Petrological,Mineralogical And Geochemical Characteristics Of A Newly Discovered Carbonaceous Chondrite From Xinjiang

Shanshan 002 is the first and only carbonaceous chondrite discovered in the desert area of China so far.Ordinary chondrites took the major role in the Chinese desert meteorites collection event before,and the occurrence probability of carbonaceous chondrites is extremely low.The discovery of Shanshan 002 have a significant meaning in Chinese cosmochemistry and meteorology study,that there may be an enrichment area of special meteorites in this area.In this study,the petrological and mineralogical characteristics of Shanshan 002 meteorite were illustrated.The research objects include calcium-aluminum-rich inclusions(CAIs),amoeboid olivine aggregates(AOAs),chondrules,mineral fragments and matrix.In one of the slices studied,various types of calcium-aluminum-rich inclusions were observed,with a volume ratio of about 3%,including: melilite-spinel-rich inclusions,spinel-melilite inclusions and hibonite-rich inclusions.Various types of chondrules were found in Shanshan 002,most of those were mafic chondrules,including: porphyritic olivine chondrules,porphyritic olivine pyroxene chondrules,barred olivine chondrules,radial chondrules,cryptocrystalline chondrules and composite chondrules,the volume ratio is 48%.Among those chondrules,the porphyritic chondrules should be formed by condensation,and the composite chondrules may be related to partial melting.In addition to the mafic chondrules,two aluminum-rich chondrules were found.They are the transition product between the mafic chondrules and the calcium-aluminum-rich inclusions.The matrix occupies about 44% of the volume ratio in Shanshan 002.The metal And sulfide accounts for about 5% by volume.After comparing Shanshan 002 with Ningqiang carbonaceous chondrites,the differences between the two types of carbonaceous chondrites were found,and a genetic connection analysis was made.Finally,through scanning electron microscopy petrographic observations and elemental content analysis of single-mineral electron probes in micro-areas,we determined Shanshan 002 into carbonaceous chondrites with a rock type greater than 3.2.