ACCRETION OF JAPANESE ISLAND ARCS AND IMPLICATIONS FOR THE ORIGIN OF ARCHEAN GREENSTONE BELTS

The present-day region of arc-arc collision between the Izu-Bonin Arc and mainland Japan (Honshu Arc) in the western Pacific (called the Izu Collision Zone or ICZ) provides a useful kinematic model for the development of many Archean greenstone belts. The compositional assemblage, thermal structure and structural style of the crust in the ICZ are very similar to those inferred for many Archean greenstone belts. In both cases, thick, young and flaky arc crust with a high heat flux is in collision with another crustal block. The ICZ has resulted in the imbrication of very thick slices of crust and associated sediments juxtaposed against older accretionary prisms. Many Archean greenstone belts show similar geological features, and we suggest that the incremental imbrication of the crust was a common tectonic style in some Archean convergent margins.