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Yakuno Complex

Invalid synonym: Yakuno Ophiolite, Yakuno Rocks, Yakuno Complex, Yakuno Intrusive Rocks

Ultramafic -mafic rocks with associated basalts and metamorphic rocks in Maizuru Belt. Similar rocks in North zone and Central zone are called as this field name.

• Type locality: Yakuno town, Fukuchiyama city, Kyoto prefecture
• Middle - lower crust of a Paleozoic volcanic island arc (Yakuno paleo-island arc) in the ocean
• Ophiolite originated from oceanic type, island-arc type and back-arc basin type oceanic crusts
• Mafic rocks: Silurian - Carboniferous (426 - 341 Ma, Nd-Sm)
• Meta-gabbro: Carboniferous - Permian (343 Ma, Nd-Sm, 270 - 250 Ma, K-Ar)
• Granitoids: early Permian (285, 282 Ma, U-Pb)
• Intruded in: Oshima Formation

• Sedimentary facies: Marine
• Sedimentary facies (Oshima, Fukui pref.): Ocean floor crust
• Sedimentary facies (Ayabe, Kyoto pref.): Ocean floor crust
• Sedimentary facies (Yakuno, Kyoto pref.): Back-arc basin
• Sedimentary facies (Kamigori, Hyogo pref.): Island-arc crust
• Sedimentary facies (Ohara, Okayama pref.): Island-arc crust
• Lithofacies: Meta-gabbro
• Lithofacies (Minor): Diabase, Ultramafic rocks, Granitoids, Mica gneiss
• Lithofacies (Yakuno, Kyoto pref.): Meta-basalt, Meta-dolerite, Meta-gabbro
• Lithofacies (Yakuno, Kyoto pref., Minor): Troctolite
• Lithofacies (Kamigori, Hyogo pref.): Cumulate from tholeiitic magma of an island arc
• Lithofacies (Kamigori, Hyogo pref., Minor): Mafic rocks originated from shoshonite
• Lithofacies (Ohara, Okayama pref.): Cumulate from tholeiitic magma of an island arc
• Lithofacies (Ohara, Okayama pref., Minor): Mafic rocks originated from shoshonite

• Distribution (Width): 4.5 km
• Upper limit: Unconformity (Uchiura Group, Aobasan Andesites)
• Lower limit: Thrust fault (Ultra-Tamba Belt, Hiraki Formation, Tatsuno Formation)

------ Conformity, ~~~~~~ Unconformity, ~~~--- Local unconformity, '''/,, Interfingered, :::::: Fault, /--/-- Thrust, +__+__ Ground surface, ?--?-- Unknown

• Distribution: Fukui pref. - Kyoto pref. - Hyogo pref. - Okayama pref.
• Distribution: Cape Nokogirisaki - Miyadome - Kobitani - Inumi - Somegatani - Nagatani - Mushigano, Oi city, Oi county, Fukui pref.; Urasoko, Tsuruga city, Fukui pref.; Hiki - Takarao - Yokotsumi - Mount Myokensan - Wada, Takahama city, Oi county, Fukui pref.; Wadata, Obama city, Fukui pref.; Oyama - Mihamatoge pass - Nohara - Sezaki - Tochio - Tanaka - Cape Kanagamisaki - Cape Naryumisaki - Yura - Cape Bakuchimisaki, Maizuru city, Kyoto pref.; Ayabe city, Kyoto pref.; Yakuno town, Fukuchiyama city, Kyoto pref.; Asago city, Hyogo pref.; Kamigori city, Ako county, Hyogo pref.; Ohara - Kuroyabu, Mimasaka city, Okayama pref.

• Kimura et al. (2019) Jour. Geol. Soc. Japan, vol.125, no.2, pp.153-165 DOI
• Suda and Hayasaka (2009) Jour. Geol. Soc. Japan, vol.115, no.6, pp.266-287 DOI
• Takemura et al. (2009) Jour. Geol. Soc. Japan, vol.115, Supplement, pp.123-137 DOI
• Kurimoto and Makimoto (1990) Geology of the Fukuchiyama District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 97p. (in Japanese with English abstract 5p.)
• Igi and Kuroda (1965) Oeyama, Explanatory Text of the Geological Map of Japan, Scale 1:50,000, Geological Survey of Japan, 81p. (in Japanese with English abstract 12p.)
• Igi et al. (1961) Maizuru, Explanatory Text of the Geological Map of Japan, Scale 1:50,000, Geological Survey of Japan, 49p. (in Japanese with English abstract 9p.)
• Hirokawa et al. (1958) Obama, Explanatory Text of the Geological Map of Japan, Scale 1:50,000, Geological Survey of Japan, 31p. (in Japanese with English abstract 8p.)
• Hirokawa and Kuroda (1958) Tangoyura, Explanatory Text of the Geological Map of Japan, Scale 1:50,000, Geological Survey of Japan, 23p. (in Japanese with English abstract 9p.)
• Hirokawa and Kuroda (1957) Nokogirizaki, Explanatory Text of the Geological Map of Japan, Scale 1:50,000, Geological Survey of Japan, 22p. (in Japanese with English abstract 9p.)