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Carbonate sediments transported into the mantle at subduction zone settings account for the majority of the carbon flux into the Earth's interior and are thus critical to the deep carbon cycle. Understanding carbon storage volumes in the deep earth requires knowledge of the degree to which carbonate sediments are stored in the arc lithosphere or descend to the deep mantle. Here, we use petrological‐thermomechanical modeling to indicate that solid‐state diapirs dominate the removal of carbon from subducting plates, which may be the principal carbon‐release mechanism for the Cyclades (Greece) and Costa Rican forearcs. We find that forearc diapirs remove up to ∼80% of subducting carbon and develop diagonally upward, resulting in massive carbon storage in the subarc lithosphere. Outgassing from the carbon storage may cause high carbon outputs and explain volcanic gas with high δ13C at some subduction zones, affecting atmospheric CO2 concentration. Plain Language Summary Whereas many concepted models for the fate of subducting carbon, mainly from the sedimentary carbonates, have been proposed, it remains unclear to which extend these ideas are consistent with carbon balance between the shallow and deep reservoirs. The dynamic processes by which carbon release from subducting sediments and the transit into the shallow reservoirs above subarc depths remain largely unanswered. In this study, we account for metamorphic decarbonation and coupled with thermomechanical models, to investigate the dynamics of subducting sediments and associated carbon flux. Results show that solid‐state diapirs formed in the forearc remove substantial amounts of sedimentary carbon, which are much more than that via subarc diapirs and metamorphic reactions, and indicate that they dominate the carbon release from subducting sediments. The massive carbon stored in the overlying lithosphere reservoir is formed via the diagonal transport of forearc diapirs provided that a thick sediment, a young oceanic plate, and slow convergence are present. We argue that the remobilization of sedimentary carbon in the subarc lithosphere can provide an efficient mechanism for the abnormally high decarbonation efficiency of the volcanism in subduction zones, therefore regulating the Earth's climate. Key Points We conduct 2D petrological‐thermomechanical models to explore the sediment subduction and recycling in subduction zones Young oceanic plates, slow convergence rates, and thick sediments promote forearc diapirs and cause high decarbonation efficiency Forearc diapirs dominate removal of carbon from the subducting plate and reduce the proportion of the carbon released at subarc depths

En application de l'accord de Paris sur le climat et de ses engagements internationaux, la France a inscrit en 2019 dans la loi I'objectif d'atteindre la neutralite carbone en 2050. La mobilisation pour le climat impose une acceleration de la decarbonation de I'economie et des modes de vie, une reduction des consommations d'energie ainsi qu'une redefinition de notre systeme energetique encore dependant aux deux tiers des energies fossiles, en s'appuyant sur les energies bas-carbone : renouvelables et nucleaire. Cette transition doit permettre egalement d'assurer la securite de l'approvisionnement en energie et de reduire la dependance aux importations, de preserver la competitivite de I'economie et de proteger les consommateurs frangais. Elle represente un defi industriel majeur.

Carbon release during continental rifting is thought to regulate atmospheric CO2 levels. Supercontinent dispersal‐induced extensional tectonics is similar during the Late Ediacaran and Jurassic, while they exhibit different increases in atmospheric CO2 concentration. The underlying mechanism of distinct CO2 emissions remains to be understood. Here, we conduct petrological‐thermomechanical modeling to show that metamorphic decarbonation and melting of carbonates that are derived from subducted sediments are ubiquitous during continental extension. We find that the hotter lithosphere and deeper storage of these carbonates cause more significant amounts of rift‐related CO2 release through volcanoes and faults. They may cause ∼12%–77% larger decarbonation efficiency, providing an efficient driving mechanism for a ∼31% larger increase in atmospheric CO2 levels during the Late Ediacaran than throughout the Jurassic. The rapid eruption and deposition of recycled carbonatite volcanic ash may contribute to the production of Late Ediacaran marine carbonates with the largest negative δ13C (−12‰). Plain Language Summary The Late Ediacaran and Jurassic periods witnessed rapid increases in atmospheric CO2 concentration and significant negative carbon isotope excursions in marine carbonates during the Earth's history, but the dynamics of their changes remain enigmatic. In this study, we present high‐resolution petrological‐thermomechanical models of how these processes occur. Our results indicate that the extensional tectonics drives trans‐crustal faulting and thereby results in remobilized subcontinental lithospheric carbonates of subducted sedimentary origin (SLCSS) to melt and migrate upward along these faults. The efficiency of CO2 release from these carbonates via metamorphic reaction decarbonation is promoted by the deeper storage and hotter lithosphere, which can reach up to ∼12%–77% larger. Recycled carbonatite volcanic ash may rapidly erupt and deposit in shallow marine habitats following the emission of CO2 enriched in 13C, resulting in the formation of large negative δ13C in Late Ediacaran and Jurassic. We suggest that metamorphic CO2 degassing of remobilized subcontinental lithospheric mantle carbonates of subducted sedimentary origin (SLMCS) combined with a hotter lithosphere may be responsible for a 31% greater increase in atmospheric CO2 and the largest negative δ13C of −12‰ in the Late Ediacaran. Key Points Numerical modeling of decarbonation of subducted sedimentary carbonates during continental rifting Thermal structure of the continental lithosphere and carbon storage depth control the efficiency of CO2 degassing Decarbonation of stored sedimentary carbonates during continental rifting accounts for CO2 concentrations and negative δ13C in Late Ediacaran

