北川中泥盆统金宝石组渗滤豆发育特征及其形成环境研究

发布时间：2018-10-31 06:47

【摘要】：本次研究主要通过岩石薄片、有机碳总量、碳氧同位素、锶同位素、X-衍射、微量及稀土元素等分析测试方法,对渗滤豆的内部结构及其核心和包壳层的碳氧同位素特征、锶同位素特征、稀土元素配分模式、核心及渗滤豆尺寸等特征进行了深入研究,并与渗滤豆围岩、围岩中的生物化石及飞仙关组鲕粒灰岩等样品进行对比,确定其核心与包壳为不同沉积时期不同流体环境的产物,北川泥盆系金宝石组顶部渗滤豆层既非巨鲕、亦非核形石,而是大气淡水淋滤的结果。渗滤豆形成于弱氧化-弱还原的过渡环境,其包壳中可见大量葛万藻丝体,包壳中TOC含量可达0.1%,同时包壳中有机碳同位素值出现极大负偏,反映渗滤豆的形成与微生物的活动存在密切联系,属于微生物岩的范畴。渗滤豆的形成需要含有生物碎屑的富有机质泥岩、暴露并遭受大气水的淋滤作用、微生物围绕生物碎屑核心的生长等环境条件,渗滤豆在垂向上的发育具有明显的分带性,靠近暴露面,渗滤豆包壳越厚,而远离暴露面,渗滤豆包壳逐渐变薄甚至完全消失。
[Abstract]:In this study, the internal structure of percolation bean and the carbon and oxygen isotopic characteristics of the core and the cladding layer of the percolation bean were studied by means of the analysis and test methods of thin rock slice, total organic carbon, carbon and oxygen isotopes, strontium isotopes, X-ray diffraction, trace and rare earth elements, etc. The characteristics of strontium isotope, REE distribution model, core and percolation bean size were studied in depth, and compared with the samples of the surrounding rock of leachate, bifossils in surrounding rock and oolitic limestone of Feixianguan formation, etc. The core and cladding are determined to be the products of different fluid environments in different sedimentary periods. The percolation bean layer at the top of the Devonian gold gem formation in Beichuan is neither a giant oolitic nor a nucleated stone but the result of atmospheric fresh water leaching. The leachate was formed in a weak oxidation-weak reduction transition environment. A large number of GE Wan algae filaments were found in the cladding, and the TOC content in the cladding could reach 0.1, and the organic carbon isotopic values in the cladding showed a great negative bias. It reflects that the formation of leachate is closely related to the activity of microorganism and belongs to the category of microbial rock. The formation of percolation beans requires organic mudstone rich in organic matter containing bioclastic materials, exposed and subjected to atmospheric water leaching, and microbes are surrounded by the growth of bioclastic core. The development of percolation beans in vertical direction has obvious zonation. Close to the exposed surface, the percolation shell became thicker, but away from the exposed surface, the percolation shell gradually thinned or disappeared completely.
【学位授予单位】：成都理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P588.248

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