显生宙以来海水锶同位素组成研究的回顾与进展

An Overview of the Strontium Isotopic Composition of Phanerozoic Seawater

显生宙以来海水锶同位素组成演化是地球外部圈层物质循环研究的一个重要领域,在地质历史期间地球表层环境变化研究中的意义不言而喻。显生宙以来海水锶同位素组成研究先后经历了早期阶段、积累阶段和集成阶段。在早期阶段,原始的样品成岩蚀变评估、较低的仪器分析精度导致大部分锶同位素数据不具地层学意义,大多数研究工作仅处于初始探索阶段;在积累阶段,逐渐成熟的样品成岩蚀变评估、较高的仪器分析精度使得这一领域的研究持续进行,尤其是新生代高分辨率海水锶同位素演化曲线的建立和发展催生了一个新的交叉学科分支——锶同位素地层学;在集成阶段,不断积聚的高质量锶同位素数据融合成了多个显生宙以来海水锶同位素数据库,日益成为解决地层学、岩石学、矿床学、水文学以及有关应用等问题的有效工具之一。目前显生宙以来海水锶同位素组成研究仍有诸如样品内部信息保存性差异、样品年龄不确定性、古老样品定年精度不高、寒武纪样品材料与地层疑问、样品中微量铷污染、^(86)Sr和^(88)Sr同位素分馏、实验室之间分析偏差、数据拟合不确定性等方面问题未圆满解决,难以实现锶同位素地层学更具实用性和适用性。试图较系统地总结不同时期显生宙以来海水锶同位素组成演化研究的阶段性和差异性,以期为今后进行更深入的研究提供一些思考角度。

Strontium isotopic evolution of the Phanerozoic seawater is an emerging research field of the material cycle in the Earth＇ s outer-spheres.It is greatly significant for the research of the environmental change on the Earth＇s surface during the geological history.The researches of the strontium isotopic evolution of the Phanerozoic seawater have gone through three stages：The early stage,the accumulated stage,and the integrated stage.In the early stage,the primitive evaluation of the diagenetic alteration and the low precision of the analytical instruments resulted in most strontium isotope data without stratigraphic significance.Most researches were only at the initially exploratory stage.In the accumulated stage,the gradually mature evaluation of the diagenetic alteration and higher precision of the analytical instruments made ongoing progress in the researches,especially the establishment and development of the high-resolution strontium isotopic evolution curves of the Cenozoic seawater had spawned a new interdisciplinary branch：Strontium isotope stratigraphy.In the integrated stage,the accumulated high-quality strontium isotope data had been integrated into some strontium isotope database of Phanerozoic seawater.These dalabases are becoming one ol the effective tools to solve the problems in the stratigraphy.petrologv.ore deposit,hy-drology,and other related applications.Currently,many problems still have not been satisfactorily resolved in the researches of the strontium isotopic evolution of the Phanerozoic seawater,such as the preservation differences of the original seawater information in a sample,the age ol uncertainty of samples,lower dating accuracy of more ancient samples,the materials and stratigraphic questions of the Cambrian samples,trace rubidium contamination of samples,the isotope fractionation between ^86Sr and ^88Sr,the interlaboratory bias,the uncertainty of the data fitting,etc.These problems are the difficulties to possess more practicability and applicability of strontium isotope stratigraphy.Rased on the summary of the research progress, we attempted to systematically summarize the stages and differences of the researches of strontium isotopic composition of Phanerozoic seawater at different periods.We wish this paper offer some perspective to the researches of strontium isotopic composition of Phanerozoic seawater in future.