EPMAによるTh-U-Pb化学アイソクロン年代測定法の開発と鉱物粒子年代測定への展開

• 鈴木 和博

  名古屋大学年代測定総合研究センター

書誌事項

タイトル別名

• Development of the Th-U-total Pb isochron method and its application to the subgrain dating of U- and Th-bearing accessory minerals
• 2010年度日本地球化学会賞受賞記念論文 EPMAによるTh-U-Pb化学アイソクロン年代測定法の開発と鉱物粒子年代測定への展開
• 2010ネンド ニホン チキュウ カガクカイショウ ジュショウ キネン ロンブン EPMA ニ ヨル Th U Pb カガク アイソクロン ネンダイ ソクテイホウ ノ カイハツ ト コウブツ リュウシ ネンダイ ソクテイ エ ノ テンカイ

抄録

The wide utilization of radiometric ages for orogen analyses would not been possible without monazite and zircon that are sufficiently robust to preserve their original U and Th and accumulated radiogenic Pb even through overgrowth during high temperature geologic events. Monazite and zircon discriminate strongly against the daughter Pb during crystallization. The CHIME (chemical Th-U-total Pb isochron method) is a new approach to the dating of micrometer-sized domains in monazite and zircon grains on the basis of the precise EPMA analyses of Th, U and Pb. Although the EPMA dating inherits the classic Th-U-Pb chemical dating, the CHIME method provides a significant advantage by adopting the regression-based technique that has the ability to work with minerals containing substantial initial Pb. The age- and composition-mapping can identify two or more chronologically homogeneous domains that are separated by age gaps within a single grain. Critical comments include the chemical criteria that discriminate possibly concordant EPMA zircon and monazite analyses from discordant ones. The in-situ CHIME dating and mapping of zircon and monazite in polished thin sections coupled with compositional mapping of associate garnet has a great chronological potential for the analysis of the detailed sequence of geologic events. The improved CHIME method revealed that (1) the garnet granulite and the eclogite in the Hongseong area of the Gyeonggi Massif within the Korean Peninsula have different evolutional histories as opposed to the current view of the formation by a single Permo-Triassic collision, (2) the widespread Permo-Triassic paragneiss in the massif are in fact an exotic metamorphic terrain thrusted over the Proterozoic basement complex at ca. 240Ma, and (3) Permo-Triassic overprints on the latter are attributable to contact metamorphism from the hot allochthon.

収録刊行物

• 地球化学

  地球化学 45 (3), 113-128, 2011

  一般社団法人日本地球化学会

キーワード

• CHIME
• Subgrain dating
• Age mapping
• Monazite
• Zircon
• EPMA

詳細情報

• CRID: 1390001205742929792
• NII論文ID: 110008722891
• NII書誌ID: AN00141280
• DOI: 10.14934/chikyukagaku.45.113
• ISSN: 21885923
• ISSN: 03864073
• NDL書誌ID: 11232213
• Web Site: https://ndlsearch.ndl.go.jp/books/R000000004-I11232213
• 本文言語コード: ja
• データソース種別:
  • JaLC
  • NDL
  • CiNii Articles
  • KAKEN
• 抄録ライセンスフラグ: 使用不可