北海道中央部,鮮新世～前期更新世火砕流堆積物中の花崗岩質包有物の岩石学的意義

• 池田 保夫

  Department of Geology and Mineralogy, Hokkaido University

書誌事項

タイトル別名

• Petrological significance of granitic inclusions from Pliocene-early Pleistocene pyroclastic flow deposits in central Hokkaido, Japan.

抄録

Mineral and chemical compositions of granitic inclusions in the Pliocene-early Pleistocene rhyolitic pyroclastic flow deposits of central Hokkaido are very similar to those of the host rhyolitic pyroclastic flow deposits, but different from those of the basement Tertiary granites. The Sr isotope ratios of both of the pyroclastic flow deposits and the granitic inclusions range from 0.7032 to 0.7040, which are notably lower than those of the Tertiary granites (0.7050-0.7054) and the metamorphic rocks (0.7044-0.7071) of the Hidaka Belt. Such evidence indicates that the granitic inclusions are not derived from the basement rocks, but are co-magmatic with the rhyolitic pyroclastic flows. The water vapor pressure and temperature of the magma which produced both the rhyolitic pyroclastic flows and the granitic inclusions are estimated to be 1 kb and 600°-750°C. Hence, it may be interpreted that the rhyolitic pyroclastic flows are eruptive equivalents of a shallow granitic pluton. The low Sr ratios suggest that the source material of the volcano-plutonic association may not be ascribed to the older upper crust, but to a certain kind of lower crust or upper mantle material.

収録刊行物

• 岩石鉱物鉱床学会誌

  岩石鉱物鉱床学会誌 79 (2), 60-80, 1984

  一般社団法人　日本鉱物科学会

詳細情報

• CRID: 1390282681192357120
• NII論文ID: 130003884524
• DOI: 10.2465/ganko1941.79.60
• ISSN: 18830765
• ISSN: 00214825
• 本文言語コード: en
• データソース種別:
  • JaLC
  • Crossref
  • CiNii Articles
• 抄録ライセンスフラグ: 使用不可