北海道, 神居古潭構造帯北部, 音威子府西方域に分布する蛇紋岩メランジェと蛇紋石鉱物 [in Japanese] The serpentinite melange and serpentine minerals in the western Otoineppu area of the northern Kamuikotan tectonic belt, Hokkaido [in Japanese]
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Serpentinite melange in the western Otoineppu area, northern Kamuikotan tectonic belt, which is mostly surrounded by the Early Cretaceous Sorachi Group Greenstones, contains many metamorphosed tectonic blocks. The blocks are 1) basic meta-volcanic rocks with well preserved original texture, 2) epidote amphibolite with well-zoned epidote, and 3) very weakly metamorphosed hornblende gabbro. The chemical compositions of relic clinopyroxene in the Upper Sorachi Greenstones and in the hornblende gabbro blocks suggest an orogenic belt origin whereas the chemistry of the Lower Sorachi Greenstones is similar to that of abyssal tholeiites.<br> Judging from bulk chemistry, the serpentinite has derived mostly from harzburgite. Antigorite is the only serpentine mineral recognized in the serpentinites of the study area. Three types of serpentinite are discriminated; type A with fine grained antigorite with mesh structure occures, type B with coarse grained flake-shaped antigorite, and type C with coarse grained sutured antigorite.<br> Texturally type A serpentinite is transposed to type B and then to type C. Antigorite with mesh structure contains higher H<sub>2</sub>O than serpentinite of type B and C. Type C serpentinite is rich in Al<sub>2</sub>O<sub>3</sub> and poor in MgO. The three types of serpentinites and mixed-type serpentinite have been separately mapped.
- Journal of Mineralogical and Petrological Sciences
Journal of Mineralogical and Petrological Sciences 90(7), 234-246, 1995-07-05
Japan Association of Mineralogical Sciences