Search

Abstract: The crystal structure and bonding environment of K2Ca(CO3)2 bütschliite were probed under isothermal compression via Raman spectroscopy to 95 GPa and single crystal and powder X-ray diffraction to 12 and 68 GPa, respectively. A second order Birch-Murnaghan equation of state fit to the X-ray data yields a bulk modulus, $${K}_{0}=46.9$$ K 0 = 46.9 GPa with an imposed value of $${K}_{0}^{\prime}= 4$$ K 0 ′ = 4 for the ambient pressure phase. Compression of bütschliite is highly anisotropic, with contraction along the c-axis accounting for most of the volume change. Bütschliite undergoes a phase transition to a monoclinic C2/m structure at around 6 GPa, mirroring polymorphism within isostructural borates. A fit to the compression data of the monoclinic phase yields $${V}_{0}=322.2$$ V 0 = 322.2  Å3$$,$$ , $${K}_{0}=24.8$$ K 0 = 24.8 GPa and $${K}_{0}^{\prime}=4.0$$ K 0 ′ = 4.0 using a third order fit; the ability to access different compression mechanisms gives rise to a more compressible material than the low-pressure phase. In particular, compression of the C2/m phase involves interlayer displacement and twisting of the [CO3] units, and an increase in coordination number of the K+ ion. Three more phase transitions, at ~ 28, 34, and 37 GPa occur based on the Raman spectra and powder diffraction data: these give rise to new [CO3] bonding environments within the structure.

Pressure solution is inferred to be a significant contributor to sediment compaction and lithification, especially in carbonate sediments. For a sediment deforming primarily by pressure solution, the compaction rate should be directly related to the rate of calcite dissolution, transport along grain contacts, and calcite reprecipitation. Previous experimental work has shown that there is evidence that deformation in wet calcite grain packs is consistent with control by pressure solution, but considerable ambiguity remains regarding the rate limiting mechanism. We present the results of laboratory compaction experiments designed to directly measure calcite dissolution and precipitation rates (recrystallization rates) concurrently with strain rate to test whether measured rates are consistent with predicted rates both in absolute magnitude and time evolution. Recrystallization rates are measured using trace element chemistry (Sr/Ca, Mg/Ca) and isotopes (87Sr/86Sr) of fluids flowing slowly through a compacting grain pack as it is being triaxially compressed. Imaging techniques are used to characterize the grain contacts and strain effects in the post-experiment grain pack. Our data show that calcite recrystallization rates calculated from all three geochemical parameters are in approximate agreement and that the rates closely track strain rate. The geochemically inferred rates are close to predicted rates in absolute magnitude. Uncertainty in grain contact dimensions makes distinguishing between surface reaction control and diffusion control difficult. Measured reaction rates decrease faster than predicted from standard pressure solution creep flow laws. This inconsistency may indicate that calcite dissolution rates at grain contacts are more complex, and more time-dependent, than suggested by geometric models designed to predict grain contact stresses. [ABSTRACT FROM AUTHOR]

BACKGROUND: Magnesium oxide (MgO) is favored for solid‐state carbon dioxide (CO2) capture due to its high theoretical adsorption capacity, abundant reserves, low cost, and environmental friendliness. However, its practical application in industry is hindered by low CO2 adsorption capacity under moderate operating conditions. In this work, MgO was modified by a deposition method using LiNO3, NaNO3, KNO3, Na2CO3 and K2CO3 as additives. RESULTS: The study determines optimal ratios within the [(Li, Na, K)x − (Na, K)]y/MgO system, specifically identifying x = 0.5 and y = 0.15 as most effective. At 275 °C under pure CO2 conditions, the adsorption capacity peaks at 0.631 g CO2 g−1 adsorbent. Effective regeneration of the adsorbent occurs at 400 °C under 100% N2 for 15 min. Under Integrated Gasification Combined Cycle (IGCC) conditions, the adsorption capacity stabilizes at 0.462 g g−1 after 20 cycles, representing a 25% decrease from initial capacity. CONCLUSION: Experimental findings demonstrate that the inclusion of alkali metal salts in MgO precursors enhances the adsorbent's microstructure, thereby improving its CO2 capture efficiency and bolstering cycling stability. This research enhances our understanding of the factors influencing CO2 adsorption and cyclic stability in alkali metal salt‐promoted MgO, providing valuable insights for further refinement in the formulation and synthesis protocols of MgO‐based CO2 adsorbents. © 2024 Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]

Catalytic cycloaddition of CO2 with propylene oxide (PO) is a sustainable pathway for the synthesis of propylene carbonate (PC), and the design of efficient heterogeneous catalysts is a hot research topic in both C1 chemistry and functional materials. In this work, graphitic carbon nitride (g‐C3N4) materials were prepared using urea (U) and melamine (M) as precursors through one‐step thermal condensation and then applied as catalyst supports for ZnBr2. As heterogeneous catalysts, the synthesized composites (ZnBr2/g‐C3N4‐MU) exhibited higher activity in the cycloaddition reaction of CO2 to PC than ZnBr2/g‐C3N4‐M and ZnBr2/g‐C3N4‐U. The preparation temperature of ZnBr2/g‐C3N4‐MU could affect the distributions of nitrogen species and acidic strength, which thus determined the final catalytic activity. More importantly, the loading of ZnBr2 not only introduced acidic sites but also enhanced the strength of alkaline sites of g‐C3N4‐MU, enabling ZnBr2/g‐C3N4‐MU materials as acid–base bifunctional catalysts in cycloaddition of CO2 with PO. [ABSTRACT FROM AUTHOR]

The oxalate-carbonate pathway (OCP) involves degradation of soil oxalate to carbonate. To exploit and manage this natural mineralization of assimilated atmospheric CO2 into stable carbonates, improved understanding of this complex biotransformation process is needed. A strain of oxalate-degrading bacteria, Azospirillum sp. OX-1, was isolated from soil, and its secondary products of calcium oxalate degradation were analyzed and characterized using SEM, XRD, TG/DTG-DTA and FTIR-spectroscopy. The molecular mechanism of calcium oxalate degradation was also analyzed using proteomics. The results showed, for the first time, that OX-1 could not only degrade calcium oxalate to calcium carbonate, but also that the process was accompanied by synthesis of methane. Proteomic analysis demonstrated that OX-1 has a dual enzyme system for calcium oxalate degradation, using formyl-CoA transferase (FRC) and thiamine pyrophosphate (ThDP)-dependent oxalyl-CoA decarboxylase (OXC) to form calcium carbonate. Up-regulated expression of enzymes related to methane synthesis was also detected during calcium oxalate degradation. Since methane is also a potent greenhouse gas, these new results suggest that the utility of exploiting the OCP to reduce atmospheric CO2 must be re-evaluated and that further studies should be conducted to reveal how widespread the methane producing capacity of strain OX-1 is in other bacteria and soil environments. [ABSTRACT FROM AUTHOR]

ABSTRACT CO2 is a significant greenhouse gas, and is considered as a copious renewable carbon reagent. From a synthetic perspective, it can be used as a sustainable and substitute C1 building block because of its nontoxic, nonflammable, and abundant nature. The transformation of a wide range of organic molecules with CO2 into numerous efficient commodities is a defining feature of recent success in this sector. Because of its numerous applications, photocatalysts and visible light‐mediated synthesis of carbamates and cyclic carbonates using CO2 have drawn a lot of interest from researchers. This mini review mainly focusses on the different one‐pot reactions that are proven to be efficacious for chemical fixation of CO2 in producing industry‐based compounds of carbamates and carbonates with the creation of CO, CH, CC, and CN bonds. [ABSTRACT FROM AUTHOR]

The Neoproterozoic carbonate rocks of the Araras Group (Amazon Craton) and the Sete‐Lagoas and Salitre Formations (São Francisco Craton) share a statistically indistinguishable single‐polarity (reversed) characteristic direction. This direction is associated with paleomagnetic poles that do not align with the expected directions for primary detrital remanence. We employ a combination of classical rock magnetic properties and micro imaging/chemical analysis (in thin sections) using synchrotron radiation to examine these remagnetized carbonate rocks. Magnetic data indicate that most samples lack the anomalous hysteresis properties typically associated with carbonate remagnetization (except for distorted loops). Through a combination of Scanning Electron Microscopy with Energy Dispersive X‐ray Spectroscopy (SEM‐EDS), X‐ray Fluorescence (XRF), and X‐ray Absorption Spectroscopy (XAS), we identified subhedral/anhedral magnetite, or spherical grains with a core‐shell structure of magnetite surrounded by maghemite. These grains are within the pseudo‐single domain size range, as do most of the iron sulfides, and are spatially associated with potassium‐bearing aluminosilicates. While fluid percolation and organic matter maturation play a role, smectite‐illitization appears to be crucial for the growth of these phases. X‐ray diffraction analysis, in addition, identifies these silicates as predominantly highly crystalline illite, suggesting exposure to epizone temperatures. These temperatures were likely reached during the final stages of the Gondwana assembly (Cambrian), but remanence was only locked in afterward, in successive cooling events during the Early Middle Ordovician. This is supported by the carbonates' paleomagnetic pole positions compared to Gondwana's apparent polar wander path, and the absence of reversals, contrasting with the high reversal frequency of the Late Ediacaran/Cambrian. Plain Language Summary: Carbonate rocks serve as important records of ancient climates and host magnetic minerals capable of documenting the evolution of Earth's magnetic field. Nevertheless, their original magnetization, acquired during sedimentation, is frequently supplanted by a secondary magnetization, originating from various geological processes altering local thermochemical stability. For carbonate rocks, this remagnetization process is often associated with a "magnetic fingerprint." In South America, carbonate rocks from different sedimentary basins (hundreds of kilometers apart) exhibit statistically similar magnetic components that deviate from their formation origin, indicating secondary processes. This multidisciplinary study integrates classical paleomagnetic analysis with micro‐chemical and imaging analysis to comprehend the geological phenomena responsible for remagnetizing such an extensive continental area. We demonstrate that not all remagnetized samples display the anticipated magnetic fingerprint. Highly detailed chemical analysis confirms the presence of nanoscopic magnetic minerals spatially correlated with clay minerals indicating that while organic matter transformation may play a significant role, clay mineral transformation is a key phenomenon governing remagnetization in these rocks. However, our data also supports the notion that these rocks underwent heating during the final assembly of the ancient continental landmass, Gondwana, and a sequential cooling event is suggested as locking their magnetization in the state observed today. Key Points: Remagnetized Neoproteorozoic carbonates in Brazil may not consistently display anomalous hysteresis parametersSynchrotron‐based analysis revealed pseudo‐single domain‐sized magnetite spatially correlated with aluminosilicates (smectite‐illite)The Late Cambrian assembly of Gondwana thermally reset the carbonates' remanence, eventually blocking it (470–460 Ma) during gradual cooling [ABSTRACT FROM AUTHOR]

