Study On The Genesis Of The Siliceous Rocks During The Transition Period Of Guadalupian-Lopingian In Zunyi Area,Northern Guizhou

This paper focuses on the siliceous sedimentary events of the Permian Guadelupo-Leping transitional period in the Zunyi area of northern Fujian,from the stratigraphy,petrology,mineralogy and geochemistry of the siliceous rocks in the Maokou Formation.Based on the characteristics,the mechanism of siliceous rocks is studied,and the types,spatial and temporal distribution,sedimentary environment and formation process of siliceous rocks in the Zunyi area of northern Hebei are determined.The paleogeography,paleostructure,paleoclimatic and paleontological evolution of the basin during this period are The study of manganese ore mineralization provides an important window.Through the ZK1103 drilling in the study area,the Nancha manganese mine,the Xiping Datong,the Tongyujing anticline,the Cemao village,the Dashanwo,the Shijiazhai,the Tangcun stratigraphic section and the sample collection,the siliceous rocks in the study area are all It is stored in the 2nd strata of the Maokou Formation and has three different types of output:one is the“Bainitang layer”carbon siliceous limestone at the bottom of the manganese belt in the“Qianzhong Trench”;the second is closely surrounding the“Bainitang layer”.The“layer”is a“Chengqiangshi”siliceous rock distributed in strips;the third is a meteorite strip or meteorite nodule deposited in the normal shallow sea carbonate platform.At the same time,the collected samples were subjected to hand specimens and microscopic observation,as well as main trace elements and Si isotope geochemical tests.The“Bainitang layer”is a special set of siliceous rock,which is a dark gray,gray-black thin layer to medium-thick layered carbon siliceous limestone with strip-like,layered,tuberculous structures and visible in local layers.Meteorite nodules,carbonaceous components are heavy,easy to soil hands,with horizontal bedding;microscopically visible amorphous gelatinous structure,hidden-microcrystalline structure,fibrous structure,rich in biological fossils;SiO₂ average content of 39.69%The correlation between K₂O,Na₂O and Al₂O₃ is very good.U/Th value is>1,V/Cr value is 2.66,the distribution curve of rare earth elements is"flat",and the value of?30Si is between-0.09^-0.67.The“Chengqiangshi”siliceous rock is similar to the wall shape.The distribution around the Zunyi manganese mine is grayish white to white thick layered to massive.The rock mass is white,milky white or pale yellow siliceous rock,and the local iron is brown or brown.It has a blocky,breccia-like,strip-like structure and a common metasomatic structure.Under the microscope,quartz shows cryptocrystalline and microcrystalline morphology.It can be seen that the residual structure of limestone bioclastics is replaced by siliceous materials;SiO₂average The content of 98.44%,K₂O,Na₂O and Al₂O₃ have no correlation,U/Th value>1,V/Cr value is 1.00,the distribution curve of rare earth elements is“flat”,?³⁰Si value is between0.03¹.47;normal marine Sedimentary meteorite strips or meteorite nodules,siliceous strips and bio-limestones are rhythm,and meteorite nodules are found in layered limestone,dense and hard,block-like,microscopically showing siliceous rock mineral composition including micro Crystal quartz,chalcedony,visible bioclastic;SiO₂ average content 91.33%,K₂O,Na₂O and Al₂O₃correlation is very good,U/Th value>1,V/Cr value of 0.3,rare earth element distribution curve is"flat"The law of trace element enrichment is similar to that of“Chengqiangshi”siliceous rock.Based on the study of siliceous rock stratigraphy,petrology,mineralogy and geochemistry,the results show that the genesis of siliceous rocks in the Maokou Formation in the G-L transition period in Zunyi area of northern Hebei Province are different.Normal marine sedimentary meteorite strips or meteorite nodules are formed in the normal shallow sea environment of the limited sea platform,which is less affected by hot water deposition.The“Bainitang layer”carbon siliceous limestone is formed in the inner platform of the confined sea otter.The deep-water reduction environment of the basin phase,the silicon is derived from hot water,formed by the deposition of hot water jets,and is close to the vicinity of the nozzle;the“wall-walled”siliceous rock is formed by metasomatism,and the metamorphic original rock is a block of normal deposition in the platform.The bio-lime rock,after which the hydrothermal fluid migrates upward along the fissure channel,and the siliceous material replaces the limestone deposited earlier to form siliceous rock.