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1. Effects of Improved 17 O Correction on Interlaboratory Agreement in Clumped Isotope Calibrations, Estimates of Mineral‐Specific Offsets, and Temperature Dependence of Acid Digestion Fractionation

   https://doi.org/10.1029/2018GC008127  

   Petersen, S. V. ; Defliese, W. F. ; Saenger, C. ; Daëron, M. ; Huntington, K. W. ; John, C. M. ; Kelson, J. R. ; Bernasconi, S. M. ; Colman, A. S. ; Kluge, T. ; et al ( July 2019 , Geochemistry, Geophysics, Geosystems)

   The clumped isotopic composition of carbonate‐derived CO₂(denoted Δ₄₇) is a function of carbonate formation temperature and in natural samples can act as a recorder of paleoclimate, burial, or diagenetic conditions. The absolute abundance of heavy isotopes in the universal standards VPDB and VSMOW (defined by four parameters:R¹³_VPDB,R¹⁷_VSMOW,R¹⁸_VSMOW, andλ) impact calculated Δ₄₇values. Here, we investigate whether use of updated and more accurate values for these parameters can remove observed interlaboratory differences in the measured T‐Δ₄₇relationship. Using the updated parameters, we reprocess 14 published calibration data sets measured in 11 different laboratories, representing many mineralogies, bulk compositions, sample types, reaction temperatures, and sample preparation and analysis methods. Exploiting this large composite data set (n= 1,253 sample replicates), we investigate the possibility for a “universal” clumped isotope calibration. We find that applying updated parameters improves the T‐Δ₄₇relationship (reduces residuals) within most labs and improves overall agreement but does not eliminate all interlaboratory differences. We reaffirm earlier findings that different mineralogies do not require different calibration equations and that cleaning procedures, method of pressure baseline correction, and mass spectrometer type do not affect interlaboratory agreement. We also present new estimates of the temperature dependence of the acid digestion fractionation for Δ₄₇(Δ*_25‐X), based on combining reprocessed data from four studies, and new theoretical equilibrium values to be used in calculation of the empirical transfer function. Overall, we have ruled out a number of possible causes of interlaboratory disagreement in the T‐Δ₄₇relationship, but many more remain to be investigated.

    

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2. Modeling the Measurement: Δ 47 , Corrections, and Absolute Ratios for Reference Materials

   https://doi.org/10.1029/2018GC008166  

   Olack, Gerard ; Colman, Albert S. ( July 2019 , Geochemistry, Geophysics, Geosystems)

   Clumped isotope studies on CO₂, Δ₄₇, that is the excess in the isotopologue containing both¹³C and¹⁸O at mass 47, can be very useful since they can give temperature estimates independent of the bulk isotopic composition. The measurement itself can be affected by a number of items. Here we develop a data processing model to examine the effects different interferences might have on the final calculated value. It incorporates known issues, for example, pressure baseline,¹⁷O excess, and shifts in absolute ratios for primary reference materials and parameters used for¹⁷O correction. We also included linearity effects as well as differences in isotopologue absolute abundances at a givenm/z. What normally would be considered acceptable mass spectrometer⁴⁵Rand⁴⁶Rlinearity can skew Δ₄₇results. That is 0.04‰/V and −0.04‰/V linearity on⁴⁵Rand⁴⁶Rrespectively would also cause an apparent shift in the parameters used for¹⁷O corrections. Measurements were made on CO₂(g) equilibrated with water, and we were able to match up the effects seen with model results. Linearity and small differences in amplitude between sample and working reference gas affected Δ₄₇determination, as did apparent shifts in isotopologue abundances under different conditions. This may (partially) account for discrepancies seen in Δ₄₇‐temperature calibrations curves between laboratories. We also developed an easy way to precisely calculate the δ¹³C and δ¹⁸O that works well in spreadsheets without the need for multiple iterations.

    

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3. A calibration equation between Δ 48 values of carbonate and temperature

   https://doi.org/10.1002/rcm.9147  

   Swart, Peter K. ; Lu, Chaojin ; Moore, Evan W. ; Smith, Megan E. ; Murray, Sean T. ; Staudigel, Philip T. ( July 2021 , Rapid Communications in Mass Spectrometry)

   Information on the temperature of formation or alteration of carbonate minerals can be obtained by measuring the abundance of the isotopologues 47 and 48 (Δ₄₇and Δ₄₈values) of CO₂released during acid dissolution. The combination of these two proxies can potentially provide a greater insight into the temperature of formation, particularly if the carbonate minerals form by non‐equilibrium processes.

