Strontium isotope dating influenced by Rubidium contamination from terrestrial material: A case study from the Cenozoic dolomite in the Xisha Islands, South China Sea

作者：Rui Wang, Kefu Yu, Brian Jones, Wei Jiang, Tianlai Fan, Yang Yang, Songye Wu · 发表于：Sedimentology · 年份：2024 · DOI：10.1111/sed.13175 · 被引用次数：3 · 研究领域：Geology and Paleoclimatology Research、Geochemistry and Elemental Analysis、Paleontology and Stratigraphy of Fossils

Abstract Strontium isotopes ( 87 Sr/ 86 Sr) are commonly used to assess the age of Cenozoic dolostones found on many isolated oceanic islands. The possible influence of Rubidium (Rb) content on the 87 Sr/ 86 Sr ratios, however, has generally been ignored. This critical issue is assessed by examining the 87 Sr/ 86 Sr ratios and elements (Rb, Sr, Al, Ti and K) of seventy‐one samples that came from a ca 339 m thick cored interval of Cenozoic dolomite on the Xisha Islands, South China Sea. For the dolomite from the upper Pliocene Yinggehai Formation (180.5 to 308.5 m; average 23% dolomite) there is a positive correlation between the 87 Sr/ 86 Sr ratios and Rb concentrations, whereas for the dolomite from the lower late Miocene Huangliu Formation (308.5 to 519 m; average >98% dolomite) such a correlation is not evident. Combined with high‐temperature experiments, correlation between Al, Ti, K, Rb and 87 Sr/ 86 Sr indicates that Rb containing old 87 Rb from terrestrial materials modified the 87 Sr/ 86 Sr ratios of the Yinggehai dolomite, but not those from the Huangliu dolomite. This is mainly attributed to the different sources of terrestrial dust carried by different East Asian monsoon systems between the late Miocene and Pliocene, and probably also influenced by the dolomitization process to some extent. To test for 87 Rb contamination, extrapolation of results from the Yinggehai dolomite and Huangliu dolomite indicate that concentrations of Rb < 1 ppm, Al < 1000 ppm, T...