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）普通陨石被描述为含有相互缩进的球粒。自己的初步研究表明，这些纹理比以前认为的要广泛得多。它们产于特定的寒武纪岩石的碎屑中，下文称之为“丛状碎屑岩”。这些岩石的结构可以解释为热的，因此塑料球粒与刚性球粒一起增生，然后瞬间压实和石化。这与目前的观点相反，即陨石球粒在母体吸积之前已经固化。普遍存在的星团球粒陨石碎屑可能表明，高温球粒的吸积过程是球粒星子形成历史的基础。本研究的目的是了解星团微行星及其母体微行星的形成条件。他们的岩相学，散装和矿物化学，氧同位素组成，库存的原始稀有气体，和他们的前太阳颗粒将进行调查。如果能够证实星团陨石在球粒仍处于塑性时（即球粒形成后数小时至数天内）吸积，我们将深入了解太阳星云非常早期的岩石形成过程，这些过程持续时间短，空间延伸有限。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.