贵州水城小牛井田晚二叠世煤的地球化学特征及成煤环境分析

发布时间：2018-06-21 12:14

本文选题：小牛井田 + 晚二叠世　；参考：《贵州大学》2017年硕士论文

【摘要】：晚二叠世时,贵州水城小牛地区处于靠近陆相的海陆过渡相部位,海水进退频繁,成煤环境特殊。晚二叠世末期,古环境剧变,当时的成煤植物经过一系列变化转变为煤层,一部分古环境信息会被植物保存下来,并保存到煤层中,因此,研究煤层有重要的古环境意义。本文运用沉积学、地球化学、煤岩学、数理统计等方面的知识,以采自小牛井田12个钻孔18个主采煤层中的140余件煤心样,以及采自盘县地区的6个井下煤层样,开展常量元素、微量元素、煤质、煤层有机碳同位素分析测试,探讨常量元素、微量元素、煤质、煤层有机碳同位素等与成煤环境之间的关系,了解常量元素、微量元素、有机碳同位素等在纵向上变化规律,揭示煤层中蕴含的古环境信息。经过研究和分析,取得了如下结论:1.通过煤中硫分、灰分等分析,认为成煤环境是控制煤质主要因素。小牛井田全硫分主要由黄铁矿硫组成,次为有机硫。根据煤中黄铁矿硫占全硫的比重以及有机硫占全硫的比重,煤层形成环境应以潮坪、三角洲环境为主。煤层中全硫分、灰分纵向变化规律可以清晰反演成煤期两次大的海侵海退旋回。海退时形成的煤层全硫分较低,灰分较高;海侵时形成的煤层全硫分较高,灰分较低。2.通过煤层中常量元素及微量元素测试分析,认为元素富集与成煤环境密切相关。微量元素的富集很大程度上受控于峨眉山玄武岩提供的陆源碎屑物质。元素的地球化学参数表明物源区在温暖、湿润条件下发生了中等程度的化学风化,泥炭在弱~强还原环境中形成。煤中微量元素B、Co、Cr、Cu、Ga、Ge、Mo、Ni、Pb、Sr、V、Zn的纵向变化规律可以用来反映古海平面变化,海退时形成的煤层微量元素含量较低,海侵时形成的煤层微量元素含量较高。3.小牛井田煤层显微煤岩组分中绝大多数为镜质组,其次为惰质组。镜质组(V)与惰质组(I)比值V/I介于1.10~2.27,泥炭层形成时为极潮湿覆水的还原环境。海侵时V/I值、镜质组(V)含量减小,惰质组(I)含量增加;海退时,V/I值、镜质组(V)含量增加,惰质组(I)含量减小。煤层有机碳同位素研究发现,靠近P/T界线附近碳同位素组成快速负偏,与前人对P/T界线附近碳同位素组成研究结果类似,推测当时火山来源CO2含量很高,导致植物中碳同位素显著负偏,二叠纪末陆地植物大绝灭可能与此相关。
[Abstract]:During the late Permian, the Mauniu area of Shuicheng, Guizhou Province was located near the continental transitional facies, with frequent advance and retreat of sea water and special coal-forming environment. At the end of the late Permian, the paleoenvironment changed dramatically, and the coal-forming plants changed into coal seams after a series of changes. Some paleoenvironmental information will be preserved by plants and stored in coal seams. Therefore, the study of coal seams has important paleoenvironmental significance. Based on the knowledge of sedimentology, geochemistry, coal petrology and mathematical statistics, more than 140 coal core samples from 18 main coal seams from 12 boreholes in Xiaoniu mine field and 6 underground coal seam samples from Panxian area are collected in this paper. The isotopic analysis of major elements, trace elements, coal quality and coal seam organic carbon were carried out, and the relationship between major elements, trace elements, coal quality, coal seam organic carbon isotopes and coal-forming environment was discussed, so as to understand the major elements and trace elements. The variation of organic carbon isotopes reveals the paleoenvironmental information contained in coal seams. After research and analysis, the following conclusions have been reached: 1. Through the analysis of sulfur and ash in coal, it is concluded that coal forming environment is the main factor to control coal quality. The total sulfur content of Mavericks mine is mainly composed of pyrite sulfur, followed by organic sulfur. According to the proportion of pyrite sulfur to total sulfur and organic sulfur to total sulfur, the coal seam forming environment should be tidal flat and delta environment. The longitudinal variation law of total sulfur and ash in coal seam can clearly invert two large transgressive and regressive cycles in coal-forming period. The total sulfur content and ash content of the coal seam formed during the sea retreat are lower and the total sulfur content of the coal seam formed during the transgression is higher than that of the coal seam formed during the transgression, and the ash content is lower than that of the other coal seam. Through the test and analysis of constant elements and trace elements in coal seam, it is considered that the enrichment of elements is closely related to the coal-forming environment. The enrichment of trace elements is largely controlled by the continental clastic material provided by the Emeishan basalt. The geochemical parameters of the elements indicate that the source area has a moderate chemical weathering under warm and humid conditions, and peat is formed in a weak to strong reduction environment. The longitudinal variation of trace element B _ (Co) C _ (Cr) C _ (C) C _ (1) C ~ (2 +) ~ (2 +) Zn in coal can be used to reflect the change of paleo sea level, the content of trace elements in coal seam formed during regression is lower, and the content of trace element in coal seam formed during transgression is higher than that in coal seam formed during transgression. In the coal seam of Xiaoniu mine field, most of the microscopic coal and rock components are vitrinite, followed by inertinite. The ratio of vitrinite (V) to inertinite (I) is between 1.10 and 2.27, and the peat formation is a very wet environment of overlying water. During transgression, the contents of vitrinite and vitrinite decreased, while that of inertinite increased, while that of vitrinite increased, and that of inertinite decreased. The study of coal seam organic carbon isotope found that the carbon isotopic composition near the P / T boundary was rapidly negative deviated, which was similar to previous studies on the carbon isotope composition near the P / T boundary. It was assumed that the CO2 content of volcanic origin was very high at that time. The carbon isotopes in plants are significantly negative skewed, which may be related to the extinction of terrestrial plants at the end of Permian.
【学位授予单位】：贵州大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P618.11

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