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Abstract Largescale volcanic eruptions and earthquakes are occurring frequently in the Philippines, and research has shown that slab metamorphism and diversity alter the impacts of subducted oceanic plates by changing water‒carbon productivity and interplate stability. Within the framework of the thermal evolution history of subducting slabs, the relationships between subduction zone seismicity characterized by both regular megathrust earthquakes and slow slip events of various magnitudes and long-term slab dehydration–decarbonation evolution in the Philippines remain poorly understood. Here, we constructed a comprehensive thermal model incorporating 3-D slab geometric data for the incoming plate and a 3-D subduction velocity field based on the MORVEL plate motion dataset for the Philippine subduction zone with high spatial and temporal resolutions. Our findings reveal that subduction seismicity and arc volcanism are prominent in belt-shaped regions with high thermal gradients (> 5 °C/km) and large-scale slab dehydration (> 0.05 wt%/km). Dehydration of serpentinite in ultramafic rocks in the subducting slab and decarbonation of carbonate minerals preferentially contribute to the generation and transport of fluids and carbonate melts, thus facilitating seismicity and carbon-rich magmatism. Our results suggest that slab geometry diversity-induced juxtaposed slab dehydration-decarbonation processes play a vital role in the generation of megathrust earthquakes below the forearc.

Largescale volcanic eruptions and earthquakes are occurring frequently in the Philippines, and research has shown that slab metamorphism and diversity alter the impacts of subducted oceanic plates by changing water‒carbon productivity and interplate stability. Within the framework of the thermal evolution history of subducting slabs, the relationships between subduction zone seismicity characterized by both regular megathrust earthquakes and slow slip events of various magnitudes and long-term slab dehydration–decarbonation evolution in the Philippines remain poorly understood. Here, we constructed a comprehensive thermal model incorporating 3-D slab geometric data for the incoming plate and a 3-D subduction velocity field based on the MORVEL plate motion dataset for the Philippine subduction zone with high spatial and temporal resolutions. Our findings reveal that subduction seismicity and arc volcanism are prominent in belt-shaped regions with high thermal gradients (> 5 °C/km) and large-scale slab dehydration (> 0.05 wt%/km). Dehydration of serpentinite in ultramafic rocks in the subducting slab and decarbonation of carbonate minerals preferentially contribute to the generation and transport of fluids and carbonate melts, thus facilitating seismicity and carbon-rich magmatism. Our results suggest that slab geometry diversity-induced juxtaposed slab dehydration-decarbonation processes play a vital role in the generation of megathrust earthquakes below the forearc. [ABSTRACT FROM AUTHOR]

The use of environmental protection policies has developed considerably over the last two decades and has generated a prolific literature. This study examines the impact of environmental policies on environmental quality for a panel of 36 OECD countries over the period from 1994 to 2018. To do this, we use matching and double‐difference methods. This enabled us to find a causal link between the environmental tax and CO2 emissions in the manufacturing and transport sectors. Furthermore, by estimating our model using fixed effects techniques, Driscoll and Kraay, Lewbel 2SLS and Quantiles, we obtained the result demonstrating that the environmental tax contributes to reducing CO2 emissions from the transport and manufacturing sectors. On the basis of these results, we suggest that taxes should be strengthened quantitatively and qualitatively in order to better target sectors known to be highly polluting. [ABSTRACT FROM AUTHOR]

Heat is involved in many processes in the food industry: drying, dissolving, centrifugation, extraction, cleaning, washing, and cooling. Heat generation encompasses nearly all processes. This review first presents two representative case studies in order to identify which processes rely on the major energy consumption and greenhouse gas (GHG) emissions. Energy-saving and decarbonating potential solutions are explored through a thorough review of technologies employed in refrigeration, heat generation, waste heat recovery, and thermal energy storage. Information from industrial plants is collected to show their performance under real conditions. The replacement of high-GWP (global warming potential) refrigerants by natural fluids in the refrigeration sector acts to lower GHG emissions. Being the greatest consumers, the heat generation technologies are compared using the levelized cost of heat (LCOH). This analysis shows that absorption heat transformers and high-temperature heat pumps are the most interesting technologies from the economic and decarbonation points of view, while waste heat recovery technologies present the shortest payback periods. In all sectors, energy efficiency improvements on components, storage technologies, polygeneration systems, the concept of smart industry, and the penetration of renewable energy sources appear as valuable pathways. [ABSTRACT FROM AUTHOR]

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[Display omitted] • Decarbonation of skarn deposits was more efficient than other carbon sources. • Skarn deposits may have contributed to the rise of CO 2 concentration at 145 Ma. • Skarn deposits may have influenced the ecological system in East Asia. Magmatic-hydrothermal systems transport metal, sulfur, and carbon from deep to shallow crust, providing materials to the society and potentially affecting Earth's long-term environment. The fluxes of elements and, accordingly the environmental effects, are ultimately functions of the time-integrated amounts and durations of magmatic-hydrothermal system. In this study, we calculate the duration of prograde metamorphism induced by fluid infiltration and amount of carbon released by skarn ore deposits. This study finds that skarn ore deposits can decarbonize CO 2 at an efficiency up to 1014 g/(y.km3), which is much higher than volcanism on different tectonic settings. The CO 2 flux of skarn deposits increased from late Jurassic to early Cretaceous and reached a maximum value to 7.8 Mt/y at J/K boundary. Our finding provided an previously unquantified but important outgassing source in the subduction zone. This result consistent with global warming pattern based on global sedimentary records. The maximum outgassing at J/K boundary may have important impact on global warming and perhaps mass extinction. [ABSTRACT FROM AUTHOR]

