We report on the mineralogy, petrography, and in situ oxygen isotopic composition of twenty-five ultrarefractory calcium-aluminum-rich inclusions (UR CAIs) in CM2, CR2, CH3.0, CV3.1–3.6, CO3.0–3.6, MAC 88107 (CO3.1-like), and Acfer 094 (C3.0 ungrouped) carbonaceous chondrites. The UR CAIs studied are typically small, < 100 μm in size, and contain, sometimes dominated by, Zr-, Sc-, and Y-rich minerals, including allendeite (Sc₄Zr₃O₁₂), and an unnamed ((Ti,Mg,Sc,Al)₃O₅) mineral, davisite (CaScAlSiO₆), eringaite (Ca₃(Sc,Y,Ti)₂Si₃O₁₂), kangite ((Sc,Ti,Al,Zr,Mg,Ca,□)₂O₃), lakargiite (CaZrO₃), warkite (Ca₂Sc₆Al₆O₂₀), panguite ((Ti,Al,Sc,Mg,Zr,Ca)_1.8O₃), Y-rich perovskite ((Ca,Y)TiO₃), tazheranite ((Zr,Ti,Ca)O_2−x), thortveitite (Sc₂Si₂O₇), zirconolite (orthorhombic CaZrTi₂O₇), and zirkelite (cubic CaZrTi₂O₇). These minerals are often associated with 50–200 nm-sized nuggets of platinum group elements. The UR CAIs occur as: (i) individual irregularly-shaped, nodular-like inclusions; (ii) constituents of unmelted refractory inclusions – amoeboid olivine aggregates (AOAs) and Fluffy Type A CAIs; (iii) relict inclusions in coarse-grained igneous CAIs (forsterite-bearing Type Bs and compact Type As); and (iv) relict inclusions in chondrules. Most UR CAIs, except for relict inclusions, are surrounded by single or multilayered Wark-Lovering rims composed of Sc-rich clinopyroxene, ±eringaite, Al-diopside, and ±forsterite. Most of UR CAIs in carbonaceous chondrites of petrologic types 2–3.0 are uniformly ¹⁶O-rich (Δ¹⁷O ∼ −23‰), except for one CH UR CAI, which is uniformly ¹⁶O-depleted (Δ ¹⁷O ∼ −5‰). Two UR CAIs in Murchison have heterogeneous Δ¹⁷O. These include: an intergrowth of corundum (∼ ‒24‰) and (Ti,Mg,Sc,Al)₃O₅ (∼ 0‰), and a thortveitite-bearing CAI (∼ −20 to ∼ ‒5‰); the latter apparently experienced incomplete melting during chondrule formation. In contrast, most UR CAIs in metamorphosed chondrites are isotopically heterogeneous (Δ¹⁷O ranges from ∼ −23‰ to ∼ −2‰), with Zr- and Sc-rich oxides and silicates, melilite and perovskite being ¹⁶O-depleted to various degrees relative to uniformly ¹⁶O-rich (Δ¹⁷O ∼ −23‰) hibonite, spinel, Al-diopside, and forsterite. We conclude that UR CAIs formed by evaporation/condensation, aggregation and, in some cases, melting processes in a ¹⁶O-rich gas of approximately solar composition in the CAI-forming region(s), most likely near the protoSun, and were subsequently dispersed throughout the protoplanetary disk. One of the CH UR CAIs formed in an ¹⁶O-depleted gaseous reservoir providing an evidence for large variations in Δ¹⁷O of the nebular gas in the CH CAIs-forming region. Subsequently some UR CAIs experienced oxygen isotopic exchange during melting in ¹⁶O-depleted regions of the disk, most likely during the epoch of chondrule formation. In addition, UR CAIs in metamorphosed CO and CV chondrites, and, possibly, the corundum-(Ti,Mg,Sc,Al)₃O₅ intergrowth in Murchison experienced O-isotope exchange with aqueous fluids on the CO, CV, and CM chondrite parent asteroids. Thus, both nebular and planetary exchange with ¹⁶O-depleted reservoirs occurred.

