Due to their common occurrence in various types of chondrites, igneous rims formed on pre-existing chondrules throughout chondrule-forming regions of the solar nebula. Although the peak temperatures are thought to reach similar values to those achieved during chondrule formation events, the heating duration in chondrule rim formation has not been well defined. We determined the two-dimensional chemical and oxygen isotopic distributions in an igneous rim of a chondrule within the Northwest Africa 3118 CV3_oxA chondrite with sub-micrometer resolution using secondary ion mass spectrometry and scanning electron microscopy. The igneous rim experienced aqueous alteration on the CV parent body. The aqueous alteration resulted in precipitation of the secondary FeO-rich olivine (Fa_40–49) and slightly disturbed the Fe-Mg distribution in the MgO-rich olivine phenocrysts (Fa_11–22) at about a 1 μm scale. However, no oxygen isotopic disturbances were observed at a scale greater than 100 nm. The MgO-rich olivine, a primary phase of igneous rim formation, has δ¹⁷O = −6 ± 3‰ and δ¹⁸O = −1 ± 4‰, and some grains contain extreme ¹⁶O-rich areas (δ¹⁷O, δ¹⁸O = ∼−30‰) nearly 10 μm across. We detected oxygen isotopic migration of approximately 1 μm at the boundaries of the extreme ¹⁶O-rich areas. Using oxygen self-diffusivity in olivine, the heating time of the igneous rim formation could have continued from several hours to several days at near liquidus temperatures (∼2000 K) in the solar nebula suggesting that the rim formed by a similar flash heating event that formed the chondrules.

由于它们在各种类型的球粒陨石中普遍存在，因此在整个太阳星云形成球粒的区域中，在预先存在的球粒上形成了火成的边缘。尽管峰值温度被认为达到与在软骨形成事件期间达到的峰值相似的温度，但是在软骨边缘形成中的加热持续时间还没有被很好地定义。我们使用二次离子质谱和扫描电子显微镜，以亚微米分辨率_确定了西北非洲3118 CV3 _oxA球粒陨石中球_粒状火成岩边缘的二维化学和氧同位素分布。火成的轮缘在CV母体上经历了水相变化。含水变化导致次生富FeO橄榄石沉淀（Fa _40–49），并在大约1μm的范围内稍微扰乱了富含MgO的橄榄石表晶中的Fe-Mg分布（Fa _11-22）。但是，没有观察到大于100 nm的氧同位素干扰。MgO的富橄榄石，火成岩轮缘形成主相，具有δ ¹⁷ O = -6±3‰和δ ¹⁸ O = -1±4‰，而一些颗粒含有极端¹⁶富O型区域（δ ¹⁷ O， δ ¹⁸ O =〜-30‰）近10微米的对面。我们在极端¹⁶的边界处检测到约1μm的氧同位素迁移O丰富的地区。利用橄榄石中氧气的自扩散性，火星边缘形成的加热时间在太阳星云中接近液相线温度（约2000 K）下可能会持续数小时至数天，这表明该边缘是由类似的闪蒸事件形成的，形成了软骨