Cement production causes 7.5% of global anthropogenic CO 2 emissions, arising from limestone decarbonation and fossil-fuel combustion 1 – 3 . Current decarbonation strategies include substituting Portland clinker with supplementary materials, but these mainly arise in emitting processes, developing alternative binders but none yet promises scale, or adopting carbon capture and storage that still releases some emissions 4 – 8 . However, used cement is potentially an abundant, decarbonated feedstock. Here we show that recovered cement paste can be reclinkered if used as a partial substitute for the lime–dolomite flux used in steel recycling nowadays. The resulting slag can meet existing specifications for Portland clinker and can be blended effectively with calcined clay and limestone. The process is sensitive to the silica content of the recovered cement paste, and silica and alumina that may come from the scrap, but this can be adjusted easily. We show that the proposed process may be economically competitive, and if powered by emissions-free electricity, can lead to zero emissions cement while also reducing the emissions of steel recycling by reducing lime flux requirements. The global supply of scrap steel for recycling may treble by 2050, and it is likely that more slag can be made per unit of steel recycled. With material efficiency in construction 9 , 10 , future global cement requirements could be met by this route. Recovered cement paste can be reclinkered if used as a partial substitute for the lime–dolomite flux used in steel recycling, which can reduce waste and carbon emissions.

The term orogenic gold deposits has been widely accepted, but there has been continuing debate on their genesis. Early syn-sedimentary or syn-volcanic models and hydrothermal meteoric-fluid models are now invalid. Magmatic-hydrothermal models fail because of the lack of consistent spatially associated granitic intrusions and inconsistent temporal relationships. The most plausible models involve metamorphic fluids, but the source of these fluids is equivocal. Intra-basin sources within deeper segments of the hosting supracrustal successions, the underlying continental crust, subducted oceanic lithosphere with its overlying sediment wedge, and metasomatized lithosphere are all potential sources. Several features of Precambrian orogenic gold deposits are inconsistent with derivation from a continental metamorphic-fluid source. These include the presence of hypozonal deposits in amphibolite-facies domains, their anomalous multiple sulfur isotopic compositions, and problems of derivation of gold-related elements from devolatilization of dominant basalts in the sequences. The Phanerozoic deposits are largely described as hosted in greenschist-facies domains, consistent with supracrustal devolatilization models. A notable exception is the Jiaodong gold deposits of China, where ca. 120-Ma gold deposits are hosted in Precambrian crust that was metamorphosed over 2000 million years prior to gold mineralization. Other deposits in China are comparable to those in the Massif Central and elsewhere in France, in that they are hosted in amphibolite-facies domains or clearly post-date regional metamorphic events imposed on hosting supracrustal sequences. If all orogenic gold deposits have a common genesis, the only realistic source of fluid and gold is from devolatilization of a subducted oceanic slab with its overlying gold-bearing sulfide-rich sedimentary package, or the associated metasomatized mantle wedge, with CO2 released during decarbonation and S- and ore-related elements released from transformation of pyrite to pyrrhotite at about 500 °C. Although this model satisfies all geological, geochronological, isotopic, and geochemical constraints, and is consistent with limited computer-based modeling of fluid release from subduction zones, the precise mechanisms of fluid flux are model-driven and remain uncertain. From an exploration viewpoint, the model re-emphasizes the ubiquitous occurrence of orogenic gold deposits in subduction-related orogenic belts and importance of continental-scale lithosphere-tapping fault and shear zones to focus large volumes of auriferous fluid. It confirms the importance of the consistent spacing between world-class deposits, broadly equivalent to the depth of the Moho, as derived from empirical observations.

Carbon dioxide capture and storage (CCS) technology is an effective CO2 fixation technology, as documented by the special report produced by Working Group III of the Intergovernmental Panel on Climate Change. Today, this technology has become important due to the threat of global warming and climate change. Furthermore, the development of carbon dioxide capture and utilization (CCU) technology, which reuses the captured CO2, has been prioritized in recent years to accelerate the deployment of “CCUS.” For both utilization and storage, CO2 capture is a key process that determines how efficiently decarbonation is able to meet the global target. Regardless of the maturity of various types of CO2 capture technologies, amines are the most widely used chemical species. This paper contains a brief overview of CCUS followed by a discussion of several aspects of amine-based CO2 capture technologies.Carbon dioxide capture and storage (CCS) technology has become important due to the threat of global warming and climate change. Furthermore, the development of carbon dioxide capture and utilization (CCU) technology, which reuses the captured CO2, has been prioritized in recent years to accelerate the deployment of “CCUS.” Amine-based CO2 capture is a key process for realizing a carbon neutral society.

