滇东北镇雄西部栖霞—茅口组碳酸盐岩地球化学特征及环境意义

GEOCHEMICAL CHARACTERISTICS AND ENVIRONMENTAL SIGNIFICANCE OF THE CARBONATE ROCKS IN QIXIA-MAOKOU FORMATION IN WESTERN ZHENXIONG,NORTHEASTERN YUNNAN

镇雄县安家坝一带中二叠统栖霞组-茅口组地层出露较好,沉积连续。以此剖面为基础,连续采集碳酸盐岩样品42个,根据其显微特征、元素相关性、元素组份含量及相关元素的比值特征,探讨了研究区碳酸盐岩沉积地球化学特征与古环境意义。研究表明(1)样品中CaO与SiO_2、MgO呈现出比较明显的负相关关系,且后两者在岩石中的含量很低,说明样品在沉积和成岩过程中受陆源物质影响或改造的程度较小。(2)通过对元素含量以及相关元素比值的垂向分布特征分析,如Sr/Ba、MgO/CaO和V/V+Ni等,对不同沉积阶段进行了古水深和古氧相等方面的研究,数据表明茅口组沉积环境相比栖霞组具有较明显的差异。

Qixia-Maokou Formation in Middle Permain , in Anjiaba of Zhenxiong County, is well outcropped and continuously deposited. Making this section as the research object, collecting 42 samples of carbonate rocks , based on the microscopic characteristics , the elements correlation , the elements content as well as the ratio characteristics of the related elements, the geochemical characteristics and the paleo environmental significance of the carbonate rocks in the study area were discussed. Some conclusions have been drawn. Firstly there are obvious negative correlations between CaO and Si0 2, MgO in the rock samples, and the contents of the latter two in rocks are rather low, which both indicate that the samples are less affected and transformed by the terrigenous material in the process of deposition and diagenesis. Secondly, based on the analysis of the element contents and the vertical distribution characteristics of the relevant elements ratios , such as Sr/ Ba, MgO/CaO and Y/Y ＋ Ni etc, and the study of the paleo-water depth and the paleo-oxygenation facies in different sedimentary stages , the data show that compared with Qixia Formation, the sedimentary environment of Maokou Formation has obvious difference.