THE DARK INCLUSIONS IN ZHAODONG CHONDRITE AND BOXIAN CHONDRITE AND THEIR GENETIC SIGNIFICANCE
肇东和亳县陨石中的黑包体及其成因意义

There are some dark inclusions in Zhaodong chondrite(L_4) and Boxian chondrite(LL_(3-4)). These dark inclusions are similar to chondrules in shape and size, but they differ from chondrules in mineral components and texture. Dark inclusions are composed of fine-grained olivines and other silicate mineral microcrystallines, but no glass. The silicate mineral microcrystallincs are of analogic lowcalcium pyroxene or plagioclase composition. Each dark inclusion possesses an accumulation and is of ten surrounded by a black ring composed of metal Fe-Ni, troilite and silicate mineral microcrystallines. Therefore, it is inferred that dark inclusions arc acccumulations of nebula condensates and are semifinished chondrules, but they did not melt. A model of chondrule-form is established: nebula condensated to form dust, dust accreted to form dark inclusions, dark inclusions were melted to form chondrules.