瀬戸内海西部、芸予諸島の後期中新世火山岩類(芸予火山岩類)及び前-中期中新世火山岩類(瀬戸内海火山岩類)について  [in Japanese] Late Miocene volcanic rocks (Geiyo volcanic rock) and earloy-middle Miocene volcanic rocks(Setouchi volcanic rocks) from the Geiyo Islands in the western Setouchi region, southwest Japan  [in Japanese]

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Abstract

Miocene volcanic rocks were discovered in the Geiyo Islands, western Setouchi region of southwest Japan. These occur as dikes or volcanic necks with marginal pyroclastic rocks. The volcanic rocks are composed of high-alkali tholeiitic olivine basalt, olivine andesite and bronzite andesite, in which the olivine andesite from Oge-shima chemically corresponds to high magnesian andesite.<br> Whole rock K-Ar age determinations were carried out on olivine basalts, olivine andesites and bronzite andesites. An olivine andesite from Osakishimo-shima and two bronzite andesites from Okamura-shima yielded late Miocene ages of 8.2±0.7 Ma, 7.8±0.4 Ma and 8.0±0.4 Ma, respectively. It follows that subalkaline volcanism distinctively occurred at late Miocene age in the western Setouchi region. Accordingly, we give a name of “Geiyo volcanic rocks” to these volcanic rocks, which include late Miocene high-alkali tholeiitic olivine basalt reported from the adjacent area.<br> On the other hand, olivine basalts from Okubi-shima and Ko-oge-shima give middle Miocene ages of 12.8±0.6 Ma and 15.4±0.8 Ma, respectively. In addition, an olivine andesite from Oge-shima has been dated as 17.4±0.9 Ma, indicating early Miocene age. On the basis of the radiometric ages, petrography and whole rock chemistry, these volcanic rocks are considered to be a member of the Setouchi volcanic rocks.

Journal

  • Japanese Magazine of Mineralogical and Petrological Sciences

    Japanese Magazine of Mineralogical and Petrological Sciences 29(2), 20-27, 2000-05-30

    Japan Association of Mineralogical Sciences

References:  43

Cited by:  2

Codes

  • NII Article ID (NAID)
    10011128936
  • NII NACSIS-CAT ID (NCID)
    AA1146088X
  • Text Lang
    JPN
  • Article Type
    Journal Article
  • ISSN
    1345630X
  • NDL Article ID
    5617383
  • NDL Source Classification
    ZM46(科学技術--地球科学--岩石・鉱物・鉱床)
  • NDL Call No.
    Z15-117
  • Data Source
    CJP  CJPref  NDL  J-STAGE 
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