Characteristics And Classification Of Lin Dong Meteorite Breccia In Inner Mongolia

There are often different types of breccia in chondrites,which are formed on the surface of meteorites by impact.Therefore,the breccia of chondrites is of great significance in studying the impact and history of meteorites.Lin Dong meteorite is an ordinary chondrite with strongly fractured structure,which contains many kinds of breccias of different meteorite types.The abundant breccia suggest that the meteorite should come from the surface of its parent body,and it is a regolith breccia of ordinary chondrite.Therefore,this meteorite is of great significance in exploring the impact history of the ordinary chondrites parent body.In this paper,the petrological and mineral chemical characteristics of different meteorite breccia are studied in detail by means of optical microscope,scanning electron microscope and electron probe,and then the meteorite types of the parent body are discussed.At the same time,the impact history of the parent body and its thermal metamorphism on surface are discussed.According to the study,Lin Dong meteorite is a fragmentation structure,with breccia and matrix accounting for about 50.0vol% respectively.Among the breccia,the meteorite types of breccia are: LL5 breccia,LL4breccia,LLimpact melting breccia,LL5 globular breccia,Achondrite breccia.LL3 globular breccia,H5 breccia.However,the composition of olivine and low-calcium pyroxene in different types of breccia matrix is very uniform,olivine Fa=28.0mol%-30.4mol%,low-calcium pyroxene Fs=22.8mol%-24.8 mol%,and the vary of composition in olivine and low-calcium pyroxene is very small.Both Fa and FS values PMD were less than 5%.In addition,the abundance of Fe-Ni metals and sulphides is small(4.1vol%).According to the comprehensive analysis of mineral composition and metal content mentioned above,the parent body of Lin Dong meteorite is LL5 type ordinary chondrite.Seven different types of breccia or six types of meteorite types different from parent body indicate that the meteorite type of Lin Dong meteorite is different from that of meteorite parent.The meteorite breccia represents at least six different impacts.However,the composition of olivine and low-calcium pyroxene of different types of breccia is homogeneous,especially H5-type breccia and achondrite breccia,It is shown that the surface breccia of the ordinary chondrite parent body underwent thermal metamorphism during the process of consolidation after collision and fragmentation,and the mineral composition of different types of breccia had migrated,resulting in the homogenization of the thermal metamorphism of the mineral composition.