The purpose of this study was to examine the effects of environment-conscious information about goods and showcase in commercial environment on forming an intention for environment-conscious behavior. Questionnaire survey was carried out with 60 university students divided the perspectives of customers (in Experiment 1) or store employees (in Experiment 2). The results indicate that participants viewed their purchasing and working behaviors as environmentally conscious behaviors. The presentation of information about environmentally conscious goods and showcase influenced forming a specific intention of environmentally conscious behavior, from both consumer and employee perspectives. Additionally, information about the environmentally conscious of showcase influenced forming a general goal intention of environmentally conscious behavior in both perspectives, as well as a specific intention of environmentally conscious behavior from the employee perspective. However, information about the environmentally conscious of goods didn't influence forming a specific intention of environmentally conscious behavior from either perspective. [ABSTRACT FROM AUTHOR]

Aqueous fluids are essential to extract slab‐trapped carbon at forearc to subarc depths and interpret the decarbonation efficiency of global subduction zones. A large amount of carbon survives beyond subarc depths. The behavior of such carbon, however, remains unclear owing to a lack of experimental studies. Here, we investigate the decarbonation behavior of carbonated oceanic crust containing different amounts of H2O at pressures from subarc depths to the top of the mantle transition zone. We find that calcium‐rich carbonatitic liquids can form at temperatures of ∼950–1,150°C at depths below ∼150–300 km, corresponding to warm/cold thermal regimes in most subduction zones. Therefore, hydrous carbonatitic liquids should be pervasive in subduction zones, while extensive dehydration reactions and fluid activities are critical for creating carbonatitic liquids and preventing most of the surviving carbon from being subducted into the deep Earth. Plain Language Summary: The deep recycling of CO2 and H2O in subduction zones is key for understanding the habitability and climate change of Earth. Here, we use a high‐pressure and high‐temperature instrument, the multi‐anvil press, to investigate the fate of subducted carbon in oceanic crust. We find that H2O can depress the decarbonation temperature of subducted oceanic crust by hundreds of °C. Most of the surviving carbon that descends to depths below ∼150 km may be released into the upper mantle by hydrous carbonatitic liquids, rather than entering the lower mantle. The fate of such carbon has not been well constrained, but it is important to understand this process because CO2 released into the convecting upper mantle is key to constraining the origin of the deep carbon reservoir. Key Points: Effect of H2O on the decarbonation behavior of subducted oceanic crust was investigatedHydrous carbonatitic liquids can form at ∼950–1,150°C at depths below ∼150 kmFluid activity is critical for removing most of the surviving carbon beyond subarc depths [ABSTRACT FROM AUTHOR]

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This paper reports an experimental investigation into the kinetics of magnesium carbonate calcination, conducted using a broad spectrum of heating rates (0.1°C/s to 179.9°C/s) in an air environment for a thin layer bed with Biot number < 0.1. These heating rates surpass those typically employed in thermogravimetric analysers (< 1°C/s) by many orders of magnitude. It was found that higher heating rates led to lower activation energies, as demonstrated by a 24.5% reduction in activation energy, E, from 220.8 kJmol−1 to 166.6 kJmol−1, for an increase in the heating rate from 0.1°C/s to 102.9°C/s. Furthermore, a higher heating rate led to a non-linear reduction in the residence time required to achieve the maximum conversion fraction. For instance, the time required for magnesite calcination to attain a conversion fraction from X=0.1 to X=0.84 decreased by a factor of eight, from 1920 s to 240 s, for only a three-fold increase in the heating rate, from 59.2°C/s to 179.9°C/s. These increases were associated with a higher specific surface area, highlighting the strong influence of the heating rate on the kinetics of magnesium carbonate calcination.It was also found that the highest specific surface area of cases examined for magnesite occurs for a heating rate of 59.2°C/s and a temperature less than 950°C, which avoids significant sintering. Increasing the temperature beyond 950°C reduces the specific surface area by causing sintering.

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The carbonation behavior of calcium-containing sorbents, CaO and Ca(OH)2, was investigated under pressurized CO2 at nominal room temperature. The carbonation reaction was mechanically driven via reactive ball milling. The carbonation rate was determined by monitoring the CO2 pressure inside the sealed milling jar. Two different versions of CaO were fabricated as starting materials. The addition of citric acid in CaO synthesis resulted in a significant increase in sorbent surface area, bringing up the conversion of CO2 from 18% to 41% after 3 h of reactive milling. The hydroxide formation from these two oxides closed the surface area gap. Nevertheless, we found that hydroxides had a higher initial carbonation rate and greater final CO2 uptake than their oxide counterparts. However, the formation of byproduct water limited the further carbonation of Ca(OH)2. When we added a controlled amount of water to the CaO-containing milling jar, the highest carbonation rate and most extensive CO2 uptake were attained due to the in situ formation of reactive Ca(OH)2 nanoparticles. We saw CaCO3 X-ray diffraction peaks only when Ca(OH)2 was involved in this low-temperature carbonation, indicating that the grain growth of CaCO3 is easier on the Ca(OH)2 surface than on the CaO surface. We used the Friedman isoconversional method to calculate the effective activation energy of decarbonation for the high surface area CaO sorbent milled with water. The average effective activation energy was found to be about 72 kJ mol−1, and its magnitude started to decrease significantly from 50% sorbent regeneration. The drastic change of the effective activation energy during decarbonation suggests that CaCO3, formed at nominal room temperature by reactive milling under pressurized CO2, should undergo a more drastic morphology change than the typical thermally carbonated CaCO3. [ABSTRACT FROM AUTHOR]

Stable isotope analysis of δ13C and δ15N have been broadly used in ecological studies to access trophic interactions between organisms, and the flow of energy and contaminants among systems and through the trophic chain. These questions can be addressed based on the organic carbon assimilated by the organisms to acquire energy. However, for many kinds of samples, like suspended particulate organic matter (SPOM), inorganic carbon is also present at high proportions, and it is not assimilated by organisms during the metabolic process. In this sense, we tested the benefit of extracting inorganic carbon from SPOM samples with HCl fumigation, by comparing the δ13C and δ15N of acidified and non-acidified samples. We calculated a correction model and ran a MixSIAR model to evaluate the implications of using non-acidified samples when evaluating carbon contributions to organisms. We found a decrease of -2.78 ± 0.05‰ in the δ13C of acidified samples, which was high enough to change the results and interpretation of the simulations in the MixSIAR models. The δ15N was not altered. The correction model provided results similar to the acidified samples and could be used when acidification is not possible. We suggest acidifying SPOM samples for ecological studies assessing trophic relationships and energy flow, as the δ13C can be modified due to the content of inorganic carbon and the productivity of the environment, influencing interpretation of the ecological relationships among organisms and systems. [ABSTRACT FROM AUTHOR]