Small bifunctional molecules are attractive for use as models in different areas of knowledge. How can their functional groups interact in solids? This is important to know for the prediction of the physical and chemical properties of the materials based on them. In this study, two new hydrogen-bonded organic frameworks (HOFs) based on sterically demanding molecular compounds, bis(1-hydroxy-2-methylpropane-2-aminium) sulfate (1) and 2-methyl-4-oxopentan-2-aminium hydrogen ethanedioate hydrate (2), were synthesized and fully characterized by means of FTIR and NMR spectroscopies, as well as by X-ray powder diffraction and thermogravimetric analyses. Their molecular and crystal structures were established through single-crystal X-ray diffraction analysis. It was shown that both compounds have a layered structure due to the formation of a 2D hydrogen-bonding network, the layers being linked by systematically arranged Van der Waals contacts between the methyl groups of organic cations. To unveil some dependencies between the chemical nature of bifunctional molecules and their solid structure, Hirschfeld surface (HS) analysis was carried out for HOFs 1, 2, and their known congeners 1-hydroxy-2-methylpropan-2-aminium hemicarbonate (3) and 1-hydroxy-2-methylpropan-2-aminium (1-hydroxy-2-methylpropan-2-yl) carbamate (4). HS was performed to quantify and visualize the close intermolecular atomic contacts in the crystal structures. It is clearly seen that H–H contacts make the highest contributions to the amino alcohol based compounds 1, 3 and 4, with a maximal value of 65.2% for compound 3 having CO32− as a counterion. A slightly lower contribution of H–H contacts (64.4%) was found for compound 4, in which the anionic part is represented by 1-hydroxy-2-methylpropan-2-yl carbamate. The significant contribution of the H–H contacts in the bifunctional moieties is due to the presence of a quaternary carbon atom with a short three-carbon chain. [ABSTRACT FROM AUTHOR]

The conventional use of polyurethane in various applications is hindered by significant challenges, such as toxicity concerns, moisture sensitivity, and environmental impact. In response, there has been a notable surge in research focusing on bio-based alternatives, particularly non-isocyanate polyurethanes (NIPUs), aligning with sustainable development objectives. NIPUs offer a promising solution by eliminating the need for isocyanates, employing cyclic carbonates and diamines instead. Out of various sources available, non-traditional vegetable oils present a viable starting material for cyclic carbonate synthesis due to their availability, renewability, and affordability. However, despite the growing interest in NIPUs, there remains a scarcity of literature on the utilization of non-traditional oils for their development. This short review aims to fill this gap by providing an overview of bio-based NIPUs synthesized from non-traditional vegetable oils such as jatropha oil, castor oil, lignin oil, linseed oil, and rubber seed oil. The review covers the synthesis methods of NIPUs via polyaddition reactions of carbonates and amines, detailing properties, advantages, and applications of each oil-based NIPU. Furthermore, by identifying research gaps and proposing potential solutions, this paper aims to encourage researchers to consider non-traditional oils for NIPU synthesis, facilitating significant advancements in the field. [ABSTRACT FROM AUTHOR]

Aqueous alteration in planetesimals is one of the earliest geological processes in the solar system. The timing of aqueous alteration sheds light on the timescale of material evolution through water–rock interaction in small bodies. The 53Mn-53Cr decay system, where a short-lived radionuclide 53Mn decays to 53Cr with a half-life of 3.7 Myr, is a powerful tool for dating carbonates in primitive meteorites that formed during aqueous alteration. In CI chondrites and samples returned from asteroid Ryugu, a major carbonate mineral is dolomite (CaMg(CO 3) 2) and could be dated precisely because of their relatively high Mn abundances. However, the lack of a proper dolomite standard for secondary ion mass spectrometry (SIMS) hinders us from obtaining accurate Mn/Cr ratios of carbonates, resulting in erroneous formation ages. In this work, we synthesized Mn-, Cr-, and Fe-bearing crystalline dolomite as standard materials and evaluated the relative sensitivity factor (RSF) of Mn/Cr for SIMS analysis, namely, the ratio of Mn/Cr obtained using SIMS to true Mn/Cr. We found that the RSF values of the dolomite standards range from 0.8 to 0.9, slightly higher than that of calcite (CaCO 3) (∼0.7), and increase with their Fe contents. We used the newly evaluated RSF values to date dolomite in the Ivuna CI chondrite and obtained an initial 53Mn/55Mn ratio of (3.95 ± 0.49) × 10−6 (95 % confidence interval) and the corresponding absolute age of 4564.0 + 0.6/−0.7 Ma. Our new initial 53Mn/55Mn ratio is 26 ± 19 % higher than that obtained by a previous study for the same dolomite grain using a calcite standard. This difference is consistent with the difference between the RSF values of dolomite and calcite. Based on these results, we updated the initial 53Mn/55Mn ratio previously reported for dolomite in the Ryugu sample A0058 to be (3.21 ± 0.66) × 10−6, which corresponds to an absolute age of 4562.8 + 1.0/−1.2 Ma. This age seems to be the best estimate for the formation age of dolomite in Ryugu currently available. [ABSTRACT FROM AUTHOR]

The scarce carbonate record on the Martian surface is one of the fundamental unsolved issues for paleoclimate and environmental evolution. Whether carbonates first formed and then dissolved due to a transition in global environments or whether Mg–Fe carbonates never extensively formed due to geochemical kinetics thresholds remains unknown. In this study, we experimentally examined the preservation potential of siderite in Mars‐relevant fluids, including ultrapure water, H2O2, NaClO4, NaClO3, NaCl, Na2SO4, NaHCO3, and Na2SiO3 solutions, at 277 K. The effects of the water/rock ratio at WR10 and WR100 on dissolution rates were also investigated. We found that siderite dissolution and subsequent oxidation and hydrolysis of leached Fe did not substantially acidify the solutions. The siderite dissolved relatively rapidly in the chloride and chlorate solutions and slowly in the silica or bicarbonate solutions. In a circum‐neutral to slightly alkaline aqueous environment with oxidative species, the mobility of leached Fe was limited, leading to the formation of goethite or lepidocrocite, which clustered on the siderite surface. The longest lifetime of 1‐mm siderite grains was found in the Na2SiO3 solution at WR100, which was estimated to range from 198 ka to 198 Ma. Water‐limited, silica‐rich, and oxidative aqueous environments benefit siderite preservation on the Martian surface. Our results support that the lack of voluminous siderite on Mars may be primarily due to the inhibition of its formation rather than alteration and dissolution after its presence, consistent with the recent detection of Mg–Fe carbonate at Gale Crater and Jezero Crater. Plain Language Summary: Despite the predominant carbon dioxide atmosphere, the distribution of carbonate outcrops on Mars detected to date is very limited. The discrepancy between the CO2‐dominant atmosphere and scarce carbonate records is one of the key issues for understanding the paleoclimate and environmental evolution of Mars. We experimentally investigated the preservation potential of siderite in eight Mars‐relevant fluids under water‐limited versus water‐abundant scenarios at 277 K. We found that water‐limited conditions, silica‐rich environments, and the presence of oxidants in aqueous environments generally benefit siderite preservation. The longest lifetime of 1‐mm siderite grains is present in silica‐rich solutions, estimated to range from 198 ka to 198 Ma. In a neutral to alkaline aqueous environment with oxidative species, the mobility of leached iron is limited, and the Fe precipitates are mainly in the form of goethite or lepidocrocite, accumulating on the siderite surface. Martian aqueous environments can efficiently preserve siderite. Therefore, the lack of voluminous siderite on Mars may be because siderite was never extensively formed rather than altered and dissolved after its presence. Key Points: Siderite dissolves relatively fast in chloride‐ and chlorate‐fluids and slowly in silica‐ and bicarbonate‐fluidsWater‐limited, silica‐rich, and oxidative aqueous environments favor siderite preservation on the Martian surfaceThe scarcity of voluminous siderite on Mars may be due to the inhibition of its formation rather than its dissolution after its presence [ABSTRACT FROM AUTHOR]

