Recent petrological studies on the Sambagawa metamorphic belt in Shikoku have recognized that the coarse-grained eclogite-bearing lithologies (so-called tectonic blocks in earlier studies) in the Besshi area exclusively preserve evidence for the early Sambagawa metamorphism, which can be related to onset of the Sambagawa subduction system during Early Cretaceous (c. Ma). Geological mapping and associated multidisciplinary studies on the regional (spatially widespread) Sambagawa metamorphism

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... h the eclogite-facies and main metamorphisms) have revealed the tectonic framework of the Late-Cretaceous Sambagawa subduction zone as follows: (i) a spreading ridge was approaching close to the trench; (ii) the subducting slab was coupled with the convective mantle at depth of > km; (iii) thickness of the hanging-wall continental crust waskm; and (iv) the forearc mantle wedge ( -km depth) was largely serpentinized. These features allow us to draw a semi-quantitative cross-section of the Sambagawa subduction zone at around -Ma, implying that boundary conditions for thermo-mechanical modeling aiming to simulate exhumation of high-P/T metamorphic rocks are now well constrained. It has also become clear that ultramafic blocks dispersed in the higher-grade part of the Sambagawa belt were derived from the mantle wedge, i.e. the corresponding part of the belt has been re-evaluated as a fossil subduction boundary of a relatively warm subduction zone. Field-based petrological studies in the Sambagawa belt can, therefore, have potential to provide invaluable information on material behaviors at the slab-mantle wedge interface including domains of episodic tremor and slip (ETS) in presentday warm subduction zones.