Journal of the Faculty of Science, Hokkaido University. Series 4, Geology and mineralogy;Vol.XXI, No.3

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The Takadomari Serpentinites in the Kamuikotan Ophiolite Belt, Hokkaido, Japan

Igarashi, Toshihiko;Katoh, Takayuki;Niida, Kiyoaki

Permalink : http://hdl.handle.net/2115/36732

Abstract

Within the Kamuikotan Ophiolite Belt, a large serpentinite mass more than 10×12 km is observed around Takadomari as a tectonic unit of dismembered ophiolite. The Takadomari serpentinites show an east-facing layered structure composed primarily of dunite, harzburgite, and olivine-orthopyroxenite layers. More than 120 dykes of microdiorite-microgabbro were found in the serpentinite mass and clearly show an intrusive relation. The serpentinization is characterized by a progressive crystallization of antigorite replacing lizardite and chrysotile serpentines crystallized retrogressively. The Takadomari mass is regarded as a dismembered ophiolite unit which is situated at the base of the Horokanai ophiolite complex. High pressure and low temperature type metamorphic rocks such as glaucophane schist are considered to be a tectonic unit lifted up by the Takadomari serpentinites.

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