The Thermal Evolved Gas Analyzer (TEGA) analysis of surface and icy subsurface Phoenix landing site soils consisted of low (300–700°C) and high (>700°C) temperature CO2 evolutions that were attributed to organic carbon (83–1,484 μgC/g) and Ca‐rich carbonate (1.1–2.6 wt.%). Total carbon abundances ranged from 1,143 to 4,905 µgC/g, which is the highest soil carbon concentration so far detected on Mars. Low temperature CO2 was attributed to oxidized organic C (e.g., oxalates, acetates), while hydrocarbon combustion was indicated in two soils by the detection of coevolved CO2 and O2 (perchlorate). Combustion reactions may have prevented the detection of hydrocarbon masses in the Phoenix landing site soils. Organic C was likely derived from meteoritic and igneous/hydrothermal sources, but microbiological sources cannot be excluded. CO2 evolved at high temperatures was consistent with Ca‐rich carbonate along with possible minor contributions from macromolecular organic carbon and mineral/glass vesicle CO2. Carbon detected in the Phoenix landing site soil and other landing site soils and sands (e.g., Gale/Jezero craters) would be consistent with global organic C and carbonate in soils and sand across Mars. However, oxidizing water thin films derived from the near‐surface ice in the Phoenix soils favor Ca‐carbonate over Fe‐carbonate, which is likely more stable in the ice‐free regions of Mars (e.g., Gale/Jezero craters). The global carbon budget on Mars inferred from these results emphasizes that Mars Sample Return should yield carbon bearing soil/rock that would allow the identification of the origin of carbon and any possible connections to ancient martian microbiology. Plain Language Summary: The Phoenix Lander's Thermal Evolved Gas Analyzer (TEGA) analyzed surface and subsurface icy soils of the martian northern plains in 2008. The TEGA instrument heated scooped soils to 1,000°C and measured evolved gases (e.g., CO2, O2, H2O) to quantify the presence of volatile bearing phases (e.g., organics, carbonates, salts). Some TEGA results have been previously published; however, this report describes unreported TEGA results. The TEGA instrument detected low (300–700°C) and high (>700°C) temperature CO2 evolutions that were attributed to organic carbon and Ca‐rich carbonate. Total carbon abundances as high as 4,905 µgC/g were detected which is the highest soil carbon concentration detected on Mars to date. Organic C sources include meteoritic and igneous/hydrothermal sources, but microbiological origins cannot be excluded. Ca‐rich carbonate may have been inherited from local sediments or was derived from dissolved CO2 reactions with the soil in migrating water thin‐films from subsurface ice. The carbon detections at the Phoenix and other landing sites suggest that Mars Sample Return of surface soil/rock should contain carbon that can be used to identify the origin(s) of carbon. Key Points: Phoenix landing site soils have the highest soil carbon concentration (up to 4,905 µgC/g) of any soil measured on MarsOrganic C (83–1,484 μgC/g) was likely derived from meteoritic sources with possible contributions from igneous/hydrothermal sourcesCa‐carbonate (1.1–2.6 wt.%) was inherited from local sediments or derived from soil reactions with dissolved CO2 in water thin‐films [ABSTRACT FROM AUTHOR]

The minor and trace element compositions of biogenic carbonates such as foraminifera are important tools in paleoceanography research. However, most studies have focused primarily on samples with element to calcium (El/Ca) ratios higher than the El/Ca range often found in benthic foraminifera. Here, we systematically assess the precision and accuracy of foraminifera elemental analysis across a wide range of El/Ca especially at relatively low ratios, using a method on a Thermo Scientific iCAP Qc quadrupole Inductively Coupled Plasma Mass Spectrometer (ICP‐MS). We focus on two benthic foraminifera species, Hoeglundina elegans and Cibicidoides pachyderma, and prepared a suite of solution standards based on their typical El/Ca ranges to correct for signal drift and matrix effects during ICP‐MS analysis and to determine analytical precision. We observe comparable precisions with published studies at high El/Ca, and higher relative standard deviations for each element at lower El/Ca, as expected from counting statistics. The overall long‐term analytical precision (2σ) of the H. elegans‐like consistency standard solutions was 6.5%, 4.6%, 5.0%, for Li/Ca, Mg/Ca, Mg/Li, and 6.4%, 10.0%, 4.2% for B/Ca, Cd/Ca, Sr/Ca. The precision for H. elegans‐like Mg/Li is equivalent to a temperature uncertainty of 0.5–1.1°C. Measurement precisions were also assessed based on three international standards (one solution and two powder standards) and replicate measurements of H. elegans and C. pachyderma samples. We provide file templates and program scripts that can be used to design calibration and consistency standards, prepare run sequences, and convert the raw ICP‐MS data into molar ratios. Key Points: Higher relative standard deviations are reported at lower element/calcium values, as expected from counting statisticsConsistency standards having similar ratios to the unknown samples provide an accurate estimate of errorsFor the Hoeglundina elegans Mg/Li—temperature proxy, analytical precision (2σ) is equivalent to a temperature uncertainty of 0.5–1.1°C [ABSTRACT FROM AUTHOR]

Boron geochemistry from biogenic carbonates offer valuable information about ocean pH and CO2 chemistry. However, application to geological carbonate deposits suffers from analytical difficulties in obtaining geochemical signals exclusively from the carbonate phase. Sequential leaching with reagents and acids has the potential to overcome such an issue. There is, however, little systematic investigation about the efficiency of sequential leaching in isolating carbonate‐associated boron from siliciclastic matrix. Here, we developed a sequential leaching protocol and applied it to methane‐derived‐authigenic‐carbonate samples. Using the leachate δ11B signatures, elemental composition, and mineral composition of residues, we show that the sequential leaching is able to improve the separation of boron from different phases. Buffered hydrogen peroxide removes organic matter and also some silicate phases resulting low δ11B values. Leaching with NH4Ac removes adsorbed boron though may also partially leach some carbonate phases. The first few leaching steps with diluted acetic acid dissolve carbonate phases. Depending on the sample type, these may also capture some remaining adsorbed boron from the preceding NH4Ac leaching. Once the adsorbed boron is completely removed, as indicated by the progressively higher δ11B values during the following acid leaching steps, representative carbonate composition can be derived. The accuracy of this protocol is demonstrated with leaching experiments using artificial deep sea coral carbonate and clay mixtures that give the representative carbonate‐associated δ11B within error of the pure coral value. Our results provide insights into characteristic signatures derived from silicates and organic matter that need to be considered in boron isotope analyses of impure marine carbonates. Key Points: Boron signals from geological carbonate deposits are difficult to isolate from siliciclastic components of mixed matrix samplesA calibrated sequential leaching protocol was developed to extract boron from the carbonate phase of mixed carbonate‐silicate limestonesSuccessful separation is possible in samples with only 25% carbonate, provided the protocol is adjusted for carbonate content [ABSTRACT FROM AUTHOR]

The lanthanide (Ln) elements are critical materials that are typically extracted/mined together. Their separation by use of solvent extraction from acidic media is well known; however, there are few studies in basic media with carbonate anions. We investigated the complexation of Eu(III) and Tb(III) carbonates as solids and solutions in alkaline K2CO3, wherein we sought to access a Tb(IV) carbonate complex through ozonolysis. L3‐edge XANES of Eu and Tb carbonate solids, colorless solutions, and a red‐hued Tb solution (obtained by ozonolysis) all showed Ln(III) cations. The absence of evidence for a Tb(IV) complex was confirmed through XAS and EPR analyses, despite the solution exhibiting a deep red color. For solids and solutions, EXAFS results indicate molecular Ln(III)‐carbonato anions. In terms of the Eu(III) carbonate coordination number, the coordination does not change upon dissolution of the solid sample. Furthermore, EXAFS for the solutions revealed evidence for the association of potassium cations with the Ln(III)‐carbonato anions. This direct observation of contact ion pairing by EXAFS at room temperature is rare. The insights into Ln(III) carbonate complexation and solution speciation afforded by XANES‐EXAFS, FT‐IR, and EPR provides perspectives that serve as benchmarks for future computational and experimental efforts focused on caustic‐side solvent extraction of Ln(III) ions. [ABSTRACT FROM AUTHOR]

On Earth, carbonate minerals are widely used as recorders of the geological environments in which they formed. Here, we present a method designed to retrieve the crystal chemistry of Fe‐Mg carbonate minerals using infrared remote sensing or Raman spectroscopy. We analyzed a suite of well‐characterized Fe‐Mg carbonate minerals for which Raman spectra were obtained in two different laboratories, and IR spectra were measured in reflectance and transmission from the visible range to 25‐μm. We built calibration lines for the dependence of fundamental and harmonic vibrational modes position to the Mg# (defined as Mg# = 100 × Mg/(Mg + Fe + Ca + Mn)). These calibrations should enable retrieval of Mg# based on spectroscopic observations with a typical accuracy of 10. We discuss the framework of applicability of these calibrations and apply them to a typical CRISM spectrum of carbonates from the Nilli Fossae region of Mars. Key Points: Fundamental FeMg carbonate mode position have a linear dependence to Mg# for Fe‐Mg carbonate mineralHarmonic bands at 2.3 and 2.5 also have a linear dependence of their position with Mg# for Fe‐Mg carbonate mineralsWe present calibration curves of Mg# versus fundamental and harmonic vibration position than can be used to retrieve crystal chemistry [ABSTRACT FROM AUTHOR]