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• Refrigerant charge amount needed throughout the year is nearly constant in GSHP. • In low-charge systems, the refrigerant dissolved in oil is a substantial amount. • Heating the crankcase reduces the tot refrigerant charge amount needed in the system. • Domestic space heating with less than 150 g of R290 is achievable. This paper presents experimental results from a brine-to-water heat pump used for space heating at low temperature, with a low refrigerant charge of R290 (propane). Performance and refrigerant distribution were analysed in every test condition studied. Performance results show a declared heating capacity of 9.5 kW , obtaining a specific capacity (C c) of 48.7 kW rm kg − 1 and a seasonal coefficient of performance of 4.01. In terms of refrigerant distribution, at the nominal point, 41.5% of the refrigerant is located in the compressor, mainly dissolved in the oil, and the rest is separated almost evenly in both heat exchangers, 23.9% in the condenser and 27.8% in the evaporator; having the lines and accessories (pneumatic-ball valves) the remaining 6.8%. Due to this fact, reducing oil solubility by heating the crankcase or increasing the superheat (SH) has a positive impact on the refrigerant charge reduction, but it also affects the coefficient of performance. [ABSTRACT FROM AUTHOR]

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

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

Achieving net-zero emissions in the maritime sector requires adopting carbon-neutral practices in terms of shipbuilding, operation and recycling. However, research integrating life cycle and energy analysis is missing to inform decision-makers. Consequently, the paper presents models combining a model-based life cycle assessment (MBLCA) and ship energy simulations to examine the footprints of a generic New Panamax Containership (DTC). Analyses were conducted to assess the energy and carbon effects of using synthetic methanol as marine fuel. The life-cycle analysis confirms the overwhelming prevalence of operations in the total greenhouse gases emission during the ship's lifetime. The analysis highlights the potential of carbon savings if the vessel consumes methanol produced from neutral energy and renewable carbon sources. However, the magnitude of shipping fuel requirements may profoundly impact energy infrastructures while still requiring large volumes of carbon offset credits. The paper confirms the usefulness of integrating life-cycle analysis and energy modelling to discuss future energy scenarios. The completeness of the models also allows for future research analysing other energy solutions. • The paper assesses GWP100, energy intensity, and renewable carbon needs of a New-Panamax vessel using heavy fuel oil or carbon-neutral methanol. • The methodology integrates a novel energy modelling tool into ISO life cycle analysis for maritime decarbonation research. • Findings indicate that operational energy consumption accounts for 60%–98% of the vessel's total carbon footprint. • Results reveal that 80% of the shipbuilding carbon footprint is attributable to the production of steel and main machinery. • The authors underscore the importance of cradle-to-grave approaches, accounting for externalities in fuel substitution strategies supporting decarbonation. [ABSTRACT FROM AUTHOR]

The role that subducted carbonates play in sourcing and storing carbon in the deep Earth's interior is uncertain, primarily due to poor constraints on the stability of carbonate minerals when interacting with mantle phases. Magnesite (MgCO 3) is the most prominent carbonate phase to be present at all mantle pressure-temperature conditions. In this study, we combined multi-anvil apparatus and laser-heated diamond anvil cell experiments to investigate the stability of magnesite in contact with iron-bearing bridgmanite. We examined the presence of melt, decarbonation, and diamond formation at shallow to mid-lower mantle conditions (25 to 68 GPa; 1350 to 2000 K). Our main observation indicates that magnesite is not stable at shallow lower mantle conditions. At 25 GPa and under oxidizing conditions, melting of magnesite is observed in multi-anvil experiments at temperatures corresponding to all geotherms except the coldest ones. Whereas, at higher pressures and under reducing conditions, in our laser-heated diamond-anvil cell experiments, diamond nucleation is observed as a sub-solidus process even at temperatures relevant to the coldest slab geotherms. Our results indicate that magnesite was reduced and formed diamonds when in contact with the ambient peridotite mantle at depths corresponding to the shallowest lower mantle (33 GPa). Thus, we establish that solid magnesite decomposes at depths of ∼700 km as it contacts the ambient mantle. Consequently, the recycling of carbonates will hinder their transport deeper into the lower mantle. [Display omitted] • The stability of magnesite (MgCO 3) was investigated in the presence of iron-bearing bridgmanite at conditions from 25 to 68 GPa and temperatures covering all subduction geotherms (1350 K to 2000 K). • Magnesite reacts with iron-bearing bridgmanite to form diamonds at conditions relevant to the coldest geotherm. • Subduction of magnesite, and more generally carbonates, is limited to the top of the lower mantle (∼700 km depths), even along cold slabs geotherm. [ABSTRACT FROM AUTHOR]

Carbonate minerals as a dominant carbon host can be transported to the Earth’s deep interior via subduction of the oceanic lithosphere, and their physicochemical behavior potentially has a significant influence on the compositional heterogeneity and physical properties in the deep mantle. In this study, we measured the electrical conductivity of natural siderite at 1–3 GPa and 100–700°C using a complex impedance analyzer in a large volume multi-anvil high-pressure apparatus. A sharp increase in conductivity was observed at ∼400°C under various pressures, and subsequently, the electrical conductivity keeps anomalously high values in the whole temperature range owing to a small quantity of interconnected highly conductive phases (graphite and magnetite) produced from the low degree decarbonation of siderite. The change in electrical conductivity and activation enthalpy suggest that the conduction mechanisms before and after low degree decarbonation of siderite are the small polaron (electron hopping in Fe2+–Fe3+) and highly conductive phases, respectively. Our results indicate the incipient decarbonation temperatures at 1–3 GPa are considerably lower than the decomposition boundary of siderite determined by phase equilibrium experiments, implying the initial decarbonation reaction of Fe-bearing carbonates in the subducting oceanic crust occurs at a shallower depth. The 30 vol.% of siderite is required to enhance the electrical conductivity of (Mg, Fe)CO3 solid solutions. Magnetite and graphite generated from the decarbonation reaction of the siderite component of Fe-bearing carbonate make a significant contribution to the high conductivity anomaly observed in the slab-mantle wedge interface.

