Phenocrystic hornblendes from Tertiary andesites and dacites, Kagawa Prefecture, Japan.

DOI
  • UJIKE OSAMU
    Shikoku Offlce, Geological Survey of Japan
  • ONUKI HITOSHI
    Institute of Mineralogy, Petrology and Economic Geology, Tohoku University

Bibliographic Information

Other Title
  • 香川県産第三紀安山岩および石英安山岩中の斑晶角閃石

Abstract

Studies on volcanic hornblendes have been carried out with special reference to the relationship in chemistry to their host rocks from Kagawa Prefecture, Japan. The quantity of Si and AlIV in the hornblende seems to depend to a considerable extent on that of free silica in a magma represented by the rock. The groundmass contains about 4 times as much K2O as the hornblende does, and the coefficient of partition of K and Na between the groundmass and the hornblende is 2.2 on an average. It is deduced from considerations of phase relations in the rocks, two-pyroxene geothermometer and the chemistry of hornblendes that the hornblendes ware crystallized at temperatures above 900°C from magmas probably undersaturated with water. A precipitation of some iron-rich phases together with the hornblende must be required to produce a typical cale-alkaline trend. Hornblende-controlled fractionation at a phenocrystic stage of magmatic crystallization must change the residual melt into a peraluminous composition.

Journal

Details 詳細情報について

  • CRID
    1390001206216584832
  • NII Article ID
    130003884294
  • DOI
    10.2465/ganko1941.71.389
  • ISSN
    18830765
    00214825
  • Text Lang
    en
  • Data Source
    • JaLC
    • Crossref
    • CiNii Articles
  • Abstract License Flag
    Disallowed

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