The nature and origin of ureilites

Berkley, J. L.; Taylor, G. J.; Keil, K.; Harlow, George E.; Prinz, M.

doi:10.1016/0016-7037(80)90119-2

Cited by 171 publications

(232 citation statements)

References 41 publications

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“…Presumably some of this scatter stems from inadequate sampling, and also from disparate extents of solid C oxidation in the abortive smelting episode that produced the olivine reduction rims without noticeably affecting the cores. However, several of the ureilites with low Fo and low C combinations, Goalpara and Haverö, have no more than typical extents of rim development (Marvin and Wood 1972;Berkley et al 1980) and have been analyzed for C multiple times (Mueller 1969;Wiik 1972;Grady et al 1982, Grady et al 1985Bogard et al 1973), and yet they consistently show low C concentrationsin clear contradiction of the end-member smelted-cores model, at least for application to all ureilites. Fig.…”

Section: Mass Balance For Carbonmentioning

confidence: 99%

“…Singletary and Grove (2003) argued that the worst "outlier" sample, Dingo Pup Donga, "might not be representative" because it is brecciated. However, Dingo is a monomict breccia that has only undergone moderate shock (Berkley et al 1980;Mittlefehldt et al 1998), and moderate shock can hardly be expected to increase modal pigeonite or induce major rim-reduction of the olivines. Also, one of the samples of Warren et al (2006), Hammadah al Hamra (HaH) 126, has rim development to the extent of at least 80% of the olivine and yet near-average (∼30%) modal pigeonite.…”

Section: Implications Of Inferred Catastrophic Breakup Vis-à-vis Smelmentioning

confidence: 99%

“…The mg population agreement is far from perfect, however. Out of several hundred olivine cores that have been characterized from ∼8 polymict ureilites (105 from North Haig alone) (Berkley et al 1980), only two grains have been reported to have mg > 90 mol%: one in North Haig (Berkley et al 1980) and one in Elephant Moraine (EET) 83309 (Warren and Kallemeyn 1989). The overwhelming majority of polymict ureilite olivine cores have mg < 85 mol% (Berkley et al 1980;Jaques and Fitzgerald 1982;Ikeda and Prinz 2001;Goodrich et al 2004).…”

Section: Asteroidal Setting For Ureilite Petrogenesismentioning

confidence: 99%

“…In a few of the least shocked samples, the intergranular C phase is euhedral graphite (e.g., Berkley and Jones 1982). Takeda (1987) was the first to propose that ureilites formed as mantle restites, contrary to the oncepopular view that they originated as igneous cumulates (e.g., Berkley et al 1980;Goodrich et al 1987). Today, largely in consideration of the great oxygen-isotopic diversity among ureilites (Clayton and Mayeda 1988), most authors assume that most ureilites formed as asteroidal mantle restites (e.g., Warren and Kallemeyn 1992;Scott et al 1993;Singletary and Grove 2003;Goodrich et al 2004;Kita et al 2004).…”

Section: Introductionmentioning

confidence: 99%

“…Most ureilites show obvious vestiges of what was, at least in a loose sense, an iron-smelting process. Their mafic silicates, especially their olivines, feature distinctive reduced (FeO-depleted, Fe-metal-sprinkled) rims (e.g., Berkley et al 1980;Singletary and Grove 2003). However, these rims are discrete subvolumes of the grains (e.g., Singletary and Grove 2003).…”

Section: Introductionmentioning

confidence: 99%

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Ureilite petrogenesis: A limited role for smelting during anatexis and catastrophic disruption

Warren

Huber

2006

Meteoritics &Amp; Planetary Science

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Abstract-A popular model for ureilites assumes that during anatexis in an asteroidal mantle, pressure-buffered equilibrium smelting (partial reduction coincident with partial melting) engendered their conspicuous mafic-silicate-core mg diversity (75-96 mol%). Several mass-balance problems arise from this hypothesis. Smelting inevitably consumes a large proportion of any plausible initial carbon while generating significant proportions of Fe metal and copious proportions of CO gas. The most serious problem concerns the yield of CO gas. If equilibrium smelting produced the ureilites' entire 21 mol% range in olivine-core mg, the proportion of gas within the asteroidal mantle (assuming plausibly low pressure <∼80 bar) should have reached ≥85 vol%. Based on the remarkably stepwise cooling history inferred from ureilite texture and mineralogy, a runaway, CO-leaky process that can loosely be termed smelting appears to have occurred, probably triggered by a major impact. The runaway scenario appears likely because, by Le Châtelier's principle, CO leakage would tend to accelerate the smelting process. Also, the copious volumes of gas produced by smelting would have led to explosive, mass-leaky eruptions into the vacuum surrounding the asteroid. Loss of mass would mean diminution of interior pressure, which would induce further smelting, leading to further loss of mass (basalt), and so on. Such a disruptive runaway process may have engendered the ureilites' distinctive reduced olivine rims. But the only smelting, according to this scenario, was a short-lived disequilibrium process that reduced only the olivine rims, not the cores; and the ureilites were cooling, not melting, during the abortive "smelting" episode.

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