The number of pore volumes to breakthrough is one of the most critical indicators of wormhole characterization in the matrix acidizing process. This number is often needed for experimental work that is time-consuming and costly. In this article, an empirical model was used to evaluate the acidizing procedure in the carbonate cores, including limestone and dolomite. This empirical model measures the number of wormholes formed in the carbonate cores after acid injection by using the conservation of mass law. This approach maintained the transport relative reaction rates of core and acid within the wormhole structure during the wormhole formation procedure. In addition, this empirical model accounted for changes in acid concentration as an injected fluid flow. Also, the changes in carbonate porosity, the effect of the Damköhler number, and injection rate were included in the model. Compared to other experimental and semi-empirical works, the established model gave an excellent assessment of 95.45% for the average accuracy and 0.9933 for the average coefficient of determination. Therefore, an empirical technique to approximate this number in the carbonate formations with high accuracy using physical core and acid properties is herein proposed. [ABSTRACT FROM AUTHOR]

The linkage between the variation of the seawater Mg budget and the long-term carbon cycle can be elucidated by seawater Mg isotope composition (δ26Mg). However, obtaining primary seawater δ26Mg signatures from marine archives is challenging due to the widespread alteration of diagenesis. Aragonite, a common primary marine carbonate, can effectively record seawater δ26Mg but is prone to alteration and transformation into calcite during early diagenesis. Therefore, a comprehensive understanding of Mg isotope behavior during the aragonite–calcite transition is essential to enhance the applicability of aragonite δ26Mg. In this study, we investigate the variation of aragonite δ26Mg during diagenesis with a limited supply of Mg by conducting a series of well-controlled aragonite–calcite transition experiments in a closed system. The experimental conditions encompass temperatures of 60 and 90 °C, the presence of Ca and Na in the solution, varying Na concentrations, as well as the presence of calcite seed. Results demonstrate that the significant decrease of bulk carbonate δ26Mg is accompanied by a substantial amount of Mg released into the solution during the aragonite–calcite transition, and the amount of released Mg is controlled by fluid chemistry via altering Mg partitioning in calcite. Furthermore, Mg isotope fractionation during calcite precipitation is influenced by temperature, ionic strength, and the presence of calcite seed, while kinetics played a negligible role in our experiments. Combined with previous experiments, the temperature-dependent Mg isotope fractionation during calcite precipitation in unseeded experiments is Δ26Mg cal-sol = (−0.13 ± 0.06) × 106/T2 – (0.47 ± 0.68). This fractionation is systematically higher than that of seeded experiments by 0.3–0.6 ‰ from 15 to 90 °C and can mainly be attributed to differences in surface free energy between homogeneous and heterogeneous calcite nucleation. These findings offer fundamental understandings of the Mg isotope behavior during the aragonite–calcite transformation, providing useful insights for interpreting the variation of δ26Mg in experimental and natural carbonates and facilitating ancient seawater δ26Mg reconstruction. [ABSTRACT FROM AUTHOR]

We combine published and new mineralogical data on most major taxa of brachiopods from all over the world, to investigate patterns and controls on brachiopod carbonate mineralogy. Measurements of 1726 specimens in 162 species (including 56 fossil species) ranged from 79°N to 74°S and from intertidal to almost 4000 m deep. Calcareous brachiopods mostly create strong resilient valves of very low-Mg calcite ($\bar{\chi }$ χ ¯ = 1.3 wt% MgCO3). The substrate-cemented Craniida ($\bar{\chi }$ χ ¯ = 8.9 wt% MgCO3) and Thecideida ($\bar{\chi }$ χ ¯ = 6.5 wt% MgCO3) are unusual in precipitating calcite with higher Mg content. This is the first study to find bimineralic brachiopods; a few species show a combination of low-Mg ($\bar{\chi }$ χ ¯ = 0.8 wt% MgCO3) and intermediate-Mg calcite ($\bar{\chi }$ χ ¯ = 7.2 wt% MgCO3) (sensu Smith AM, Key MM Jr, Gordon DP. 2006. Skeletal mineralogy of bryozoans: taxonomic and temporal patterns. Earth-Science Reviews. 78:287–306.). While Mg in calcite varies systematically among valve layers and sometimes along the growth axis, we found no consistent difference between valves of the same individual. A weak latitudinal signal indicates some overall temperature control of Mg, but in general, brachiopods are active calcifiers, precipitating low-Mg calcite even when Mg:Ca ratio in seawater is high. The drivers on brachiopod mineralogy are individual, environmental, and phylogenetic – resulting in complex variability. [ABSTRACT FROM AUTHOR]

In numerous carbonate reservoirs in the Middle East, peloidal packstone‐grainstones are rock types with excellent pore storage potential in micritised microporous grains. However, the origin of the micro‐porosity and associated micro‐spar remains unclear, and one hypothesis is that both micro‐spar and porosity originate from early marine micritisation and were later altered during subsequent diagenesis (i.e. cementation recrystallisation). The south‐eastern coast of the Arabian Gulf is recognised as a modern, albeit miniature, depositional setting analogue to Mesozoic carbonate sequences that form the supergiant reservoirs of the Middle East. Using optical microscopy, backscattered scanning electron microscopy and carbon and oxygen stable isotope analysis the present study aims to document the nature of internal microstructures of micritic envelopes and peloids from the surface sediments of various sub‐environments of the Abu Dhabi Lagoon. Results highlight a high degree of diversity and heterogeneities of most micritic envelopes and peloids observed across the sub‐environments. First, carbonate grains from ooid and bioclastic shoals show the simpler micritic envelopes. Here, micritic envelopes and peloids show sparse microborings filled with banded radial aragonite cement, a pattern of production of cryptocrystalline texture (e.g. micritisation) that is similar to the sequence of micritisation observed in the modern sediment of the Great Bahama Bank. Conversely, in the subtidal and intertidal zones with mangroves or seagrass, the micritic envelopes and peloids are much more complex and show multiple generations of microborings that are either empty or filled with carbonate materials of varying types (i.e. various cements, fragments, etc.). [ABSTRACT FROM AUTHOR]

Copyright of Geologia USP: Série Científica is the property of Geologia USP 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.)

Anthropogenic activities on land will affect the carbon system in coastal waters. This condition will affect the role of coastal waters as a source or sink of carbon. This research will examine the distribution of carbonate systems and estimate CO2 fluxes. Water samples were taken at 30 stations as well as measuring in situ water parameters including pH, temperature, salinity, and pressure. Alkalinity was analysed based on the titration method, chl-a using the fluorometer method, and carbonate system parameters (pCO2(sea) and DIC) calculated using CO2SYS.xlsm. The pCO2(atm) value is calculated based on atmospheric data from satellite data, including the saturation vapour pressure of sea air in the atmosphere, fraction mol of CO2, and sea level pressure. Pearson correlation analysis was used to see the correlation between the measured parameters and CO2 flux. Carbon flux is determined based on the difference between atmospheric and oceanic pCO2. The DIC calculation result was in the range of 1,946.09 µmol/kg - 2,061.65 µmol/kg and the total alkalinity was 2,156.86 µmol/kg - 2,264.71 µmol/kg. Based on this value, Jepara coastal waters have pCO2(sea) of 573,800 micro-atmospheric (µatm) which is higher than pCO2(atm) (i.e., 386,772 µatm). The input of organic/inorganic carbon resulting from anthropogenic processes on land has influenced Jepara coastal waters which act as a source of CO2 into the atmosphere amounting to 103,799 mmol/m2/day. The results of this research can be used as a reference for managing coastal areas to achieve low carbon emissions. [ABSTRACT FROM AUTHOR]

Earth scientists have leveraged carbon isotope records to interpret Earth history and establish chronostratigraphic frameworks for decades (e.g., Halverson et al., 2005, https://doi.org/10.1130/b25630.1; Kaufman & Knoll, 1995, https://doi.org/10.1016/0301‐9268(94)00070‐8; Knoll et al., 1986, https://doi.org/10.1038/321832a0; Saltzman & Thomas, 2012, https://doi.org/10.1016/b978‐0‐444‐59425‐9.00011‐1; Scholle & Arthur, 1980, https://doi.org/10.1306/2f91892d‐16ce‐11d7‐8645000102c1865d). Increasingly detailed and nuanced approaches have been applied to understanding carbon isotope records in light of local‐ and regional‐scale processes that complicate interpretations. The recent work of Gazdewich et al. (2024, https://doi.org/10.1029/2023gc011376) is a prescient example, in which they conduct a series of analyses to constrain the influence of authigenic carbonate burial on the global carbon isotope mass balance during the Late Devonian. Here, I briefly review some recent developments in quantitative approaches to understanding carbon isotope values measured from carbonate rocks (δ13Ccarb), with a focus on comparisons of measured δ13Ccarb values, models for understanding what controls δ13Ccarb values, and correlation tools for aligning δ13Ccarb stratigraphies. These new approaches are elucidating carbon isotope records across Earth history and may prove to be transformative for our understanding of the global carbon cycle. Plain Language Summary: The ratio of stable carbon isotopes measured in carbonate rocks (δ13Ccarb) has long been used as a tool for geologists to estimate the relative ages of ancient rocks by matching trends in δ13Ccarb between localities. Recent work has demonstrated that biological and geological processes at local and regional scales can influence δ13Ccarb, making the matching between localities more complicated. Because of this, increasingly detailed and nuanced approaches have been developed to understand trends in δ13Ccarb. Gazdewich et al. (2024, https://doi.org/10.1029/2023gc011376) recently provided a new protocol for constraining the degree to which one of these geological processes–the burial of in situ‐forming carbonate minerals (authigenic carbonate)–impacted δ13Ccarb values during the Late Devonian (382.7–358.9 million years ago). In this commentary, I provide context for this advancement, highlighting other recent developments in quantitative approaches for understanding δ13Ccarb values. These new approaches have the potential to significantly improve our understanding of the global carbon cycle through time, as inferred by changes in δ13Ccarb across Earth history. Key Points: Quantitative and nuanced approaches are revealing the impact of local‐ and regional‐scale processes on δ13Ccarb values and correlationDespite complications, δ13Ccarb correlation still appears to often yield realistic chronostratigraphic frameworks across Earth historyA full accounting of the uncertainties associated δ13Ccarb values is needed for future interpretations, and to improve our understanding of the global carbon cycle across Earth history [ABSTRACT FROM AUTHOR]

