Southward extrusion of eclogite-bearing mafic-ultramafic bodies in the Sanbagawa belt, central Shikoku, Japan

摘要: Abstract Several mafic rock masses, which have experienced eclogite facies metamorphism, are distributed in flat-lying non-eclogitic schists an intermediate structural level (thermal core) of the Sanbagawa belt. The largest, Iratsu mass, and associated peridotite, Higashi-Akaishi extend E–W for about 8 km, N–S 3 surrounded by pelitic, basic quartz schists. mass consists metabasites gabbroic basaltic origin, with intercalations ultramafic rocks, felsic gneiss, schist metacarbonate. can be divided into two layers along a WNW-trending metacarbonate layer. peridotite garnet clinopyroxenite. It is situated beneath western half their mutual boundary dips gently or steeply to N NE. These masses underwent eclogite, subsequent epidote-amphibolite metamorphism as has been reported elsewhere. Iratsu–Higashi-Akaishi surrounding rocks ductile deformation under (or lower P–T) metamorphic conditions. Their foliation generally trends WNW moderately NNE, mineral lineation mostly plunges In S NW, Kinematic analysis structures outcrops oriented samples performed determine shear senses. Consistent top-to-the-north, normal fault displacements observed eclogite-bearing epidote amphibolite mass. Top-to-the-northeast top-to-the-northwest also occur pelitic–quartz on northern side bottom south, reverse (top-to-the-south) movements recognized serpentinized observations provide following constraints kinematics masses: (1) northward displacement relative Higashi-Akaishi, (2) north (3) southward thrusting upon south. exhumation process explained extrusion.