球粒陨石中富Ca、Al包体成因研究进展与演化模式

The Evolvement Models and Progress of Research on Formation of Ca-,Al-rich inclusions in Chondrites

富Ca、Al包体(简称CAI)形成于太阳星云演化的最初始阶段,其成因模式主要包括:气—固凝聚、熔融结晶和部分熔融以及高温蒸发作用等。最近,通过对不同球粒陨石化学群中的CAI进行岩石学特征对比研究,发现不同化学群中的CAI具有相似的大小和类型分布特征,表明不同球粒陨石化学群中的CAI极可能具有相似的起源。该结果,与前人的氧同位素、Al—Mg同位素体系以及稀土元素等研究得到的结论一致。不同球粒陨石化学群中的CAI具有相似的成因,并很可能形成于太阳星云的相同区域,随后迁移到不同球粒陨石群的吸积区域。

Ca-, Al-rich inclusions （CAIs） are the earliest assemblages formed in the solar nebula. The formation models of CAIs include gas—soild condensation, crystallization from melting or partial melting and high-temperature evaporating residues. The latest study show similar distribution patterns of the petrographic types and sizes of CAIs in various chondrites. The petrographic characters argue that CAIs in various chemical groups of chondrites formed under similar processes and conditions probably in a same region in the solar nebula. This is consistent with previous studies of oxygen isotopes, Al—Mg isotopic system and rare earth elements, which suggest a same reservoir of CAIs in various chondrites.During and/or after formation, CAIs were transported into different locations where various groups of chondrites accreted.