富碳质地质样品Re-Os同位素体系研究进展  

A Review of Research Progress on Re-Os Isotopic System of Carbon-enriched Geological Samples

作　　者：李欣尉[1,2] 李超 周利敏[1,2] 赵鸿 屈文俊[1,2] LI Xinwei;LI Chao;ZHOU Limin;ZHAO Hong;QU Wenjun(National Research Center for Geoanalysis,Beijing 100037,China;Key Laboratory of Re-Os Isotope Geochemistry,China Geological Survey,Beijing 100037,China)

机构地区：[1]国家地质实验测试中心,北京100037 [2]中国地质调查局铼-锇同位素地球化学重点实验室,北京100037

出　　处：《岩矿测试》2023年第2期221-238,共18页Rock and Mineral Analysis

基　　金：国家自然科学基金青年基金项目(41703059);中国地质科学院基本科研业务费项目(CSJ-2021-05X)。

摘　　要：Re-Os同位素定年技术在富有机质沉积岩、低变质沉积岩、湖相沉积物、煤、油气藏样品等富碳质地质样品的尝试和成功应用,使其成为直接厘定地层沉积时代、重大地质事件发生时限和机制、古环境重建、油气藏直接定年、油气演化过程推演等研究的关键技术手段。然而,受到富碳质地质样品中极低的Re和Os丰度、采样方式以及地质作用等因素的影响,很多样品的Re-Os等时线年龄和初始Os同位素比值精度超过10%,不能有效地评价海水Os的真实来源和地质作用程度,影响了对不同沉积体系及油气演化过程中Re和Os的化学行为和Re-Os等时线年龄地质意义的理解。由此,本文从富碳质地质样品的Re-Os化学行为和地质应用进展出发,对富碳质地质样品Re-Os同位素分析过程中的采样和取样方式、溶样方法、分离富集方式和标准物质选择四方面进行了总结和完善。指出以沉积速率为采样间距参考,通过预处理方式提高样品的均匀性,使用流程空白更低、对同位素分馏影响更小的溶样方法和分离富集方式进行Re-Os同位素分析,以基质匹配的地质标样进行数据监控可进一步提高样品Re-Os同位素分析质量,有助于不同类型富碳质地质样品Re和Os赋存机制研究、Re-Os同位素分析技术开发及地质应用拓展。Re and Os are relatively enriched in organic-enriched sedimentary rocks under an anoxic environment due to their organophilic property,and the seawater Os isotopic composition is recorded during the deposition of sedimentary rocks.Under certain geological conditions,the Re and Os in organic-enriched sedimentary rocks will transfer to oil-gas reservoir samples through the process of hydrocarbon generation.The enrichment mechanism of Re and Os in these carbon-enriched geological samples,such as organic-enriched sedimentary rocks,low-metamorphic sedimentary rocks,lacustrine sediments,coal,and oil-gas reservoir samples is the basis of wide geological applications.Re-Os isotopic system of organic-enriched sedimentary rocks has been applied to directly date deposition ages or stratigraphic boundary ages or oil-gas reservoirs,has been used to provide the occurrence time and explore the mechanism of major geological events,reconstructing paleo-environment,and deducing the evolution of petroleum,which has resulted in many achievements.The accumulation mechanism of Re and Os in organic-enriched sedimentary rocks plays an important role in understanding the geological significance of Re-Os isotopic data obtained from organic-enriched sedimentary rocks.In anoxic seawater,Re and Os are reduced to lower valence states of Re(Ⅳ)and Os(Ⅲ),respectively,and then Re and Os enter into organic-rich sedimentary rocks by combining with organic matter.Re and Os are enriched and fractionated during this process,enabling the Re-Os isotope system of organic-enriched sedimentary rocks to directly determine stratigraphic boundaries and sedimentary ages.The Re-Os isotope system has successfully provided accurate stratigraphic boundary ages of Devonian—Carboniferous,Cambrian—Ordovician,Ordovician—Silurian,Permian—Triassic,middle-upper Triassic,and Jurassic—Cretaceous.Furthermore,the Re-Os isotopic system has unique advantages for the strata lacking biological fossils or volcanic interlayers,which have provided the sedimentary age

关 键 词：RE-OS同位素体系 富碳质地质样品 油气演化 Re、Os化学行为 地质应用 富碳质地质标样 

分 类 号：O657.63[理学—分析化学]