摘要
天津蓟县剖面中元古界铁岭组二段叠层石灰岩中普遍发育海绿石。野外观察表明,海绿石主要分布在叠层石柱体间的泥晶灰岩中,呈薄膜状富集在叠层石鞘外缘;微观特征分析表明,海绿石呈不规则状的胶体形式,显示了原地海绿石的基本特点。电子探针的组分分析表明,铁岭组中的海绿石为中成熟度的海绿石。由于产在潮下高能柱状叠层石灰岩中,铁岭组中的海绿石并不反映低沉积速率或沉积间断的沉积条件,与现代海绿石的形成环境具有明显的差异。因此,中元古界铁岭组叠层石灰岩中的中成熟度原地海绿石是特殊沉积背景下的独特产物,为研究海绿石在地质历史时期产出的多样性提供了一个重要实例。
Glauconites are widespread in the stromatolite limestones of the upper part of the Mesoproterozoic Tiding Formation in Jixian, Tianjin, North China. Field investigation shows that glauconites are mainly distributed in the micritic limestone between stro- matolite columns as thin film centering on the outer edge of stromatolite sheath. Microscopically, they commordy occur as irregular colloids which are indicative of autochthonous typical feature. The EPMA data indicates they are moderately matured in nature. The fact that the glauconites occur in stromatomite limestones deposited in the high-energy subtidal environment suggests that they were not necessarily formed on the substrate with a low sedimentation rate or even a sedimentation hiatus; this is quite different from the case of modem glauconites. Therefore, such medium-mature autochthonous glauconite in stromatolitic limestones is formed under special sedimentary background. Its unique features of glauconite presented in this study provide an alternative case different from the commnon sense of glauconite origin.
出处
《地质通报》
CAS
CSCD
北大核心
2009年第7期985-990,共6页
Geological Bulletin of China
基金
国家自然科学基金项目<燕山地区蓟县系旋回与事件及其相关沉积学问题研究>(编号:40472065)资助
关键词
海绿石
叠层石
中元古界铁岭组
天津蓟县地区
glauconite
stromatolite
Mesoproterozoic Tieling Formation
Jixian area, Tianjin
