generation of basalts, in the studied basalts has been reported. In this study, the major element abundances and crystallization temperatures and pressures of clinopyroxenes have been reported to estimate the water content of the studied magma, which has been applied to the Wulanhada volcanic field. The calculated result displays that the water content in the Abaga melts are between 0.5% and 1.7% (standard error estimate: 0.45%; average value: 1.3%). These estimated values are in range of the Aershan–Chaihe basalts (0.19–2.7%), while it is higher than those of the mid-ocean ridge basalts (MORBs: 0.16–0.47%). The high-water content of the studied basalts may have a close relationship with the mantle transition zone, which has also been reported to contain high concentrations of H2O. Subduction related sediments and slab may contribute to high-water content of magma. In addition, the clinopyroxene-melt thermobarometer shows that clinopyroxenes generally crystallized at 1113–1246 °C at the crustal level (3.8–12.4 kbar), while olivines formed at 1243–1392 °C (assuming pressure is 13 kbar, H2O = 1.3%). We also studied whole-rock major and trace elements and Sr–Nd–Hf–O isotope compositions of the Abaga basalts. High (Ta/U)N and (Nb/Th)N values that are higher than 1, NdHf isotopic values that plot between sediments and oceanic crust, and low δ18O values (4.51–5.59‰) of the alkali basalts illustrate that a subducted oceanic slab may have been added to the studied mantle source. In addition, we decipher that sediments may also exist in the source with Ba/Th, Nb/La, Ce/Pb and Ba/La ratios and NdHf isotopic values locating between sediments and altered oceanic crust. We use sediments, depleted MORB mantle (DMM), and recycled oceanic crust to simulate mixing features among these endmembers, which demonstrates that 80% of depleted MORB mantle, 15% of altered oceanic crust, and 5% of global subducting sediment (GLOSS), with 4–5% partial melting of peridotite or pyroxenite is a proper result with which to interpret the genesis of the studied alkali basalts.

Time-resolved multi-parameter detection in a kerosene-fueled combustor using tunable diode laser absorption spectroscopy

Non-contact and real-time measurements for species concentration and temperature with high-time resolution in practical combustion environments are desired. A laser absorption system was developed for simultaneous sensing of CO, H2O concentrations and temperature with 1 kHz in a centrally staged kerosene-fueled combustor. An absorption feature near 4.98 μm in the mid-infrared region was selected for CO detection to minimize spectral interference with other combustion species in the kerosene combustion environment. Two spectral lines of H2O near 1.4 μm were used for temperature and H2O detection using a direct scan absorption strategy. The method of the developed multi-parameter measurement was validated in a laboratory-scale flat flame under various equivalence ratios. Comparisons were made between the experimental and theoretical results within the error of 5%. Time-resolved and in-situ measurements of temperature, H2O and CO concentration in the practical kerosene-fueled staged combustor were demonstrated. The transient characteristics of CO emission in different conditions were captured experimentally. It is found that the fluctuation amplitude of CO concentration increases as the equivalence ratio decreases during the pilot stage work only. There is a dramatic rise in CO emissions during the transition of combustion conditions. Strong fluctuation occurs with a low frequency at 32 Hz near lean blowoff. The location of the flame surface and the dynamic pressure have a significant coupling relationship with CO emission by analyzing measured data with high time resolution simultaneously.

Investigation of Conditions for Preparation of Ordered Nanohole Arrays by Anodization of Iron Substrates with Depression Patterns

Ordered iron oxide nanohole arrays were fabricated by the anodization of iron substrates with depression patterns formed by Ar ion milling with alumina masks in an ethylene glycol electrolyte containing NH4F and H2O. It was found that the optimization of anodization voltage, NH4F and H2O concentrations in the electrolyte, and electrolyte temperature is necessary to achieve straight pore growth induced from the depression patterns in the depth direction. The optimization of the anodization conditions enabled the formation of ordered iron oxide nanohole arrays with aspect ratios exceeding 10. The resulting ordered iron oxide nanohole arrays with high aspect ratios are expected to be applied to various functional devices such as photocatalysts and solar cells.

Assessment of vibrational-translational relaxation dynamics of methane isotopologues in a wet-nitrogen matrix through QEPAS

Here we report on a study of the non-radiative relaxation dynamic of 12CH4 and 13CH4 in wet nitrogen-based matrixes by using the quartz-enhanced photoacoustic spectroscopy (QEPAS) technique. The dependence of the QEPAS signal on pressure at fixed matrix composition and on H2O concentration at fixed pressure was investigated. We demonstrated that QEPAS measurements can be used to retrieve both the effective relaxation rate in the matrix, and the V-T relaxation rate associated to collisions with nitrogen and water vapor. No significant differences in measured relaxation rates were observed between the two isotopologues.

Are We Recording? Putting Embayment Speedometry to the Test Using High Pressure‐Temperature Decompression Experiments

AbstractDespite its increasing application to estimate magma decompression rates for explosive eruptions, the embayment speedometer has long awaited critical experimental evaluation. We present the first experimental results on the fidelity of natural quartz‐hosted embayments in rhyolitic systems as recorders of magma decompression. We conducted two high pressure‐temperature isobaric equilibrium experiments and 13 constant‐rate, continuous isothermal decompression experiments in a cold‐seal pressure vessel where we imposed rates from 0.005 to 0.05 MPa s−1 in both H2O‐saturated and mixed‐volatile (H2O + CO2)‐saturated systems. In both equilibrium experiments, we successfully re‐equilibrated embayment melt to new fluid compositions at 780°C and 150 MPa, confirming the ability of embayments to respond to and record changing environmental conditions. Of the 32 glassy embayments recovered, seven met the criteria previously established for successful geospeedometry and were thus analyzed for their volatile (H2O ± CO2) concentrations, with each producing a good model fit and recovering close to the imposed decompression rate. In one H2O‐saturated experiment, modeling H2O concentration gradients in embayments from three separate crystals resulted in best‐fit decompression rates ranging from 0.012 to 0.021 MPa s−1, in close agreement with the imposed rate (0.015 MPa s−1) and attesting to the reproducibility of the technique. For mixed‐volatile experiments, we found that a slightly variable starting fluid composition (2.4–3.5 wt.% H2O at 150 MPa) resulted in good fits to both H2O + CO2 profiles. Overall our experiments provide confidence that the embayment is a robust recorder of constant‐rate, continuous decompression, with the model successfully extracting experimental conditions from profiles representing nearly an order of magnitude variation (0.008–0.05 MPa s−1) in decompression rate.