METEORITE WITH CONVENTIONAL NAME “VELYKA BALKA”: MINERALOGICAL CHARACTERISTIC AND CLASSIFICATION
Keywords:
meteorite, chondrite, texture, minerals, chondrules, chemical composition, shock metamorphism.Abstract
The results of structural and mineralogical study of meteorite with conventional name “Velyka Balka” are given. Because of absence of reliable dates from the meteorite owner, its finding circumstances caused strong doubt in the sample finding in Ukraine. On the base of optical, electron microscopy and microprobe investigations the meteorite is classified as L4-5 chondrite with shock stage S3 and weathering scale W3. The microprobe data indicate to a low variation in a composition of olivine (Fa24.1–25.2) and Ca-low pyroxene (En78.0–78.7Fs20.2–21.2Wo0.79–1.42). Composition of Ca-rich pyroxene corresponds to En47.8Wo43.7Fs8.56 and plagioclase – to Ab86.2An7.83Or6.02. The chondrite contains such evidences of shock metamorphism: (1) polycrystalline structure of kamacite and troilite grains with signs of additional deformation; (2) the presence of zone grains of taenite, coarse plesite and relics of martensite within the taenite grains; (3) wave and mosaic extinction of olivine grains; (4) the presence of shock melted veins and pockets with maskelynite containing melted troilite and chromite microcrystals. Signs of at least double collision of a parent body of the meteorite with other bodies in the asteroids belt are preserved. The second impact was less intense than the first one and caused formation of fragile and plastic deformations in the meteorite. Enhanced content of macrohondrules and the presence of filiform crystals of a chromite in maskelynite are individual features of the chondrite.
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