The Features And Origin Of Chondrules Of Kumtag 014 Meteorite

Chondrules in meteorites formed by the high temperature events of early solar system provide important information for the early solar nebula evolution.Kumtag014 is a unequilibrated chondrites which was found in the Gobi Desert near Hami,Xinjiang,China in2013.In this paper,the petrology and mineralogical characteristics of the meteorite were studied by means of optical microscope,SEM and EMPA.And silicate chondrules were the key research objects.Based on the above observation and analyses,the classification of the meteorite and the formation conditions of silicate chondrules are inferred.Kumtag014meteorite consists of chondrule?83.3vol%?,matrix?13.1vol%?and metal?3.60vol%?.Chondrules of Kumtag014 meteorite are very sharply defined,most of them are round,nearly round or elliptical;there are mainly 6 kinds of chondrules,and composite structures are found;the main mineral composition of chondrules are olivine,pyroxene and feldspar glass.The phenocrysts of chondrules are usually automorphic or hypautomorphic.The abundances of chondrules of different structural type are close to that of other non-equilibrium OC,the average diameter of the chondrules is 0.63 mm,and the diameters of chondrules with different structures vary widely and in a similar range.The matrix is opaque,nearly no recrystallization.Opaque minerals are mainly troilite,kamacite and taenite.The meteorite minerals expresses varing degrees fracture,and no impact melting sac or shock-induced melt vein was found.The opaque minerals were oxidized to different degrees,and kamacite was almost oxidized.The mineral composition of meteorites shows strong heterogeneity:olivine,Fa_{22.66?0.55-54.66?}?PMD=51.63?;low-Ca pyroxene,Fs_{19.03?4.26-41.17?}?PMD=53.49?,Wo_{1.84?0.38-4.6?}?PMD=66.22?.Average Ni is 0.16%in troilite,and maximum Ni is 7.67%in taenite.The mineral composition of chondrules of different structural types also has a great viriation.The whole rock components of each type of chondrules are obviously rich in K and Na,and exhibit lithophile/iron element fractionation.Through the above work,the main conclusions are as follows:?1?Kumtag014 meteorite is classified as ordinary chondrite?OC?of L3,the stage of shock metamorphism is S1,and the weathering grade is W2.?2?The silicate chondrules were formed by rapid condensation of droplets formed by remelting of spherical parent particles.?3?The composition of the chondrule parent body is related to the single mineral composition of the chondrules and the mineral model composition of the chondrules,but not to the other properties of the chondrules.?4?In the Kumtag 014 meteorite,different structures of chondrules are formed in the same source region,and the composition of the source region is not uniform,and the variation of nebula pressure,temperature and temperature is also not uniform.