The Haver� meteorite

Vdovykin, G. P.

doi:10.1007/bf00169522

Cited by 2 publications

(2 citation statements)

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“…For the calculation of production rates, we used the average chemical composition of ureilites (arithmetic mean of six ureilites, as listed in Vdovykin 1976) (in wt%, Mg = 21.81; Al = 0.25; Si = 18.6; S = 0.33; Ca = 0.71; Fe = 14.62; Cr = 0.508; Ti = 0.07; Mn = 0.29; Ni = 0.131). We derived the production rates based on the empirical equation of Eugster and Michel (1995) for diogenites and for shielding depth indicated by the ratio ( 22 Ne/ 21 Ne) c = 1.063.…”

Section: Resultsmentioning

confidence: 99%

Noble gases and nitrogen in the Almahata Sitta ureilite

Murty

Mahajan

Jenniskens

et al. 2010

Meteorit & Planetary Scien

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Abstract– A bulk sample (split from Almahata Sitta #36) and an acid resistant residue (from #44) have been analyzed for noble gases and nitrogen by step‐wise combustion/pyrolysis. In the bulk sample, He and Ne are a mixture of cosmogenic and trapped components. Cosmic‐ ray exposure ages of 13.8 and 16.0 Ma are calculated based on 3He, and 21Ne, respectively. Except for a small amount of cosmogenic 3He, He, and Ne in the acid‐resistant residue are not significantly above blank level. Ar, Kr, and Xe in both the bulk and residue are dominated by a trapped component, but the elemental ratios are different. While the ratios of 36Ar/132Xe and 84Kr/132Xe are about 400 and 1, respectively, in all the combustion steps of the residue, the bulk sample has about an order of magnitude more 132Xe in the corresponding combustion steps. It seems, an acid soluble phase is the host of this Xe‐rich carrier and is different from a similar phase observed in the ureilite Allan Hills 82130. Nitrogen in the bulk sample and acid residue are 21.1 ppm (−36.8‰), and 249.5 ppm (−74.3‰), respectively. Peak release of C (monitored as CO + CO2), N, Ar, Kr, and Xe occurred at the 700 °C combustion step of the residue, confirming diamond as the principal carrier for these gases. In the residue, the isotopic ratio 38Ar/36Ar shows a monotonic increase with release temperature.

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Section: Resultsmentioning

confidence: 99%

Noble gases and nitrogen in the Almahata Sitta ureilite

Murty

Mahajan

Jenniskens

et al. 2010

Meteorit & Planetary Scien

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“…4c). Haverˆ contains similar olivine aggregates (Vdovykin 1976). Although the coarse olivine aggregates have been described simply as mosaicized grains (e.g., in ALH 81101; Table 1 of Goodrich 1992), they instead appear to be annealed mosaicized olivine aggregates analogous to those in the melt portions of the OC impact-melt breccias (Fig.…”

Section: Period 3: Post-shock Annealingmentioning

confidence: 98%

Shock, post‐shock annealing, and post‐annealing shock in ureilites

Rubin

2006

Meteorit & Planetary Scien

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Abstract-The thermal and shock histories of ureilites can be divided into four periods: 1) formation, 2) initial shock, 3) post-shock annealing, and 4) post-annealing shock. Period 1 occurred ∼4.55 Ga ago when ureilites formed by melting chondritic material. Impact events during period 2 caused silicate darkening, undulose to mosaic extinction in olivines, and the formation of diamond, lonsdaleite, and chaoite from indigenous carbonaceous material. Alkali-rich fine-grained silicates may have been introduced by impact injection into ureilites during this period. About 57% of the ureilites were unchanged after period 2. During period 3 events, impact-induced annealing caused previously mosaicized olivine grains to become aggregates of small unstrained crystals. Some ureilites experienced reduction as FeO at the edges of olivine grains reacted with C from the matrix. Annealing may also be responsible for coarsening of graphite in a few ureilites, forming euhedralappearing, idioblastic crystals. Orthopyroxene in Meteorite Hills (MET) 78008 may have formed from pigeonite by annealing during this period. The Rb-Sr internal isochron age of ∼4.0 Ga for MET 78008 probably dates the annealing event. At this late date, impacts are the only viable heat source. About 36% of ureilites experienced period 3 events, but remained unchanged afterwards. During period 4, ∼7% of the ureilites were shocked again, as is evident in the polymict breccia, Elephant Moraine (EET) 83309. This rock contains annealed mosaicized olivine aggregates composed of small individual olivine crystals that exhibit undulose extinction. Ureilites may have formed by impact-melting chondritic material on a primitive body with heterogeneous O isotopes. Plagioclase was preferentially lost from the system due to its low impedance to shock compression. Brief melting and rapid burial minimized the escape of planetarytype noble gases from the ureilitic melts. Incomplete separation of metal from silicates during impact melting left ureilites with relatively high concentrations of trace siderophile elements.

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The Haver� meteorite

Cited by 2 publications

References 20 publications

Noble gases and nitrogen in the Almahata Sitta ureilite

Noble gases and nitrogen in the Almahata Sitta ureilite

Shock, post‐shock annealing, and post‐annealing shock in ureilites

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