Morocco has resolutely committed to the green transition of its economy by opting for industry decarbonation, which now imposes itself as an essential access criterion to foreign markets. Intending to include energy efficiency in the leading players in energy-intensive industries, this paper has the main objective of contributing to a better understanding of the decarbonation plans potential impact, taking the example of solar energy integrating opportunities as an action for a thrifty, sustainable, and low carbon Moroccan industry. Indeed, the paper focuses on the industrial textile sector, such as the energy-intensive industry. This sector is the first employer and the most important industrial activity; it is also an icon and the oldest industry in Morocco. This study examines the energy, economic and environmental fallout, evaluating the productions, the investment and the CO2 emissions limit. Besides, the energy industrial sector is characterized by a strong dependence on fossil imports, which increases the energy factor and price. In this regard, several geographical sites and factories were studied under six climatic regional conditions, proposing the most optimal and sustainable configurations for each location and present models with scopes and levels of energy and environment gains and investments that can inspire the sector actors. Then the present work must install concepts by inspiring local factories, accompanying the national vision, and resizing the industrial ecology. In this paper, a power of 8.88 MW is the total power installed, which provides an annual total of 8484.65 tonnes of CO2, with an average payback time between 2.6 years and 4.5 years, and attractive economic parameters, with an LCOE of 0.034 $/kWh and $181,863 for the NPC, those outputs shows the importance of environmental gains that the generalization of this strategic vision can achieve. [ABSTRACT FROM AUTHOR]

The introduction of Renewable and Recoverable Energies (R&R) into the energy mix is one of the major levers for reducing CO2 emissions, particularly for heat production. For To this end, energy systems must be put in place based in particular on innovative thermal storage technologies. The purpose of this communication is to present the MERLIN modelling/optimization environment (Hétreux G., 2022) which offers software components allowing the development of applications to help with dimensioning and operational management of multi-energy systems. By way of illustration, these tools are implemented through the study of a system composed of a concentrated solar power plant and a storage used to supply hot air to a food drying oven.

Although forming one unified class, orogenic gold deposits may be associated with a range of ore mineral assemblages controlled by a variety of gold deposition processes that have a direct impact on gold grade. Whereas, a better understanding of the deposition process may be critical for effective targeting of highly-endowed gold deposits, it is challenging to establish a direct comparison between mineral systems formed under different conditions. Accordingly our ability to predict whether contrasted mineral associations may be more or less prospective for high grade mineralization remains poor. In this paper, we compare fluid-rock interaction processes that led to the coeval formation of two contrasting gold mineral assemblages within the world-class Callie orogenic gold deposit. Stratabound and vein-hosted lodes formed within the same structural framework but with contrasting grades (∼3 g/t Au and ∼8 g/t Au, respectively). The stratabound mineralization consists of bedding-parallel sulfides in which gold is preserved in arsenopyrite micro-fractures. The vein-hosted mineralization consists of locally very high-grade (up to 10,000 ppm Au) visible gold concentrated in quartz veins. Both mineralization styles are hosted within different metasedimentary stratigraphic horizons with contrasting compositions. The stratabound mineralization occurs in iron-oxide rich siltstones whereas the vein-hosted mineralization occurs in carbonaceous siltstones. We investigate the fluid-rock interaction mechanisms of the two styles of mineralization at the Callie deposit by combining petrographic observation with whole-rock geochemistry, quantitative chlorite and gold analyses and thermodynamic modeling. Our results show that the stratabound mineralization occurred in response to sulfidation of the host-rock whereas decarbonation alteration, associated with the vein-hosted mineralization, records oxidation of the host-rock. Our investigation shows that gold deposition induced by oxidation of the host-rock produces the valuable, locally very-high grade visible gold mineralization whereas the sulfidation process lead to the formation of lower grade gold mineralization disseminated within the sulphide ore assemblage. We conclude that the nature of the host-rock applies a first-order control on the gold deposition efficiency in metasedimentary-hosted gold deposits. [ABSTRACT FROM AUTHOR]

The late Ediacaran Shuram Excursion (SE) records the most prominent negative δ 13C excursions (δ 13C = −12‰) during Earth's history. It has been hypothesized to have resulted from oxidation of dissolved organic matter, diagenetic or authigenic precipitates. However, the origin of the SE remains enigmatic; current models face challenges regarding the significant amount of atmospheric oxygen needed to balance such extensive oxidation and sustained inputs of light carbon with extremely negative C isotope compositions. Here, we show that the Doushantuo Formation at the Jiulongwan section in South China, a key stratum recording the SE event, contains mineralogical and geochemical signatures related to igneous processes. Both the occurrence of ankerite, feldspar, moissanite and euhedral quartz in the SE samples and the relatively consistent Ce anomalies of carbonate and O isotopes of quartz indicate a contribution from an igneous source. In particular, the SE samples have trace element and C isotope compositions similar to those of recycled carbonatites formed by decarbonation and melting of sedimentary carbonate rocks. These observations suggest that the deep cycle of ancient carbonate rocks, which were subjected to decarbonation during subduction, melting and eruption related to the breakup of the Rodinia supercontinent, contributed to the SE. This igneous model for the SE may provide a connection between the deep and shallow carbon cycles of the Earth. [ABSTRACT FROM AUTHOR]

