关键词: 海绿石, 成因类型, 沉积环境, 地质意义, 徐庄组

Abstract: Different types of glauconites were formed in the Cambrian Xuzhuang Formation in Dabeiwang, Xuzhou. To investigate the genesis of different types of glauconite, analysis of different aspects of glauconite was performed including its mineralogy, geochemistry and sedimentary environment. In addition, polarization microscopy, X-ray diffraction and electron microprobe are used to systematically investigate the different types of glauconite-bearing strata and glauconite to find out the indicative meaning for sedimentary facies of the different types of glauconite. The results show that there are three types of glauconite in the Xuzhuang Formation: granular, detrital illusion, and micellar. Granular glauconite shows medium-high content of potassium, high content of iron, medium-high content of aluminium in sandstone and low content of aluminium in limestone. Detrital illusion glauconite shows a large variety of potassium, iron and aluminium, and maintains the morphological characteristics of its substrates. Micellar glauconite is characterised by high potassium, high iron, and low aluminium. The genesis of granular glauconites can be explained by the verdissement theory and the glauconite in sandstone is susceptible to environmental impacts. The genesis of detrital illusion glauconite follows the layer lattice theory and the pesudomorphic replacement theory, and is subjected to metasomatism and dissolution. The composition of detrital illusion glauconite varies greatly due to strong hydrodynamic conditions. Micellar glauconites are gel-like glauconities precipitated by cementation and are formed in a stable environment.

Key words: glauconite, genesis type, sedimentary environment, geological significance, Xuzhuang Formation