不同地质时期海绿石发育特征差异及成因

Characteristic differences of glauconite formed in different geologic periods and related genetic analysis

张琴 周琛 田寒云 王凯 宋泽平 董岐石

Qin Zhang Chen Zhou Hanyun Tian Kai Wang Zeping Song Qishi Dong

具有指相意义的海绿石在赋存形态、成分组成及成因机理方面复杂多样，且广泛发育于多个地质时期。通过大量文献调研，并结合近年来国内外海绿石分析研究的实例，探究不同时期海绿石在发育特征上的差异性，并探索其成因机理的不同，以期完善海绿石的成因理论，为古地理条件分析提供科学依据。结果表明，不同时期海绿石的赋存形态可以归结为颗粒状、胶结物状和晕边状3大类。根据基质差异，颗粒状海绿石又可分为4类。前寒武纪的海绿石主要形成于石英和钾长石基质中，因而KO含量较高，成熟度较高，可以用假形置换成因理论进行解释；显生宙的海绿石主要形成于粪球粒及生物碎屑基质，其钾组分主要来源于海水，KO含量不稳定，其成因机理与KO和FeO的含量密切相关，用层状晶格理论与颗粒绿化理论进行解释更加合理。对不同时期海绿石发育的离子来源和沉积条件分析表明，充足的Fe，K，Al，Si和Mg等阳离子来源及铁氧化还原界面附近环境为海绿石形成的有利条件。

Glauconite with significance of indicating facies is complex and diverse in occurrence， composition and genetic mechanism， and widely developed in different geologic periods. The differences in respects of characteristics and genetic mechanism of glauconite developed in various geologic periods are investigated based on a review of previous researches from a large number of related case studies worldwide， with a view to improving the genetic theory of glauconite and providing a scientific basis for paleogeographic analysis. The results show that the occurrence of glauconite formed in different periods can be classified into three groups， that is the granular， cemented and halo edged groups. The granular group in turn can be subdivided into four types in terms of substrate. The Precambrian glauconite is mainly developed in substrate of quartz and K-feldspar， featuring high content of KO and high maturity， which can be interpreted via pseudo-shape replacement theory in genetic mechanism. The Phanerozoic glauconite is preferably developed in initial substrate containing fecal spherulite and bioclastic materials， featuring unstable KO content as its potassium component mainly derived from seawater， and its genetic mechanism is closely related to contents of KO and FeO， to which layer lattice theory and granular glauconization theory are more appropriate for interpretation. An integrated analysis of sedimentary environments and ion sources of glauconite in the various geologic periods， indicates that areas adjacent to Fe-redox contact surfaces with sufficient supply of cations such as Fe， K， Al， Si and Mg are favorable for the formation of glauconite.

10.11743/ogg20220115