我们报告了CM2，CR2，CH3.0，CV3.1–3.6，CO3.0–3.6中25种超难熔钙铝富集物（UR CAI）的矿物学，岩石学和原位氧同位素组成， MAC 88107（类似CO3.1）和Acfer 094（未分类C3.0）碳质球粒陨石。所研究的UR CAI通常很小，尺寸小于100μm，并且含有Zr，Sc和Y丰富的矿物（有时包括Alendeite（Sc ₄ Zr ₃ O ₁₂）和未命名的（（Ti ，Mg，Sc，Al）₃ O ₅）矿物，钙铁矿（CaScAlSiO ₆），钙矾石（Ca ₃（Sc，Y，Ti）₂ Si ₃ O ₁₂），方铅矿（（Sc，Ti，Al，Zr，Mg，Ca，□）₂ O ₃），Lakargiite（CaZrO ₃），方铁矿（Ca ₂ Sc ₆ Al ₆ O ₂₀），方铅矿（（Ti，Al，Sc ，Mg，Zr，Ca）_1.8 O ₃），富Y钙钛矿（（Ca，Y）TiO ₃），Tazheranite（（Zr，Ti，Ca）O _2-x），次方晶石（Sc ₂ Si ₂ O ₇） ，锆石（斜方晶CaZrTi ₂ O ₇）和锆石（方晶CaZrTi ₂ O ₇）。这些矿物质通常与50-200 nm大小的铂族元素块有关。UR CAI的出现方式为：（i）单个不规则形状的结节状夹杂物；（ii）未熔化的耐火夹杂物的成分-变形虫橄榄石聚集体（AOA）和蓬松的A型CAI；（iii）粗粒火成岩CAI（含镁橄榄石的Bs和致密的As型）中的残留物；（iv）遗留在软骨中的内含物。除残渣夹杂物外，大多数UR CAI均被单或多层Wark-Lovering轮辋包围，该轮辋由富含Sc的斜辉石，±钙矾石，透辉石和±镁橄榄石组成。岩石类型2–3.0的碳质球粒陨石中的大多数UR CAI均富含¹⁶ O（Δ¹⁷ O〜-23‰），除了一个CH UR CAI，这是均匀地¹⁶ O型耗尽（Δ ¹⁷ O〜-5‰）。两个UR的CAIs在Murchison的具有异质Δ ¹⁷ O.这些包括：刚玉的共生体（〜-24‰）和（钛，镁，钪，铝）₃ ø ₅（〜0‰），和一个thortveitite承载CAI（ 〜-20至〜5‰）; 后者显然在软骨形成过程中经历了不完全熔化。相反，大多数UR的CAIs在变质陨石是同位素异构（Δ ¹⁷从O范围〜-23‰至〜-2‰）中，用的Zr和Sc-富氧化物和硅酸盐，黄长石和钙钛矿被¹⁶ O型耗尽到各种度相对于均匀地¹⁶ O丰富（Δ ¹⁷O〜-23‰）锂云母，尖晶石，铝透辉石和镁橄榄石。我们得出的结论是，UR CAI是由蒸发/冷凝，聚集以及某些情况下在CAI形成区域（很可能靠近原太阳）中富含¹⁶ O的太阳组成的富含O的气体中形成的，随后发生的。散布在整个原行星盘上。形成在其中一个CH UR的CAIs的¹⁶ O型耗尽的气态储层提供证据大变化Δ ¹⁷在CH的CAIs形成区域星云气体的O操作。随后，一些UR CAI在¹⁶熔化期间经历了氧同位素交换圆盘的O耗尽区域，最可能在软骨形成时期。此外，变质的CO和CV球粒陨石中的UR CAIs，以及可能在Murchison中的刚玉-（Ti，Mg，Sc，Al）₃ O ₅共生经历了与CO，CV和CM上的水性流体的O同位素交换。球粒陨石母小行星。因此，发生了与^16个O耗尽型油藏的星云和行星交换。