The Seba eclogitic basic schists in the Sambagawa metamorphic belt of the Besshi district in central Shikoku, southwest Japan, preserve evidence of two distinct metamorphic events. These are a first eclogitic metamorphic event, and a second glaucophane-barroisitic metamorphic event. The peak metamorphic conditions of the first eclogitic metamorphic event are deduced from the mineral assemblage of schistosity-forming minerals of the eclogite facies (T=610-640℃ and P=12-24kbar; Aoya 2001). The peak eclogitic conditions were followed by a clockwise decompression P-T path, with retrogression into the epidote amphibolite facies at T=400-535℃ and P=6-7kbar. These conditions were obtained from phases replacing the minerals of the peak metamorphic conditions. The second glaucophane-barroisitic metamorphic event is defined by distinctly zoned amphiboles which suggest a prograde path from the epidote-blueschist facies to the epidote amphibolite facies. The prograde path is similar to that of surrounding non-eclogitic Sambagawa schists. The Seba eclogitic basic schists were juxtaposed with non-eclogitic Sambagawa schists during the prograde metamorphism of the non-eclogitic Sambagawa schists. These amalgamated metamorphic sequences subsequently underwent prograde metamorphism reaching the epidote-amphibolite facies, and were then exhumed to shallow crustal levels.
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