Abstract The oxalate-carbonate pathway (OCP) involves degradation of soil oxalate to carbonate. To exploit and manage this natural mineralization of assimilated atmospheric CO2 into stable carbonates, improved understanding of this complex biotransformation process is needed. A strain of oxalate-degrading bacteria, Azospirillum sp. OX-1, was isolated from soil, and its secondary products of calcium oxalate degradation were analyzed and characterized using SEM, XRD, TG/DTG-DTA and FTIR-spectroscopy. The molecular mechanism of calcium oxalate degradation was also analyzed using proteomics. The results showed, for the first time, that OX-1 could not only degrade calcium oxalate to calcium carbonate, but also that the process was accompanied by synthesis of methane. Proteomic analysis demonstrated that OX-1 has a dual enzyme system for calcium oxalate degradation, using formyl-CoA transferase (FRC) and thiamine pyrophosphate (ThDP)-dependent oxalyl-CoA decarboxylase (OXC) to form calcium carbonate. Up-regulated expression of enzymes related to methane synthesis was also detected during calcium oxalate degradation. Since methane is also a potent greenhouse gas, these new results suggest that the utility of exploiting the OCP to reduce atmospheric CO2 must be re-evaluated and that further studies should be conducted to reveal how widespread the methane producing capacity of strain OX-1 is in other bacteria and soil environments.

Abstract In numerous carbonate reservoirs in the Middle East, peloidal packstone‐grainstones are rock types with excellent pore storage potential in micritised microporous grains. However, the origin of the micro‐porosity and associated micro‐spar remains unclear, and one hypothesis is that both micro‐spar and porosity originate from early marine micritisation and were later altered during subsequent diagenesis (i.e. cementation recrystallisation). The south‐eastern coast of the Arabian Gulf is recognised as a modern, albeit miniature, depositional setting analogue to Mesozoic carbonate sequences that form the supergiant reservoirs of the Middle East. Using optical microscopy, backscattered scanning electron microscopy and carbon and oxygen stable isotope analysis the present study aims to document the nature of internal microstructures of micritic envelopes and peloids from the surface sediments of various sub‐environments of the Abu Dhabi Lagoon. Results highlight a high degree of diversity and heterogeneities of most micritic envelopes and peloids observed across the sub‐environments. First, carbonate grains from ooid and bioclastic shoals show the simpler micritic envelopes. Here, micritic envelopes and peloids show sparse microborings filled with banded radial aragonite cement, a pattern of production of cryptocrystalline texture (e.g. micritisation) that is similar to the sequence of micritisation observed in the modern sediment of the Great Bahama Bank. Conversely, in the subtidal and intertidal zones with mangroves or seagrass, the micritic envelopes and peloids are much more complex and show multiple generations of microborings that are either empty or filled with carbonate materials of varying types (i.e. various cements, fragments, etc.).

Abstract The technique of matrix acidification or acid fracturing is commonly utilized to establish communication with natural fractures during reservoir reconstruction. However, this process often encounters limitations due to filtration, which restricts the expansion of the primary acid-etching fracture. To address this issue, a computational model has been developed to simulate the expansion of an acid-etching wormhole by considering various factors such as formation process, injection duration, pressure build-up, and time-varying acid percolation rate. By analyzing the pumping displacement of acid-etching wormholes, this model provides valuable insights into the time-dependent quantities of acid percolation. It has been revealed that the filtration rate of acid-etching wormholes is strongly influenced by pumping displacement, viscosity, and concentration of the acid fluid used in stimulation as well as physical properties of the reservoir itself. Notably, viscosity plays a significant role in determining the effectiveness of acid fracturing especially in low-viscosity conditions. Acid concentration within 15% to 20% exhibits maximum impact on successful acid fracturing while concentrations below 15% or above 20% show no obvious effect. Furthermore, it was found that pumping displacement has a major influence on effective fracturing. However, beyond a certain threshold (> 5.0 m3/min), increased pumping displacement leads to slower etching distance for acids used in construction purposes. The simulation also provides real-time distribution analysis for acidity levels within eroded fractures during matrix-acidification processes and quantifies extent of chemical reactions between acids and rocks within these fractures thereby facilitating optimization efforts for design parameters related to matrix-acidification.

Sedimentary facies identification is critical for carbonate oil and gas reservoir development. The traditional method of sedimentary facies identification not only be affected by the engineer's experience but also takes a long time. Identifying carbonate sedimentary facies based on machine learning is the trend of future development and has the advantages of short time consuming and reliable results without engineers' subjective influence. Although many references reported the application of machine learning to identify lithofacies, but identifying sedimentary facies of carbonate reservoirs is much more challenging due to the complex sedimentary environment and tectonic movement. This paper compares the performance of the carbonate sedimentary facies identification using four different machine learning models, and the optimal machine learning with the highest prediction accuracy is recommended. First, the carbonate sedimentary facies are classified into the lagoon, shallow sea, shoal, fore-shoal, and inter-shoal five tags based on the well loggings. Then, five well log curves including spectral gamma ray (SGR), uranium-free gamma ray (CGR), photoelectric absorption cross-section index (PE), true formation resistivity (RT), shallow lateral resistivity (RS) are used as the input, and the manual identified carbonate sedimentary facies are used as the output of the machine learning model. The performance of four different machine learning algorithms, including support vector machine (SVM), deep neural network (DNN), long short-term memory (LSTM) network, and random forest (RF) are compared. The other two wells are used for model validation. The research results show that the RF method has the highest accuracy of sedimentary facies prediction, and the average prediction accuracy is 78.81%; the average accuracy of sedimentary facies prediction using SVM is 77.93%. The sedimentary facies predictions using DNN and LSTM are less satisfying compared with RF and SVM, and the average accuracy is 69.94% and 73.05%, respectively. The predicted carbonate sedimentary facies by LSTM are more continuous compared with other machine learning models. This study is helpful for identifying compelx sedimentary facies of carbonate reservoirs from well logs.

The formation of high-quality deep to ultra-deep carbonate reservoirs presents a topic worthy of thorough exploration. Focusing on the Ediacaran (Sinian) Dengying Formation in the Penglai area of the Sichuan Basin, we analysed genesis mechanisms of deep to ultra-deep marine carbonate reservoirs through drilling/logging, seismic data and analytical tests, which showed the dolomite reservoir primarily consists of secondary solution pores and cavities, exhibiting characteristics of vertical overlap and horizontal continuous distribution. The microbial mound beach, which represents the main dominant facies type within the reservoir, can be categorised into three types: high-quality reservoir, medium-quality reservoir and poor reservoir. The reservoir has undergone five stages: syngenetic to quasi-syngenetic, shallow burial, supergene, burial and deep burial adjustment stages. It is postulated that the development of deep to ultra-deep carbonate reservoirs is governed by sedimentary facies, with the type and structure of carbonate influencing the development and evolution of reservoir pores. Multiphase diagenetic fluids further modify and enhanced the properties of the reservoirs. Deep and ultra-deep carbonate reservoirs exhibit strong heterogeneity, and high-quality reservoirs are characterised by multi-factor joint control and multi-stage composite genesis. The lithological and structural–lithological traps associated with them commonly cluster in large areas so effective identification of favourable sedimentary facies and reservoirs is crucial for predicting deep to ultra-deep carbonate reservoirs, characterising traps and improving the success rate of drilling. KEY POINTS: The original carbonate rock fabrics influence the diagenetic pore-development processes through the type and distribution of primary pores. Multi-stage diagenetic fluids further adjust and improve the physical properties of the reservoir, ultimately determining the formation of high-quality deep to ultra-deep reservoirs. The development of high-quality deep to ultra-deep carbonate reservoirs is the result of multiple factors and multi-stage discontinuous modifications, leading to strong heterogeneity in these reservoirs. [ABSTRACT FROM AUTHOR]

Floating materials of both natural and anthropogenic origin affect marine ecosystems and human economic activities. Although the tracking of floating materials is important to manage the economic risks, it is difficult to trace them back to the events of origin, such as tsunamis and underwater volcanic eruptions. The gooseneck barnacle Lepas anserifera, a rapid colonizer in pelagic environments, is a potential "natural logger" of floating materials. In this study, we performed temperature-controlled culture experiments and growth line staining in the laboratory to quantify the growth increments of shells (scutum and tergum) consisting the capitulum of L. anserifera separately, and to examine the effects of the temperature on their growth. Following calcein staining, the growth lines of L. anserifera were visualized under a fluorescent microscope, and gross (capitular length and width) and individual (scutum and tergum) shell growth were compared. Shells grew in twice as much in the capitular length direction than in the capitular width direction owing to the larger growth increases in the scutum than in the tergum. Growth increments were unaffected by temperatures in the range from 20°C to 30°C, although the growth appeared to slow down in September and October compared with August. The stable oxygen isotope composition (δ18O) of the shells represented the water temperature as previously known, and the present results showed that 18O enriched in scutum than tergum in most cases. Further understanding for the biomineralization process of barnacles is required for the precise application of environmental proxies in barnacle shells. [ABSTRACT FROM AUTHOR]

