415国家自然科学基金(41402025)资助收稿日期:2022–05–07;修回日期:2022–05–30北京大学学报(自然科学版)第59卷第3期2023年5月ActaScientiarumNaturaliumUniversitatisPekinensis,Vol.59,No.3(May2023)doi:10.13209/j.0479-8023.2023.017北京下苇甸地区新元古代景儿峪组–寒武纪府君山组界线硅质角砾形成模式李辰卿董琳†沈冰造山带与地壳演化教育部重点实验室,北京大学地球与空间科学学院,北京100871;†通信作者,E-mail:lin.dong@pku.edu.cn摘要为探讨华北板块在新元古代与寒武纪之间沉积间断后再次接受沉积的具体过程和环境变化,选取北京西山地区下苇甸剖面青白口系景儿峪组和下寒武统府君山组的硅质沉积作为研究对象,通过沉积学、岩石学及地球化学分析,发现景儿峪组顶部硅质层及府君山组底部硅质条带角砾具有相似的接近海水的Ge/Si比值和稀土配分特征,揭示府君山组硅质条带角砾可能来自下伏景儿峪组。研究结果还表明,府君山组底部含角砾白云岩不具有层理,且其中角砾成分复杂,磨圆分选程度较低,排列杂乱,可能代表一次冰川沉积。关键词景儿峪组;府君山组;古风化壳;Ge/Si;稀土元素FormationofChertBrecciafromtheTransitionalBeddingsbetweenNeoproterozoicJingeryuFormaitonandCambrianFujunshanFormationinXiaweidianSection,BeijingLIChenqing,DONGLin†,SHENBingKeyLaboratoryofOrogenicBeltsandCrustalEvolution(MOE),SchoolofEarthandSpaceSciences,PekingUniversity,Beijing100871;†Correspondingauthor,E-mail:lin.dong@pku.edu.cnAbstractToinvestigatethespecificprocessesofdepositionandenvironmentalchangesintheNorthChinaBlockduringLateNeoproterozoictoEarlyCambrianwhenitreceiveddepositionagainafteradepositionalhiatus,chertbrecciaoftheQingbaikouSeriesJingeryuFormationandtheLowerCambrianFujunshanFormationintheXiaweidiansectionofXishanareaofBeijingwasanalyzed.Basedonpetrologicalandgeochemicalstudies,chertlayersinJingeryuFormationandchertbrecciainthebottomoftheoverlyingFujunshanFormationhavesimilarGe/Siratiosandrareearthelementpatterns.ItindicatesthatFujunshanchertbrecciamightoriginatedfromJingeryuFormation.Breccia-bearingdolomiteinthebottomoftheFujunshanFormationisblock-shaped,withoutbedding.Thebrecciaismixedincomponentandsize,withpoorsortingandroundness,anddisorderlyar...
