Thermal history of the shock-melted Antarctic LL-chondrites from the Yamato-79 collection

Okano, Osamu; Nakamura, Noboru; Nagao, Keisuke

doi:10.1016/0016-7037(90)90301-z

Cited by 14 publications

(17 citation statements)

References 43 publications

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“…Nakamura and Okano () and Okano et al. () called attention to a possible major event in LL chondrite history ~1.2 Ga ago based partly on various ages of Yamato‐790964 and paired meteorites. The Yamato‐790964 meteorite has an Rb/Sr age of 1.197 ± 0.054 Ga (Okano et al.…”

Section: Discussionmentioning

confidence: 99%

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⁴⁰Ar/³⁹Ar age of material returned from asteroid 25143 Itokawa

Park

Turrin

Herzog

et al. 2015

Meteorit & Planetary Scien

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The Hayabusa mission to asteroid 25143, Itokawa, brought back 2000 small particles, which most closely resemble material found in LL4-6 chondrites. We report an 40 Ar/ 39 Ar age of 1.3 AE 0.3 Ga for a sample of Itokawa consisting of three grains with a total mass of~2 lg. This age is lower than the >4.0 Ga ages measured for 75% of LL chondrites but close to one for Y-790964 and its pairs. The flat 40 Ar/ 39 Ar release spectrum of the sample suggests complete degassing 1.3 Ga ago. Recent solar heating in Itokawa's current orbit does not appear likely to have reset that age. Solar or impact heating 1.3 Ga ago could have done so. If impact heating was responsible, then the 1.3 Ga age sets an upper bound on the time at which the Itokawa rubble pile was assembled and suggests that rubble pile creation was an ongoing process in the inner solar system for at least the first 3 billion years of solar system history.

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Section: Discussionmentioning

confidence: 99%

“…The Yamato‐790964 meteorite has an Rb/Sr age of 1.197 ± 0.054 Ga (Okano et al. ) and an 40 Ar/ 39 Ar age of 1.26 ± 0.014 Ga (Takigami and Kaneoka ). Nakamura and Okano also noted that an H chondrite clast from the LL6 chondrite St. Mesmin had a similar age.…”

Section: Discussionmentioning

confidence: 99%

⁴⁰Ar/³⁹Ar age of material returned from asteroid 25143 Itokawa

Park

Turrin

Herzog

et al. 2015

Meteorit & Planetary Scien

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“…CK chondrites are compared with ordinary and enstatite (particularly metamorphosed) chondrites using precise IDMS data from Masuda et al (1973), Nakamura (1974), Nishikawa et al (1990), Okano et al (1990) and Nakamura et al (1994). The data is plotted in Fig.…”

Section: Negative Ce Anomaly In Ck Chondritesmentioning

confidence: 99%

“…5(b) (Eu/Sm-Sm diagram). The IDMS data obtained by Evenson et al (1978) is not considered here in order to eliminate possible systematic and/or fortuitous errors between two labora- Masuda et al (1973), Nakamura (1974), Okano et al (1990) and Nishikawa et al (1990), Nakamura et al (1994), for enstatite chondrites from Nakamura and Masuda (1973), and for carbonaceous chondrites from Nakamura (1974) (partly unpublished). In (a), the majority of the CK chondrites plot close to or below the CI ratio, while the enstatite chondrites plot above and ordinary chondrites plot on both sides.…”

Section: Negative Ce Anomaly In Ck Chondritesmentioning

confidence: 99%

Rare earth element abundances in the CK chondrites including the Kobe meteorite.

2002

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“…Cen also occurs in OCs that originated from shock‐melting at a large scale (e.g., Okano et al. ) and from local shock‐melting (e.g., Ashworth ). Oen mainly occurs in types 4–6 of EOCs that transformed from Cen during the thermal metamorphism on the parent body (e.g., Van Schmus and Wood ; Buseck et al.…”

Section: Introductionmentioning

confidence: 99%

Primordial, thermal, and shock features of ordinary chondrites: Emulating bulk X‐ray diffraction using in‐plane rotation of polished thin sections

Imae

Kimura

Yamaguchi

et al. 2019

Meteorit & Planetary Scien

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Using an X‐ray diffractometer, powder‐like diffraction patterns were acquired from in‐plane rotation of polished thin sections (PTSs) of 60 ordinary chondrites (23 H, 21 L, and 16 LL), in order to explore the thermal and shock metamorphism and its modifications of primordial features. The olivine (Ol) 130 peak position shown as Bragg indices clearly correlates with the chemical group for equilibrated ordinary chondrites (EOCs), while the peak is split or broad for unequilibrated ordinary chondrites (UOCs). The intensity ratio of kamacite may be useful for distinguishing the chemical group between H and L‐LL, but it is not definite because of heterogeneous terrestrial weathering of kamacite, especially in H chondrites. The summed intensities of the orthoenstatite (Oen) 511 and 421 peaks positively correlates with the metamorphic sequence from 3 to 6, while that of clinoenstatite (Cen) 22true1false¯ is inversely correlated. The shock stage positively correlates with the summed full width of half maximum values of the Oen 511 and 421 peaks and the FWHM of Ol 130 peak for each class. Significant amount of Oen (Pbca) transformed through Cen (C2/c) finally to Cen (P21/c) is stable at high pressure for shock stage S6 (Tenham and NWA 4719). The shock melted LL chondrite is characterized by the occurrence of Cen and abundant homogeneous olivine. The effects of both thermal and shock metamorphism are thus incorporated into the bulk X‐ray diffraction (XRD) data. The bulk XRD method is useful for determining the bulk mineralogy, resulting in the classification of ordinary chondrites. The method is also applicable to samples other than PTS.

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Thermal history of the shock-melted Antarctic LL-chondrites from the Yamato-79 collection

Cited by 14 publications

References 43 publications

⁴⁰Ar/³⁹Ar age of material returned from asteroid 25143 Itokawa

⁴⁰Ar/³⁹Ar age of material returned from asteroid 25143 Itokawa

Rare earth element abundances in the CK chondrites including the Kobe meteorite.

Primordial, thermal, and shock features of ordinary chondrites: Emulating bulk X‐ray diffraction using in‐plane rotation of polished thin sections

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Thermal history of the shock-melted Antarctic LL-chondrites from the Yamato-79 collection

Cited by 14 publications

References 43 publications

40Ar/39Ar age of material returned from asteroid 25143 Itokawa

40Ar/39Ar age of material returned from asteroid 25143 Itokawa

Rare earth element abundances in the CK chondrites including the Kobe meteorite.

Primordial, thermal, and shock features of ordinary chondrites: Emulating bulk X‐ray diffraction using in‐plane rotation of polished thin sections

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⁴⁰Ar/³⁹Ar age of material returned from asteroid 25143 Itokawa

⁴⁰Ar/³⁹Ar age of material returned from asteroid 25143 Itokawa