Temperature dependence of oxygen isotopic fractionation of CO2 from magnesite-phosphoric acid reaction

Sharma, Somya; Patil, D. J.; Gopalan, K.

doi:10.1007/bf02891405

Cited by 16 publications

(21 citation statements)

References 4 publications

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“…The emitted CO 2 was separated from other volatile components using a gas chromatographic column heated to 72°C, and then passed into the mass spectrometer through an open split (see Spötl and Vennemann, 2003 for further details). The oxygen isotope fractionation factors of 1.008636, 1.009861, and 1.010022 at 72°C were applied for calcite, dolomite, and magnesite during the formation of CO 2 from carbonate by phosphoric acid reaction, respectively (Rosenbaum and Sheppard, 1986;Sharma et al, 2002). The δ 13 C and δ 18 O data are reported as per mil deviations relative to V-PDB.…”

Section: Methodsmentioning

confidence: 99%

Genesis of a giant Paleoproterozoic strata-bound magnesite deposit: Constraints from Mg isotopes

Dong

Zhu

et al. 2016

Precambrian Research

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Giant strata-bound magnesite deposits are absent in modern and most Phanerozoic sedimentary environments but occur predominantly in Precambrian strata. These deposits may have formed directly through precipitation of evolved Mg-rich seawater in an evaporative shallow-marine setting or, alternatively, by epigenetic-hydrothermal replacement of the Mg-rich carbonate precursor. To test these hypotheses, we obtained the first Mg isotope data from the world's largest strata-bound magnesite deposit belt, hosted by the ca. 2.1 Ga Dashiqiao Formation in Northeast China. The Mg isotope compositions (δ 26 Mg) of most magnesite ores in the Huaziyu deposit are heavier (-0.75 ± 0.26‰) than most Proterozoic sedimentary dolomite. The Mg isotope compositions and 2 major and trace element data indicate that the magnesites are probably not of hydrothermal origin. Instead, a Mg-rich carbonate precursor precipitated from evaporating seawater in a semi-closed system. Diagenetic brines altered the Mg-rich carbonate precursor to magnesite. Subsequently, recrystallization during regional metamorphism produced coarsely crystalline and saddle magnesite. These interpretations are consistent with the geological features and other geochemical data (element concentrations and C and O isotopes) for the magnesite ores. Hence, we interpret the formation of the Huaziyu magnesite deposit to be dominated by evaporative sedimentation and brine diagenesis.

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Section: Methodsmentioning

confidence: 99%

Genesis of a giant Paleoproterozoic strata-bound magnesite deposit: Constraints from Mg isotopes

Dong

Zhu

et al. 2016

Precambrian Research

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“…One aliquot of each in-house standard was analyzed for every eight specimens. The δ 18 O compositions of carbonate minerals were corrected for reaction with phosphoric acid using the fractionation factors from Das Sharma et al (2002), taking into account the proportions of calcium and magnesium-carbonate minerals in mixed specimens. The fractionation factor for magnesite was used as a proxy for the hydrated magnesium carbonate minerals.…”

Section: Light Stable Isotopesmentioning

confidence: 99%

Carbon Dioxide Fixation within Mine Wastes of Ultramafic-Hosted Ore Deposits: Examples from the Clinton Creek and Cassiar Chrysotile Deposits, Canada

