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TWO NEW CHONDRITE‐FALLS IN JAPAN
Author(s) -
Shima Masako,
Murayama Sadao,
Wakabayashi Fumitaka,
Okada Akihiko,
Yabuki Hideo
Publication year - 1986
Publication title -
meteoritics
Language(s) - English
Resource type - Journals
eISSN - 1945-5100
pISSN - 0026-1114
DOI - 10.1111/j.1945-5100.1986.tb01226.x
Subject(s) - chondrule , chondrite , olivine , plagioclase , pyroxene , geology , meteorite , ordinary chondrite , geochemistry , mineralogy , mafic , astrobiology , physics , paleontology , quartz
In the summer of 1984, two meteorites fell in the northern part of Honshu, Japan; Aomori, at 1:50 p.m. on June 30, and Tomiya, at 1:35 p.m. on August 22. Coordinates of the falls of the Aomori and the Tomiya are at 140°47.1'E., 40°48.6'N., and 140°51.9'E., 38°22.0'N., respectively. Results of chemical analyses of major elements, ratios of Fe total /SiO 2 (0.546 and 0.803) and Fe metal /Fe total (0.332 and 0.581), and molar compositions of olivines (Fa 25 and Fa 19 ) indicate that the Aomori and the Tomiya are typical L‐ and H‐group ordinary chondrites, respectively. In the Aomori, chondrules are present as relicts in the well‐recrystallized matrix. Olivine and pyroxene are homogeneous in composition, and coarse clear feldspar, up to 100 micrometers in size, is well developed in the chondrules and matrix. Though the Aomori is a petrologic type 6 based on its texture and mineralogy, it includes a few grains of multiple twinned clinobronzite which is rarely observed in highly equilibrated ordinary chondrites. In the Tomiya, chondrules possess a fine‐grained mesostasis, and both orthopyroxene and clinobronzite are noticeable in thin sections. Plagioclase is mostly microcrystalline, but is also sparsely present as tiny, visible grains. Thus, the Tomiya was classified to be petrologic type between 4 and 5. The deformation texture of olivine, pyroxene and plagioclase indicates that both meteorites were shocked by 0.2‐0.25 Mb. In conjunction with the discussion of the frequency of meteorite‐falls, all observed falls of meteorites in Japan are tabulated in this paper.