| Co-Investigator(Kenkyū-buntansha) |
OKAMI Kazuyoshi Faculty of Tecnology, Iwate Univ. ;Associate Professor, 工学部, 助教授 (60003878)
ISHIKAWA Ken-ichi College of General Educ.,Tohoku Univ. ;Assistant, 教養部, 助手 (20158744)
KANISAWA Satoshi College of General Educ.,Tohoku Univ. ;Professor, 教養文学部, 教授 (70005784)
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| Budget Amount *help |
¥3,100,000 (Direct Cost: ¥3,100,000)
Fiscal Year 1987: ¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 1986: ¥1,700,000 (Direct Cost: ¥1,700,000)
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| Research Abstract |
Stratigraphy,geologic structure and geochemical nature of the basic to ultrabasic rocks in and around the "Hayachine Tectonic Belt" in the Kawai and Kamaishi district are re-examined. The results of the investigation are as follows:
1. In the Kawai district, the Palaeozoic rocks are divided, in ascending order, into the Hayachine Complex (Nakadake Serpentinite, Kagura Complex and Koguro Formation; Ordovi-cian-Silurian ?), Yakushigawa Formation (Ordovician?-Silurian) and Odagoe Formation (Silurian). In the Kamaishi district, it is divided into the Hayachine Complex (Kentosan Complex and Iwakurayama Complex; Silurian ?), Senjyogataki Formation (Devonian), Kogawa Formation (Carboniferous)and Kuribayashi Formation (Permian).
2. Geologic structure in the eastern marginal zone of the "Hayachine Tectonic Belt" is characterized by reverse faults and overterned folds with eastward Fergenz. On the contrary, in the western marginal zone it is characterized by reverse faults and asymmetric folds with westward Fergenz. Thus the "Hayachine Tectonic Belt" seems to form an anticlinorium.
3. The chemical nature of the basic rocks and trondhjemites of the Hayachine Complex is similar to that of oceanic basalt of oceanic plagiogranite.
4. The Hayachine Complex was formed as an oceanic crust in Ordovician or Silurian time, and is overlain by thick terrigenous sediments of Silurian age. On and after the Silurian, the "Hayachine Tectonic Belt" was a site of passive margin, then, probably in the late jurassic, a broad anticline was formed in the zone, which separated from the Southern and Northern Kitakami Massif by reverse faults, along the passive margin. The anticlinal zone is called the "Hayachine Tectonic Belt".
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