Global Crustal Metamorphism of the Eucrite Parent Body

Yamaguchi, A.; Taylor, G. J.; Keil, K.

doi:10.1006/icar.1996.0192

Cited by 161 publications

(192 citation statements)

References 1 publication

(3 reference statements)

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“…Most eucrites show evidence of metamorphism with reheating to >800°C, as evidenced by altered pyroxene compositions from subsolidus diffusion of Mg, Fe and Ca (Takeda and Graham, 1991;Yamaguchi et al, 1996Yamaguchi et al, , 1997Yamaguchi et al, , 2009). The source of this additional heat may have been from large impacts (Nyquist et al, 1986), heating at depth after burial of surface basalts (Yamaguchi et al, 1996(Yamaguchi et al, , 1997, or the differentiation into layers (Takeda, 1997). A large impact crater of 460 km diameter, 13 km depth with a large central peak, has been identified on Vesta (Thomas et al, 1997) which may have extended beyond the crust into the mantle layer and ejected many Vestoids and HEDs (McSween et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

Zinc isotopes in HEDs: Clues to the formation of 4-Vesta, and the unique composition of Pecora Escarpment 82502

Paniello¹,

Moynier²,

Beck

et al. 2012

Geochimica et Cosmochimica Acta

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The d 66 Zn (permil deviation of the 66 Zn/ 64 Zn ratio from a terrestrial standard) values for a suite of 20 non-Antarctic HED (howardite-eucrite-diogenite) meteorites and one mesosiderite, and for eight Antarctic eucrites and diogenites, were measured in order to determine the role of volatization in the formation of their presumed parent body, the asteroid 4-Vesta. The 20 non-Antarctic HEDs had d 66 Zn values that ranged from À2.0& to +1.67&, with a mean value of À0.01 ± 0.39& (2 se); this range likely represents a small-scale heterogeneity due to brecciation induced by multiple impacts. The non-Antarctic eucrites (d 66 Zn = +0.00 ± 0.58& (2 se), n = 12) were isotopically the same as the diogenites (d 66 Zn = À0.31 ± 0.80& (2 se), n = 4), and the howardites (d 66 Zn = +0.26 ± 0.37& (2 se), n = 4). On average, non-Antarctic eucrite falls were isotopically heavier (+0.50&) than non-Antarctic finds (À1.00&). The Antarctic finds studied were all unbrecciated samples, and they were significantly heavier than the non-Antarctic samples with a d 66 Zn range of +1.63& to +6.22& for four eucrites (mean, +4.32&) and +0.94& to +1.60& for three diogenites (mean + 1.23&), excluding one anomalous sample, while their Zn concentration is significantly lower than the brecciated samples. These data suggest that the unbrecciated eucrites probably represent the eucritic crust shortly after differentiation and cooling of the parent asteroid, at which time volatization of lighter zinc isotopes led to an isotopically heavy crust. Early impact events caused the ejection of these unbrecciated meteorites, which were subsequently spared from brecciation caused by multiple additional impacts on the much larger Vesta. The range of d 66 Zn values and Zn concentration for the brecciated HEDs in this study supports a major contribution to the Vestan surface by chondritic impactors (À1.30 < d 66 Zn < +0.76& for ordinary and carbonaceous chondrites). The anomalous eucrite PCA 82502 (d 66 Zn = À7.75&) is significantly isotopically lighter than the other HEDs and is the natural sample with the lightest Zn isotopic composition reported in the solar system to date. This meteorite most likely originated from a distinct parent body.

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Section: Introductionmentioning

confidence: 99%

Zinc isotopes in HEDs: Clues to the formation of 4-Vesta, and the unique composition of Pecora Escarpment 82502

Paniello¹,

Moynier²,

Beck

et al. 2012

Geochimica et Cosmochimica Acta

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“…A lava flow origin is widely accepted [2,5,6], in part because the fine grain size suggests rapid cooling. It has been further suggested that vesicular lava flows were buried under subsequent flows and widespread crustal metamorphism produced the granoblastic texture [7]. Vapor-deposited minerals within the vesicles of Ibitira formed during later crustal metamorphism [8,9].…”

Section: Introductionmentioning

confidence: 99%

Formation of vesicles in asteroidal basaltic meteorites

McCoy

Ketcham

Wilson

et al. 2006

Earth and Planetary Science Letters

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“…These clasts found in Tieschitz (H/L 3.6), Manych (LL3.4), and Bovedy (L3) have less calcic and more sodic plagioclase compositions (An 80 -85Al 16 -19 ) than MM40 (An 88 Al 12 ). Low-calcium pyroxenes from these clasts have compositions far more magnesia-rich (En 72-88 ) than MM40 (En [39][40][41][42][43][44][45][46][47][48] ). Finally, these clasts contain abundant olivine (24)(25)(26) which is absent from MM40.…”

mentioning

confidence: 99%

“…Thermal metamorphism can be due either to protracted thermal activity (due to differentiation) or to impact cratering (39). The larger an asteroid is, the longer its thermal activity lasts (40).…”

mentioning

confidence: 99%

A unique basaltic micrometeorite expands the inventory of solar system planetary crusts

Gounelle

Chaussidon

Morbidelli

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

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Micrometeorites with diameter Ϸ100 -200 m dominate the flux of extraterrestrial matter on Earth. The vast majority of micrometeorites are chemically, mineralogically, and isotopically related to carbonaceous chondrites, which amount to only 2.5% of meteorite falls. Here, we report the discovery of the first basaltic micrometeorite (MM40). This micrometeorite is unlike any other basalt known in the solar system as revealed by isotopic data, mineral chemistry, and trace element abundances. The discovery of a new basaltic asteroidal surface expands the solar system inventory of planetary crusts and underlines the importance of micrometeorites for sampling the asteroids' surfaces in a way complementary to meteorites, mainly because they do not suffer dynamical biases as meteorites do. The parent asteroid of MM40 has undergone extensive metamorphism, which ended no earlier than 7.9 Myr after solar system formation. Numerical simulations of dust transport dynamics suggest that MM40 might originate from one of the recently discovered basaltic asteroids that are not members of the Vesta family. The ability to retrieve such a wealth of information from this tiny (a few micrograms) sample is auspicious some years before the launch of a Mars sample return mission.asteroids ͉ cosmic dust ͉ differentiation

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Global Crustal Metamorphism of the Eucrite Parent Body

Cited by 161 publications

References 1 publication

Zinc isotopes in HEDs: Clues to the formation of 4-Vesta, and the unique composition of Pecora Escarpment 82502

Zinc isotopes in HEDs: Clues to the formation of 4-Vesta, and the unique composition of Pecora Escarpment 82502

Formation of vesicles in asteroidal basaltic meteorites

A unique basaltic micrometeorite expands the inventory of solar system planetary crusts

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