A weathering index for CK and R chondrites

Rubin, Alan E.; Huber, Heinz

doi:10.1111/j.1945-5100.2005.tb00178.x

Cited by 46 publications

(28 citation statements)

References 16 publications

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“…The broader field defined by CKs on Fig. 7c is probably a reflection of the variable degrees of terrestrial alteration experienced by this group (Rubin and Huber, 2005;Huber et al, 2006).…”

Section: Bulk Compositional Resultsmentioning

confidence: 99%

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The relationship between CK and CV chondrites

Greenwood¹,

Franchi²,

Kearsley³

et al. 2010

Geochimica et Cosmochimica Acta

103

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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“…The broader field defined by CKs on Fig. 7c is probably a reflection of the variable degrees of terrestrial alteration experienced by this group (Rubin and Huber, 2005;Huber et al, 2006).…”

Section: Bulk Compositional Resultsmentioning

confidence: 99%

“…At present the CK chondrite group contains only two falls, Karoonda and Kobe, the remaining 140 or so classified samples are finds which have experienced varying degrees of terrestrial weathering (Rubin and Huber, 2005;Huber et al, 2006). On a plot of Al/Mg v.…”

Section: Bulk Compositional Resultsmentioning

confidence: 99%

The relationship between CK and CV chondrites

Greenwood¹,

Franchi²,

Kearsley³

et al. 2010

Geochimica et Cosmochimica Acta

103

195

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“…The samples were then mounted Petrological type and weathering grades from Meteoritical Bulletin; shock stages from this study (by Rubin). a wi, weathering index based on the brown staining of silicates (Rubin and Huber, 2005). wi-0, <5 vol %; wi-1, 5-25 vol %; wi-2, 25-50 vol %; wi-3, 50-75 vol %; wi-4, 75-95 vol %; wi-5, >95 vol %; wi-6 significant replacement of mafic silicates by phyllosilicates.…”

Section: Samples and Analytical Techniquesmentioning

confidence: 99%

“…Table 2 lists the bulk compositions obtained by INAA of 14 CK chondrites, a clast from Tanezrouft 057, and a weathered zone in NWA 1563. The samples are classified as CK4 or CK5, with shock stages of S1 and S2, weathering grades from A to C, and weathering indices from wi-0 to wi-6 ( Rubin and Huber, 2005). Because NWA 1563 has a 'darkened weathering' zone on the external surface, we analyzed both this material and an interior sample to examine the influence of obvious terrestrial weathering.…”

Section: Introductionmentioning

confidence: 99%

Siderophile-element anomalies in CK carbonaceous chondrites: Implications for parent-body aqueous alteration and terrestrial weathering of sulfides

Huber

Rubin

Kallemeyn

et al. 2006

Geochimica et Cosmochimica Acta

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“…Analyses of weathered meteorites were checked for depletions in Ni and Co. The fact that such depletions were only found in CK and R chondrites (which have abundant sulfides and no Fe,Ni-metal), but not in ordinary chondrites, is related to decreasing modal abundances of sulfides with increasing degree of terrestrial weathering (Rubin and Huber 2005). Abnormal low values were excluded from further calculations (marked bold and gray underlayed in Tables A3-A18).…”

Section: Data Reduction and Filteringmentioning

confidence: 99%

A database of chondrite analyses including platinum group elements, Ni, Co, Au, and Cr: Implications for the identification of chondritic projectiles

Tagle

Berlin

2008

Meteorit & Planetary Scien

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Abstract-Siderophile elements have been used to constrain projectile compositions in terrestrial and lunar impact melt rocks. To obtain a better knowledge of compositional differences between potential chondritic projectile types, meteorite analyses of the elements Ru, Rh, Pd, Os, Ir, Pt, Cr, Co, Ni, and Au were gathered into a database. The presented compilation comprises 806 analyses of 278 chondrites including new ICP-MS analyses of Allende and two ordinary chondrites. Each data set was evaluated by comparing element ratios of meteorites from the same chondrite group. Characteristic element abundances and ratios were determined for each group. Features observed in the element abundance patterns can be linked directly to the presence of certain components, such as the abundance of refractory elements Os, Ir, and Ru correlating with the occurrence of refractory inclusions in CV, CO, CK, and CM chondrites. The refined characteristic element ratios appear to be representative not only for meteorites, but also for related asteroidal bodies. Chondrite element ratios were compared to previously published values from impact melt rocks of the Popigai and Morokweng impact structures confirming that an identification of the specific type of projectile (L and LL chondrite, respectively) is possible. The assessment for Morokweng is supported by the recent discovery of an LL chondrite fragment in the impact melt rocks. Ultimately, the database provides valuable information for understanding processes in the solar nebula as they are recorded in chondrites. A new type of complementarity between element patterns of CK and EH chondrites is suggested to be the result of condensation, redox, and transportation processes in the solar nebula.

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A weathering index for CK and R chondrites

Cited by 46 publications

References 16 publications

The relationship between CK and CV chondrites

The relationship between CK and CV chondrites

Siderophile-element anomalies in CK carbonaceous chondrites: Implications for parent-body aqueous alteration and terrestrial weathering of sulfides

A database of chondrite analyses including platinum group elements, Ni, Co, Au, and Cr: Implications for the identification of chondritic projectiles

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