sentences:  Active hydrothermal systems found on the submarine parts of IOCMs give us a chance to study how many of earth's important ore deposits formed.Crust and lithosphere produced by the IBM arc system during its ~50 Ma history are found today as far west as the Kyushu-Palau Ridge (just east of the West Philippine Sea Basin), up to 1,000 km from the present IBM trench.The IBM arc system is the surficial expression of the operation of a subduction zone and this defines its vertical extent.