Systematic studies of the ophiolites and associated volcanics stretching more than 1500 km from the Derni-Nanping-Pipasi-Kangxian area in the west to the Qingshuihe area of the south Dabie Mountains in the east indicate the existence of a suture zone (the Mianl(u)e suture)and a vanished paleo-ocean basin (the Mianlue paleo-ocean basin) in the region. From west to east, ophiolitic melange associations distribute discontinuously along the suture. Rock assemblages include ophiolite, island arc and oceanic island rock series. The Mianlue paleo-ocean basin experienced its major formation and expending episode during the Carboniferous-Permian period. The finding of the suture zone and the paleo-ocean basin is tectonically significant in timing the collision between the North China-Qinling and Yangtze blocks and determining the formation and evolution of the Qinling orogenic belt.