An experimental study of chondrule formation from chondritic precursors via evaporation and condensation in Knudsen cell: Shock heating model of dust aggregates
An experimental study of chondrule formation from chondritic precursors via evaporation and condensation in Knudsen cell: Shock heating model of dust aggregates
复制标题
球粒前体通过努森槽蒸发和冷凝形成球粒的实验研究：尘埃聚集体的冲击加热模型
DOI：
10.1016/j.epsl.2017.05.040
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发表时间：
2017
影响因子：
5.3
通讯作者：
Isobe Hiroshi
中科院分区：
文献类型：
--
作者：
Imae Naoya;Isobe Hiroshi
球粒是直径为1.5毫米的火成岩天体，形成于最早期的太阳系，通过短暂的加热事件，分为两种类型：主要（I型，FeO贫乏）和次要（II型，FeO丰富）。使用不同氧化还原条件和晶粒尺寸的各种耐火材料，在IW-2至IW-3.8下进行球粒再生实验，冷却速率主要为100 ° C/h，峰值温度主要在1450 ° C，并且主要在100 Pa下在努森电池中提供在峰值温度下电荷和周围气体之间的接近化学平衡。使用固体缓冲剂控制胶囊中的蒸气压。在接近平衡的金属贫铁起始材料中的铁成分显着蒸发之后和期间，发生结晶。这导致了类似于I型球粒的产物的形成。尘状橄榄石颗粒发生在收费的前体II型球粒含有粗铁橄榄石，但这种颗粒是不常见的I型球粒。因此，细粒的亚铁基质而不是II型球粒是I型球粒的主要前体。I型陨石球粒可能是在与目前实验系统相似的条件下通过蒸发和冷凝演化而来的。在实验中逸出的残余气体可能凝结形成基质，导致互补的成分。矩阵和原始球粒的集群可能已被回收，形成主代球粒起源于冲击加热。
Chondrules, igneous objects of ∼1 mm in diameter, formed in the earliest solar system via a transient heating event, are divided into two types: main (type I, FeO-poor) and minor (type II, FeO-rich). Using various chondritic materials for different redox conditions and grain sizes, chondrule reproduction experiments were carried out at IW-2 to IW-3.8, with cooling rates mainly ∼100°C/h, with peak temperatures mainly at 1450 °C, and mainly at 100 Pa in a Knudsen cell providing near chemical equilibrium between the charge and the surrounding gas at the peak temperatures. Vapor pressures in the capsule were controlled using solid buffers. After and during the significant evaporation of the iron component from the metallic iron-poor starting materials in near equilibrium, crystallization occurred. This resulted in the formation of a product similar to the type I chondrules. Dusty olivine grains occurred in charges that had precursor type II chondrules containing coarse ferroan olivine, but such grains are not common in type I chondrules. Therefore fine-grained ferroan matrices rather than type II chondrules are main precursor for type I chondrules. The type I chondrules would have evolved via evaporation and condensation in the similar conditions to the present experimental system. Residual gas, which escaped in experiments, could have condensed to form matrices, leading to complementary compositions. Clusters of matrices and primordial chondrules could have been recycled to form main-generation chondrules originated from the shock heating.