The Leoville (CV3) accretionary breccia

Kracher, A.; Keil, K.; Kallemeyn, G. W.; Wasson, J. T.; Clayton, Robert N.; Huss, Glenn I.

doi:10.1029/jb090is01p00123

Cited by 49 publications

(54 citation statements)

References 29 publications

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“…High-Co, low-Ni metal grains (up to 39 wt% Co) have been found in equilibrated LL chondrites (Afiattalab and Wasson 1980;Rubin 1990). Such occurrences have also been observed in a few unequilibrated chondrites: in Colony CO3 , in two xenoliths in Leoville CV3 (Kracher et al 1985), in the ungrouped carbonaceous chondrite Ningqiang (Hua et al 1995), and in Y-74660 LL3.0 (Kimura 2000). In Krymka, many analyses of metal grains in different samples did not bring in Co content values higher than 2 wt% in kamacite and 1.5 wt% in tetrataenite (Rambaldi and Wasson 1984;Perron and Bourot-Denise 1992 and unpublished), except for one kamacite grain and one tetrataenite grain with 2.7 and 2 wt% Co, respectively (Semenenko et al 1987).…”

Section: High-co Metal Grainsmentioning

confidence: 97%

Shock-melted material in the Krymka LL3.1 chondrite: Behavior of the opaque minerals

Semenenko

Perron

2005

Meteoritics &Amp; Planetary Science

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Abstract-Six large millimeter-to centimeter-size regions of one specimen of the Krymka LL3.1 ordinary chondrite show evidence of having been completely or nearly completely shock-melted in situ, a phenomenon rarely observed in primitive chondrites. The shock pressure, nominally in the range of 75-90 GPa, could only have been 30-35 GPa in a porous material like fine-grained matrix. The melted regions have an igneous texture and their silicates are zoned and unequilibrated. Large metal-troilite intergrowths formed in these regions. The metal has a nickel content corresponding to martensite and the troilite contains up to 4.2 wt% nickel. Melting must have been very short and cooling very fast (>100 °C/h at high temperature). The metal contains up to 0.7 wt% phosphorus. Abundant chromite crystals and sodium-iron phosphate glass globules are found in troilite. The differences in composition between the opaque phases found in the melted regions and those generally observed in unmetamorphosed chondrules are assigned to melting under closed system conditions. Surprisingly high Co concentrations (up to 13 wt%) were found in some metal grains in or at the periphery of melted regions. They likely resulted from sulfurization of metal by sulfur vapor produced during the shock. After solidification, at least one other shock led to mechanical effects in the melted regions.

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Section: High-co Metal Grainsmentioning

confidence: 97%

Shock-melted material in the Krymka LL3.1 chondrite: Behavior of the opaque minerals

Semenenko

Perron

2005

Meteoritics &Amp; Planetary Science

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“…Some CM clasts similar to PV3 apparently arrived at velocities high enough to be shocked and dehydrated but not high enough to be vaporized. In general, dark carbonaceous chondrite-like clasts in other meteorite classes (e.g., CV3 chondrites; Kracher et al 1985; see references in Wasson and Wetherill 1979) are a poor match to known CM meteorites. It is unclear whether a selection bias exists.…”

Section: Cm-like Clasts In the Asteroid Population And The Inner Solamentioning

confidence: 99%

On the origin of shocked and unshocked CM clasts in H‐chondrite regolith breccias

Rubin

Bottke

2009

Meteorit & Planetary Scien

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Abstract--CM chondrite clasts that have experienced different degrees of aqueous alteration occur in H-chondrite and HED meteorite breccias. Many clasts are fragments of essentially unshocked CM projectiles that accreted at low relative velocities to the regoliths of these parent bodies. A few clasts were heated and dehydrated upon impact; these objects most likely accreted at higher relative velocities. We examined three clasts and explored alternative scenarios for their formation. In the first scenario, we assumed that the H and HED parent bodies had diameters of a few hundred kilometers, so that their high escape velocities would effectively prevent soft landings of small CM projectiles. This would imply that weakly shocked CM clasts formed on asteroidal fragments (family members) associated with the H and HED parent bodies. In the second scenario, we assumed that weakly shocked CM clasts were spall products ejected at low velocities from larger CM projectiles when they slammed into the H and HED parent bodies. In both cases, if most CM clasts turn out to have ancient ages (e.g., ~3.4-4

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“…Leoville consists of two individual stones; the first, weighing 1.629 kg, was recovered prior to 1965 and the second 6.5 kg stone was recovered in 1966 (Kracher et al 1985). Leoville has experienced a higher degree of terrestrial weathering than Vigarano, as it was found buried in the soil (Kracher et al 1985), indicating that it had an extended residence time in a subsurface environment. At least one calcite occurrence has been reported in the literatures (Sylvester et al 1993).…”

Section: Leovillementioning

confidence: 99%

Carbonates in Vigarano: Terrestrial, preterrestrial, or both?

Abreu

Brearley

2005

Meteoritics &Amp; Planetary Science

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Abstract-Studies of two separate stones of the CV3 chondrite Vigarano have revealed the presence of previously unreported occurrences of calcite. In the first stone, calcite occurs as thin veins in a type B CAI. In contrast, observations of the second stone, which was recovered one month after its fall, show three calcite occurrences: networks of veins, vesicle fillings in the fusion crust, and pseudomorphic replacement of augite associated with a porphyritic olivine chondrule. The most common occurrence is as veins ranging in thickness from <1 μm to 25 μm and extending for more than several hundred μm. Some veins crosscut the fusion crust and are connected to a carbonate coating on the exterior of the meteorite. Extensive minor element zoning occurs in carbonate masses, indicating variations in the fluid composition and/or redox potential during carbonate growth. Based on the textural evidence and a comparative study with carbonate veins in the CV3 chondrite Leoville, we conclude that the veins are terrestrial in origin. We propose a model for rapid carbonate formation in which calcite precipitation is driven by hydrolysis and oxidation in the meteorite interior that move the fluid composition to alkaline values. In addition, both stones also contain minor occurrences of carbonate that are not readily explained by terrestrial alteration. Minor carbonate in a type B CAI occurs in the first stone and calcite occurs as pseudomorphic replacement of augite in the second stone. Both of these occurrences appear to be preterrestrial, probably asteroidal in origin.

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The Leoville (CV3) accretionary breccia

Cited by 49 publications

References 29 publications

Shock-melted material in the Krymka LL3.1 chondrite: Behavior of the opaque minerals

Shock-melted material in the Krymka LL3.1 chondrite: Behavior of the opaque minerals

On the origin of shocked and unshocked CM clasts in H‐chondrite regolith breccias

Carbonates in Vigarano: Terrestrial, preterrestrial, or both?

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