中部九州内帯花崗岩類のRb-Sr全岩アイソクロン年代
スポンサーリンク
概要
- 論文の詳細を見る
Rb-Sr whole rock isochron ages were determined for Middle Cretaceous granitic rocks and S-type tonalites in central Kyushu, southwest Japan. The former granites are divided into two age groups; the older group with a range of 140-160 Ma (Kunisaki tonalite: 142.2±2.1 Ma and Yamanaka granodiorite: 164.0±14.7 Ma) and the younger group with a range of 100-120 Ma (Watada granodiorite: 101.6±7.2 Ma, Nioki granite: 116.9±7.3 Ma, Haki granodiorite: 118.0±11.3 Ma, Kusano granite: 100.6±3.7 Ma, Kikuchi granodiorite: 121.3±8.4 Ma and Tamana granite: 116.8±12.7 Ma). The older granitic rocks would have been formed related to the subduction of the Farallon-Izanagi ridge, and the younger ones to that of the Kula-Pacific ridge along the eastern margin of the Eurasia plate. The S-type tonalite in the Higo area, which were derived from anatexis of pelitic granulite in the Higo metamorphic terrane, also shows a well defined whole rock isochron of 229 Ma, but the genesis of the tonalite was clearly different from those of the other granitic rocks in central Kyushu. Sr initial ratios of these granitic rocks show low values of 0.7044〜0.7056 except very for Kusano granite (Sr I=0.7065) and Higo S-type tonalite (Sr I=0.7068). They are very simliar to those of the San'in region, but different from those of the Ryoke-Sanyo region in southwest Japan, although the granitic and related metamorphic rocks excluding Sangun metamorphic rocks in central Kyushu have been thought to be a western extension of Ryoke belt. Newly analysed Rb-Sr whole rock isochron ages are harmony with a thought that the Cretaceous granitic igneous activities were migrated from central Kyushu toward the east in the Ryoke-Sanyo region, whereas Sr initial ratios of granitic rocks shed a light on the difference of mantle-crust composition between central Kyushu and the Ryoke-Sanyo region.
- 日本地質学会の論文
- 1993-04-30
著者
関連論文
- 北海道樺戸地域から産する中新世ソレアイト玄武岩
- O-26 中部ベトナムコンツム地塊,衝突帯における苦鉄質火成活動の化学的特徴(東南アジアの地殻形成史とテクトニクス : 地質学・岩石学からのアプローチ,口頭発表,一般講演)
- ベトナム中部・コンツム地塊にみられる大陸衝突変成作用の温度-圧力-時間履歴(23.変成岩とテクトニクス)
- 飛騨帯の西方延長:とくに鳥取県大山西方溝口町で発見された片麻岩類と圧砕岩類について
- B58 矢筈岳火山岩類と沖縄トラフの火山岩類にみられる地球化学的類似性
- 438 東南極、リュッツォホルム岩体ブライボーグニーパの含斜方輝石ミグマタイト(変成岩)
- 7) 領家花崗岩の起源物質
- B25 近畿北西部、扇ノ山火山岩類の Nd-Sr 同位比
- 305 大分県国東半島における花崗岩類・変成岩類
- 220 領家ナップコンプレックスの花崗岩質岩類のRb-Sr年代