Tanakura Tectonic Line

Figure 1.62. Location of epithermal-type deposits in Japan (Shikazono and Shimizu, 1988a). 1 Green tuff and subaerial volcanic region of Tertiary/Quaternary ages, 2 Main Paleozoic/Mesozoic sedimentary terranes, 3 Main metamorphic terranes. TTL Tanakura tectonic line, ISTL Itoigawa-Shizuoka tectonic line, MTL Median tectonic line. Open circle epithermal Au-Ag vein-type deposits, solid circle epithermal base metal vein-type deposits, open triangle epithermal Au disseminated-type deposits.

Southward migration of Southwest Japan as a drawer between a right-lateral system to the west and a left-lateral one to the east along the Tanakura Tectonic Line (Otsuki and Ehiro, 1978) or a clockwise rotation of Southwest Japan about a pole located in the Tsushima Strait (Otofuji et al., 1987), or a combination of both (Kobayashi, 1983) have been proposed. 

In contrast, in Southwest Japan, polymetallic veins (so-called xenothermal-type deposits in the sense of Buddington (1935) or subvolcanie hydrothermal type in the sense of Cissartz (1928, 1965) and Schneiderhohn (1941, 1955) occur. Examples of these deposits are Ashio, Tsugu, Kishu and Obira. All these vein-type deposits have formed at middle Miocene age in western part of Tanakura Tectonic Line under subaerial environment. In these deposits, many base-metal elements (Sn, W, Cu, Pb, Zn) and small amounts of Au and Ag are concentrated. These deposits are associated with felsic volcanic and plutonic rocks along the Median Tectonic Line (MTL) or south of MTL. 

Figure 1.171. Map showing location of the Tsugu gold-antimony deposit. 1 Green-tuff region, 2 outer zone of southwestern Japan, TTL Tanakura tectonic line, ISTL Itoigawa-Shizuoka tectonic line, MTL Median...

Tagiri, M. and Okura, C. (1979) Metavolcanic rocks from the Hitachi and the Keisuku mountain block districts, with special reference to their magmatic series and the Tanakura Tectonic Line. J. Geol Soc. Japan, 85, 679-689 (in Japanese with English abst.). 

MTL Median Tectonic Line TTL Tanakura Tectonic Line Legend I Hida Terrane 2 South Kitakami Terrane 3 Akiyoshi Terrane 4 Suo Terrane 5 Maizuru Terrane 6 Ultra-Tanba Terrane 7 Mino Terrane 8 Sanbagawa Terrane 9 Shimanto Terrane. 

Figure 1.2. Distribution of the stratiform Cu-sulfide and chert-hosted Mn deposits in Japan (Sato and Ka.se, 1996). MTL Median Tectonic Line TTL Tanakura Tcetonic Line ISTL Itoigawa-Shizuoka Tectonic Line BTL Butsuzo Tectonic Line.

Figure 38.5 Distribution of pre-Neogene Terranes of Japan and reconstruction of Early Cretaceous Japan (modified and adapted from Tazawa, 1993). Asterisk shows the fossil locality of Okutadami. Solid black arrow shows the direction of left-lateral strike-slip motion along the Tanakura-Median Tectonic Line in Early Cretaceous time.

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