The similarities between CV and CK chondrites are so substantial that some studies have argued for a common parent body origin. These similarities also mean that they are susceptible to misclassification as one another. It is, therefore, important to accurately classify CV and CK chondrites to properly compare the properties of the two groups and evaluate the single parent body hypothesis. In this study, we re‐evaluate the current classification of Northwest Africa (NWA) 2900 as a CV3 chondrite. Based on chondrule abundance (~13%), average chondrule diameter (1.11 ± 0.67 mm), iron content in chondrule olivine (Fa₁ to Fa₃₅ with a peak near ~Fa₃₁) and matrix olivine (Fa₃₃ to Fa₃₆), magnetite abundance (~4 vol%), elemental abundances in olivine (Cr₂O₃, Al₂O₃, TiO₂, MnO, NiO, and CaO) and magnetite (Cr₂O₃, Al₂O₃, TiO₂, and NiO), and comparison with previously reported data for CV and CK chondrites, we propose that the classification of NWA 2900 be changed from CV3 chondrite to CK3 chondrite, with characteristics most similar to those of the CK3.8 subtype. We additionally suggest minor modifications to the compositional criteria used to distinguish between CV and CK chondrites and demonstrate that NWA 2900 extends the range of bulk oxygen isotope compositions of CK chondrites.

中文翻译：

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将西北非洲2900的球粒陨石从CV3重新分类为CK3

CV和CK球粒陨石之间的相似性是如此之大，以至于一些研究争辩说共同的母体起源。这些相似之处还意味着它们很容易彼此错误分类。因此，重要的是准确地对CV和CK球粒陨石进行分类，以正确地比较两组的特性并评估单个母体假说。在这项研究中，我们重新评估了西北非洲（NWA）2900作为CV3球粒陨石的分类。根据软骨的丰度（〜13％），平均软骨直径（1.11±0.67 mm），软骨橄榄石中的铁含量（Fa ₁至Fa ₃₅并在〜Fa ₃₁附近达到峰值）和基质橄榄石（Fa ₃₃至Fa ₃₆），磁铁矿丰度（〜4 vol％），橄榄石（Cr ₂ O ₃，Al ₂ O ₃，TiO ₂，MnO，NiO和CaO）和磁铁矿中的元素丰度（Cr ₂ O ₃，Al ₂ O ₃，TiO ₂，以及NiO），并与先前报告的CV和CK球粒陨石的数据进行比较，我们建议将NWA 2900的分类从CV3球粒陨石更改为CK3球粒陨石，其特性与CK3.8亚型最相似。我们还建议对用于区分CV和CK球粒陨石的成分标准进行少量修改，并证明NWA 2900扩展了CK球粒陨石的整体氧同位素组成范围。