虎峪沟长城系底部富硅火山岩、火山碎屑岩及其中富铁钛熔体包裹体的发现  

The discovery of siliceous volcanic rocks,volcaniclastic rocks,and iron-titanium-rich melt inclusions at the bottom of the Great Wall System in Huyugou

作　　者：孙嘉婧 谢玉玲[1] 于超 曲云伟 夏加明 SUN Jia-jing;XIE Yu-ling;YU Chao;QU Yun-wei;XIA Jia-ming(Civil and Resource Engineering School,University of Science and Technology Beijing,Beijing 100083,China)

机构地区：[1]北京科技大学土木与资源工程学院,北京100083

出　　处：《岩石矿物学杂志》2024年第5期1235-1250,共16页Acta Petrologica et Mineralogica

基　　金：国家重点研发计划项目(2017YFC0601300);自然科学基金重点项目(41930427)。

摘　　要：元古宙是地球演化的关键时期,对该时期岩石记录的研究为理解前寒武纪地球演化提供了重要依据。对岩石成因的正确解读是岩石大地构造研究的基础,也是基于岩石记录揭示地球环境变化的前提。华北克拉通长城系底部普遍发育一套富硅的层状岩石,被认为是一套由裂谷沉积形成的海相石英砂岩和硅质岩浅变质而成。本文以北京昌平虎峪沟出露的长城系底部常州沟组富硅层状岩石为研究对象,通过详细的野外地质观察,典型样品的岩矿相、SEM/EDS(扫描电镜/X射线能谱)分析、CL(显微阴极发光)成像分析、石英原位LA-ICP-MS(电感耦合等离子质谱)分析以及石英中熔体包裹体的岩相学、显微测温、马弗炉加温-淬火实验和包裹体成分的SEM/EDS、EPMA(电子探针)、LRM(显微激光拉曼光谱)分析等,提出了长城系底部富硅层状岩石的火山成因新认识。研究结果表明,长城系底部富硅层状岩石包括碎屑结构(前人定义的石英砂岩)和镶嵌结构(前人定义的石英岩)两类,其矿物组成主要为石英和钾长石,另外还含有少量锆石、金红石等。碎屑结构岩石中石英、钾长石碎屑可见棱角-次棱角状,且钾长石未见黏土化的边缘。两类岩石中石英的CL多显示蓝紫色的发光特征。另外,据石英钛饱和温度计估算的形成温度集中在550~650℃之间,也显示了高温石英的特征。两类岩石中的石英和钾长石中均发育有富铁钛的两相熔体包裹体。熔体包裹体显微测温结果表明,熔体包裹体在加温过程中至1000℃后,不混溶两相的成分持续变化,并在1050℃发生颜色深浅的反转,在约1350℃左右临界均一。马弗炉加温淬火实验也证实,在加温至1350℃淬火后的样品中的两相熔体包裹体发生了均一。SEM/EDS和EPMA结果表明,熔体包裹体的主要成分为铁、钛的氧化物,暗色部分相对富铁,而浅色部分相对富钛,熔体包裹体两相The Proterozoic Eon is a critical period of the Earth's evolution,and the study of its rock records in this period is important for understanding the Earth's evolution in the Precambrian.The correct interpretation of rock genesis is the basis of the study of rock geotectonics and the premise of revealing the change of earth environment based on rock records.A set of silicon-rich layered rocks generally developed at the bottom of the Changcheng System in the North China Craton,which is considered to be a set of marine quartz sandstones and siliceous rocks formed by shal-low metamorphism in rift valley deposition.This paper focuses on the silica-rich layered rocks of Changzhougou Formation at the bottom of the Great Wall System exposed in Huyugou,Changping,Beijing.Through detailed field geological observations,petrological and mineral analysis of typical samples,SEM/EDS(Scanning Electron Mi-croscopy/X-ray Spectroscopy),CL(Cathodoluminescence)imaging,in-situ LA-ICP-MS(Laser Ablation-induc-tively Coupled Plasma Mass Spectrometry)analysis of quartz,and petrological,micro-thermometry,muffle furnace heating-quenching experiments,and SEM/EDS,EPMA(Electron Probe Microanalysis),LRM(Laser Raman Mi-croscopy)analysis of melt inclusions in quartz,a new understanding of the volcanic origin of the silicon-rich strati-fied rocks at the bottom of the Great Wall System has been proposed.The results indicate that the silicon-rich strati-fied rocks at the bottom of the Great Wall System include two types:clastic structures(previously defined as quartz“sandstone”)and mosaic structures(previously defined as“quartzite”).The main mineral compositions are quartz and K-feldspar,with minor amounts of zircon,rutile,and other minerals.In the clastic structure rocks,quartz and K-feldspar clasts exhibit angular to subangular shapes,and K-feldspar shows no signs of clay alteration at the edges.The CL of quartz in the two types of rocks mostly shows blue-purple luminous characteristics.Addi-tionally,the formation temperature estimated by

关 键 词：华北克拉通 长城系 富硅火山岩 熔体包裹体 熔体不混溶 

分 类 号：P588.14[天文地球—岩石学] P588.211[天文地球—地质学]