Meeting the goal of reaching zero emissions by 2050 requires profound changes in the production of bulk materials, cement and concrete. For construction sector, this transition is also dependent on the evolution of demand, stemming from changes in the population structure and practice in structural design. Many timelines have been produced suggesting pathways to zero emissions, but none have looked at the required investment level, or the feasibility of transition looking at the level of single plants being shut, transformed or built within a single country. In this paper, we have looked at transition pathways in the United Kingdom as a function of the available funding and the possible emergence of transformative technologies. We find that trade is a necessary component of the transition, allowing for continued construction while the production apparatus is upgraded. Our results further suggest that the current level of investment is consistent with today's carbon price but falls short of what is necessary to achieve net zero by 2050. Finally we find that pathways assuming that CCS will be available at scale are particularly susceptible to overshoot their emissions target if the technological deployment fails to materialise. This is because they combine heavy investments, immature technology and concentrated risk. [Display omitted] [ABSTRACT FROM AUTHOR]

• Sediment is the source of the earliest slab-derived fluids. • The serpentinizing fluids experienced extensive interaction with subducted basalts. • Breakdown of basalt plagioclase affected chemistry of the earliest fluids. • Breakdown of plagioclase resulted in calcium carbonate precipitation. • Lawsonite and rodingite appear as stable phases after plagioclase breakdown. The geochemistry of Mariana forearc serpentinites sheds light on how the subducting slab starts to devolatilize. International Ocean Discovery Program Expedition 366 targeted three serpentinite seamounts: Yinazao, Fantangisña and Asùt Tesoru, with corresponding slab depths of 13, 14 and 18 km, respectively. The fluid-mobile elements (FMEs) B, Rb, Cs, and Li become more enriched in the eruptive serpentinites with increasing slab depth. Yinazao serpentinites show strongly elevated Sr and Ba contents, which complements depletions in these elements seen in mafic clasts entrained in the serpentinites. Correlations between the FMEs and 87Sr/86Sr of the serpentinites reflect interactions among slab fluid, mantle and the subducting slab. With the enrichments of Sr-Ba in the Yinazao and B-Rb-Cs-Li in the Asùt Tesoru serpentinites, their 87Sr/86Sr converge toward values similar as those of the mafic clasts from values between sediments and the mantle. These observations indicate that sediment is the source of the earliest slab-derived fluids, which experienced extensive interaction first with mantle wedge peridotites to produce high pH fluids, and later with subducted seamount basalts. The decomposition of plagioclase in subducting basalts leads to precipitation of CaCO 3 from the high pH serpentinizing fluids and elevated Ca-Sr-Ba contents under low carbonate alkalinity conditions, as seen in the Yinazao serpentinites. The breakdown of clay minerals after lawsonite formation and the lizardite-antigorite transition release geochemically distinct fluids, with high B-Rb-Cs-Li and low Sr. This episode of fluid release results in the dissolution of CaCO 3 precipitated in the shallow subduction channel, and the generation of rodingite assemblages and epidote. Finally, these fluids evolve to have high carbonate alkalinity and low Ca-Sr-Ba contents, as seen in Asùt Tesoru serpentinites as well as those in South Chamorro and Conical Seamounts. This study reveals early plagioclase breakdown via high pH fluids in the subduction channel is important both for the generation of hydrous minerals and the precipitation of CaCO 3 in the subducting slab, subduction channel, and shallow mantle wedge. [ABSTRACT FROM AUTHOR]

The Finnish soapstone industry has found through practical experience that the surface of the magnesite soapstone used in fire chambers and funnels hardens over time. We have studied a magnesite soapstone used in a fireplace continuously for 60 years. The mineralogical changes, that took place during heating and subsequent cooling of the fireplace have been investigated with electron probe microanalyzer and X-ray diffractometer to find an explanation, what kind of reactions caused the hardening. We found that ferromagnesite has been altered to pseudomorphic aggregates composed of ferropericlase and magnesioferrite in the nearest ~30 mm from the surface exposed to fire. Iron has been mobilized in the uppermost 3 mm, enriched in the rims, and depleted from the cores of the ferropericlase aggregates. Magnesioferrite occurs preferably in the fire chamber side of the aggregates in the uppermost 0.20 mm. Talc rims are altered to forsterite and/or enstatite in the reaction with ferromagnesite or its alteration products in the uppermost ~1 mm. In addition, wood combustion gases caused considerable enrichment of zinc and potassium in the chamber surface rock to the depth on 0.20 mm and 3 mm, respectively. The enrichment occurred by crystallization of Zn bearing ferropericlase and magnesioferrite and by crystallization of K bearing sheet silicates.

• HCFO-1224yd(Z) is proposed as an alternative to HFC-245fa in high temperature heat pumps. • Theoretical and semi-empirical comparisons explore several energetic parameters. • Heat source temperature is 80 °C, and heat sink temperature ranges from 110 to 140 °C. • HCFO-1224yd(Z) outperforms HFC-245fa in terms of COP but its heating capacity is lower. • The TEWI metric confirms a carbon footprint emission reduction with HCFO-1224yd(Z). This paper investigates a promising low-GWP refrigerant, HCFO-1224yd(Z), as an environmentally friendly replacement for HFC-245fa in high temperature heat pumps (HTHPs). First, the thermophysical properties of both fluids were analysed, and a single-stage cycle with Internal Heat Exchanger (IHX) was modelled. Then, a semi-empirical drop-in test replacement was assessed. The low-temperature reservoir was fixed at 80 °C, whereas the high-temperature reservoir was varied from 110 to 140 °C to cover a wide range of industrial applications. The theoretical and semi-empirical results illustrate that HCFO-1224yd(Z) heating capacity becomes around 8.9% lower than HFC-245fa. However, the higher suction density of HCFO-1224yd(Z) compared to the reference fluid can compensate for this effect, reducing the compressor power consumption. Hence, HCFO-1224yd(Z) presents a COP increase up to 4.5% compared to the reference fluid. At high-temperature reservoir of 140 °C, HCFO-1224yd(Z) shows a COP of 2.33, whereas HFC-245fa only reaches 2.23. The carbon footprint assessment illustrates a significant equivalent CO 2,eq emissions reduction down to 90%, depending on the country (carbon emission factor). Therefore, HCFO-1224yd(Z) can be used as an alternative to HFC-245fa in HTHP systems due to its beneficial operating, energetic and environmental characteristics. [ABSTRACT FROM AUTHOR]

