We propose a simple model of chondrule formation that is supported by our new experiments. With a laser-heating and inert-gas-cooling technique, we obtained evaporation and condensation pathways starting with chondritic compositions till ends, and extracted ‘relative volatilities’ of elements from them. Above boiling points, we observed numerous silicate droplets being ejected from collapsed cavities of vapor bubbles on the surface of molten sample, known as jet-droplets. We postulate jet-droplets as origin of chondrules. The formation mechanism of jet-droplets requires a dense and large solid body (>3 cm across), named ‘duston’, for chondrule precursors. Our chondrule formation model presumes dustons having CI-like composition. Upon boiling, a duston ejects jet-droplets from its molten surface and simultaneously forms an adiabatically expanding vapor cloud around it. The jet-droplets supercool and incorporate the supersaturated vapor and fine condensates while they travel through the cloud, thus completing their makeup as chondrules. The compositions and the mixing ratio of the three components (jet-droplet, vapor and condensate) can be exactly predicted by using relative volatilities of elements, given the chondrule composition to be fitted and the conditions: vaporization degree (VD) and redox state (f_s) of the duston. We attempt to reproduce bulk compositions of chondrules in total of 600. About 75% chondrules are successfully matched with specific combinations of VD and f_s for each chondrule. The model altogether explains 3.5 features of chondrules: maximum size and size-frequency distribution; chemical variety; and textural variety.

中文翻译：

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泡沫成球粒岩-I。蒸发和冷凝实验，形成软骨

我们提出了一个简单的软骨形成模型，该模型得到了我们的新实验的支持。通过激光加热和惰性气体冷却技术，我们获得了从软骨成分一直到结束的蒸发和冷凝途径，并从中提取了元素的“相对挥发度”。在沸点以上，我们观察到从熔融样品表面上的气泡破裂腔中喷出的大量硅酸盐小滴，称为射流小滴。我们假设喷射液滴是软骨的起源。喷射液滴的形成机理需要软骨状前体的致密且大的固体（宽度> 3 cm），称为“ duston”。我们的软骨形成模型假定尘土具有类似CI的成分。煮沸后 尘土从熔融表面喷出喷射液滴，同时在其周围形成绝热膨胀的蒸气云。喷射液滴过冷，并在它们穿过云层时融合了过饱和的蒸气和细小的冷凝物，从而完成了它们的球状化妆。可以通过使用元素的相对挥发性来精确预测三种成分（喷射液滴，蒸气和冷凝水）的成分和混合比，并确定要适合的球状成分和条件：汽化度（VD）和氧化还原状态（f _s）。我们尝试复制总计600个的球状团块。对于每个球状团，成功将约75％的球状团与VD和f _s的特定组合成功匹配。该模型共解释了软骨的3.5个特征：最大尺寸和尺寸-频率分布；化学品种 和质地的多样性。