Petrological And Mineralogical Characteristics Of Two Ordinary Chondrites From Hami,Xinjiang

In this paper,we study two pieces of common chondrite which are newly discovered on the Gobi desert in Hami,Xinjiang.In order to study the petrological and miner alogical characteristics of the two meteorites,classify the types of meteorites,whether the two meteorites are paired or not,and the cooling history of the two meteorites in the matrix,three instruments including optical microscope,scanning electron microscope and electron probe were used to study the two meteorites.1.The olivine Fa values of M2020001 meteorite range from 17.0 to 17.9,with an average of 17.4;The Fs value of pyroxene ranges from 14.6 to 15.7,the Co content of serpentine ranges from 3.8 to 4.8 mg /g,and the composition is homogeneous.The PMD values of olivine and pyroxene are less than 5.In M 202001,the matrix abundance is 13.2 vol%,the metal abundance is about 8.2 vol%,and the grain size of secondary growth stone is about 48.0% ?m.The matrix is transparent,coarse-grained and recrystallized.The boundary of the spherulites can not be observed,and most of them are residual spherulites.The internal structure of a small number of spherulites can be seen.The transparent miner als of M2020001 meteorite are all broken irregularly,with wavy extinction under orthogonal light and slender veins.about62.4% of metal minerals and sulfides in M2020001 meteorite are oxidized,and metal oxidation veins are common.In this study,M2020001 meteorite is divided into H5 type,impact met amorphic grade S3 and weathering grade W3 ordin ary chondrite.2.The olivine Fa of M2020002 meteorite r anges from 17.4 to 17.9,the pyroxene Fs ranges from 15.0 to 17.7,the serpentine,the Co content r anges from 3.3 to 3.6mg/g,and the maximum Ni content of nivalite is 55.8 wt%;The content of Co in serpentine ranges from 3.3 mg/g to 3.6 mg/g,and the average content of Ni is 6.5 wt%.The mineral composition is homogeneous,and the PMD values of olivine and pyroxene are less than 5.In M2020002,the abundance of pellets is 78.3 vol%,and the average diameter of pellets is about 310.0% ? m.The matrix abundance was 12.9vol%,the feldspar particles are very small,the matrix is translucent,the spherulite structure is clearly visible,and some boundaries can be distinguished.The transparent minerals of M2020002 meteorite are broken irregularly,and wave like extinction occurs under orthogonal light.The M2020002 meteorite does not contain shock veins and melt sacs.The oxidation degree of metal miner als is low.There are weak oxid ation edges on the edge of iron nickel metal and sulfide,and there are small metal oxid ation veins.The amount of metal minerals and sulfides less than 20 vol% are oxidized.In this study,M2020002 is classified as H4 type,impact met amorphic grade S2,we athering grade W1 ordinary chondrite.3.Although meteorites M2020001 and M2020002 are collected from Hami,Xinjiang,with similar gray black crust and chemical group H,their rock types are different.M2020001 meteorite is type 5 and M2020002 meteorite is type 4.There are some differences in the content of elements.It is proved that meteorites M2020001 and M2020002 are not paired meteorites.4.The metal cooling rate of meteorites M2020001 and M2020002 is about1?/myr-10 ?/Myr.