Item type |
紀要論文(ELS) / Departmental Bulletin Paper(1) |
公開日 |
2001-10-01 |
タイトル |
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タイトル |
CHIME ages of xenotime, monazite and zircon from beryllium pegmatites in the Napier Complex, Khmara Bay, Enderby Land, East Antarctica |
言語 |
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言語 |
eng |
キーワード |
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言語 |
en |
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主題Scheme |
Other |
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主題 |
pegmatite |
キーワード |
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言語 |
en |
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主題Scheme |
Other |
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主題 |
beryllium |
キーワード |
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言語 |
en |
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主題Scheme |
Other |
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主題 |
Antarctica |
キーワード |
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言語 |
en |
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主題Scheme |
Other |
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主題 |
Archean |
キーワード |
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言語 |
en |
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主題Scheme |
Other |
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主題 |
CHIME dating |
キーワード |
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言語 |
en |
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主題Scheme |
Other |
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主題 |
Napier Complex |
資源タイプ |
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資源タイプ識別子 |
http://purl.org/coar/resource_type/c_6501 |
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資源タイプ |
departmental bulletin paper |
ID登録 |
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ID登録 |
10.15094/00003088 |
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ID登録タイプ |
JaLC |
ページ属性 |
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内容記述タイプ |
Other |
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内容記述 |
P(論文) |
著者名(英) |
Grew, Edward S.
Suzuki, Kazuhiro
Asami, Masao
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著者所属(英) |
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en |
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Department of Geological Sciences, University of Maine |
著者所属(英) |
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en |
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Nagoya University Center for Chronological Research |
著者所属(英) |
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en |
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Department of Earth Sciences, Faculty of Science, Okayama University |
抄録(英) |
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内容記述タイプ |
Other |
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内容記述 |
Dating by the chemical Th-U-total Pb isochron method (CHIME) was carried out on xenotime, monazite and zircon from beryllium pegmatites intruded at about 2500 Ma in the ultrahigh-temperature metamorphic Napier Complex. No meaningful results were obtained on zircon from an associated Be-free pegmatite. All analyzed mineral grains are chronologically heterogeneous, and apparent ages range from -2460 Ma to 550 Ma with conspicuous concentration at 2200, 1700 and 700 Ma. The 2168±36 Ma age for the chronologically homogeneous, non-metamict core of a large xenotime grain dates intense post-emplacement deformation and metamorphism, possibly the granulite-facies event M-2 proposed by E.S. Grew et al. (Polar Geosci., 13, 1, 2000) to explain the breakdown of sapphirine and quartz to sillimanite, surinamite, orthopyroxene and/or garnet in the pegmatites and their host rocks. CHIME ages near ~1700 Ma and ~700 Ma could result from incomplete resetting by amphibolite-facies events (M-3, -4) between ~1100 and ~500 Ma. In general, the minerals appeared to have experienced no significant new growth during the later events, so that the effect of these events is expressed in the U-Th-Pb system in the original mineral. Because most of the ages were obtained on non-metamict portions of the analyzed grains, we doubt that metamictization can be the cause of most of the observed chronological heterogeneity. The lack of evidence for the ~2500 Ma emplacement age in the CHIME data could be due to the reliance on total concentrations of Th, U and Pb, which may be more affected by subsequent deformation and metamorphism than the isotope ratios measured in conventional U-Pb dating. |
雑誌書誌ID |
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収録物識別子タイプ |
NCID |
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収録物識別子 |
AA1130866X |
書誌情報 |
Polar geoscience
巻 14,
p. 99-118,
発行日 2001-10
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出版者 |
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出版者 |
National Institute of Polar Research |