Thermal history of the enstatite chondrites from silica polymorphs

Makotoki Kimura, M. K. Weisberg, Y. Lin, A. Suzuki, E. Ohtani, Ryuji Okazaki

Research output: Contribution to journalArticle

27 Citations (Scopus)

Abstract

Here we report the results of our petrologic and mineralogical study of enstatite (E) chondrites in order to explore their thermal histories. We studied silica phases in 20 E chondrites by laser micro Raman spectroscopy to determine the silica polymorphs they contain. Silica phases are commonly present in E chondrites and their polymorphs reflect the physical conditions of formation. The samples studied here include EH3-5, EL3-6, E chondrite melt rocks, and an anomalous E chondrite. We identified quartz, tridymite, cristobalite, and silica glass in the samples studied. EH4-5 and EH melt rocks are divided into high and low temperature classes based on niningerite-alabandite solid solutions. EH3, EL3, and some EH melt rocks of the high temperature class contain tridymite and cristobalite. We suggest that tridymite and cristobalite crystallized in chondrules and E chondrite melts, followed by rapid cooling, leading to the survival of these silica polymorphs. EH4 and EL4 chondrites also contain tridymite and cristobalite in their chondrules, indicating that these silica polymorphs survived low temperature metamorphism (as estimated from opaque mineral geothermometers) because of the sluggishness of the transition to a more stable polymorph. Tridymite and cristobalite in EL6 chondrites reflect the high temperature processes experienced by these meteorites. On the other hand, some EH5 chondrites and EH melt rocks of the low temperature class contain quartz, which may be a product of the transition from tridymite or cristobalite during a long period of low temperature metamorphism. Although the thermal history of E chondrites have been previously estimated from opaque minerals, such compositions mainly reflect low temperature processes. However, we can reconstruct the primordial thermal processes and subsequent cooling histories of E chondrites from their silica polymorphs. The E chondrites have complicated thermal histories, which produced the observed variations among them.

Original languageEnglish
Pages (from-to)855-868
Number of pages14
JournalMeteoritics and Planetary Science
Volume40
Issue number6
DOIs
Publication statusPublished - Jan 1 2005

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enstatite chondrite
enstatite
chondrites
chondrite
silica
histories
tridymite
silicon dioxide
cristobalite
history
melt
rocks
chondrule
rock
metamorphism
quartz
minerals
cooling
silica glass
Raman spectroscopy

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Space and Planetary Science

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Thermal history of the enstatite chondrites from silica polymorphs. / Kimura, Makotoki; Weisberg, M. K.; Lin, Y.; Suzuki, A.; Ohtani, E.; Okazaki, Ryuji.

In: Meteoritics and Planetary Science, Vol. 40, No. 6, 01.01.2005, p. 855-868.

Research output: Contribution to journalArticle

Kimura, Makotoki ; Weisberg, M. K. ; Lin, Y. ; Suzuki, A. ; Ohtani, E. ; Okazaki, Ryuji. / Thermal history of the enstatite chondrites from silica polymorphs. In: Meteoritics and Planetary Science. 2005 ; Vol. 40, No. 6. pp. 855-868.
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