Sedimentary Feature And Tectonic Environment About The Cherts Of The Taiyuan Formation In Jiaozuo Area

The paper study mainly storm deposit of limestone and cherts's Sedimentary characteristics and Tectonic environment in Jiaozuo area,by using reserach method of and Geochemical analysis based on the cherts. Meanwhile, through combining regional tectonic setting and geometric characteristic of basement in southern part of the North China Basin,the paper ananlyses sedimentation characteristics and structural environment of Taiyuan Formation in Jiaozuo, the southern part of North China Block. The main conclusions are as follows:1. Storm deposit of the limestone developed mainly in L4,L5 and L6 of Taiyuan Formation in JiaoZuo.The limestone is divided into 3 sequences from bottom to top on the basis of sedimentary structure:(1) The lower part of shell debris deposits lag plot;(2) The middle Texture layer of marl;(3) The upper mudstone. This sequence of storm deposit exertses cyclicity in the study area. According to these vertical sequences,the process of storm activity can be divided into growth period, fastigium, attenuation period and Interval. The difference between storm deposit in Jiaozuo area and typical storm deposit is that the former is with earthquake probably.The earthquake led to strong change of sedimentary stratum before it is solidified completely. The result is that rock stratums are mixed together, and paleoearthquake relic, such as Ball-and-pillow structure, earthquake wedge and syndepositional fault.2. Through analysis of the major elements,trace elements and REE elements of cherts from Taiyuan formation in Jiaozuo,the southern part of North China Block , according to the trace elements As,Sb are more enrichment, the characteristics of A1-Fe-Mn triangle diagram,U-Th discrimination diagrams,Fe-Mn-(Ni+Co+Cu)×10 triangular diagram and Zr-Cr diagram,it is indicated that the cherts were derived from hot water; The NASC-normalized flat REE patterns with weak negative Ce anomalies and positive Eu anomalies and the lower ratio of La/Yb indicate that the cherts are hydrothermal sediments;the lower ratio of the major elements TiO₂ and Al₂O₃,the diagram of Fe₂O₃/TiO₂- Al₂O₃/(Al₂O₃+Fe₂O₃)and the characteristics of Al₂O₃/(Al₂O₃+Fe₂O₃),Ce/Ce*(0.672-0.85)and (La/Ce)N(1.207-1.665) implied a setting of continental margin. 3. Through the above analysis, according to the changes of geometric characteristic of the Basin from Benxi Formation to Taiyuan Formation, combined with the tectonic setting of Taiyuan Formation during the deposition period.North China basin probably has been impacted by the southern Mianlue ocean,which became the leading force in the sedimentation process of coal stratum of North China basin.