High-temperature chondrule accretion in primitive chondrites and its relevance for theories of chondrule formation and planetary accretion

一些原始的（不平衡的）普通球粒陨石被描述为含有相互压痕的球粒。我自己的初步研究表明，这些纹理比以前认为的要广泛得多。它们出现在特定球粒陨石的碎屑中，下文称之为“簇状球粒陨石”。这些岩石的结构可以解释为，热的和塑性的球粒与刚性的球粒一起积聚，随后是瞬间的压实和岩化。这与目前认为球粒在母体增生之前就已经固化的观点相反。星团球粒陨石碎屑的普遍存在可能表明高温球粒吸积过程是球粒类星子形成历史的基础。本研究计划旨在了解星团球粒陨石及其母星子的形成条件。它们的岩石学、体积和矿物化学、氧同位素组成、原始稀有气体的库存和它们的太阳前颗粒将被研究。如果能够证实星团球粒陨石是在球粒还具有可塑性的时候形成的，即在球粒形成后的几小时到几天内，我们就可以深入了解太阳星云非常早期的岩石形成过程，这个过程持续时间很短，空间扩展有限。这将不可避免地影响目前的球粒形成和星子吸积模型。

Some primitive (unequilibrated) ordinary chondrites have been described to contain mutually indented chondrules. Own preliminary studies show that these textures are much more widespread than previously thought. They occur in clasts of specific chondritic rocks, which are named “cluster chondrites” hereafter. The textures of these rocks may be interpreted such that hot and hence plastic chondrules accreted together with rigid chondrules, followed by instantaneous compaction and lithification. This is in contrast to current views that chondrules were already solidified before parent body accretion. The ubiquity of cluster chondrite clasts may indicate that the process of hightemperature chondrule accretion was fundamental to the formation history of chondritic planetesimals. The present research proposal is intended to understand the formation conditions of cluster chondrites and their parental planetesimals. Their petrography, bulk and mineral chemistry, oxygen isotopic composition, inventory of primordial noble gases, and their presolar grains will be investigated. If it can be confirmed that cluster chondrites accreted while chondrules where still plastic, i.e. within hours to a few days after chondrule formation, we would get insight into very early rock forming processes of short duration and limited spatial extension of the solar nebula. This would inevitably influence the current models for chondrule formation and planetesimal accretion.