四国中央部三波川帯の地質構造の研究史に関する若干の考察 : 地域構造地質学の方法論

Tectonics of the Sambagawa Belt was first comprehensively studied by Hara et al.(1977), distinguishing four main tectonic phases (in chronological order): formation of Iithologic layering-parallel schistosity, Nagahama phase of folding with southward vergence associating formation of nappes, Ozu phase of folding with southward vergence, and Hijikawa phase of sinistral en echelon upright folding. The metamorphic facies analysis of the schists of the Sambagawa Belt and Northern Chichibu Belt in central Shikoku was first performed by Kurata & Banno (1974) and Higashino (1975), clarifying that the facies series of pelitic schists defined by minerals crystallized during the highest-temperature phase of metamorphism can be explained in terms of chlorite zone, garnet zone and biotite zone.
Banno et al. (1978), Banno and Sakai (1989), Wallis (1990,1995) and Wallis et al.(1992) have been regarded the distribution of the mineral zones as a thermo-mechanical continuum throughout all phases of deformation. However, Hara et al. (1988, 1990, 1992) and Hara and Shiota (1996) have pointed out that individual mineral zones are nappes which show distinct deformational and metamorphic histories, and that the highest-temperature metamorphism of the garnet zone nappe (Fuyunose nappe) occurred when the Fuyunose nappe schist had been coupled with the biotite zone nappes (Saruta nappe I and II) which were exhuming, and in addition, that the highest-temperature metamorphism of the chlorite zone nappe (Sogauchi nappe) occurred when the Sogauchi nappe schist had been coupled with the Fuyunose and Saruta nappe schists which were exhuming, and furthermore, that the Saruta ～ Sogauchi nappe schists had been exhumed onto an off-scraped sequence (Northern Chichibu Zone) along the mechanical boundary of consuming plates. The methodological differences between the students of the former and the students of the latter have been investigated in this paper with respect to Shimizu and Yoshida's (2004) comments on the research history of tectonics of the Sambagawa Belt.