Study On The Characteristics And Formation Mechanism Of Siliceous Rocks In Ebian Xianfeng Area Of Southwestern Sichuan

In view of the origins and genesis of the siliceous deposits in the Ediacaran and the problems in the study of the late Ediacaran-Lower Cambrian geological events,this study was based on the Sinian(Xianfeng section)and the late Ediacaran-the early Cambrian Mai Di Ping group(Lao Ya Cun section)as the breakthrough point,and summed up the predecessors to the Xianfeng Area in Ebian.On the basis of field outcrop,section identification,major and trace element,isotope test data analysis of samples,the siliceous rock has done a systematic study on the types of siliceous rocks,structural features,vertical phase changes of siliceous rocks,siliceous causes and sources in the study area.The origin and formation of the silicon rich sediments in the ocean of the Ediacaran period are discussed,and the changes in the genesis and origin of the siliceous rocks in the late Ediacaran-the early Cambrian period are also explained.(1)Previous researches on siliceous and siliceous dolomite in Xianfeng Area have been carried out for many times.It is considered that it is the origin of hot water and hydrothermal fluids that come from deep faults.(2)In order to explore the source and formation mechanism of silicon deposits in Ediacaran,first of all,the types of siliceous rocks in Xianfeng was studied.According to structural features,the Xianfeng silicon was divided into seven types: the Layered silicaite,the Stacked silicalite,the Tubercular silicalite,the Banded silicalite,the Block silicalite,the Silicified silicalite,the Porous and pulse silicalite.Different types of sources and causes are different.Through the analysis of major trace,rare earth,and silicon isotope analysis,it is found that siliceous materials in the Dengying section Dengying Formation should be the common source of seawater and hot water,and seawater is the main source,not predecessors' research.The hydrothermal fluid from the deep faults is the siliceous material from volcanic eruptions.(3)In order to try to explain the changes in the silicon and source of the late Ediacaran –early Cambrian,the section of Laoyacun was studied in detail,according to siliceous field origins.It is divided into silicic nodules,siliceous and siliceous bands in the pores,and is characterized by silicification(anaesthetization)under the microscope.Based on the analysis of thin slices and main traces,it is believed that the siliceous matter in the upper Xiangling Dengying Formation has turned into hot water generation.At the same time,it has been found through research that the Lower Cambrian siliceous material is a common source of hot water and biology,combined with Eu/Eu* drape.In phase change,it is believed that the top silicity of the upper Sinian Dengying Formation is from the occurrence of the Xingkai rift movement in the Lower Cambrian Madiping Formation,and the siliceous thermal fluid enters the Dengying Formation from top to bottom,resulting in a light shadow.The group's silica becomes a hydrothermal source.