Mineralogy and petrology of amoeboid olivine inclusions in CO3 chondrites: Relationship to parent‐body aqueous alteration

Chizmadia, L. J.; Rubin, Alan E.; Wasson, J. T.

doi:10.1111/j.1945-5100.2002.tb01163.x

Cited by 121 publications

(147 citation statements)

References 33 publications

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“…As discussed previously (section 5.2.3), there is clear evidence that CVs are somewhat lower grade in terms of thermal metamorphism than the CK3s. Studies of induced thermoluminescence indicate that, at least in terms of their silicate and oxide constituents, CVs are of relatively low petrographic grade, ranging from 3.0 to 3.3 (Guimon et al, 1995), whereas comparison with the CO metamorphic sequence (Scott and Jones, 1990;Chizmadia et al, 2002) indicates that most CK3s are grade 3.5 and above. It therefore remains entirely possible that both the CK and CV group are derived from a single thermally stratified parent body analogous to that which has been postulated for the ordinary chondrites (Wood, 2003;Trieloff et al, 2003).…”

Section: Ck and CV Chondrites: How Many Parent Bodies?mentioning

confidence: 99%

“…By analogy with CAIs in CO3 chondrites the feldspathoidal-rich areas replace primary melilite and hence indicate that Camel Donga 003 is at least 3.5 in petrographic grade (metamorphic scale of Scott and Jones (1990), as modified by Chizmadia et al (2002)). …”

Section: Acknowledgementsmentioning

confidence: 99%

“…It is now well established that refractory inclusions in carbonaceous chondrites are highly susceptible to parent body alteration. In CO chondrites, for which a well-development metamorphic sequence has been established (Scott and Jones, 1990;Chizmadia et al, 2002), refractory inclusions show a clear sequence of changes in response to increasing degrees of thermal metamorphism (Greenwood et al, 1992;Russell et al, 1998). Melilite-bearing inclusions are abundant in CO3.0-3.4, rare in 3.5 and absent from types 3.6 to 3.8, where they are replaced by a fine-grained intergrowth of feldspathoids (metamorphic scale of Scott and Jones (1990), as modified by Chizmadia et al, (2002)).…”

Section: Refractory Inclusionsmentioning

confidence: 99%

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The relationship between CK and CV chondrites

Greenwood¹,

Franchi²,

Kearsley³

et al. 2010

Geochimica et Cosmochimica Acta

104

195

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CK chondrites are highly oxidized meteorites containing abundant magnetite and trace amounts of Fe,Ni-metal. Although the group is predominately composed of equilibrated meteorites (types 4 to 6), in recent years a significant number of new samples have been classified as being either CK3 or CK3-anomalous. These unequilibrated CKs often display a close affinity with members of the CV oxidized subgroup. CKs and CVs (oxidized subgroup) may therefore form a continuum and by implication could be derived from a single common parent body. To investigate the relationship between these two groups a detailed study of the oxygen isotope composition, opaque mineralogy and major and trace element geochemistry of a suite of CV and CK chondrites has been undertaken. The results of oxygen isotope analysis confirm the close affinity between CV and CK chondrites, while excluding the possibility of a linkage between the CO and CK groups. Magnetites in both CV and CK chondrites show significant compositional similarities, but high Ti contents are a diagnostic feature of the latter group. The results of major and trace element analysis demonstrate that both CV and CK chondrites show overlapping variation. Supporting evidence for a single common source for both groups comes from their similar cosmic-ray exposure age distributions. Recent reflectance spectral analysis is consistent with both the CVs and CKs being derived from Eos family asteroids, which are believed to have formed by the catastrophic disruption of a single large asteroid. Thus, a range of evidence appears to be consistent with CV and CK chondrites representing samples from a single thermally stratified parent body. In view of the close similarity between CV and CK chondrites some modification of the present classification scheme may be warranted, possibly involving integration of the two groups. One means of achieving this would be to reassigned CK chondrites to a subgroup of the oxidized CVs. It is recognized that a full evaluation of this proposal may require further study of the still poorly understood CK3 chondrites. ACCEPTED MANUSCRIPT3

