Ureilitic breccias: clues to the petrologic structure and impact disruption of the ureilite parent asteroid

Goodrich, C. A.; Scott, E. R. D.; Fioretti, A. M.

doi:10.1016/j.chemer.2004.08.001

Cited by 167 publications

(417 citation statements)

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“…2). The polymict ureilite DaG 319, which contains feldspathic lithologies that may be derived from the missing silicate melts from the ureilite parent body (Cohen et al, 2004;Downes and Mittlefehldt, 2006;Goodrich et al, 2004;Ikeda and Prinz, 2001;Kita et al, 2004), has 187 Os/ 188 Os of 0.1262 ± 0.0004 (2σ) indistinguishable from the monomict ureilite average [0.1257 ± 0.0024 (1σ)]. Inverse Os concentrations and Os isotopic compositions of the ureilites are (r 2 =0.66) correlated (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…On the basis of their silicate mineralogy, the monomict ureilites are classified into three different types: olivine-pigeonite, olivine-orthopyroxene, and augite-bearing. Succinct descriptions of the classification of monomict ureilites are given in Goodrich et al (2004Goodrich et al ( , 2006. Most monomict ureilites show coarse-grained igneous textures with mineral grains joining in abundant 120° triple junctions.…”

Section: Introductionmentioning

confidence: 99%

“…Petrographically, the monomict ureilites consist predominantly of olivine, pyroxene (mostly pigeonite, but also orthopyroxene and augite) and ≤10% dark interstitial material consisting of carbon polymorphs (graphite, diamond, lonsdaleite, chaoite), metal, sulfides, and fine grained silicates (Goodrich, 1992;Goodrich et al, 2004;Mittlefehldt, 2003;Mittlefehldt et al, 1998). This material also occurs as veins that intrude the sili-cates along fractures and cleavage planes.…”

Section: Introductionmentioning

confidence: 99%

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Osmium isotope systematics of ureilites

Rankenburg

Brandon

Humayun

2007

Geochimica et Cosmochimica Acta

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The 187 Os/ 188 Os for twenty-two ureilite whole rock samples, including monomict, augite-bearing, and polymict lithologies, were examined in order to constrain the provenance and subsequent magmatic processing of the ureilite parent body (or bodies). The Re/Os ratios of most ureilites show evidence for a recent disturbance, probably related to Re mobility during weathering, and no meaningful chronological information can be extracted from the present data set. The ureilite 187 Os/ 188 Os ratios span a range from 0.11739 to 0.13018, with an average of 0.1258 ± 0.0023 (1σ), similar to typical carbonaceous chondrites, and distinct from ordinary or enstatite chondrites. The similar mean of 187 Os/ 188 Os measured for the ureilites and carbonaceous chondrites suggests that the ureilite parent body probably formed within the same region of the solar nebula as carbonaceous chondrites. From the narrow range of the 187 Os/ 188 Os distribution in ureilite meteorites it is further concluded that Re was not significantly fractionated from Os during planetary differentiation and was not lost along with the missing ureilitic melt component. The lack of large Re/Os fractionations requires that Re/Os partitioning was controlled by a metal phase, and thus metal had to be stable throughout the interval of magmatic processing on the ureilite parent body.3

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Osmium isotope systematics of ureilites

Rankenburg

Brandon

Humayun

2007

Geochimica et Cosmochimica Acta

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“…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: 93%

“…The first-order classification of ureilites is typically based on their olivine-core mg. Many authors (e.g., Goodrich 1992;Sinha et al 1997;Lee et al 2003;Goodrich et al 2004;Grove 2003, 2004) have argued or assumed that the great diversity ) of the ureilite maficsilicate core compositions was engendered mainly by varied degrees of smelting of an initial proto-ureilitic material with uniform, or near-uniform, olivine-core mg. In these models, the range of olivine-core mg developed as a result of systematic smelting, buffered by the modest range of pressure within the mantle, or upper mantle, of a moderately large asteroid.…”

Section: Introductionmentioning

confidence: 99%

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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Achondrites and Irons

Mittlefehldt

McCoy

2014

Special Publications

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Ureilitic breccias: clues to the petrologic structure and impact disruption of the ureilite parent asteroid

Cited by 167 publications

References 50 publications

Osmium isotope systematics of ureilites

Osmium isotope systematics of ureilites

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

Achondrites and Irons

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