   We have precipitated calcium carbonates at seven temperatures between 5 and 65°C and measured their δ⁴⁸values using a Thermo‐253 plus isotope ratio mass spectrometer. The values were transformed to Δ₄₈values in the conventional manner and then converted to the carbon dioxide equilibrium scale.

   Using the Δ₄₈values, we have established an empirical calibration between temperature and Δ₄₈values:urn:x-wiley:09514198:media:rcm9147:rcm9147-math-0001

   The calibration line produced allows the determination of the temperature of natural carbonates using the Δ₄₈values and agrees with the measurements of the Δ₄₇and Δ₄₈values of some carbonates assumed to have formed under equilibrium conditions.

    

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4. Internal isotopic variability of Neogene carbonate concretions: Constraining formational growth mechanisms and isotopic disequilibrium

   https://doi.org/10.1111/sed.13087  

   Smith, Megan E. ; McNeill, Donald F. ; Murray, Sean T. ; Swart, Peter K. ( February 2023 , Sedimentology)

   Carbonate concretions collected from the Dominican Republic present a valuable opportunity to evaluate the internal isotopic variations within concretions that have never been exposed to deep burial or structural deformation. Here, three concretions from the Neogene (Late Miocene–Early Pliocene) Cibao Basin are investigated, utilizing a multi‐isotope (δ¹³C, δ¹⁸O, δ³⁴S_CASand ∆₄₇values) high‐resolution approach, to constrain the microenvironmental conditions associated with multiple stages of concretion growth. Isotopic variability and potential disequilibrium effects, which can influence geological interpretations utilizing concretions, are also considered. The petrographic characteristics and geochemical profiles indicate internal differences relating to concretion growth mechanisms and environmental changes, driven by sea‐level fluctuations. The δ³⁴S values of carbonate‐associated sulphate indicate a closed system environment; however, the overall values are influenced by sulphide oxidation within the sediments, resulting in a complex signal. The ∆₄₇‐derived temperatures of the concretions range between 29 to 55°C, indicating significantly warmer temperatures than are measured from the host sediments, which average 24°C. This indicates that carbonate concretion ∆₄₇values are in disequilibrium with their environments of formation, likely related to ion diffusion in the pore fluids or isotopic fractionation associated with microbial processes. Here geochemical variations within concretions are utilized to assess the environmental conditions and microbial interactions after sediment deposition. However, for future studies, caution should be taken when using concretions for making environmental assessments as the signals can be influenced by a multitude of processes, even prior to diagenetic alteration.

    

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5. Chemical composition tuning induced variable and enhanced dielectric properties of polycrystalline Ga2‐2xWxO3 ceramics

   https://doi.org/10.1002/eng2.12300  

   Zade, Vishal B. ; Rajkumar, Mohan R. ; Broner, Ron ; Ramana, Chintalapalle V. ( December 2020 , Engineering Reports)

   We report on the tunable and enhanced dielectric properties of tungsten (W) incorporated gallium oxide (Ga₂O₃) polycrystalline electroceramics for energy and power electronic device applications. The W‐incorporated Ga₂O₃(Ga_2−2xW_xO₃, 0.00 ≤ x ≤ 0.20; GWO) compounds were synthesized by the high‐temperature solid‐state chemical reaction method by varying the W‐content. The fundamental aspects of the dielectric properties in correlation with the crystal structure, phase, and microstructure of the GWO polycrystalline compounds has been investigated in detail. A detailed study performed ascertains the W‐induced changes in the dielectric constant, loss tangent (tanδ) and ac conductivity. It was found that the dielectric constant increases with addition of W in the system as a function of temperature (25°C‐500°C). Frequency dependence (10²‐10⁶ Hz) of the dielectric constant follows the modified Debye model with a relaxation time of ∼20 to 90 μs and a spreading factor of 0.39 to 0.65. The dielectric constant of GWO is temperature independent almost until ∼300°C, and then increases rapidly in the range of 300°C to 500°C. W‐induced enhancement in the dielectric constant of GWO is fully evident in the frequency and temperature dependent dielectric studies. The frequency and temperature dependent tanδreveals the typical behavior of relaxation loses in GWO. Small polaron hopping mechanism is evident in the frequency dependent electrical transport properties of GWO. The remarkable effect of W‐incorporation on the dielectric and electrical transport properties of Ga₂O₃is explained by a two‐layer heterogeneous model consisting of thick grains separated by very thin grain boundaries along with the formation of a Ga₂O₃‐WO₃composite was able to account for the observed temperature and frequency dependent electrical properties in GWO. The results demonstrate that the structure, electrical and dielectric properties can be tailored by tuning W‐content in the GWO compounds.

    

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