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Section: Ck and CV Chondrites: How Many Parent Bodies?mentioning

confidence: 99%

Section: Acknowledgementsmentioning

confidence: 99%

Section: Refractory Inclusionsmentioning

confidence: 99%

See 1 more Smart Citation

The relationship between CK and CV chondrites

Greenwood¹,

Franchi²,

Kearsley³

et al. 2010

Geochimica et Cosmochimica Acta

104

195

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“…Scott & Jones (1990) and Sears et al (1991) completed the classification of this group, defining the main petrologic types. Those relatively pristine, highly unequilibrated COs are classified as subgroup CO 3.0, while those experiencing a higher degree of thermal metamorphism are classified as 3.8 (Chizmadia et al 2002). In between this sequence we found different degrees of metamorphic products.…”

Section: The Co Groupmentioning

confidence: 87%

The Effect of Aqueous Alteration and Metamorphism in the Survival of Presolar Silicate Grains in Chondrites

Trigo‐Rodríguez

Blum

2009

Publ. – Astron. Soc. Aust

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Abstract:Relatively small amounts (typically between 2 and 200 ppm) of presolar grains have been preserved in the matrices of chondritic meteorites. The measured abundances of the different types of grains are highly variable from one chondrite to another, but are higher in unequilibrated chondrites that have experienced little or no aqueous alteration and/or metamorphic heating than in processed meteorites. A general overview of the abundances measured in presolar grains (particularly the recently identified presolar silicates) contained in primitive chondrites is presented. Here we will focus on the most primitive chondrite groups, as typically the highest measured abundances of presolar grains occur in primitive chondrites that have experienced little thermal metamorphism. Looking at the most aqueously altered chondrite groups, we find a clear pattern of decreasing abundance of presolar silicate grains with increasing levels of aqueous alteration. We conclude that measured abundances of presolar grains in altered chondrites are strongly biased by their peculiar histories. Scales quantifying the intensity of aqueous alteration and shock metamorphism in chondrites could correlate with the content of presolar silicates. To do this it would be required to infer the degree of destruction or homogenization of presolar grains in the matrices of primitive meteorites. To get an unbiased picture of the relative abundance of presolar grains in the different regions of the protoplanetary disk where first meteorites consolidated, future dedicated studies of primitive meteorites, IDPs, and collected materials from sample-return missions (like e.g. the planned Marco Polo) are urgently required.

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“…Table 2. Average compositions of spinel in CAIs (wt%) gest that the CO3 chondrites of different subtypes from 3.0 to 3.8 (Chizmadia et al, 2002) constituted the same, single parent body.…”

Section: Discussionmentioning

confidence: 99%

Northwest Africa 1232—a CO3 carbonaceous chondrite with two lithologies

Kiriishi

Tomeoka

2008

Journal of Mineralogical and Petrological Sciences

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Northwest Africa 1232 (NWA 1232) is a carbonaceous chondrite consisting of two lithologies (A and B) that are separated by a sharp boundary. A petrographic and mineralogical study indicates that both lithologies can be classified as type CO3. However, olivine in lithology B chondrules is more enriched in Fe than in lithology A, whereas olivine in lithology B matrix is more depleted in Fe than in lithology A. Chondrules and Ca -Al -rich inclusions (CAIs) in lithology B show a higher degree of nephelinization than those in lithology A. These differences can be explained by that lithology B has gone through a higher degree of thermal metamorphism than lithology A. These two lithologies probably represent rocks that have been thermally metamorphosed at different locations within a single CO parent body and later mixed to form the present combined rock during a brecciation process.

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Mineralogy and petrology of amoeboid olivine inclusions in CO3 chondrites: Relationship to parent‐body aqueous alteration

Cited by 121 publications

References 33 publications

The relationship between CK and CV chondrites

The relationship between CK and CV chondrites

The Effect of Aqueous Alteration and Metamorphism in the Survival of Presolar Silicate Grains in Chondrites

Northwest Africa 1232—a CO3 carbonaceous chondrite with two lithologies

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