Root canal irrigation endodontic solutions have effects on the chemistry of dentin. Infrared spectroscopy is a non-destructive chemical characterization method where the strength of absorption often correlates with mineral or organic composition. To survey effects of commonly used irrigation solutions on the composition of root dentin as detected by widely-available Fourier transform infrared spectroscopy (FTIR) methods. Electronic databases were searched for articles published between 1983 to 2023. After risk of bias assessments (OHAT), studies were grouped according to effects per irrigation solution. Inclusion criteria comprised in vitro studies that used extracted human or bovine teeth, treated by irrigation solutions characterized using FTIR spectroscopy and presenting spectral data. Publications that did not present spectra were excluded. A wide range of concentrations, durations, and treatment protocols have been tested but only 30 out of 3452 studies met our inclusion criteria. Different FTIR methods were used with Attenuated Total Reflection (ATR) variant being the most common (21 studies). Investigated solutions included sodium hypochlorite (NaOCl), ethylenediaminetetraacetic-acid (EDTA), 1-hydroxyethylidene-1–1-diphosphonic-acid (HEDP), peracetic-acid (PAA), glycolic-acid (GA), and citric-acid (CA) though most focused on NaOCl and EDTA. All solutions had detectable effects in the FTIR signature of dentin. NaOCl mainly affects the organics, revealing reduced amide/phosphate ratios with increasing concentrations. EDTA mainly effects the inorganic component, with the effects increasing with time and concentration, yet glycolic acid has stronger effects than EDTA on dentin. Beyond the type of irrigant and dentin exposure durations, concentration and protocol of application had strong effects. There is a lack of studies comparing similar irrigants under conditions that mimic clinical scenarios analyzing bulk sample because FTIR of powder dentin differs from FTIR of bulk dentin. The ideal root-canal irrigant should combine local disinfection properties with minimal compositional effects on healthy dentin. FTIR methods appear reliable to identify important changes in root dentin chemical composition. Such information can help understand when endodontic irrigation might lead to root degradation or possibly contribute to long term failures such as vertical fractures. Awareness of chemical damage from irrigation procedures may help clinicians select procedures that reduce deleterious effects on the root canal structures. [Display omitted] [ABSTRACT FROM AUTHOR]

The sediments of closed-basin lakes on the margin of the East Asian summer monsoon (EASM) are valuable archives of past changes in hydroclimate and dust activity and thus potentially can help us to understand future climate changes. We present high-resolution, well-dated records of the grain size and carbonate mineralogy from Lake Bayanchagan, northern China, spanning the last 11.5 ka. Grain-size endmember (EM) analysis distinguished four EMs, each linked to different sediment transport processes. EM1 (0.4–0.6 μm) and EM3 (14–102 μm) reflect the strength of regional dust activity, whereas EM2 (1.3–31 μm) represents variations in local hydrodynamic conditions related to lake-level changes and EM4 (68–500 μm) is associated with local dust activity. Our results show that a high lake level and weakened dust activity occurred during 10–5.8 ka, as indicated by increased EM2 and decreased EM3, respectively. After 5.8 ka, EM2 decreased as the three other EMs increased, and dolomite appeared in the sediments while calcite decreased—indicating both a decline in lake level and strengthened dust activity. The fluctuations in lake level and dust activity are in good agreement with precipitation variations reconstructed from other records, which are in turn correlated to movement of the EASM rainfall belt, in response to temperature changes. [ABSTRACT FROM AUTHOR]

The effect of microbial binding for the stabilization of steep carbonate slopes is well documented in Cenozoic examples but its significance and relationship with abiotic marine cements in Paleozoic reef systems and steep slopes is not clearly established. Here, samples from a Late Silurian (Ludlovian) reef complex are evaluated by using an integrated approach that involves petrographic and isotope analyses, cathodoluminescence microscopy, and environmental scanning electron microscopy. This study reveals the in situ production of mineral fabrics of microbial origins, including micrite, peloidal micrite with dendritic fabrics, meniscus, and bridge-like cements. This study stresses the leading role of microbes in the early lithification stages that led to the stabilization of Silurian steep carbonate slopes. These findings are further supported by the occurrence of fossilized microbes and extracellular polymeric substance. The micritic cements are the first step in the diagenetic paragenesis followed by abiotic fibrous and equant calcite cements whose stable isotope values are in concert with estimated values of calcite precipitated in equilibrium with Silurian seawater. Results from this project provide insights into the relationship between microbial binding and early abiotic marine cements in ancient reef systems and, further, provide evidence for a consortia of microbes that existed 440 Ma ago. [ABSTRACT FROM AUTHOR]

Lacustrine carbonates are a powerful archive of paleoenvironmental information but are susceptible to post‐depositional alteration. Microbial metabolisms can drive such alteration by changing carbonate saturation in situ, thereby driving dissolution or precipitation. The net impact these microbial processes have on the primary δ18O, δ13C, and Δ47 values of lacustrine carbonate is not fully known. We studied the evolution of microbial community structure and the porewater and sediment geochemistry in the upper ~30 cm of sediment from two shoreline sites at Green Lake, Fayetteville, NY over 2 years of seasonal sampling. We linked seasonal and depth‐based changes of porewater carbonate chemistry to microbial community composition, in situ carbon cycling (using δ13C values of carbonate, dissolved inorganic carbon (DIC), and organic matter), and dominant allochems and facies. We interpret that microbial processes are a dominant control on carbon cycling within the sediment, affecting porewater DIC, aqueous carbon chemistry, and carbonate carbon and clumped isotope geochemistry. Across all seasons and sites, microbial organic matter remineralization lowers the δ13C of the porewater DIC. Elevated carbonate saturation states in the sediment porewaters (Ω > 3) were attributed to microbes from groups capable of sulfate reduction, which were abundant in the sediment below 5 cm depth. The nearshore carbonate sediments at Green Lake are mainly composed of microbialite intraclasts/oncoids, charophytes, larger calcite crystals, and authigenic micrite—each with a different origin. Authigenic micrite is interpreted to have precipitated in situ from the supersaturated porewaters from microbial metabolism. The stable carbon isotope values (δ13Ccarb) and clumped isotope values (Δ47) of bulk carbonate sediments from the same depth horizons and site varied depending on both the sampling season and the specific location within a site, indicating localized (μm to mm) controls on carbon and clumped isotope values. Our results suggest that biological processes are a dominant control on carbon chemistry within the sedimentary subsurface of the shorelines of Green Lake, from actively forming microbialites to pore space organic matter remineralization and micrite authigenesis. A combination of biological activity, hydrologic balance, and allochem composition of the sediments set the stable carbon, oxygen, and clumped isotope signals preserved by the Green Lake carbonate sediments. [ABSTRACT FROM AUTHOR]

A significant proportion of marine calcium carbonate sediments are comprised of metastable minerals that are susceptible to diagenetic alterations during burial. These reactions can reset the geochemical signature of sediments and pore fluids and influence elemental cycling in the ocean. However, the timing and mechanisms by which these reactions take place are poorly constrained. This study uses cores drilled on the slope of the Great Bahama Bank to provide quantitative constraints on important diagenetic reactions; namely respiration-driven dissolution, authigenic carbonate mineral formation, and conversion of aragonite to low Mg calcite (LMC). We perform detailed mineralogical characterization using newly acquired, high resolution X-ray diffraction (XRD) data and over 1000 reanalyzed XRD scans, characterize sediments texturally and elementally using electron microprobe data, calculate pore fluid saturation state with respect to aragonite using a Pitzer ion interaction approach, and use pore fluid chemistry and experimental distribution coefficients to predict authigenic carbonate compositions. These data suggest that aerobic organic matter oxidation, enabled by the advection of oxygenated seawater throughout the upper ∼ 30 m interval of sediment, causes undersaturation and thus dissolution of biogenic high Mg calcite (HMC) and aragonite. Deeper, anaerobic organic matter oxidation takes over and causes supersaturation, promoting authigenic precipitation in the form of HMC, which in turn decreases pore fluid Mg/Ca and promotes aragonite conversion to LMC. One novel aspect of this study is the identification of three types of calcites using the newly acquired XRD and electron microprobe data. Based on their unique crystallographic characteristics and chemical compositions, these types of calcites are interpreted to represent pelagic biogenic LMC, bank-derived biogenic HMC, and authigenic HMC precipitated from pore fluids. Notably, the composition of the authigenic calcite matches that predicted to precipitate from pore fluids using an empirical Mg partition coefficient in calcite. Calcites that form authigenically and from aragonite via replacement are suggested to recrystallize with burial as evidenced by the decrease in Mg content and micro-strain. This process-based geochemical framework assigns diagenetic processes to a specific depth window within the sediment column and paves the way for a mechanistic understanding of carbonate diagenesis, one that is rooted in thermodynamic and kinetic bases. [ABSTRACT FROM AUTHOR]

The Youjiang metallogenic province (YMP) is a famous ore-concentrating area in South China, known for its substantial Carlin-type gold deposits, antimony deposits, and mercury deposits. Previous studies have yielded conflicting views regarding the ages of mineralization in this area, particularly regarding the occurrence of Yanshanian versus Indosinian ore-forming events during the Mesozoic era. To resolve these discrepancies, this study utilized in situ LA-ICP-MS U-Pb dating on carbonate minerals from the Lannigou Carlin-type Au deposit, the Lanmuchang Hg-(Tl) deposit, and the Sixiangchang Hg deposit to accurately determine their mineralization ages. Our results indicate that the three deposits formed at 137 ± 9 Ma, ~97 Ma, and 454 ± 21 Ma, respectively. By integrating previously reported geochronological data, we propose that the low-temperature Au-As-Sb-Hg-Tl deposits in the YMP were formed during two major periods, Late Triassic and Late Jurassic to Cretaceous, with the latter being more prevalent. Additionally, there was a Paleozoic hydrothermal mercury mineralization event at the northeastern edge of this region. These newly acquired data significantly enhance our understanding of multistage, low-temperature mineralization events in the YMP. Our study also demonstrates that in situ carbonate U-Pb dating is an excellent method for investigating the timing of low-temperature mineralization events. [ABSTRACT FROM AUTHOR]

