富有机质样品Re-Os同位素定年实验方法

Re-Os isotopic dating procedures for organic-rich samples

近年来,铼—锇(Re-Os)同位素体系在确定含油气系统烃源岩沉积年龄、烃类生成、运移、后期调整改造年龄(古油藏热裂解、硫酸盐热化学还原反应等)以及油源示踪方面取得了一系列成果。但是,富有机质样品的Re-Os同位素体系存在元素丰度低、赋存形式复杂、同位素体系封闭性影响因素以及Os同位素组成均一机制不清等诸多难题,进而导致其构建的等时线年龄误差相对较大。通过测年样品筛选、富有机质样品化学前处理、实验流程空白控制以及国际参考标样监控等4个方面,对现有的富有机质样品的Re-Os同位素分析测试全流程进行了总结与完善,可为拟开展含油气系统Re-Os定年工作的研究人员提高数据质量,构建理想的Re-Os等时线。

The rhenium-osmium(Re-Os)geochronometer is newly developed technology and has been regarded as a promising radiometric tool for the direct dating of the deposition of source rock,hydrocarbon generation,migration and consequent alteration(e.g.,thermal cracking,thermochemical sulphate reduction),and oil-source correlation.However,the complex nature of Re-Os systems in organi-rich samples,including their relatively low elemental contents,multiple origins and occurrences,ambiguous homogenization mechanisms of 187 Os/188 Os and our limited understanding of the closed system of Re-Os systematics etc.,often result in the relatively large uncertainties of obtained isochrones.In this paper,to improve their data quality and yield ideal Re-Os isochrons,the existing Re-Os isotopic analysis method was improved by the terms of sample selection and screening,chemical pretreatment,total analytical blank control and international reference material monitoring.Results showed that a comprehensive guide to researching working in Re-Os geochronology for petroleum system analysis can be available.