We investigated crystal structure and the local structure changes during the thermal decomposition of hydromagnesite by using in situ high-temperature XRD and ex situ high-temperature X-ray total scattering measurements. Hydromagnesite displayed anisotropic thermal expansion up to 220 °C. The a and c lattice parameters exhibited an increase trend with temperature, whereas the b lattice parameter and β angle did not show a regular trend with temperature. The relative expansion between 25 and 220 °C followed the c/c0 > a/a0 ≫ b/b0. At 260 °C, the a, b, and c lattice parameters significantly decreased. Above 280 °C, hydromagnesite underwent a structural collapse with dehydration and dehydroxylation reactions, but was never accompanied by nucleation and growth of crystal phases up to 425 °C. During the thermal decomposition from hydromagnesite to periclase, the Mg atoms maintained the octahedral coordination environments in the structure. [ABSTRACT FROM AUTHOR]

In this work, the Na 2 CO 3 of the sodium manganese ferrite thermochemical cycle was substituted by different eutectic or eutectoid alkali carbonate mixtures. Substituting Na 2 CO 3 with the eutectoid (Li 0.07 Na 0.93 ) 2 CO 3 mixture resulted in faster hydrogen production after the first cycle, shifting the hydrogen production maximum toward shorter reaction times. Thermodynamic calculations and in situ optical microscopy attributed this fact to the partial melting of the eutectoid carbonate, which helps the diffusion of the ions. Unfortunately, all the mixtures exhibit a significant loss of reversibility in terms of hydrogen production upon cycling. Among them, the nonsubstituted Na mixture exhibits the highest reversibility in terms of hydrogen production followed by the 7%Li-Na mixture, while the 50%Li-Na and Li-K-Na mixtures do not produce any hydrogen after the first cycle. The loss of reversibility is attributed to both the formation of undesired phases and sintering, the latter being more pronounced in the eutectic and eutectoid alkali carbonate mixtures, where the melting of the carbonate is predicted by thermodynamics.

The characterization of particles in suspension in river plumes contributes to the assessment of net particulate organic carbon (POC) fluxes and to a better understanding of the anthropogenic and climatic impact on blue carbon. Prior to POC analysis in natural waters, inorganic carbon (in the form of carbonates) must be removed. This step is generally carried out by acid leaching. However, the presence of mineral matrices (in turbid waters) may hinder total decarbonation, which may result in biased measurements. This work checks the quality of decarbonation through the analysis of carbon stable isotope ratio (δ13C), considering suspended particles discharged by three rivers into coastal waters under flooding conditions. Carbonates were removed by adding variable volumes of 2N hydrochloric acid (HCl) to filters. Carbon concentrations and stable isotopic ratios were analyzed. Values of δ13Corg (stable isotope ratio of organic carbon) allow the identification of incompletely decarbonated samples. If a small amount of detrital carbonates resists the usual decarbonation treatment, δ13Corg can be significantly shifted towards less negative values, suggesting the need of more efficient decarbonation methods in order to improve the accuracy of organic carbon measurements. Even in the case of a high Corg/Ctotal ratio, the impact of remaining carbonates on the δ13Corg value is strong because δ13Cinorg is significantly different. The sensitivity of δ13Corg measurement might therefore be used to validate POC measurements in estuarine and coastal waters. [ABSTRACT FROM AUTHOR]

The acidification of samples for the simultaneous measurement of stable carbon (δ13C) and nitrogen (δ15N) isotopes represents an important methodological question still not clarified because the removal of calcium carbonate (CaCO3) from samples may affect the outcome of the stable-isotope analysis. We investigated the effect of acidification on samples of 25 different taxa of benthic marine organisms from a rocky shore, to determine whether acidification affects the isotopic values of δ13C and δ15N. After washing with distilled water and drying, each sample was divided into two parts; one part was acidified by adding 1 M HCl with a pipette, until no more CO2 was released, whereas the other part was retained as a non-acidified sample. Organisms with little CaCO3 showed no difference in carbon isotopic signatures after acidification, from those in the non-acidified part. Some organisms with a high CaCO3 content did show differences in carbon isotopic signatures after acidification. The nitrogen isotopic signature presented a significant difference; however, to what extent this difference is biologically important is discussed. Avoiding sampling parts containing a high concentration of carbonate is an efficient way to circumvent this problem. Acidification of samples as a pre-treatment for isotopic analysis is not useful for marine organisms without calcareous structures and is necessary only when the sampled parts contain significant amounts of carbonate. [ABSTRACT FROM AUTHOR]