The marine Upper Jurassic rocks of the Franconian Alb consist largely of micritic carbonate of partly dolomitized reef mounds and bedded basinal limestone. All carbonates were lithified in the shallow (centimeters, meters) subsurface and have a wide range of ∂13C (≤ + 3‰ to − 10‰VPDB) but always negative ∂18O (− 1 to − 6‰VPDB). Dolomite and reef limestone show the highest ∂18O and ∂13C values. The most negative ∂13C (≥ − 10‰) occurs mainly as cement in dolomite of a basinal, partly dolomitic, biostrome interval. Basinal limestone shows intermediate ∂13C values. Because freshwater diagenesis and elevated temperatures cannot explain the observed isotope values, pH is here considered a major factor influencing the isotope signal of micritic limestone. The bulk sediment isotope signal was reset to lower values, from an original lime mud with ∂13C ≥ 3‰ and a ∂18O of ≥ + 1‰, as a result of biochemically induced diagenesis. Carbonate, probably mostly aragonite but occasionally including dolomite, was dissolved in a zone where low pH developed as a result of organic matter degradation. Dissolved carbonate was translocated by diffusion and re-precipitated as cement (ca. 50vol%) in a zone with elevated pH where all in situ lime mud ∂18O was reset. Imported cement carbonate precipitated in equilibrium with the pore fluid with negative isotope values, whereas ∂13C of the in situ lime mud remained unmodified. The negative shift of the bulk ∂13C and ∂18O is variable and depends on pH and the contribution of 12C from anaerobic sulfate reduction in the zone of cement precipitation. This produced an ubiquitous covariance of ∂18O and ∂13C. Incorporation of seawater-derived Mg2+ during recrystallization of carbonate can account for the local dolomitization. Elevated 87Sr/86Sr ratios are explained as a result of interaction of clay minerals with the stationary pore fluids. This study shows that the isotopic signal produced by biochemically induced shallow submarine subsurface carbonate diagenesis can be indistinguishable from freshwater diagenesis, that ∂18O and ∂13C of the bulk rock are always reset, and that carbonates can show, in the presence of clay minerals, elevated 87Sr/86Sr ratios even when the pore fluids were never exchanged. [ABSTRACT FROM AUTHOR]

The felsic volcanogenic tuff known as 'green bean rock' (GBR) and its carbonates are widely dispersed across the western Yangtze Block. This study investigates the origin, tectonic setting and genesis of GBR, as well as the environmental disruptions evident in carbonates from the western edge of the Yangtze Block. The analyses include mineralogy, whole‐rock geochemistry and the isotopic composition of zircon Hf, carbon and oxygen in GBR samples from the western edge of the Yangtze Block. The geochemical profile of GBR shows enriched LREE, Th and U content, depleted levels of Nb, Ta, Sr, Ba, K, Rb and Ti, and strong‐to‐moderate negative Eu anomalies (δEu = 0.15–0.18). Zircon Hf isotopes exhibit S‐type geochemical affinities with low negative εHf(t) values (−13.3 to −5.7) and TDM2 ages of 1684–2110 Ma. This suggests that the volcanic ashes originate from the magma of an intermediate to felsic composition. X‐ray directionality data show that the most prevalent clay minerals are illite and illite/smectite. Lithium fixed in these minerals is likely to have leached from brine. Early Triassic variances in δ13C profiles are reliable indicators of environmental disturbances, pointing to cycles of devastation and restoration in marine ecosystems, interspersed with extraneous events including volcanic activity. The study posits that volcano eruptions may have prolonged biotic recovery after the end‐Permian mass extinction. [ABSTRACT FROM AUTHOR]

The unconfined compressive strength (UCS) is a crucial factor of rock strength parameters for estimating the in situ stresses of the rock, designing the most effective fracture design, predicting the best mud weight, and mitigating drilling issues. UCS is commonly determined by subjecting rock samples to uniaxial or triaxial strains until they fail. Laboratory tests provide a direct and more precise estimation of UCS. However, it is unable to generate a continuous profile along the well (i.e., limited to specific depth intervals) due to the presence of specimens, expense, and time consumption. Consequently, other approaches were devised to overcome the gaps in the UCS prediction by utilizing wire-line log data. Several empirical correlations for predicting UCS are derived from well-log data, particularly the porosity, density, and sonic logs. In this paper, the previous correlations for predicting the UCS of carbonate formation have been evaluated using measured data of UCS. The results show that the compressional wave velocity (VP) is the best well log parameter for estimating carbonate formation's unconfined compressive strength, and Yasar and Erdogan correlation best predicts the UCS that fit the measured data for carbonate formations. Thus, Yasar and Erdogan correlation has been chosen to estimate a continuous profile of UCS across the entire depth of carbonate formation in the Rumaila oil field. [ABSTRACT FROM AUTHOR]

In deep carbonate reservoirs, testing and production with open-hole completion can help release the maximum production capacity. However, because the reservoir is subjected to high in situ stress, if the test pressure differential is too large, the wellbore collapse and instability will occur easily, causing downhole accidents. Therefore, it is necessary to determine the state of the borehole during the open-hole test in the carbonate reservoir and analyze the ultimate test pressure differential accordingly to ensure test safety. Considering the characteristics of open-hole completion, based on the mechanical properties of the carbonate reservoir and the stress distribution around the borehole during testing, a calculation method of the elastic zone, plastic zone, and residual failure zone around the open-hole wellbore was proposed. Regarding actual engineering data, a criterion for the overall stability of the open-hole section had been established from three aspects: the volume ratio of the plastic zone; the failure zone around the wellbore; and the failure angle on the borehole wall. According to this criterion, it is possible to determine the ultimate pressure differential during the open-hole test process and provide theoretical support for designing the open-hole completion test and production parameters for deep carbonate reservoirs. [ABSTRACT FROM AUTHOR]

This manuscript documents the diagenetic progression from deposition to early burial of freshwater low‐Mg calcite mud within a Holocene sequence of the Everglades and Florida Bay (Florida, USA). During initial, in situ burial, the texturally‐complex, organic‐rich mud, exhibits high susceptibility to alteration, within a primarily dissolution‐driven realm. Seaward, a brackish‐water transitional burial environment currently displays evidence of mixed precipitation and dissolution. This brackish stage burial alteration may be due to fluid exchange (a relatively high fluid‐to‐rock ratio) in a submerged estuary setting. Lastly, the burial environment in Florida Bay records a transgression from freshwater to near‐normal marine conditions. This island setting currently exhibits a diagenetic trend towards low‐Mg calcite precipitation in intervals of both the marine and freshwater mud. Burial of freshwater mud beneath nearly 3 m of marine mud during rising sea level appears to have preserved a considerable amount of original textures, as compared with younger freshwater deposits now within the transitional brackish‐water setting. Geochemical and textural data within the freshwater mud sections suggest that complex early diagenesis begins shortly after burial at the site of formation, and perhaps even during deposition. The findings herein document three major implications for coastal zone paludal carbonates: (i) that incipient textural diagenesis in low‐Mg calcite crystals can be extremely early and the stability and petrographic fidelity of these deposits are vulnerable due to the open, trellis‐like structure of the crystals; (ii) relatedly, the stable isotope signature of the original low‐Mg calcite crystals is also vulnerable to alteration by secondary precipitation within the open crystal structure; and (iii) during marine transgression, the paludal calcite crystals likely experience a shift from interstitial fluids that are dissolution‐dominated (freshwater) to more precipitation‐dominated as marine fluids overtake the pore fluid regime. Because palustrine deposits are used as palaeoenvironmental archives, it is important to understand their diagenetic and preservation potential. This study has implications for those concerned with the deposition, reactivity and preservation potential of continental and microbial carbonates. [ABSTRACT FROM AUTHOR]

Modified polystyrenes having tertiary ether linkages or carbonate linkages were degrade by irradiation of near‐infrared light (NIR) and subsequent heating. The polymer films containing a photoacid generator and commercially available photon upconversion nanoparticle (UCNP) were decomposed to form isobutene and/or carbon dioxide by irradiation of NIR and subsequent heating. The thermal decomposition behaviors of the polymers were investigated and discussed in terms of the chemical structures of degradable units. The thermal stability of the polymers was found to be in the order: tertiary ester > tertiary carbonate. We believe that the degradation of NIR and subsequent heating contributes easy recycling of composite materials. [ABSTRACT FROM AUTHOR]

