Post-crystallization reheating and partial melting of eucrite EET90020 by impact into the hot crust of asteroid 4Vesta ∼4.50 Ga ago

Yamaguchi, A.; Taylor, G. J.; Keil, K.; Floss, C.; Crozaz, G.; Nyquist, L. E.; Bogard, D. D.; Garrison, D. H.; Reese, Y.; Wiesmann, H.; Shih, C.-Y.

doi:10.1016/s0016-7037(01)00681-0

Cited by 88 publications

(111 citation statements)

References 47 publications

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“…Several eucrites have petrologic evidence of large cratering events. A cumulate eucrite, Moore County, and several basaltic eucrites (e.g., Ibitira and EET 90020) show of evidence of rapid cooling from high temperature, implying a large-scale impact event during thermal metamorphism (Miyamoto and Takeda 1994;Miyamoto et al 2001;Yamaguchi et al 2001). This petrologic evidence is consistent with the recent discovery of craters up to ∼450 km in diameter on asteroid 4 Vesta (Thomas et al 1997).…”

Section: Origin Of Dhofar 007 and Comparison With Silicate Clasts In supporting

confidence: 78%

An anomalous eucrite, Dhofar 007, and a possible genetic relationship with mesosiderites

Yamaguchi

Setoyanagi

Ebihara

2006

Meteoritics &Amp; Planetary Science

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Abstract-We studied the texture, mineralogy, and bulk chemical composition of Dhofar 007, a basaltic achondrite. Dhofar 007 is a polymict breccia that is mostly composed of coarse-grained granular (CG) clasts with a minor amount of xenolithic components, such as a fragment of Mg-rich pyroxene. The coarse-grained, relict gabbroic texture, mineral chemistry, and bulk chemical data of the coarse-grained clast indicate that the CG clasts were originally a cumulate rock crystallized in a crust of the parent body. However, in contrast to monomict eucrites, the siderophile elements are highly enriched and could have been introduced by impact events. Dhofar 007 appears to have experienced a two-stage postcrystallization thermal history: rapid cooling at high temperatures and slow cooling at lower temperatures. The presence of pigeonite with closely spaced, fine augite lamellae suggests that this rock was cooled rapidly from higher temperatures (>0.5 °C/yr at ∼1000 °C) than typical cumulate eucrites. However, the presence of the cloudy zone in taenite and the Ni profile across the kamacite-taenite boundaries indicates that the cooling rate was very slow at lower temperatures (∼1-10 °C/Myr at <600-700 °C). The slow cooling rate is comparable to those in mesosiderites and pallasites. The two-stage thermal history and the relative abundance of siderophile elements similar to those for metallic portions in mesosiderites suggest that Dhofar 007 is a large inclusion of mesosiderite. However, we cannot rule out a possibility that Dhofar 007 is an anomalous eucrite.

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Section: Origin Of Dhofar 007 and Comparison With Silicate Clasts In supporting

confidence: 78%

An anomalous eucrite, Dhofar 007, and a possible genetic relationship with mesosiderites

Yamaguchi

Setoyanagi

Ebihara

2006

Meteoritics &Amp; Planetary Science

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“…The most recent work of Yamaguchi et al (2001) refines earlier conclusions and presents a 4-stage model on the thermal history of parts of 4 Vesta's crust. It includes the initial crystallization of eucritic rocks from lava flows or dikes on or near the surface followed by some brecciation, burial due to overflowing lava, and a second short reheating event.…”

Section: Introductionsupporting

confidence: 68%

New eucrite Dar al Gani 872: Petrography, chemical composition, and evolution

Patzer

Hill

Boynton

2003

Meteorit & Planetary Scien

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According to our results, DaG 872 is a Mg-rich main group eucrite, i.e., a monomict noncumulate basaltic eucrite displaying a predominant coarse-grained relict subophitic and a fine-grained granulitic texture. The meteorite also shows pockets of late-stage mesostasis and is penetrated by several calcite veins due to terrestrial weathering. Finally, it exhibits shock phenomena of stage 1-2 including heavily fractured mineral components, undulose extinction of plagioclase, kinked lamellae, and mosaicism in pyroxenes corresponding to peak pressures of ~20 GPa. In view of petrographic criteria as well as compositional and exsolution characteristics of its pyroxenes, the sample represents a metamorphic type 5 eucrite. Assuming the metamorphic type to be a function of burial depth on the parent body and taking into account the relatively high shock stage, the excavation of DaG 872 was likely induced by a major impact event. Prior to this point, DaG 872 apparently underwent a 4-stage geological evolution that is reflected by intricate textural and mineralogical features.

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“…Previous studies of eucrites have reported the presence of tridymite (e.g. Delaney et al, 1984a;Yamaguchi et al, 2001), cristobalite (e.g. Yamaguchi and Mikouchi, 2005;Chennaoui Aoudjehane and Jambon, 2007), and quartz (Treiman et al, 2004).…”

Section: Electron Microprobementioning

confidence: 99%