PETROGRAPHIC AND MINERAL CHEMICAL STUDY OF THE ZHUANGHE AND GUANGMINGSHAN METEORITES

The Zhuanghe and Guangmingshan meteorites fell in 1976 and 1996, respectively. Both of them fell in Zhuanghe city, Liaoning province, within a distance about 20 km apart. These two meteorites are similar in texture, mineral modal composition and mineral chemistry) and are classified as H5 chondrites. Their final equilibrium temperatures are lower than 500℃ according to the two-pyroxene thermometer. Cooling rate of Guangmingshan in its asteroidal body is 10-100℃/Ma, based on the correlation between the band width and composition of taenite; Zhuanghe probably cooled slower, as indicated by common occurrence of tetrataenite. Guang-mingshan was weakly shocked, showing only fracturing of silicates; it is classified into S1 of shock grade. Undulant distinction of silicates is common in Zhuanghe, and there are also fine-grained impact-induced melt veins, suggesting a shock grade of S2.