内蒙古林东普通球粒陨石的角砾特征  

Breccia characteristics of Lindong ordinary chondrite from Inner Mongolia

作　　者：欧荣林 缪秉魁[1,2,3,4] 黄丽霖 班振瑶[1,2,3,4] OU Rong-lin;MIAO Bing-kui;HUANG Li-lin;BAN Zhen-yao(a.Guangxi Key Laboratory of Hidden Metallic Ore Deposits Exploration,Guilin University of Technology,Guilin 541006,China;Institute of Meteorites and Planetary Materials Research,Guilin University of Technology,Guilin 541006,China;Guangxi Academician Workstation for Cosmochemistry and Planetary Science,Guilin University of Technology,Guilin 541006,China;Key Laboratory of Planetary Geological Evolution of Universities in Guangxi,Guilin University of Technology,Guilin 541006,China)

机构地区：[1]桂林理工大学广西隐伏金属矿产勘查重点实验室,广西桂林541006 [2]桂林理工大学陨石与行星物质研究中心,广西桂林541006 [3]桂林理工大学广西天体化学与行星科学院士工作站,广西桂林541006 [4]桂林理工大学行星地质演化广西高校重点实验室,广西桂林541006

出　　处：《桂林理工大学学报》2020年第2期284-298,共15页Journal of Guilin University of Technology

基　　金：国家自然科学基金项目(41776196,41173077);科技部国家科技基础条件平台项目(2005DKA21406);广西科技基地及人才专项(桂科AD1850007)。

摘　　要：林东陨石是一块具有强烈碎裂结构的普通球粒陨石,其中包含多种不同陨石类型的角砾。丰富的角砾碎屑表明该陨石来自其母体表层,为表土角砾岩。陨石的角砾和基质各约占一半,其中含有LL5型角砾、LL4型角砾、LL冲击熔融型角砾、LL5球粒型角砾、无球粒陨石型角砾、LL3球粒型角砾和H5型等类型角砾。不同类型角砾基质中的橄榄石和低钙辉石成分比较均一,橄榄石Fa=28.0 mol%~30.4 mol%,低钙辉石Fs=22.8 mol%~24.8 mol%,二者Fa和Fs的PMD值均小于5%。陨石的Fe-Ni金属和硫化物丰度较低,模式含量为4.1vol%。根据矿物成分和金属含量分析,林东陨石母体为LL5型普通球粒陨石。7种不同类型角砾或6种不同于陨石母体类型角砾的组成表明,林东陨石母体源区至少经历了6次不同的撞击事件。不同类型角砾以及H5型角砾和无球粒陨石角砾中橄榄石和低钙辉石成分均一的特点,表明普通球粒陨石母体表层角砾岩在碰撞碎裂后固结成岩的过程中发生了热变质平衡作用。此外,林东陨石母体表面发生矿物成分平衡作用,可能指示了小行星母体表面存在较高的变质温度,因此,林东陨石母体的位置可能具有日心距小、环境温度高的特点。Lindong meteorite is an ordinary chondrite with strong fractured structure,with different kinds of meteorite types breccias.The abundant breccias indicate that the meteorite comes from parent body surface,and is a regolith breccia.The breccias and matrix of the meteorite account for about half of the total respectively,including LL5 breccia,LL4 breccia,LL impact melting breccia,LL5 chondrule breccia,achondrite breccia,LL3 chondrule breccia and H5 breccia.The composition of olivine and low-calcium pyroxene in different types of breccia matrix is relatively uniform,olivine Fa=28.0mol%-30.4mol%,low-calcium pyroxene Fs=22.8mol%-24.8mol%,and both PMD of Fa and Fs values are less than 5mol%.The Fe-Ni metal and sulfide abundance of the meteorite are low and their mode content is 4.1vol%.According to the analysis of mineral composition and metal content,the parent body of Lindong meteorite is an LL5 type ordinary meteorite.Seven different types of breccias or six different types of breccias from the LL5 parent body indicate that the source region of the Lindong meteorite had experienced at least six different impact events.The characteristics of the olivine and the low-calcium pyroxene in different types breccias and H5 breccia and achondrite breccia indicate that the regolith breccia of the ordinary chondrites has a thermal metamorphism in the process of consolidation and diagenesis after the collision.In addition,the balance of the mineral composition on the Lindong meteorite parent body surface may indicate that asteroid parent surface has a high metamorphic temperature,so the location of the Lindong meteorite parent body may have relatively smaller heliocentric distance and higher ambient temperature.The meteorite is of great significance in exploring the original positions of asteroid bodies.

关 键 词：普通球粒陨石 表土角砾岩 不同类型角砾 热变质作用 林东陨石 

分 类 号：P185.83[天文地球—天文学]