Dipple²,

et al. 2009

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Carbon dioxide (CO2) is sequestered through the weathering and subsequent mineralization of the chrysotile mine tailings at Clinton Creek, Yukon Territory, and Cassiar, British Columbia, Canada. Accelerated weathering is attributed to a dramatic increase in surface area, which occurs during the milling of ore. We provide a detailed account of the natural process of carbon trapping and storage as it occurs at Clinton Creek and Cassiar, including mineralogy, modes of occurrence, methods of formation for carbonate alteration, light stable isotope geochemistry, and radiocarbon analysis. Powder X-ray diffraction data were used to identify weathering products as the hydrated magnesium carbonate minerals nesquehonite, and less commonly lansfordite [MgCO3⋅5H2O]. Textural relationships suggest that carbonate precipitates formed in situ after milling and deposition of tailings. Samples of efflorescent nesquehonite are characterized by δ 13 C values between 6.52 and 14.36 per mil, δ 18 O values between 20.93 and 26.62 per mil, and F 14 C values (fraction of modern carbon) between 1.072 and 1.114, values which are consistent with temperature-dependent fractionation of modern atmospheric CO2 during mineralization. Samples of dypingite ± hydromagnesite collected from within 0.2 m of the tailings surface give δ 13 C values between -1.51 and +10.02 per mil, δ 18 O values between +17.53 and +28.40 per mil, and F 14 C values between 1.026 and 1.146, which suggests precipitation from modern atmospheric CO2 in a soil-like environment. Field observations and isotopic data suggest that hydrated magnesium carbonate minerals formed in two environments. Nesquehonite formed in an evaporative environment on the surface of tailings piles, and dypingite and hydromagnesite formed in the subsurface environment with characteristics similar to soil carbonate. In both cases, these minerals †

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“…In general, stable isotope and clumped isotope measurements of carbonates are performed by reacting the sample carbonate with concentrated (>100%) anhydrous phosphoric acid, 2,5,9,23–26 followed by an analysis of the evolved CO 2 using a gas‐source isotope ratio mass spectrometer 2 . Notable primary techniques for the acid digestion reactions are the “sealed vessel (SV) method” and the “common acid bath (CAB) method” 27 .…”

Section: Introductionmentioning

confidence: 99%

Isotopic fractionation during acid digestion of calcite: A combined ab initio quantum chemical simulation and experimental study

Pramanik

Chatterjee

Fosu

et al. 2020

Rapid Comm Mass Spectrometry

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Rationale:Carbonate clumped isotope analysis involves the reaction of carbonate minerals with phosphoric acid to release CO 2 for measurement in a gas-source isotope ratio mass spectrometer. Although the clumped isotope proxy is based on the temperature dependence of 13 C-18 O bonding preference in the mineral lattice, which is captured in the product CO 2 , there is limited information on the phosphoric acid reaction mechanism and the magnitude of clumped isotopic fractionation (mass 63 in CO 3 2− to mass 47 in CO 2 ) during the acid digestion. Methods:We studied the reaction mechanism for the phosphoric acid digestion of calcite using first-principles density functional theory. We identified the transition state structures for each reaction involving different isotopologues and used the corresponding vibrational frequencies in reduced partition function theory to estimate the Δ 47 acid fractionation. Experimental Δ 47 data were acquired by processing the sample CO 2 gas through the dual-inlet peripheral of a ThermoFinnigan MAT253 isotope ratio mass spectrometer. Results:We showed that the acid digestion reaction, which results in the formation of CO 2 enriched with 13 C-18 O bonds, began with the protonation of calcium carbonate in the presence of water. Our simulations yielded a relationship between the Δ 47 acid fractionation and reaction temperature as Δ 47 = −0.30175 + 0.57700 × (10 5 /T 2 ) -0.10791 × (10 5 /T 2 ) 2 , with T varying between 298.15 and 383.15 K. Conclusions:We propose a reaction mechanism that shows a higher slope (Δ 47 acid fractionation vs. 1/T 2 curve) for the phosphoric acid digestion of calcite than in previous studies. The theoretical estimates from the present and earlier studies encapsulate experimental observations from both "sealed vessel" and "common acid bath" acid digestion methods.

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Temperature dependence of oxygen isotopic fractionation of CO2 from magnesite-phosphoric acid reaction

Cited by 16 publications

References 4 publications

Genesis of a giant Paleoproterozoic strata-bound magnesite deposit: Constraints from Mg isotopes

Genesis of a giant Paleoproterozoic strata-bound magnesite deposit: Constraints from Mg isotopes

Carbon Dioxide Fixation within Mine Wastes of Ultramafic-Hosted Ore Deposits: Examples from the Clinton Creek and Cassiar Chrysotile Deposits, Canada

Isotopic fractionation during acid digestion of calcite: A combined ab initio quantum chemical simulation and experimental study

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