Geochemical Characteristics And Genesis Of Siliceous Rocks Of Changxing Formation In Northwest Sichuan

Understanding the characteristics and genesis of siliceous mineralization is of guiding significance for understanding the sedimentary evolution of the region.This article through to the northwest of Sichuan,on the basis of literature research,selected the field measured section and section observation,through the system of sampling observation of the siliceous rocks samples chip,siliceous rock geochemical data processing analysis,in the northwest of Sichuan Changxing formation of siliceous rock geochemical characteristics and genetic analysis summary and understanding.The results of the characteristics of the main elements in the study finally confirmed that Al₂O₃ was abundant in the siliceous rocks of the Changxing formation,while the content of Na₂O and MgO was not high.Relatively speaking,the contents of K,Ca,Mn,Al and Ti are more similar to those of siliceous rocks?biogenic?.The study on the triangle diagram of Al-Fe-Mn and the content of K₂O/Na₂O and MgO and Al/?Al+Fe+Mn?shows that the siliceous rocks in the Changxing formation are formed under the action of multiple factors?mainly volcanism and biological action?rather than a single factor.The trace element characteristic analysis shows that the content of Ba and Sr in the siliceous rocks of Changxing formation in northwest Sichuan is relatively low.The U element is relatively rich,and the Th element is relatively small.In northwest Sichuan Changxing formation of siliceous rocks,meanwhile,the content of trace elements is also more than the classic hydrothermal genesis of siliceous rock,classical biogenic siliceous rocks,but this kind of trace elements in general more than classic hydrothermal genesis of siliceous rock,classical biogenic basic categories of the siliceous rocks,further illustrates the siliceous rocks in northwest Sichuan Changxing group could be the result of biological and volcanic a variety of hybrid origin.REE characteristics analysis results show that REE in the siliceous rocks of Changxing formation has no excessive REE elements,but moderately enriched heavy REE elements.Minor Eu positive anomaly and Ce negative anomaly can be confirmed from the Eu,Ce anomaly and rare earth element partition pattern diagram,and thus the characteristics of submarine hot water deposition can be clarified.From the analysis results of geochemical characteristics and sedimentary characteristics of siliceous rocks in the paper,we can judge that the siliceous sediments of the Changxing formation in northwest Sichuan are mainly chalcedone-quartz radiolarian rocks,which are a kind of representative biogenic siliceous rocks.The origin of biogenesis and the origin of volcanism are two basic ways of the formation of siliceous rocks.Rich siliceous hydrothermal fluid is associated with deep faults,a large number of deep hydrothermal siliceous bring direct deposit in the rift valley deep hydrothermal genesis of siliceous rock formation,hydrothermal trophic elements lead to the proliferation of siliceous radiolarians in hydrothermal environments,after the death of settlement or accumulation formation of biogenic siliceous rocks,or doped into the hydrothermal sedimentation of the siliceous rocks formed in the mixture formation siliceous rocks.The sedimentary characteristics of the siliceous rocks in the Changxing formation have recorded the tectonic and paleogeographic changes in the late Permian in the northwestern Sichuan Basin.This can not only reflect the volcanic hydrothermal activities at the same stage,but also intuitively express the influence of the hydrothermal activities on the stratigraphic deposits in the northwest of Sichuan Basin.And the theoretical significance of this effect is very prominent,which is conducive to the smooth development of more scientific research.In addition,from the perspective of geological event research and evolution analysis in the late Permian tectonic process,the practical significance is also outstanding.