OPHIOLITES IN THE JAPANESE ISLANDS - TYPICAL SEGMENT OF THE CIRCUM-PACIFIC MULTIPLE OPHIOLITE BELTS

Japanese ophiolites range from early Paleozoic to Cenozoic in age, and their residual peridotite ranges from fertile lherzolite to strongly depleted, calcic clinopyroxene-free harzburgite. They occur as nappes and melanges in a nappe pile that is made up mainly of forearc and deep-sea sediments that have been accumulating in the subduction zones since late Paleozoic time. Older ophiolites occupy upper structural positions in the nappe pile. The wide temporal and petrologic variations, as well as the fact that the ophiolites are younger going downward through a nappe pile, are common features among the circum-Pacific ophiolite belts. The time and space distribution of the Japanese ophiolites most closely resembles that in the Klamath Mountains of the western United States.