Experimental modeling of decarbonation reactions with the formation of Mg,Fe-garnets and CO2 fluid during mantle-crustinteractions was carried out in a wide range of the upper-mantle pressures and temperatures. Experimental studies were performed in the MgCO3-Al2O3-SiO2 and (Mg,Fe)CO3-Al2O3-SiO2 systems in the pressure range 3.0-7.5 GPa and temperature range 950-1450 °C (t = 10-60 h), using a multianvil high-pressure apparatus of the "split-sphere" type (BARS). Experiments were carried out with a specially designed high-pressure buffered cell with a hematite container that prevents the diffusion of hydrogen into a Pt-capsule with a sample. It has been experimentally established that in the MgCO3-Al2O3-SiO2 system decarbonation occurs by the schematic reaction MgCO3 + SiO2 + Al2O3 Mg3Al2Si3O12 + CO2 at 1100 ± 20 °c (3.0 GPa), 1150 ± 20 °C (6.3 GPa), and 1400 ± 20 °C (7.5 GPa) and in the (Mg,Fe)CO3-Al2O3- SiO2 system, by the reaction (Mg,Fe)CO3 + SiO2 + Al2O3 (Mg,Fe)3Al2Si3O12 + CO2 at 1000 ± 20 °C (3.0 GPa), 1150 ± 20 °C (6.3 GPa), and 1400 ± 20 °C (7.5 GPa). Based on Raman spectroscopic characterization of the synthesized garnets, the position of the main modes R, ?2, and ?1 in the pyrope has been determined to be 364, 562, and 924-925 cm-1, respectively, and that in pyrope-almandine, 350-351, 556-558, and 918-919 cm-1. The effectiveness of the hematite container was demonstrated by means of mass spectrometry analysis. It has been found that the fluid composition corresponded to pure CO2 in all experiments. The P,T-positions of decarbonation curves leading to the formation of a CO2 fluid in assemblage with pyrope and pyrope-almandine have been experimentally reconstructed and compared with the previous calculation and experimental data. It has been established that the experimentally reproduced reaction lines with the formation of pyrope + CO2 or pyrope-almandine + CO2 assemblages are shifted to lower temperatures by 50-150 °? relative to the calculated ones. When considering the obtained results with regard to the stability of natural carbonates of various compositions in subduction settings, it has been found that at depths of ~90-190 km Mg,Fe-carbonates react with oxides in the temperature range 1000-1250 °C, and at depths of ~225 km, at 1400 °C. [ABSTRACT FROM AUTHOR]

This paper analyses the interaction between centralised carbon emissive technologies and distributed intermittent non-emissive technologies. In our model, there is a representative consumer who can satisfy her electricity demand by investing in distributed generation (solar panels) and by buying power from a centralised firm at a price the firm sets. Distributed generation is intermittent and induces an externality cost to the consumer. The firm provides non-random electricity generation subject to a carbon tax and to transmission costs. The objective of the consumer is to satisfy her demand while minimising investment costs, payments to the firm and intermittency costs. The objective of the firm is to satisfy the consumer's residual demand while minimising investment costs, demand deviation costs, and maximising the payments from the consumer. We formulate the investment decisions as McKean–Vlasov control problems with stochastic coefficients. We provide explicit, price model-free solutions to the optimal decision problems faced by each player, the solution of the Pareto optimum, and the Stackelberg equilibrium where the firm is the leader. We find that, from the social planner's point of view, the carbon tax or transmission costs are necessary to justify a positive share of distributed capacity in the long-term, whatever the respective investment costs of both technologies are. The Stackelberg equilibrium is far from the Pareto equilibrium and leads to an over-investment in distributed energy and to a much higher price for centralised energy. [ABSTRACT FROM AUTHOR]

The amount of H2O and CO2 that is carried into deep mantle by subduction beyond subarc depths is of fundamental importance to the deep volatile cycle but remains debated. Given the large uncertainties surrounding the spatio‐temporal pattern of fluid flow and the equilibrium state within subducting slabs, a model of H2O and CO2 transport in slabs should be balanced between model simplicity and capability. We construct such a model in a two‐part contribution. In this Part I of our contribution, thermodynamic parameterization is performed for the devolatilization of representative subducting materials—sediments, basalts, gabbros, peridotites. The parameterization avoids reproducing the details of specific devolatilization reactions, but instead captures the overall behaviors of coupled (de)hydration and (de)carbonation. Two general, leading‐order features of devolatilization are captured: (1) the released volatiles are H2O‐rich near the onset of devolatilization; (2) increase of the ratio of bulk CO2 over H2O inhibits overall devolatilization and thus lessens decarbonation. These two features play an important role in simulation of volatile fractionation and infiltration in thermodynamically open systems. When constructing the reactive fluid flow model of slab H2O and CO2 transport in the companion paper Part II, this parameterization can be incorporated to efficiently account for the open‐system effects of H2O and CO2 transport. Key Points: Parameterized slab devolatilization facilitates treatment of open‐system behavior during fluid flowFractional loss of H2O inhibits overall devolatilization and thus CO2 releaseH2O infiltration not only promotes decarbonation but also promotes overall devolatilization [ABSTRACT FROM AUTHOR]

The geologic carbon cycle plays a fundamental role in controlling Earth's climate and habitability. For billions of years, stabilizing feedbacks inherent in the cycle have maintained a surface environment that could sustain life. Carbonation/decarbonation reactions are the primary mechanisms for transferring carbon between the solid Earth and the ocean–atmosphere system. These processes can be broadly represented by the reaction: CaSiO 3 (wollastonite) + CO 2 (gas) ↔ CaCO 3 (calcite) + SiO 2 (quartz) . $\text{CaSi}{{\text{O}}_{\text{3}\,\,\left(\text{wollastonite} \right)}}+\text{C}{{\text{O}}_{\text{2}\,\,\left(\text{gas} \right)}}\leftrightarrow \text{CaC}{{\text{O}}_{\text{3}\,\,\left(\text{calcite} \right)}}+\text{Si}{{\text{O}}_{\text{2}\,\,\left(\text{quartz} \right)}}.$ This class of reactions is therefore critical to Earth's past and future habitability. Here, we summarize their significance as part of the Deep Carbon Obsevatory's "Earth in Five Reactions" project. In the forward direction, carbonation reactions like the one above describe silicate weathering and carbonate formation on Earth's surface. Recent work aims to resolve the balance between silicate weathering in terrestrial and marine settings both in the modern Earth system and through Earth's history. Rocks may also undergo carbonation reactions at high temperatures in the ultramafic mantle wedge of a subduction zone or during retrograde regional metamorphism. In the reverse direction, the reaction above represents various prograde metamorphic decarbonation processes that can occur in continental collisions, rift zones, subduction zones, and in aureoles around magmatic systems. We summarize the fluxes and uncertainties of major carbonation/decarbonation reactions and review the key feedback mechanisms that are likely to have stabilized atmospheric CO2 levels. Future work on planetary habitability and Earth's past and future climate will rely on an enhanced understanding of the long-term carbon cycle. [ABSTRACT FROM AUTHOR]

