埋藏后生作用对生物壳体^(87)Sr/^(86)Sr的影响研究  

THE EFFECT OF DIAGENESIS ON ^(87)Sr/^(86)Sr RATIOS IN ORGANIC SHELLS

作　　者：刘秀明[1] 王世杰[1] 贾玉鹤[1] 董丽敏[1] 

机构地区：[1]中国科学院地球化学研究所环境地球化学国家重点实验室,贵阳550002

出　　处：《矿物学报》2000年第3期314-320,共7页Acta Mineralogica Sinica

基　　金：国家自然科学基金!(批准号 :49673 2 0 1)资助

摘　　要：根据小渡口剖面 2 8层有孔虫、介形虫、腹足类生物壳体的微观观察、微量元素及其比值、87Sr/86Sr与微量元素特征对比以及水 -岩反应87Sr/86Sr的混合模式 ,显示生物壳体遭受了埋藏后生作用 ,但对生物壳体原始的87Sr/86Sr比值基本没有改变或影响甚微 ,推测参与埋藏后生作用的流体与生物壳体具有相近的Sr同位素组成或较悬殊的Sr含量。同时 ,实际研究表明评价和判别埋藏后生作用对生物壳体原始87Sr/86Sr比值影响的方法较多 ,但各有其局限性 ;合理研究方法应以壳体87Sr/86Sr比值与微观特征和其他地球化学特征的对比来判别。The subtle difference in texture detected by SEM and trace element concentrations of the fossil samples of foraminifera, ostracode, gastropod from the 28th bed of the Xiaodukou profile in Nihewan, Hebei, shows that some modifications of organic shells result from diagenetic alteration. However, the model of water\|rock interaction implies that the modification of strontium isotope is dependent on the differences in strontium contents and \{\}\+\{87\}Sr/\+\{86\}Sr ratios between fluids and organic shells during water\|rock interaction. The diagrams of Sr\|Mn, \{\}\+\{87\}Sr/\+\{86\}Sr\|Sr, \{\}\+\{87\}Sr/\+\{86\}Sr\|Mn, \{\}\+\{87\}Sr/\+\{86\}Sr\|1/Sr indicate that the Xiaodukou fossil shells record the original \{\}\+\{87\}Sr/\+\{86\}Sr ratios. Meanwhile, some criteria with shortcomings are not always the reliable indicators. The \{\}\+\{87\}Sr/\+\{86\}Sr ratios of shells compared with textural and other geochemical methods may be a sound criteria to evaluate the effect of diagenetic alteration on \{\}\+\{87\}Sr/\+\{86\}Sr ratios in organic shells.

关 键 词：埋藏后生作用 生物壳体 锶87/锶86 沉积岩 

分 类 号：P588.2[天文地球—岩石学] P593[天文地球—地质学]