Abstract Aluminum-rich (Al2O3 > 10 wt%) chondrules (ARCs) are important chondritic components that petrologically link two other major chondritic components, ferromagnesian chondrules (FMCs) and calcium-aluminum-rich inclusions (CAIs), which formed in different regions of the protoplanetary disk. They are closely related to FMCs as indicated by their similar igneous textures, mineral assemblages, and Al-Mg isotope systematics; meanwhile, they have genetic a relationship with CAIs as indicated by their distinctly Al2O3-rich compositions and occasional occurrences of relict CAI minerals. In order to further understand their formation mechanism and genetic relationships to FMCs and CAIs, nine ARCs and three ARC-related objects from Allende (CV3 oxidized), Leoville (CV3 reduced), and the ungrouped Ningqiang carbonaceous chondrites were studied for petrology, mineralogy, bulk compositions, rare earth element (REE) abundances, and in situ oxygen isotopic compositions. Our results suggest that (i) ARCs crystallized from incompletely molten droplets with crystallization sequences mainly determined based on their bulk compositions. Projection of their bulk compositions onto the forsterite-saturated tridymite-diopside-spinel diagram allows us to classify them into Al-rich [Sp], Al-rich [En], and Al-rich [Plag]; (ii) ARC precursors are mixtures of refractory materials and the precursors of FMCs, in which the refractory materials have diverse sources rather than a single type of CAI/AOA (amoeboid olivine aggregate); this is inferred from the bulk compositions, relict minerals (both coarse- and fine-grained spinel, olivine, and Al-Ti-diopside), and various CAI-like REE patterns (unfractionated Group I/III and highly fractionated Group II/II-like) of ARCs. The sources include AOAs and igneous Type B/C CAIs; (iii) ARCs were melted in the FMC-forming region, possibly by the same heating mechanism or during the same transient heating event, which is consistent with the similar oxygen isotopic compositions of their phenocrysts (Δ17O = −5.2 ± 1.7‰, 2SD). Thus, we consider that ARCs formed by melting of mixtures of diverse refractory components with the FMC precursors in the FMC-forming region.

中文翻译：

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CV 球粒陨石中富铝球粒的起源：将多种难熔组分掺入铁镁球粒形成区

摘要 富铝 (Al2O3 > 10 wt%) 球粒状体 (ARCs) 是重要的球粒状体成分，在岩石学上将另外两种主要的球粒状体成分铁镁质球粒 (FMCs) 和富含钙铝的包裹体 (CAI) 联系起来，它们形成于地球的不同区域。原行星盘。它们与 FMC 密切相关，正如它们相似的火成岩质地、矿物组合和 Al-Mg 同位素系统学所表明的那样；同时，它们与 CAI 之间存在遗传关系，如其明显富含 Al2O3 的成分和偶尔出现的残余 CAI 矿物所表明的。为了进一步了解它们的形成机制和与 FMC 和 CAI 的遗传关系，来自阿连德（CV3 氧化）、Leoville（CV3 还原）的 9 个 ARC 和 3 个 ARC 相关物体，并对未成群的宁强碳质球粒陨石进行了岩石学、矿物学、整体成分、稀土元素 (REE) 丰度和原位氧同位素组成的研究。我们的结果表明 (i) ARC 从不完全熔融的液滴中结晶，结晶顺序主要取决于它们的整体组成。将它们的整体成分投影到镁橄榄石饱和的鳞石英-透辉石-尖晶石图上，我们可以将它们分为富铝 [Sp]、富铝 [En] 和富铝 [Plag]；(ii) ARC 前体是耐火材料和 FMC 前体的混合物，其中耐火材料具有多种来源，而不是单一类型的 CAI/AOA（变形虫橄榄石骨料）；这是从大量成分、残余矿物（粗粒和细粒尖晶石、橄榄石、和 Al-Ti-透辉石），以及 ARC 的各种类 CAI REE 模式（未分级的 I/III 族和高度分级的类 II/II）。来源包括 AOA 和火成岩 B/C 型 CAI；(iii) ARCs 在 FMC 形成区域熔化，可能通过相同的加热机制或在相同的瞬态加热事件期间，这与其斑晶的类似氧同位素组成一致 (Δ17O = -5.2 ± 1.7‰, 2SD) . 因此，我们认为 ARC 是由不同耐火组分的混合物与 FMC 形成区域中的 FMC 前体熔融形成的。可能通过相同的加热机制或在相同的瞬态加热事件期间，这与其斑晶的类似氧同位素组成一致（Δ17O = -5.2 ± 1.7‰，2SD）。因此，我们认为 ARC 是由不同耐火组分的混合物与 FMC 形成区域中的 FMC 前体熔融形成的。可能通过相同的加热机制或在相同的瞬态加热事件期间，这与其斑晶的类似氧同位素组成一致（Δ17O = -5.2 ± 1.7‰，2SD）。因此，我们认为 ARC 是由不同耐火组分的混合物与 FMC 形成区域中的 FMC 前体熔融形成的。