Analysis On Sedimentary Environment And Its Controlling Factors Of Mesoproterozoic Bingmagou Formation In Jiyuan,Western Henan Province

Sedimentology,stratigraphy and tectonic evolution of southern North China Craton in Mesoproterozoic have been hot issues.The tectonic setting of Xiong'er Group has long been a hot debate in southern North China Craton,although the predecessors have done a lot of research.The Bingmagou formation is the initial clastic sedimentary sequence overlaid the Xiong'er Group with angular unconformity,has a great significance to the Xiong'er Group and the tectonic setting of southern North China Craton.Based on the field reconnaissance and profile measurement,the sedimentary characteristics of the Mesoproterozoic Bingmagou formation in Jiyuan,Western Henan Province are studied.Sedimentology,geochemistry,stratigraphy and methods are comprehensively used to study the sedimentary environments and tectonic setting of Bingmagou Formation in Jiyuan area,and the conclusions as follows:(1)The purplish conglomerates of Bingmagou Formation are the main rocks with the particle size decreasing from bottom to top,with the psephicity becoming better.The rest parts are pebbly sandstones and gritstones.The granulometric parameters and cumulative curve of sandstones indicate Bingmagou formation is gravity flow deposits,and the trend of cumulative curve also illustrates decreasing hydrodynamic conditions.Comprehensive analysis of all aspects,the turbulence of the current and appearance of intermittent catastrophic flood are the main sedimentary characteristics during the peroid of Bingmagou formation.The sedimentary environment is alluvial fan-fan delta,in which the debris flow,distributary channel and sheet flood microfacies can be identified.(2)Based on the analysis of geochemical characteristics of major elements of sandstones collected from Bingmagou Formation in Jiyuan,Western Henan.The results show,the Mesoproterozoic Bingmagou Formation is characterized by low maturity litharenite.The chemical index of alteration(CIA)suggests that the sandstones have a low grade of chemical weathering.The index of compositional variability(ICV)shows the sandstones might be first cycle products,which in an active sedimentary environment.(3)The volcanic debris is the main composition of the conglomerates from Bingmagou Formation in Jiyuan.Combined with the discrimination diagram of sedimentary provenance illuminates sediment source is characterized by intermediate and felsic igneous rocks and quartzite erea,and indicates that the provenance of the Bingmagou Formation belongs to the active continental margin and the continental island arc with minor provenance from the Passive Margin.Combined with previous research,it suggests the Bingmagou Formation is formed in the back-arc basin,and the Xiong'er group is volcanic rocks related to the continental island arc by subduction.The Mesoproterozoic tectonic of southern North China Craton is an active continental margin.Various methods are comprehensively used to discovery the deposition environment of Bingmagou Formation in Jiyuan,and its provenance and tectonic setting are discussed in this paper.The research has an important significance for the Mesoproterozoic sedimentary environment evolution in the southern margin of the North China Craton.