We report on the discovery of 33 oxygen-anomalous grains from the CH3/CB_b3 chondrite Isheyevo and the CR2 chondrite Northwest Africa (NWA) 801. Oxygen isotopic compositions indicate the origin of the majority grains in stellar outflows of low-mass (∼1.2 to ∼2.2 M _⊙), solar-metallicity red giant or asymptotic giant branch stars, while highly ¹⁷O-enriched grains probably have nova origins. Isotopic compositions of the eight ¹⁸O-rich grains, including an extremely ¹⁸O-rich grain (∼16 times solar ¹⁸O/¹⁶O ratio), are reproduced by zone mixing of SNe II ejecta. Close-to-normal silicon, magnesium, and calcium isotopic compositions of grains are consistent with the isotope exchange in the interstellar medium or the meteorite parent body, while two grains with Si isotopic anomalies and one grain with Mg isotopic anomalies reflect the Galactic chemical evolution. An Isheyevo clast showed several hot spots with moderate to high ¹⁵N enrichments, including a hot spot with an extreme ¹⁵N excess of (7225 316)‰. However, no correlation between ¹⁵N enrichment and presolar oxygen-rich grain abundance is found. Grains with elliptical shapes probably indicate primary condensation feature. Two complex grains possibly display decoupling of the isotopic and elemental compositions in the grain formation environments. The low silicate-to-oxide abundance ratio for the fine-grained chondrule rims in NWA 801 likely reflects the preferential destruction of silicates due to terrestrial weathering. In NWA 801, the presolar O-rich grain abundance in fine-grained chondrule rims is higher than in the interchondrule matrix, similar to the trend observed for some aqueously altered chondrites of petrologic type 2.

我们报告了从 CH3/CB _b 3 球粒陨石 Isheyevo 和 CR2 球粒陨石西北非 (NWA) 801 中发现的 33 个氧异常颗粒。氧同位素组成表明了低质量（~ 1.2 到 ∼2.2 M _⊙ )，太阳金属度红巨星或渐近巨星分支星，而高度¹⁷ O 富集的颗粒可能有新星起源。八个富含¹⁸ O 的颗粒的同位素组成，包括一个极其富含¹⁸ O 的颗粒（约¹⁶倍太阳¹⁸ O/ ¹⁶O 比率），通过 SNe II 喷射物的区域混合再现。晶粒接近正常的硅、镁、钙同位素组成与星际介质或陨石母体中的同位素交换一致，而两粒硅同位素异常和一粒镁同位素异常反映了银河系的化学演化. 一个 Isheyevo 碎屑显示了几个具有中到高¹⁵ N 富集的热点，其中一个热点的¹⁵ N极度过量（7225 316）‰。然而，¹⁵发现了 N 富集和太阳前富氧颗粒丰度。具有椭圆形状的颗粒可能表明主要凝结特征。两种复杂的颗粒可能在颗粒形成环境中表现出同位素和元素组成的解耦。NWA 801 中细粒球粒边缘的低硅酸盐与氧化物丰度比可能反映了由于陆地风化导致的硅酸盐优先破坏。在 NWA 801 中，细粒球粒边缘的太阳前富 O 颗粒丰度高于球粒间基质，类似于一些 2 型岩石水蚀变球粒陨石观察到的趋势。