中文摘要：

使用硒的7步连续化学提取技术，对采自贵州寒武纪牛蹄塘组和湖北恩施二叠纪茅口组富硒碳质岩中的水溶态、可交换态、有机态、元素态、酸性提取态、硫化物／硒化物态和残渣态硒进行了比较研究，应用氢化物-原子荧光法测定了岩石总硒和各结合态硒。结果表明，恩施二叠纪沙地新鲜富硒碳质硅质岩和碳质页岩中的硒主要以有机结合态和硫化物／硒化物态硒为主，残渣态硒较低；遵义松林早寒武世碳质硅质岩中的硒主要以有机结合态和硫化物态硒为主，碳质页岩与镍钼矿层中则以有机结合态、残渣态和硫化物态硒为主，斑脱岩中主要以有机结合态、元素态和可交换态硒为主。根据硒结合态的这种分布特征，推测二叠纪、寒武纪富硒碳质岩中硒初始富集的生物地球化学过程略有差异：前者碳质硅质岩中主要以微生物还原为主，碳质页岩中则是微生物还原作用和生物同化吸收或吸附兼而有之；后者主要以生物同化吸收或吸附为主，微生物还原次之。

英文摘要：

A comparative study was conducted to investigate selenium fractionation in Se-rich carbonaceous rocks from the lower Cambrian Niutitang and Permian Maokou formations, which are located in Zunyi of Guizhou Province and Enshi of Hubei Province, respectively. Seven operationally defined Se fractions in Se-rich carbonaceous rocks were determined by the modified sequential-extraction procedure suitable for carbonaceous shale. These fractions include water-soluble, ligand-exchangeable, base-soluble （organic-bounded）, elemental, acetic acid-soluble, sulfide/selenide, and residue. The total Se in rock and Se concentrations in individual fractions were measured by HG-AFS. The results showed that the sulfide/selenide and organic-bounded Se were the predominant forms of Se present in the carbonaceous chert and carbonaceous shale from the lower Permian Maokou formation while residue Se was generally lower. The sulfide/selenide and organic-bounded Se were still the major forms in carbonaceous chert of the lower Cambrian Niutitang formation while the organic-bounded, residue and sulfide/selenide fractions were prevalent in carbonaceous shale and Ni-Mo ore. Organic-bounded Se and elemental Se were the dominant forms in bentonite, and in lesser amount the ligand-exchangeable Se. These facts indicated that there exists certain difference in the biogeochemical process of Se accumulation between two rock types from Lower Permian Maokou and Cambrian Niutitang formations. For the former formation, the Se microbe reduction was prevalent in the carbonaceous chert, while in the carbonaceous shale the algal assimilation or adsorption occurred simultaneously with microbe reduction. For the later formation, the algal assimilation or adsorption was be the main biogeochemical process for Se enrichment, while the Se reduction by microbes played a secondary role.