Trace element content of metals from H- and LL-group chondrites

Rambaldi, E. R.

doi:10.1016/0012-821x(77)90220-5

Cited by 51 publications

(48 citation statements)

References 18 publications

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“…Trace element and Ni abundances of the coarse metal separate from PV (PVD) ( Table 7) are grossly similar to that of average metal in H4-6 chondrites Rambaldi 1977;Kong et al 1995), but are different in detail. In both PVD and two samples of coarse metal analyzed by Rubin et al (2001), Ga and Au abundances are higher than in H chondrites.…”

Section: Bulk Compositionmentioning

confidence: 88%

“…The values for both measurements are significantly higher than for typical metal in H chondrites (14 ± 2 ppm; average and standard deviation of data given by Rambaldi 1977;Kong et al 1995) and are similar to that found in metal from IIE iron meteorites (25 ± 3 ppm) (Wasson and Wang 1986;Ebihara et al 1997). …”

Section: Bulk Compositionmentioning

confidence: 91%

“…10) could indicate a low content of an HREE-rich phase such as clinopyroxene, which is widely depleted in PV compared to H chondrites (see Modal Composition section). Figure 11 compares measured siderophile element abundances in different samples with a simple model in which various amounts of average H chondrite metal are mixed with average H chondrite non-metallic fraction, using as constraints the composition of metal and silicates in H chondrites and the bulk composition of H chondrites Rambaldi 1977;Kong et al 1995;Wasson and Kallemeyn 1988). This model tests whether variations in siderophile element abundances are caused by variations in metal abundance alone, assuming that metal maintains a constant H-chondrite-like composition.…”

Section: Chemical Fractionations and Mixing Modelsmentioning

confidence: 99%

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Portales Valley: Petrology of a metallic-melt meteorite breccia

Ruzicka

Killgore²,

Mittlefehldt

et al. 2005

Meteoritics &Amp; Planetary Science

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available online at http://meteoritics.org 261 Abstract-Portales Valley (PV) is an unusual metal-veined meteorite that has been classified as an H6 chondrite. It has been regarded either as an annealed impact melt breccia, as a primitive achondrite, or as a meteorite with affinities to silicated iron meteorites. We studied the petrology of PV using a variety of geochemical-mineralogical techniques. Our results suggest that PV is the first well-documented metallic-melt meteorite breccia. Mineral-chemical and other data suggest that the protolith to PV was an H chondrite. The composition of FeNi metal in PV is somewhat fractionated compared to H chondrites and varies between coarse vein and silicate-rich portions. It is best modeled as having formed by partial melting at temperatures of ∼940-1150 °C, with incomplete separation of solid from liquid metal. Solid metal concentrated in the coarse vein areas and S-bearing liquid metal concentrated in the silicate-rich areas, possibly as a result of a surface energy effect. Both carbon and phosphorus must have been scavenged from large volumes and concentrated in metallic liquid. Graphite nodules formed by crystallization from this liquid, whereas phosphate formed by reaction between P-bearing metal and clinopyroxene components, depleting clinopyroxene throughout much of the meteorite and growing coarse phosphate at metal-silicate interfaces. Some phosphate probably crystallized from P-bearing liquids, but most probably formed by solid-state reaction at ∼975-725 °C. Phosphate-forming and FeO-reduction reactions were widespread in PV and entailed a change in the mineralogy of the stony portion on a large scale. Portales Valley experienced protracted annealing from supersolidus to subsolidus temperatures, probably by cooling at depth within its parent body, but the main differences between PV and H chondrites arose because maximum temperatures were higher in PV. A combination of a relatively weak shock event and elevated pre-shock temperatures probably produced the vein-and-breccia texture, with endogenic heating being the main heat source for melting, and with stress waves from an impact event being an essential trigger for mobilizing metal. Portales Valley is best classified as an H7 metallic-melt breccia of shock stage S1. The meteorite is transitional between more primitive (chondritic) and evolved (achondrite, iron) meteorite types and offers clues as to how differentiation could have occurred in some asteroidal bodies.

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Section: Bulk Compositionmentioning

confidence: 88%

Section: Bulk Compositionmentioning

confidence: 91%

Section: Chemical Fractionations and Mixing Modelsmentioning

confidence: 99%

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Portales Valley: Petrology of a metallic-melt meteorite breccia

Ruzicka

Killgore²,

Mittlefehldt

et al. 2005

Meteoritics &Amp; Planetary Science

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“…The Ni contents indicate that the "silicate" fraction still contains traces (50.5 wt%) of taenite (high-Ni, low-Co metal), whereas kamacite (high Co, low-Ni metal) could not be detected (<O. I wt"/. The incomplete separation of taenite is probably due to the smaller grain size of taenite (Rambaldi, 1976(Rambaldi, , 1977. The observed siderophile concentrations in the silicates indicate that >95% of the metal has been separated from the silicate fraction.…”

Section: Bulk Metal Contentsmentioning

confidence: 99%

“…2d,f) show systematic deviations from the predicted correlations. Although these deviations can partly be attributed to contributions of metallic Cu (Rubin, 1994) and of a finegained Ir-rich metal phase (Rambaldi, 1976(Rambaldi, , 1977, they are not completely understood. Therefore, Cu and Ir were not used for calculating the amount of oxidized metal.…”

Section: Siderophile Contentsmentioning

confidence: 99%

Concentrations of siderophile elements in nonmagnetic fractions of Antarctic H‐ and L‐chondrites: A quantitative approach on weathering effects

Welten

1999

Meteorit & Planetary Scien

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Abstract-The nonmagnetic separates of Antarctic H-and L-chondrite finds fiom the Lewis Cliff stranding area are enriched in Fe and siderophile elements such as Ni, Co, Cu, As, Ir, and Au, relative to those of nonAntarctic falls. The siderophile enrichments are caused by the oxidation of metallic Fe-Ni to nonmagnetic hydrous Fe-Ni oxides. The concentrations of Fe, Ni, and Co in each sample were used to calculate the amount of oxidized metal, which serves as a quantitative measure of the degree of weathering. The amount of oxidized metal is generally between 1-10 wt?? and shows a rough correlation with the qualitative A-B-Cweathering classification for increasing rustiness. No clear correlation was found between weathering and terrestrial age, although meteorites older than 0.2 Ma contain on the average -50% more oxidized metal. Also, no correlation was found between the degree of weathering and the natural thermoluminescence (TL) level, which is dominated by the thermal history in space rather than by the thermal history in or on the Antarctic ice. The only significant parameter for the degree of weathering seems to be the location of find, with the most weathered specimens being found in a part of the stranding area where melt-water ponds are known to occur. This observation confirms that the occasional presence of liquid water plays an important role in the Antarctic weathering process and explains the poor correlation of the degree of weathering of Antarctic meteorites with terrestrial age and surface exposure age.

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