The first known natural occurrence of calcium monoaluminate, in a calcium‐aluminum‐rich inclusion from the CH chondrite Northwest Africa 470

Ivanova, М. А.; Petaev, M. I.; MacPherson, G. J.; Nazarov, M. A.; Taylor, L. A.; Wood, John A.

doi:10.1111/j.1945-5100.2002.tb01032.x

Cited by 23 publications

(25 citation statements)

References 28 publications

(28 reference statements)

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“…Brearley and Jones (1998) give a thorough report of the occurrences and chemistry of this phase. These phases exhibit virtually no chemical variations whatsoever and are always close to theoretical stoichiometry (Aléon et al, 2002;Ivanova et al, 2002;Ma et al, 2011;Weber and Bischoff, 1994). This is true even when coexisting hibonite (in the case of grossite) contains substantial titanium and magnesium.…”

Section: Perovskitementioning

confidence: 83%

“…This is true even when coexisting hibonite (in the case of grossite) contains substantial titanium and magnesium. Ivanova et al (2002) argued that this chemical purity is due to the fact that aluminum atoms in both grossite and CaAl 2 O 4 are in tetrahedral rather than octahedral coordination, unlike hibonite, thus providing no suitable site for titanium and negating possible coupled substitution with magnesium. There are now known to be two naturallyoccurring polymorphs of CaAl 2 O 4 a low-pressure form, krotite (Ma et al, 2011), that is likely a high-temperature condensate, and a high-pressure form, dmitryivanovite , that likely forms by shock metamorphism of krotite.…”

Section: Perovskitementioning

confidence: 97%

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Calcium–Aluminum-Rich Inclusions in Chondritic Meteorites

MacPherson

2014

Treatise on Geochemistry

105

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Section: Perovskitementioning

confidence: 83%

Section: Perovskitementioning

confidence: 97%

Calcium–Aluminum-Rich Inclusions in Chondritic Meteorites

MacPherson

2014

Treatise on Geochemistry

105

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“…The CAIs from R chondrite are, considering the sizes of the inclusions, as stated already above, very small, similar to the CAIs in ordinary and enstatite chondrites. Corundum (Bar-Matthews et al 1982;MacPherson et al 1983MacPherson et al , 1984, melilite, grossite Bischoff 1994, 1997;, and CaAl 2 O 4 (Ivanova et al 2002) are completely absent, and hibonite is a very rare phase. Due to these and other mineralogical characteristics, we conclude that CAIs similar to melilite-rich or -bearing Type A and B CAIs mainly found in CV3 chondrites (like Allende; e.g., MacPherson and Grossman 1979;Grossman 1980;MacPherson et al 1988;Brearley and Jones 1998, and references therein) are not present in R chondrites.…”

Section: Similar Cais Within Other Groups Of Chondritesmentioning

confidence: 99%

Ca,Al‐rich inclusions in Rumuruti (R) chondrites

Rout¹,

Bischoff²

2008

Meteorit & Planetary Scien

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We studied 20 R chondrites and found 126 Ca,Al-rich objects (101 CAIs, 19 Al-rich chondrules, and 6 spinel-rich fragments). Based on mineralogical characterization and analysis by SEM and electron microprobe, the inclusions can be grouped into six different types: (1) simple concentric spinel-rich inclusions (42), (2) fassaite-rich spherules, (3) complex spinel-rich CAIs (53), (4) complex diopside-rich inclusions, (5) Al-rich chondrules, and (6) Al-rich (spinel-rich) fragments. The simple concentric and complex spinel-rich CAIs have abundant spinel and, based on the presence or absence of different major phases (fassaite, hibonite, Na,Al-(Cl

