岩脈中の花こう岩質包有物のジルコン U-Pb 年代から推定される奈良県吉野地域の中央構造線南方に伏在する中新世花こう岩質岩体  [in Japanese] Possible presence of the concealed Miocene granitic body to the south of Median Tectonic Line, Yoshino district, Nara Prefecture, inferred from zircon U-Pb age of the granitic enclave in dike  [in Japanese]

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Abstract

奈良県吉野町樫尾の吉野川に沿って分布する玄武岩・流紋岩複合岩脈から約1m径の花こう岩質包有物を見出した.この包有物の起源を探るため全岩化学分析とレーザーアブレーションICP質量分析法によるジルコンのU-Pb年代測定を行った.その結果全岩化学組成は外帯花こう岩類の一員である大峯花こう岩質岩と類似すること,最も若い年代を示すジルコン群がら求めた花こう岩質岩の固結年代は13.2±1.0Maであることが判った.これらから中央構造線南方に中新世の花こう岩質岩の潜頭岩体が存在すると推定される.

A granitic enclave, ca. lm in diameter, was found in a basalt/rhyolite composite dike along the Yoshino River at Ifashio in the central part of Nara Prefecture, Southwest Japan. The dike intruded into Mesozoic accretionary complex, and there are no outcrop of granitic rocks in the vicinity. To clarify the origin of the granitic enclave, we carried out whole rock chemical analysis with XRF and U-Pb zircon dating using laser ablation ICP-MS. The whole rock composition of the granitic enclave is within the range of the Ohmine granitic rocks, one of the member of the Middle Miocene granitic rocks of Outer Zone of Southwest Japan. The time of the solidffication of the granitic enclave is estimated to be 13.2 ± 1.0 Ma based on the youngest zircon U-Pb results. These facts suggest the existence of concealed middle Miocene granitic body beneath the Kashio region.

Journal

  • The Journal of the Geological Society of Japan

    The Journal of the Geological Society of Japan 109(12), 689-696, 2003-12-15

    The Geological Society of Japan

References:  33

Cited by:  6

Codes

  • NII Article ID (NAID)
    110003009773
  • NII NACSIS-CAT ID (NCID)
    AN00141768
  • Text Lang
    JPN
  • Article Type
    Journal Article
  • ISSN
    00167630
  • NDL Article ID
    6803802
  • NDL Source Classification
    ZM49(科学技術--地球科学--地質)
  • NDL Call No.
    Z15-174
  • Data Source
    CJP  CJPref  NDL  NII-ELS  J-STAGE 
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