書誌事項
- タイトル別名
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- Graphitization of carbonaceous material and rejuvenation of K-Ar white mica age in contact aureole in eastern Yamaguchi Prefecture, Southwest Japan.
- ヤマグチケン トウブ ノ セッショク ヘンセイタイ ニ オケル タンシツブツ ノ セキボクカ ト K Ar シロウンモ ネンダイ ノ ワカガエリ
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抄録
The Jurassic accretionary complex in eastern Yamaguchi Prefecture, Southwest Japan, is intruded by Late Cretaceous granite, generating a contact aureole more than 2 km wide which is divided into the biotite and cordierite mineral zones. X-ray diffraction analyses of carbonaceous material were carried out for pelitic rocks collected systematically not only from the contact aureole but also from its outer side. The apparent interplanar spacing d002 values of carbonaceous material rapidly decrease from 3.590 to 3.371 Å in the upper biotite zone, and reach 3.353 Å in the cordierite zone. Although all d002 data from the lower biotite zone and from the outside are calculated to be around 3.6 Å, the peak shapes can be divided into three types in a figure of peak-height versus peak-width at half height : Types I, II and III with advance of graphitization. Types I and II occur both in the lower biotite zone and in the outside, whereas Type III yields only in the lower biotite zone. These aspects suggest that graphitization caused by contact metamorphism has slightly advanced in the lower biotite zone.Rejuvenation of K-Ar white mica ages in the contact aureole reported by Takami et al. (1993) was examined on the basis of the graphitization. In the lower biotite zone where the d002 values are more than 3.5 Å, K-Ar ages change systematically from 122 to 97 Ma, indicating that rejuvenation of the ages has rapidly advanced. In the upper biotite and cordierite zones where the d002 values are less than 3.5 Å, the ages (83-86 Ma)coincide with those of the granite (82 and 86 Ma), implying that the rejuvenation has completed. These results indicate that a metamorphic temperature represented by d002=3.5 Å mostly coincides with the closure temperature of K-Ar white mica system. The value of d002=3.5 Å is therefore an useful indicator for considering the degree of rejuvenation of K-Ar age.
収録刊行物
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- 地質学雑誌
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地質学雑誌 106 (2), 151-160, 2000
一般社団法人 日本地質学会
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詳細情報 詳細情報について
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- CRID
- 1390282681211490048
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- NII論文ID
- 110003013100
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- NII書誌ID
- AN00141768
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- COI
- 1:CAS:528:DC%2BD3cXhsV2ktbo%3D
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- ISSN
- 13499963
- 00167630
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- NDL書誌ID
- 5298121
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- 本文言語コード
- ja
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- データソース種別
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- JaLC
- NDL
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- 抄録ライセンスフラグ
- 使用不可