湖泊无机碳酸盐矿物氧同位素组成差值及其单矿物同位素组成的确定  

Evaluation of Oxygen Stable-Isotope Fractionation and Single Mineral Isotope Composition from Lacustrine Inorganic Precipitated Carbonates

作　　者：曾承[1] 吴鑫 钱晨阳 

机构地区：[1]阜阳师范学院社会发展学院,安徽阜阳236041 [2]青海省安全生产科学技术中心,青海西宁810001 [3]青海注安工程咨询有限公司,青海西宁810001

出　　处：《盐湖研究》2010年第1期21-28,共8页Journal of Salt Lake Research

基　　金：阜阳师范学院2008年度博士科研启动项目;阜阳师范学院教学研究项目(2008JYXM45);湖北省教育厅科学技术研究重点项目(B200625003);中国科学院黄土与第四纪地质国家重点实验室开放基金项目(SKLLQG0713);国家自然科学基金(40872114)

摘　　要：湖积物中不同无机碳酸盐矿物常常混杂在一起，其氧同位素组成（δ^18O）差异会影响碳酸盐δ^18O环境信息提取的可靠性。不同矿物之间δ^18O差值明显且幅度不一。20—25℃时生成的白云石比共生的方解石富集δ^18O可能为0‰～9‰不等，亦或方解石比白云石可能更富集δ^18O达0‰-12．3‰。常温状态，相同条件下形成的文石δ^18O值较方解石高出0‰～1‰，或者方解石较文石δ^18O值高出0‰—4．47‰。镁方解石中MgCO3的mol百分含量每增加1％，其δ^18O值相对于纯方解石δ^18O值增加0．06‰～0．17‰。在利用碳酸盐δ^18O进行气候及环境研究时，不能根据某种差值进行校正，而应进行单矿物测试。由此，对不同无机碳酸盐矿物的分离及同位素测试、推算方法进行了归纳和述评。Lacustrine inorganic precipitated carbonate minerals generally appear in the form of several types co-existing in the sediments. It is of importance to calibrate a possible disparity of oxygen isotope composition（δ^18Oc） between co-existing carbonates whilst using δ^18Oc as one of the environment proxies for the study of regional climatic evolution. The fractionation differences in δ^18Oc between inorganic precipitated dolomite and calcite can be 9‰ to 12.3‰ at 20 -25℃, with marked fractionation differences ranging from 1‰ to 4.47‰ between aragonite and calcite at 20-25℃. As MgCO3 molar content increases by 1% ,δ^18O of magnesian carbonate can be enriched by 0. 06‰ to 0. 17‰. While the δ^18O is impossible to be calibrated to one certain carbonate mineral based on a possible disparity, the testing of single carbonate mineral δ^18O becomes the best choice. The separating methods of different carbonate minerals, and the testing and calculating methods of single carbonate mineral δ^18Oc, proposed in the previous researches, are reviewed in the paper.

关 键 词：无机碳酸盐 氧同位素 白云石 文石 方解石 

分 类 号：P597.2[天文地球—地球化学]