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“…1-4), is texturally and mineralogically most similar to the majority of CAIs in the previously studied CH chondrites Acfer 182, ALH 85085, PCA 91467, NWA 470, NWA 739, and NWA 770 (MacPherson et al 1989;Kimura et al 1993;Weber et al 1995aWeber et al , 1995bKrot et al 1999aKrot et al , 1999bKrot et al , 2002aKrot et al , 2006aIvanova et al 2001Ivanova et al , 2002. Oxygen and magnesium isotopic compositions of these CAIs reported by Krot et al (2007Krot et al ( , 2008b) support this conclusion: most of them are 16 O-rich and have small or unresovlable excesses of 26 Mg.…”

Section: Comparison Of the Isheyevo Refractory Inclusions With Those mentioning

confidence: 58%

Refractory inclusions in the CH/CB‐like carbonaceous chondrite Isheyevo: I. Mineralogy and petrography

Krot

Ulyanov

Ivanova

2008

Meteorit & Planetary Scien

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Abstract-The CH/CB-like chondrite Isheyevo consists of metal-rich (70-90 vol% Fe,Ni-metal) and metal-poor (7-20 vol% Fe,Ni-metal) lithologies which differ in size and relative abundance of Fe,Nimetal and chondrules, as well as proportions of porphyritic versus non-porphyritic chondrules. Here, we describe the mineralogy and petrography of Ca,Al-rich inclusions (CAIs) and amoeboid olivine aggregates (AOAs) in these lithologies. Based on mineralogy, refractory inclusions can be divided into hibonite-rich (39%), grossite-rich (16%), melilite-rich (19%), spinel-rich (14%), pyroxeneanorthite-rich (8%), fine-grained spinel-rich CAIs (1%), and AOAs (4%). There are no systematic differences in the inclusion types or their relative abundances between the lithologies. About 55% of the Isheyevo CAIs are very refractory (hibonite-rich and grossite-rich) objects, 20-240 μm in size, which appear to have crystallized from rapidly cooling melts. These inclusions are texturally and mineralogically similar to the majority of CAIs in CH and CB chondrites. They are distinctly different from CAIs in other carbonaceous chondrite groups dominated by the spinel-pyroxene ± melilite CAIs and AOAs. The remaining 45% of inclusions are less refractory objects (melilite-, spinel-and pyroxene-rich CAIs and AOAs), 40-300 μm in size, which are texturally and mineralogically similar to those in other chondrite groups. Both types of CAIs are found as relict objects inside porphyritic chondrules indicating recycling during chondrule formation.We infer that there are at least two populations of CAIs in Isheyevo which appear to have experienced different thermal histories. All of the Isheyevo CAIs apparently formed at an early stage, prior to chondrule formation and prior to a hypothesized planetary impact that produced magnesian cryptocrystalline and skeletal chondrules and metal grains in CB, and possibly CH chondrites. However, some of the CAIs appear to have undergone melting during chondrule formation and possibly during a major impact event. We suggest that Isheyevo, as well as CH and CB chondrites, consist of variable proportions of materials produced by different processes in different settings: 1) by evaporation, condensation, and melting of dust in the protoplanetary disk (porphyritic chondrules and refractory inclusions), 2) by melting, evaporation and condensation in an impact generated plume (magnesian cryptocrystalline and skeletal chondrules and metal grains; some igneous CAIs could have been melted during this event), and 3) by aqueous alteration of pre-existing planetesimals (heavily hydrated lithic clasts). The Isheyevo lithologies formed by size sorting of similar components during accretion in the Isheyevo parent body; they do not represent fragments of CH and CB chondrites.

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The first known natural occurrence of calcium monoaluminate, in a calcium‐aluminum‐rich inclusion from the CH chondrite Northwest Africa 470

Cited by 23 publications

References 28 publications

Calcium–Aluminum-Rich Inclusions in Chondritic Meteorites

Calcium–Aluminum-Rich Inclusions in Chondritic Meteorites

Ca,Al‐rich inclusions in Rumuruti (R) chondrites

Refractory inclusions in the CH/CB‐like carbonaceous chondrite Isheyevo: I. Mineralogy and petrography

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