Metal and associated phases in Bishunpur, a highly unequilibrated ordinary chondrite

Rambaldi, E. R.; Wasson, J. T.

doi:10.1016/0016-7037(81)90127-7

Cited by 95 publications

(41 citation statements)

References 26 publications

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“…They reflect the relatively low Ni contents of the olivine starting materials prior to reduction. This difference between normal metal from meteorites and metal inclusions in dusty olivines shows that dusty olivines were formed by reprocessing previous generations of olivines from chondrules or magmatic rocks in which olivines had already undergone Ni depletion by complete or partial equilibration with metal (Rambaldi and Wasson 1981;Jones 1996;Jones and Danielson 1997). It is also important to note that the relative heterogeneity in the composition of the Fe metallic blebs in natural dusty olivines does not necessarily imply several episodes of recycling since our experiments show that only one pulse of reduction can be responsible for such heterogeneity.…”

Section: Discussionmentioning

confidence: 99%

“…From texture or composition of the metal phase, a number of studies also came to this conclusion. For instance, Rambaldi and Wasson (1981) observed metal (frequently Cr and Si-rich) coalescence and expulsion textures in chondrules from Bishunpur. In a study of the very unequilibrated Semarkona chondrite, Grossman and Wasson (1987) deduced that the metal chondrule rims were derived from their interiors.…”

Section: Discussionmentioning

confidence: 99%

“…The Bishunpur chondrite is one of the most unequilibrated ordinary chondrites containing essentially unaltered chondrules with pristine nebular signatures (Rambaldi and Wasson 1981). The San Carlos olivines were annealed at a high temperature, below their melting point, and at low oxygen fugacity.…”

Section: Samples and Experimental Proceduresmentioning

confidence: 99%

“…Such dusty cores are commonly surrounded by clear olivine rims, similar in composition to normal grains of the host chondrules (e.g., Rambaldi and Wasson 1982;Jones 1996;Jones and Danielson 1997). The tiny metal blebs within olivines are poorer in Ni than the more abundant spherical metal grains present in chondrule interiors (Rambaldi and Wasson 1981). The occurrences of both metallic blebs and FeO depletion in olivine have been interpreted as the result of a solid state reduction of more ferroan olivines (Boland and Duba 1981;Rambaldi 1981;Nagahara 1981;Rambaldi and Wasson 1982;Rambaldi et al 1983;Connolly et al, 1994;Libourel and Chaussidon 1995;Jones 1996;Jones and Danielson 1997).…”

Section: Introductionmentioning

confidence: 99%

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Experimental study and TEM characterization of dusty olivines in chondrites: Evidence for formation by in situ reduction

Leroux¹,

Libourel²,

Lemelle³

et al. 2003

Meteorit & Planetary Scien

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Abstract-An analytical transmission electron microscopy (ATEM) study was undertaken in order to better understand the formation conditions of dusty olivines (i.e., olivines containing abundant tiny inclusions of Fe-Ni metal) in primitive meteorites. Dusty olivines from type I chondrules in the Bishunpur chondrite (LL3.1) and from synthetic samples obtained by reduction of San Carlos olivines were examined. In both natural and experimental samples, micron size metal blebs observed in the dusty region often show preferential alignments along crystallographic directions of the olivine grains, have low Ni contents (typically <2 wt%), and are frequently surrounded by a silica-rich glass layer. These features suggest that dusty olivines are formed by a sub-solidus reduction of initially fayalitic olivines according to the following reaction:Fe 2 SiO 4 in olivine = 2Fe metal + xSiO 2 in melt + (1−x) SiO in gas + (3−x)/2O 2 in gas Some volatilization of SiO gas may account for the apparent excess of metal relative to silica-rich glass observed in both experimental and natural samples. Comparison with experimentally produced dusty olivines suggests that time scales of the order of minutes usually inferred for chondrule formation are also adequate for the formation of dusty olivines. These observations are in agreement with the hypothesis that at least part of the metal phase in chondrites originated from reduction during chondrule formation.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Samples and Experimental Proceduresmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Experimental study and TEM characterization of dusty olivines in chondrites: Evidence for formation by in situ reduction

Leroux¹,

Libourel²,

Lemelle³

et al. 2003

Meteorit & Planetary Scien

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“…On the other hand, the absence of P-bearing sulfides in the Dhofar 225 chondrite, which is probably a metamorphosed CM chondrite (Ivanova et al, 2002), may indicate that these sulfides are unstable already above 245°C (temperature of tochilinite decomposition). Owing to thermal metamorphism, the P-bearing sulfides could transform into the Ca phosphate + troilite + pentlandite + metal assemblage, which is characteristic of many chondrites (e.g., Rambaldi and Wasson, 1981;Murrell and Burnett, 1983;Rubin and Grossman, 1985).…”

Section: Formation Conditionsmentioning

confidence: 99%

Phosphorus-bearing sulfides and their associations in CM chondrites

et al. 2009

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-Phosphorus-bearing Fe and Ni sulfides represent a new type of phosphorus compounds and are characteristic accessory phases of CM chondrites. The proportions of atoms in the sulfides can be approximated by the equation (Fe + Ni)/P = 0.965 ± 0.003 (1 σ ) · S / P + 1.255 ± 0.036 (1 σ ) . Sulfides with high S/P ratios are systematically richer in Fe and poorer in Ni compared with low-S/P sulfides. Their characteristic minor elements are Cr, Ca, Co, K, and Na. The contents of Cr and Ca may reach several weight percent, but their incorporation does not affect the relation between (Fe + Ni)/P and S/P. This is also true of light elements (O and H), which probably occur in the P-bearing sulfides in certain amounts. The sulfides are usually associated with schreibersite, barringerite, eskolaite, and daubreelite. A negative correlation was observed between the Fe/Ni ratios of coexisting P-bearing sulfides and phosphides. Metallic iron was never found in association with the sulfides. It can be suggested that P-bearing sulfide is a primary phase rather than a secondary alteration product formed under the conditions of the CM chondrite parent body. This phase had to be stable in the solar nebula after the formation of Ca-Al inclusions and before the condensation of Fe-Ni metal. At high temperatures, P-bearing sulfide with low Fe/Ni and S/P ratios coexists with schreibersite in the solar gas. During condensation schreibersite is replaced by barringerite, which is accompanied by a decrease in the Fe/Ni ratio of phosphides and an increase in the S/P and Fe/Ni ratios of P-bearing sulfides. Trace element data suggest that the P-bearing sulfides could be formed in the solar nebula by the sulfidization of a precursor phase of extrasolar origin.

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Chemistry of the Solar Nebula

Fegley

1993

The Chemistry of Life’s Origins

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Metal and associated phases in Bishunpur, a highly unequilibrated ordinary chondrite

Cited by 95 publications

References 26 publications

Experimental study and TEM characterization of dusty olivines in chondrites: Evidence for formation by in situ reduction

Experimental study and TEM characterization of dusty olivines in chondrites: Evidence for formation by in situ reduction

Phosphorus-bearing sulfides and their associations in CM chondrites

Chemistry of the Solar Nebula

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