Lithium garnets have been widely studied as promising electrolytes that could enable the next-generation all-solid-state lithium batteries. However, upon exposure to atmospheric moisture and carbon dioxide, insulating lithium carbonate forms on the surface and deteriorates the interfaces within electrodes. Here, we report a scalable solid sintering method, defined by lithium donor reaction that allows for complete decarbonation of Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12 (LLZTO) and yields an active LiCoO 2 layer for each garnet particle. The obtained LiCoO 2 coated garnets composite is stable against air without any Li 2 CO 3 . Once working in a solid-state lithium battery, the LiCoO 2 -LLZTO@LiCoO 2 composite cathode maintains 81% of the initial capacity after 180 cycles at 0.1 C. Eliminating CO 2 evolution above 4.0 V is confirmed experimentally after transforming Li 2 CO 3 into LiCoO 2 . These results indicate that Li 2 CO 3 is no longer an obstacle, but a trigger of the intimate solid-solid interface. This strategy has been extended to develop a series of LLZTO@active layer materials. Formation of insulating lithium carbonate on surface of lithium garnets hinders their application as solid electrolyte in lithium ion batteries. Here the authors explore a scalable sintering approach to utilize the undesired Li 2 CO 3 and improve the active material-electrolyte interface within cathodes.

The fate of subducted CO 2 remains the subject of widespread disagreement, with different models predicting either wholesale (up to 99%) decarbonation of the subducting slab or extremely limited carbon loss and, consequently, massive deep subduction of CO 2 . The fluid history of subducted rocks lies at the heart of this debate: rocks that experience significant infiltration by a water-bearing fluid may release orders of magnitude more CO 2 than rocks that are metamorphosed in a closed chemical system. Numerical models make a wide range of predictions regarding water mobility, and further progress has been limited by a lack of direct observations. Here we present a comprehensive field-based study of decarbonation efficiency in a subducting slab (Cyclades, Greece), and show that ~40% to ~65% of the CO 2 in subducting crust is released via metamorphic decarbonation reactions at forearc depths. This result precludes extensive deep subduction of most CO 2 and suggests that the mantle has become more depleted in carbon over geologic time. The fate of subducted CO 2 remains debated, with estimates mainly from numerical predictions varying from wholesale decarbonation of the shallow subducting slab to massive deep subduction of CO 2 . Here, the authors present field-based data and show that ~40% to ~65% of the CO 2 in subducting crust is released via metamorphic decarbonation reactions at forearc depths.

Spatial control over features within multifunctional catalysts can unlock efficient one-pot cascade reactions, which are themselves a pathway to aviation biofuels via hydrodeoxygenation. A synthesis strategy that encompasses spatial orthogonality, i.e., one in which different catalytic species are deposited exclusively within discrete locations of a support architecture, is one solution that permits control over potential interactions between different sites and the cascade process. Here, we report a Pd doped hierarchical zeolite, in which Pd nanoparticles are selectively deposited within the mesopores, while acidity is retained solely within the micropores of ZSM-5. This spatial segregation facilitates hydrodeoxygenation while suppressing undesirable decarboxylation and decarbonation, yielding significant enhancements in activity (30.6 vs 3.6 mol dodecane mol Pd −1 h −1 ) and selectivity (C 12 :C 11 5.2 vs 1.9) relative to a conventionally prepared counterpart (via wet impregnation). Herein, multifunctional material design can realise efficient fatty acid hydrodeoxygenation, thus advancing the field and inspiring future developments in rationalised catalyst design. Hierarchical ZSM-5 boosts fatty acid hydrodeoxygenation by compartmentalization of catalytic sites. Separating acid sites within micropores and metal nanoparticles in mesopores provides control over the reaction and reduces unwanted side reactions.

The presence of carbonates in inclusions in diamonds coming from depths exceeding 670 km are obvious evidence that carbonates exist in the Earth’s lower mantle. However, their range of stability, crystal structures and the thermodynamic conditions of the decarbonation processes remain poorly constrained. Here we investigate the behaviour of pure iron carbonate at pressures over 100 GPa and temperatures over 2,500 K using single-crystal X-ray diffraction and Mössbauer spectroscopy in laser-heated diamond anvil cells. On heating to temperatures of the Earth’s geotherm at pressures to ∼50 GPa FeCO 3 partially dissociates to form various iron oxides. At higher pressures FeCO 3 forms two new structures—tetrairon(III) orthocarbonate Fe 4 3+ C 3 O 12 , and diiron(II) diiron(III) tetracarbonate Fe 2 2+ Fe 2 3+ C 4 O 13 , both phases containing CO 4 tetrahedra. Fe 4 C 4 O 13 is stable at conditions along the entire geotherm to depths of at least 2,500 km, thus demonstrating that self-oxidation-reduction reactions can preserve carbonates in the Earth’s lower mantle. Carbonates are shown to exist in the lower mantle as seen in diamond inclusions, but thermodynamic constraints are poorly understood. Here, the authors synthesise two new iron carbonate compounds and find that self-oxidation-reduction reactions can preserve carbonates in the mantle.