Acid Fractionation Factor of Oxygen Isotopes in Mixed Calcite–Dolomite Samples: Implications for Data Correction

IF 1.8 3区化学 Q4 BIOCHEMICAL RESEARCH METHODS

Rapid Communications in Mass Spectrometry Pub Date : 2025-07-22 DOI:10.1002/rcm.10108

Linlin Cui, Xu Wang, Lianjun Feng, Xiaomei Zhang

{"title":"Acid Fractionation Factor of Oxygen Isotopes in Mixed Calcite–Dolomite Samples: Implications for Data Correction","authors":"Linlin Cui, Xu Wang, Lianjun Feng, Xiaomei Zhang","doi":"10.1002/rcm.10108","DOIUrl":null,"url":null,"abstract":"<div>\n \n \n <section>\n \n <h3> Rationale</h3>\n \n <p>The conventional method for measuring carbon and oxygen isotopes in carbonates involves the reaction of carbonate minerals with phosphoric acid (PPA) to generate CO<sub>2</sub>, followed by purification and isotopic analysis. During this reaction, a temperature-dependent oxygen isotope acid fractionation factor (AFF) is introduced, as not all oxygen is released in CO<sub>2</sub>. Although the temperature dependence of AFF has been extensively studied in pure carbonate minerals, little research has been conducted on AFF variations in mixed carbonate minerals with diverse chemical and mineralogical compositions. This study aims to investigate the range of AFF variations in carbonates containing multiple mineral phases.</p>\n </section>\n \n <section>\n \n <h3> Methods</h3>\n \n <p>Oxygen isotope compositions of CO<sub>2</sub> produced from CaCO<sub>3</sub>-MgCO<sub>3</sub> mixed minerals reacting with PPA at 25°C, 50°C, 70°C, and 90°C were analyzed using a GasBench II system coupled with a Thermo Finnigan Delta V Plus isotope ratio mass spectrometer.</p>\n </section>\n \n <section>\n \n <h3> Results</h3>\n \n <p>The AFF values for CaCO<sub>3</sub>-MgCO<sub>3</sub> mixed minerals fall between those of pure calcite and dolomite, generally aligning with theoretical predictions. Additionally, the fractionation gradient (dδ<sup>18</sup>O/dT<sup>−1</sup>) increases with rising mole Mg and dolomite content, indicating a systematic trend in fractionation behavior.</p>\n </section>\n \n <section>\n \n <h3> Conclusions</h3>\n \n <p>These findings provide a framework for AFF correction based on mole Mg or dolomite content, enhancing the reliability and precision of oxygen isotope measurements in natural impure carbonates.</p>\n </section>\n </div>","PeriodicalId":225,"journal":{"name":"Rapid Communications in Mass Spectrometry","volume":"39 21","pages":""},"PeriodicalIF":1.8000,"publicationDate":"2025-07-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Rapid Communications in Mass Spectrometry","FirstCategoryId":"92","ListUrlMain":"https://onlinelibrary.wiley.com/doi/10.1002/rcm.10108","RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q4","JCRName":"BIOCHEMICAL RESEARCH METHODS","Score":null,"Total":0}

引用次数: 0

Abstract

Rationale

The conventional method for measuring carbon and oxygen isotopes in carbonates involves the reaction of carbonate minerals with phosphoric acid (PPA) to generate CO₂, followed by purification and isotopic analysis. During this reaction, a temperature-dependent oxygen isotope acid fractionation factor (AFF) is introduced, as not all oxygen is released in CO₂. Although the temperature dependence of AFF has been extensively studied in pure carbonate minerals, little research has been conducted on AFF variations in mixed carbonate minerals with diverse chemical and mineralogical compositions. This study aims to investigate the range of AFF variations in carbonates containing multiple mineral phases.

Methods

Oxygen isotope compositions of CO₂ produced from CaCO₃-MgCO₃ mixed minerals reacting with PPA at 25°C, 50°C, 70°C, and 90°C were analyzed using a GasBench II system coupled with a Thermo Finnigan Delta V Plus isotope ratio mass spectrometer.

Results

The AFF values for CaCO₃-MgCO₃ mixed minerals fall between those of pure calcite and dolomite, generally aligning with theoretical predictions. Additionally, the fractionation gradient (dδ¹⁸O/dT⁻¹) increases with rising mole Mg and dolomite content, indicating a systematic trend in fractionation behavior.

Conclusions

These findings provide a framework for AFF correction based on mole Mg or dolomite content, enhancing the reliability and precision of oxygen isotope measurements in natural impure carbonates.

查看原文本刊更多论文

混合方解石-白云石样品中氧同位素的酸性分馏因子：数据校正的意义

测量碳酸盐中碳氧同位素的传统方法包括碳酸盐矿物与磷酸（PPA）反应产生二氧化碳，然后进行纯化和同位素分析。在这个反应中，引入了一个温度依赖的氧同位素酸分馏因子（AFF），因为不是所有的氧都以CO2的形式释放。虽然人们对纯碳酸盐矿物中AFF的温度依赖性进行了广泛的研究，但对具有不同化学和矿物组成的混合碳酸盐矿物中AFF变化的研究却很少。本研究旨在探讨含多矿物相碳酸盐中AFF的变化范围。方法采用GasBench II系统和Thermo Finnigan Delta V Plus同位素比值质谱仪，分析CaCO3-MgCO3混合矿物与PPA在25°C、50°C、70°C和90°C反应产生的CO2的氧同位素组成。结果CaCO3-MgCO3混合矿物的AFF值介于纯方解石和白云石之间，与理论预测基本一致。分馏梯度（dδ18O/dT−1）随Mg摩尔数和白云石含量的增加而增大，表明分馏行为有系统的趋势。结论这些发现为基于摩尔Mg或白云石含量的AFF校正提供了框架，提高了天然不纯碳酸盐中氧同位素测量的可靠性和精度。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

求助全文

约1分钟内获得全文求助全文

来源期刊

Rapid Communications in Mass Spectrometry 化学-分析化学

CiteScore

4.10

自引率

5.00%

发文量

219

审稿时长

2.6 months

期刊介绍： Rapid Communications in Mass Spectrometry is a journal whose aim is the rapid publication of original research results and ideas on all aspects of the science of gas-phase ions; it covers all the associated scientific disciplines. There is no formal limit on paper length ("rapid" is not synonymous with "brief"), but papers should be of a length that is commensurate with the importance and complexity of the results being reported. Contributions may be theoretical or practical in nature; they may deal with methods, techniques and applications, or with the interpretation of results; they may cover any area in science that depends directly on measurements made upon gaseous ions or that is associated with such measurements.