中国地质2023，Vol.50Issue(6)：1817-1836,20.DOI:10.12029/gc20200303001
宁夏灵武侏罗系直罗组碎屑岩地球化学特征及源区构造背景分析
Geochemical characteristics of clastic rocks from the Jurassic Zhiluo Formation in Lingwu,Ningxia and analysis of tectonic background of the source area
摘要
Abstract
This paper is the result of geological survey engineering. [Objective]The Zhiluo Formation represents a transitional phase in the lake's advancement and retreat within the broader context of Jurassic geological evolution.Its tectonic background holds paramount importance in exploring the inception timeline of fault-fold belt development along the western margin of the Ordos Basin.This study focuses on the Zhiluo Formation,specifically clastic rocks,from the Jurassic period in the Lingwu area,Ningxia.[Methods]We conducted analyses using X-ray and ICP-MS techniques to uncover the geochemical characteristics of clastic rocks and the structural context of the source region.[Results]Our results reveal that major element correlation coefficients are generally low,while trace elements and REE exhibit high values.Notably,correlation coefficients between Al2O3 and trace elements such as Co,Ni,Cr,V,Sc,Li,Cs,Be,Ga,Tl,Cu,Pb,Zn,and Sn exceed 0.9,and the correlation coefficients between TiO2 and Nb are at 0.98.This suggests that the primary source of sediment is terrigenous clastic material.Enrichment concentration-type elements(K>1,CV>1)include Zr,U,and CaO,while enrichment dispersion-type elements(K>1,CV<1)consist of Al2O3,Fe2O3,MgO,Sr,Ba,U,Co,V,Sc,Li,and Pb.Poorly dispersive elements(K<1,CV<1)encompass SiO2,TiO2,MnO,Na2O,K2O,P2O5,Rb,Th,Nb,Ta,Ni,Cr,Cs,Be,Ga,Tl,Cu,Zn,As,Sn,and REE.No elements fall under the poor concentration type(K<1,CV>1).[Conclusions]The average values for key oxide combinations of main elements are TiO2(0.54),TFe2O3+MgO(4.58),Al2O3/SiO2(0.58),and Al2O3/SiO2(0.18),indicating similarity to an active continental margin.A trace element spider diagram demonstrates the rocks of the Zhiluo Formation's richness in Rb,K,and U,which are large ion lithophile elements,and a significant deficit in Nb,Sr,P,and Ti.The chondrite-standardized REE distribution curve depicts a gentle right-leaning pattern,signifying LREE enrichment and HREE relative depletion.In terms of geochemical indices,the CIA(70.76-81.88)for mudstone exceeds the ICV(1.02-1.6)for sandstone,while mudstone ICV(0.7-1.14)remains mostly less than or equal to 1.This suggests that the Zhiluo Formation in the Lingwu area exhibits little to no recycling and is characteristic of primary sedimentation in the context of tectonic activity with a moderate degree of differentiation.Correlation diagrams indicates that tectonic background of the source region is primarily associated with an active continental margin.Additionally,it exhibits some links to continental island arc systems,suggesting an active continental margin or an active continental margin subduction zone,potentially resembling an Andean-type active continental margin.关键词
侏罗系/直罗组/碎屑岩地球化学/构造背景/地质调查工程/灵武/宁夏Key words
Jurassic/Zhiluo Formation/geochemistry of clastic rocks/tectonic background/geological survey engineering/Lingwu/Ningxia分类
天文与地球科学引用本文复制引用
陶瑞,海连富,王磊,宋扬,李海峰,林丽,梅超,白金鹤..宁夏灵武侏罗系直罗组碎屑岩地球化学特征及源区构造背景分析[J].中国地质,2023,50(6):1817-1836,20.基金项目
宁夏自然科学基金项目(2021AAC03446)与宁夏优秀人才支持计划(JTGC2019023)联合资助. Supported by the projects of Ningxia Natural Science Foundation(No.2021AAC03446)and the Ningxia Excellent Talent Support Program(No.JTGC2019023). （2021AAC03446）
