摘要
海绿石作为一种典型的沉积相指示矿物,其分类及成因研究一直是矿物学和岩石学界关注的焦点。基于海绿石成因理论研究现状,结合国内外大量海绿石研究实例,分析原地、准原地和异地海绿石的不同特征及其地质意义,并探讨和完善海绿石的分类体系及成因。结果表明:原地海绿石的成因假说较多,目前比较公认的颗粒绿化理论和假形置换理论可以解释颗粒状和微孔隙中海绿石的成因,但仍然无法解释砂岩中大量胶结物状海绿石的成因。不同类型海绿石在元素组成、成熟度、形态、赋存环境上存在很大差异。原地海绿石富集于凝缩段,成熟度较高,元素特征反映沉积环境。准原地海绿石以多期次成因的包壳状为特征。碎屑海绿石元素特征与沉积环境往往不符,多见颗粒状,常富集于大型层理砂岩中。鉴于目前海绿石分类体系仍比较混乱,按"成因机制"和"是否搬离生成地点",建立了"原生"和"次生"及"原地"和"异地"海绿石的分类体系。提出"自生淀胶理论"解释胶结物状、晕边状、包壳或薄膜状海绿石的成因,并用大量实例证明了自生胶结物状海绿石的存在。海绿石在指示沉积环境、岩石定年、改造岩石储集物性等方面具有重要的研究意义。
Origin and classification of glauconite, a typical kind of sedimentary facies indicator, have long been the hot topics of mineralogy and sedimentology. This paper investigates the characteristics of autochthonous, parautochthonous and allochthonous glauconite, and documents its classification systems and genesis based on previous researches on the genesis of glauconite and a large number of case studies of glauconite worldwide. Several hypotheses have been proposed to inter- pret the genesis of autochthonous glauconite. The results suggest that the grain verdissement and pseudomorphic replace- ment hypotheses are applicable for the interpretation of the genesis of granular and autochthonous glauconite in the micro- scopic pores of shale, but are inapplicable for the interpretation of the formation of glauconite cement in intergranular pores in sandstones. Different types of glauconite show significant differences in elemental composition, maturity, morpho- logy and hosting environment. Autochthonous glauconite tends to accumulate in a thin layer of condensed section, and shows high maturity. Its element-composition features, thus, are symptomatic of depositional environment. Parautoch- thonous glauconite is characterized by multi-stage involucrums. Detrital glauconite generally accumulates in sandstones with large-scale bedding structure, and is commonly oval or granular. Its element-composition features cannot be used as the indicators of sedimentary environments. New classification systems are proposed to replace the current confused classi- fication systems of glauconite. The glauconites are divided into ＂primary＂ vs. ＂secondary＂ classes and ＂autochthonous＂ vs. ＂allochthonous＂ categories, according to two main criteria （i. e. , genesis and whether removing from the initial forma- tion place）. An authigenic precipitation and cementation theory is proposed to interpret the genesis of glauconite that shows shapes of cement, halo edge and involucrum. Moreover, the existence of the authigenic glauconite cement is proved by a large number of case studies. Glauconite, therefore, plays a significant role in diagnosis sedimentary environment, rock dating and improving reservoir physical properties.
出处
《石油与天然气地质》
EI
CAS
CSCD
北大核心
2016年第6期952-963,共12页
Oil & Gas Geology
基金
国家自然科学基金项目(41302081)
教育部留学回国启动基金项目(ZX20140267)
关键词
原地海绿石
异地海绿石
成熟度
分类体系
自生淀胶理论
沉积环境
autochthonous glauconite, alloehthonous glauconite, maturity, classification system, authigenic precipitationand cementation theory, sedimentary environment