The molecular composition of soil organic matter (SOM) of two calcareous soils highly rich in carbonates was assessed before and after decarbonation by acid washing with HCl through 13C-CPMAS-NMR spectroscopy and off-line thermochemolysis coupled with gas chromatography and mass spectrometry (THM-GC-MS). The acidic treatment promoted a considerable concentration of organic matter in both soils, thus improving the identification of molecules otherwise not easily detectable. Decarbonation induced only a slight loss of soil organic carbon (SOC), corresponding to 1.4 and 2.7% for A and B soils respectively. The acidic treatment also led to an increase in the organic carbon/total nitrogen (OC/N) ratio in soil A, while an opposite variation was found for the second soil. Moreover, variations in the concentration and molecular distribution of specific compound classes present in SOM were caused by the acid washing of soils. As confirmed by both 13C-CPMAS-NMR and thermochemolysis results, the molecules most susceptible to the acid treatment were the carbohydrates, lignin monomers (G14 and G15), fatty acids (C18 saturated and unsaturated), fatty acids of microbial origin (C15, C17, and C19), hydroxy acids (C16, C18), and dioic acids (C18) which represent the components weakly bound to the organic matrix. Our findings not only showed the efficacy of the decarbonation treatment of calcareous soils with 3 N HCl, but also indicated how the acidic washing can improve the differentiation of soils on the basis of SOM molecular characteristics. [ABSTRACT FROM AUTHOR]

Abstract We report on laser-heated diamond anvil cell (LHDAC) experiments in the FeO–MgO–SiO 2 –CO 2 (FMSC) and CaO–MgO–SiO 2 –CO 2 (CMSC) systems at lower mantle pressures designed to test for decarbonation and diamond forming reactions. Sub-solidus phase relations based on synthesis experiments are reported in the pressure range of ∼35 to 90 GPa at temperatures of ∼1600 to 2200 K. Ternary bulk compositions comprised of mixtures of carbonate and silica are constructed such that decarbonation reactions produce non-ternary phases (e.g. bridgmanite, Ca-perovskite, diamond, CO 2 –V), and synchrotron X-ray diffraction and micro-Raman spectroscopy are used to identify the appearance of reaction products. We find that carbonate phases in these two systems react with silica to form bridgmanite ±Ca-perovskite + CO 2 at pressures in the range of ∼40 to 70 GPa and 1600 to 1900 K in decarbonation reactions with negative Clapeyron slopes. Our results show that decarbonation reactions form an impenetrable barrier to subduction of carbonate in oceanic crust to depths in the mantle greater than ∼1500 km. We also identify carbonate and CO 2 –V dissociation reactions that form diamond plus oxygen. On the basis of the observed decarbonation reactions we predict that the ultimate fate of carbonate in oceanic crust subducted into the deep lower mantle is in the form of refractory diamond in the deepest lower mantle along a slab geotherm and throughout the lower mantle along a mantle geotherm. Diamond produced in oceanic crust by subsolidus decarbonation is refractory and immobile and can be stored at the base of the mantle over long timescales, potentially returning to the surface in OIB magmas associated with deep mantle plumes. Highlights • Experiments were made in the systems FMS-CO2 and CMS-CO2 at lower mantle pressures. • Carbonate in these systems react with silica in the lower mantle. • Decarbonation reactions with negative P–T slopes form CO 2 or diamond plus oxygen. • Carbonate in oceanic crust is limited to ∼1500 km depth along subduction geotherms. • Diamond is the stable form of carbon in oceanic crust at ambient mantle temperature. [ABSTRACT FROM AUTHOR]

• Minor fluid-rock interaction in marble aureoles. • Most fluids escaped through veins, limiting decarbonation reactions. • Thermal history and rock rheology impact the extent of decarbonation. • Fluid traverses brittle-ductile transition undergoes decompression and boiling. Fluid-driven contact metamorphism in the Gangdese Arc, resulting from Late Cretaceous intrusions, led to a diverse range of aureoles in carbonate sequences in southern Tibet. These include extensive carbon loss in calc-silicate rocks with minor calcite remnants and minimal carbon loss in predominantly pure marble formations. Many studies connecting contact metamorphism and decarbonation flux focus on metacarbonate aureoles comprising calc-silicate assemblages, while marble formations represent a less prominent endmember. To investigate the factors determining decarbonation extent, we analyzed the thermobarometric, geochemical, and isotopic signatures of two representative marble aureoles in southern Tibet. Our findings suggest that isobarically exsolved magmatic fluid from a neighboring ∼64 Ma granodiorite pluton led to limited fluid-rock interaction in the marble aureole. Based on the petrologic observations, we present a conceptual model to elucidate this process. The heating and fluid infiltration were brief, likely due to short-lived intrusion events. Consequently, a thin ductile layer was formed adjacent to the pluton, while the majority of the country rock remained brittle. The lithostatic fluid in the ductile layer likely escaped through structurally weak zones, creating veins along the boundary between the pluton and marble. The fluids traversed the brittle-ductile transition experienced a sudden pressure drop from lithostatic in the ductile rock to hydrostatic in the brittle regime. The boiling fluid escaped by brecciating the brittle country rock and resulted in brecciation and stockwork of veins. In both cases, most fluid escaped through pathways, preventing infiltration into the country rock and decarbonation reactions. In contrast, a longer-lived heat source would have produced more extensive ductile country rocks, allowing for widespread fluid infiltration and calc-silicate formation. Thus, the thermal history of the intrusion and the rheology of the country rock significantly influence the extent of decarbonation in contact aureoles. [ABSTRACT FROM AUTHOR]