Slopes adjacent to the Bahamian carbonate platform revealed a large variety of depositional processes. In this study, we present a synthesis summarizing 109,000 km2 of bathymetric and reflectivity data with ∼7,900 km of seismic lines and 311 m of sediment cores that were obtained over the last 50 years. These data are used to develop a conceptual model of sedimentation patterns on Quaternary carbonate slope systems and their interaction with the adjacent shallow‐water carbonate platforms. Our data highlight that during the Quaternary, factors controlling large‐scale sedimentation on Bahamian slopes have numerous similarities as they have higher sedimentation rates during interglacials. At a small scale, every slope has its own characteristics that are contemporary controlled by two main characteristics: (a) facies on the adjacent shallow‐water platform, and (b) the impact of shallow‐ and deep‐water currents. Large‐scale tectonics influence sediment deposition as it determines the position of the islands and impacts platform facies distribution. Plain Language Summary: The factors that allow sediment to be exported from carbonate platforms to the deep‐sea need discussion. To gain a better understanding of the processes involved, the sedimentary archives of the slopes connected to these carbonate platforms are consulted. The sediments encountered vary and range from grains finer than 20 μm to coarse sandy sediments, a few millimeters in size. To understand the different processes that export those different types of sediment, we analyze various slopes of the Bahamas, a well‐known pure carbonate platform system. We used both numerical data (bathymetry, reflectivity, seismic) and sediment samples from this area and compared those records for the different Bahamian slopes. We highlighted that every slope displays a different sediment record; for every slope transect the adjacent platform facies together with deep‐sea processes (currents) determine the sediment distribution. The processes that export and transport the sediments are of equal importance. Key Points: Main factors controlling Bahamian slope sedimentation are revisedNumerous data types acquired offshore were synthesizedOur data suggest a strong influence of platform fine‐grained concentration and currents on slope sedimentation models [ABSTRACT FROM AUTHOR]

The proliferation of microbial carbon fixation is a key control on the evolution of the biosphere and global carbon cycle. Most records of these metabolisms in ancient rocks come from organic matter or fossils, which are not always preserved. Here, we present a potential proxy for microbial carbon fixation (autotrophy) based on the isotopic composition of carbonate minerals. Autotrophs influence carbonate chemistry in the cellular microenvironment by decreasing CO2 concentration and increasing the carbonate saturation state. This can induce rapid precipitation of carbonate minerals that are out of isotopic equilibrium with their environment. Recent work has identified disequilibrated dual clumped isotope compositions (∆47 and ∆48) in the skeletal fossils of marine calcifying organisms. Here we test whether the same is true of non‐skeletal carbonate fabrics associated with microbial autotrophs in modern and Eocene lakes. We found that microbial carbonate formed via autotrophic metabolism recorded lower ∆47 and higher ∆48 values (−∆47/+∆48) than predicted for thermodynamic equilibrium mineral formation. Our findings are supported by models of dual clumped isotope kinetics in the DIC system, and disequilibrium in the oxygen isotope system. We hypothesize that the inverse trajectory away from the equilibrium line (+∆47/−∆48) should be recorded by carbonates formed in association with alkalinizing heterotrophs, such as sulfate reducers. If so, carbonate dual clumped isotopes could be a powerful tool to identify the proliferation and rate of heterotrophic and autotrophic metabolisms in the carbonate rock record on Earth and (perhaps) other planets. Plain Language Summary: Primary producers have fueled the biosphere since the origin of life on Earth. The production of organic molecules by autotrophs is essential for the evolution of heterotrophic bacteria, and eventually fungi and animals. However, identifying where and when specific metabolisms were active in Earth history is challenging because we lack reliable biosignatures of these processes. Identifying the presence of ancient metabolic activity can provide context to how microorganisms steered global biogeochemical cycles and the carbon budget in ancient oceans, atmosphere, and on land. In this study, we present a potential fingerprint of microbial autotrophy (e.g., photosynthesis, methanogenesis) preserved in carbonate minerals in modern and ancient settings. Key Points: Microbial autotrophy imparts a dual clumped isotope and oxygen isotope disequilibrium signature on carbonate mineralsThis disequilibrium biosignature can be preserved in the rock record post‐burialDual clumped isotope signatures of microbially associated carbonates are differentiable from abiotic carbonates that formed from the same water and experienced the same burial history [ABSTRACT FROM AUTHOR]

[Objective] Marine red beds are distributed across various stages in geological history, are often interpreted as products of special environments, and have attracted widespread attention. The Sowa Formation in the Jurassic Qiangtang Basin is a set of sedimentary rocks composed of clastic and carbonate mixed sediments. In the Sowa Formation exposed in Bilocuo, Shuanghu county, Tibet, the red beds are mainly composed of carbonate sediments. [Methods] This study explored the causes of th red color and significance in the deposition and diagenesis of the red beds based on sedimentological, mineralogical, and geochemical methods. [Results] Field sedimentology and downhole thin section identification of these red beds revealed that the rocks are composed of grain-supported limestone, with abundant debris from cephalopods, echinoderms, bivalves, bryozoans, gastropods, and other benthic organisms. Biogenic debris and terrestrial quartz debris are the main components of the ooids, which display characteristics of a high-energy beach environment. Spectroscopic studies and scanning electron microscopy indicate that the main cause of the red color is submicron- to micron-sized pseudo-hexagonal and tetragonal hematite crystals. The coloration minerals are concentrated in the ooid cortex structure, and the cementing material is virtually devoid of coloration minerals. This suggests that during early diagenesis, particularly during the formation of ooids and peloids, iron-loving microorganisms played an important role in capturing iron oxides. Furthermore, the geochemical analysis of carbonate minerals shows that the redness is positively correlated with the flux of terrestrial debris input. Additionally, it exhibits a positive Ce/Ce* anomaly (1.1-1.3) and a pattern of enriched-middle rare earth elements "bulge", indicating that the iron oxides underwent reductive dissolution.[Conclusions] Based on these findings, the study reconstructed the red coloration process of these red beds. The input of terrestrial iron-bearing minerals provided the material basis for the red coloration, and then, during early diagenesis, reductive fluids dissolved the iron-bearing minerals, providing free iron ions for iron-loving microorganisms, allowing them to recrystallize and ultimately form hydroxyl iron and cause red coloration through chemical or biological processes. [ABSTRACT FROM AUTHOR]

Abstract The minor and trace element compositions of biogenic carbonates such as foraminifera are important tools in paleoceanography research. However, most studies have focused primarily on samples with element to calcium (El/Ca) ratios higher than the El/Ca range often found in benthic foraminifera. Here, we systematically assess the precision and accuracy of foraminifera elemental analysis across a wide range of El/Ca especially at relatively low ratios, using a method on a Thermo Scientific iCAP Qc quadrupole Inductively Coupled Plasma Mass Spectrometer (ICP‐MS). We focus on two benthic foraminifera species, Hoeglundina elegans and Cibicidoides pachyderma, and prepared a suite of solution standards based on their typical El/Ca ranges to correct for signal drift and matrix effects during ICP‐MS analysis and to determine analytical precision. We observe comparable precisions with published studies at high El/Ca, and higher relative standard deviations for each element at lower El/Ca, as expected from counting statistics. The overall long‐term analytical precision (2σ) of the H. elegans‐like consistency standard solutions was 6.5%, 4.6%, 5.0%, for Li/Ca, Mg/Ca, Mg/Li, and 6.4%, 10.0%, 4.2% for B/Ca, Cd/Ca, Sr/Ca. The precision for H. elegans‐like Mg/Li is equivalent to a temperature uncertainty of 0.5–1.1°C. Measurement precisions were also assessed based on three international standards (one solution and two powder standards) and replicate measurements of H. elegans and C. pachyderma samples. We provide file templates and program scripts that can be used to design calibration and consistency standards, prepare run sequences, and convert the raw ICP‐MS data into molar ratios.

Abstract On Earth, carbonate minerals are widely used as recorders of the geological environments in which they formed. Here, we present a method designed to retrieve the crystal chemistry of Fe‐Mg carbonate minerals using infrared remote sensing or Raman spectroscopy. We analyzed a suite of well‐characterized Fe‐Mg carbonate minerals for which Raman spectra were obtained in two different laboratories, and IR spectra were measured in reflectance and transmission from the visible range to 25‐μm. We built calibration lines for the dependence of fundamental and harmonic vibrational modes position to the Mg# (defined as Mg# = 100 × Mg/(Mg + Fe + Ca + Mn)). These calibrations should enable retrieval of Mg# based on spectroscopic observations with a typical accuracy of 10. We discuss the framework of applicability of these calibrations and apply them to a typical CRISM spectrum of carbonates from the Nilli Fossae region of Mars.

Abstract Earth scientists have leveraged carbon isotope records to interpret Earth history and establish chronostratigraphic frameworks for decades (e.g., Halverson et al., 2005, https://doi.org/10.1130/b25630.1; Kaufman & Knoll, 1995, https://doi.org/10.1016/0301‐9268(94)00070‐8; Knoll et al., 1986, https://doi.org/10.1038/321832a0; Saltzman & Thomas, 2012, https://doi.org/10.1016/b978‐0‐444‐59425‐9.00011‐1; Scholle & Arthur, 1980, https://doi.org/10.1306/2f91892d‐16ce‐11d7‐8645000102c1865d). Increasingly detailed and nuanced approaches have been applied to understanding carbon isotope records in light of local‐ and regional‐scale processes that complicate interpretations. The recent work of Gazdewich et al. (2024, https://doi.org/10.1029/2023gc011376) is a prescient example, in which they conduct a series of analyses to constrain the influence of authigenic carbonate burial on the global carbon isotope mass balance during the Late Devonian. Here, I briefly review some recent developments in quantitative approaches to understanding carbon isotope values measured from carbonate rocks (δ13Ccarb), with a focus on comparisons of measured δ13Ccarb values, models for understanding what controls δ13Ccarb values, and correlation tools for aligning δ13Ccarb stratigraphies. These new approaches are elucidating carbon isotope records across Earth history and may prove to be transformative for our understanding of the global carbon cycle.