沉积岩总有机质碳同位素分析的前处理影响  

Sample-pretreatment Effects on Analytical Results of Total Organic Carbon Isotopes in Sedimentary Rocks

作　　者：吴夏[1,2] 黄俊华[1,2] 白晓[1,2] 王友珍[1] 

机构地区：[1]中国地质大学地质过程与矿产资源国家重点实验室,湖北武汉430074 [2]中国地质大学生物地质与环境地质教育部重点实验室,湖北武汉430074

出　　处：《地球学报》2008年第6期677-683,共7页Acta Geoscientica Sinica

基　　金：国家自然科学基金项目(编号:40572098);中石化海相油气前瞻性项目(编号:G0800-06-ZS-319)联合资助

摘　　要：岩石样品中的有机质稳定碳同位素地球化学已经在重建古环境和古植被等领域得到十分广泛的应用。但对样品的前处理方法的系统研究较少。由于岩石样品前处理的方法不同而对有机碳同位素的测量结果所产生的正负偏差,从而导致不能准确地反映样品中所记录的信息。笔者通过大量条件试验,分析了前处理过程中主要影响实验结果的几种因素。①样品粒度的影响:粒度100目的样品可得理想数据,而粒度在60目时两个样品同位素值均相对偏正,200目时灰岩样品也相对偏正;②不同酸浓度的影响:在1～12N浓度酸处理样品其有机质碳同位素没有明显变化,但低等级酸所含杂质明显使数据偏负,加入15%的氢氟酸对数据没有产生明显影响;③洗除样品中残余酸和烘干温度的影响:为了避免样品中有机质的损失,而不洗除样品中残余的酸,但是样品数据明显偏负并对仪器有损坏,烘干温度100°C时样品部分有机质挥发或升华而使数据相对偏正。The carbon isotopic composition of sedimentary rocks has been widely used in geochemistry to reconstruct paleoenvironment and ancient vegetation, but insufficient systematic research has been made on the pretreatment of sedimentary rock samples. The dissimilarity of rock sample pretreatment methods affects the measurement result of organic carbon isotope, and hence the information in the sample cannot be accurately reflected. This paper analyzed the factors affecting the pretreatment. （1） Effects of the diameter of particles on the δ^13C values of organic matter： the sample crushed to 100 mesh could yield the fight data, but the values of δ^13C display a positive distribution when the sample is crushed to 60 mesh. When limestone is crushed to 200 mesh, the values of δ^13C display a positive distribution. （2） Effects of acid concentration on the δ^13C values of organic matter： the addition of different concentrations of hydrochloric acid and 15% hydrofluoric acid to the samples will not affect the experimental result. Nevertheless, due to impurities in acid, the values of δ^13C will display a negative distribution. （3） Effects of the washing out of the residual acid and the drying temperature on the δ^13C values of organic matter： in order to avoid losing organic matter in the sample, the washing out of the residual acid is not proper. Nevertheless, because of the residual acid in the samples, the values of δ^13C display a negative distribution and this may damage the instrument. At the drying temperature of 100℃, some organic matter may be lost, causing a relatively positive distribution of the δ^13C values.

关 键 词：沉积岩 有机碳同位素 样品前处理 条件试验 

分 类 号：P597.2[天文地球—地球化学]