Subhorizontal tectonic framework of the Horoman peridotite complex and enveloping crustal rocks,south‐central Hokkaido,Japan |
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| Authors: | Hiroshi Yamamoto Natsumi Nakamori Masaru Terabayashi Hafiz Ur Rehman Masahiro Ishikawa Yoshiyuki Kaneko Takashi Matsui |
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| Institution: | 1. Department of Earth and Environmental Sciences, Kagoshima University, Kagoshima 890‐0065, Japan (email: hyam@sci.kagoshima‐u.ac.jp),;2. Department of Safety Systems Construction Engineering, Kagawa University, Takamatsu 761‐0396, Japan,;3. Graduate School of Environment and Information Sciences, Yokohama National University, Yokohama 240‐8501, Japan, and;4. Faculty of Physical Sciences and Engineering, Meisei University, Hodokubo 2‐1‐1, Hino‐shi Tokyo 191‐8506, Japan;5. Present address: Faculty of Education, Meisei University, 2‐1‐1 Hodokubo, Hino‐shi, Tokyo 191‐8506, Japan |
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| Abstract: | Geological observations in the Horoman area, south‐central Hokkaido, show that the Horoman peridotite complex of the Hidaka metamorphic belt is a tectonic slice about 1200 m thick. The peridotite slab is intercalated into a gently east‐dipping structure. The underlying unit is a Cretaceous–Paleogene accretionary complex. Riedel shear planes in the sedimentary layers of the accretionary complex near the structural bottom of the peridotite slab indicate top‐to‐the‐west (thrust) displacement. The overlying unit is composed of felsic–pelitic gneisses and mafic–felsic intrusive rocks (the Hidaka metamorphic rocks). The boundary surface between the peridotite complex and metamorphic rocks forms a domal structure. Microstructures of sheared metamorphic rocks near the structural top of the peridotite slab indicate top‐to‐the‐east (normal) displacement. The results combined with previous studies suggest that the Horoman peridotite complex was emplaced onto the Asian margin (Northeast Japan) during the collision between the Asian margin and the Hidaka crustal block. |
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| Keywords: | emplacement Hokkaido Horoman peridotite structure |
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