The Mian-Lüe suture zone is a compo nent part of the Qinling-Dabie orogenic belt and one of the latest major suture zones between North and South China. It is a complica ted ophiolitic tectonic mélange zone consisting of tectonic slabs that belong t o dif ferent timestratigraphic units. Ophiolites are mainly distributed in the Lüe ya ng— Mianxian—Wuliba area, south Qinling and Suixian—Jingshan area, and south margi n o f the Dabie mountains. The ultrabasic rocks in the ophiolitic mélange zone incl u de harzbur gite and dunite which exhibit LREE depletion with remarkable positive Eu anomali es . The diabase dike swarm shows LREE enrichment but slightly negative Eu anomalie s. Metamorphosed volcanic rocks can be divided into three groups in terms of their REE geochemistry and trace element ratios of Ti/V, Th/Ta, Th/Yb and Ta/Yb. The f irst group is the MORBtype basalts with LREE depletion, representing the fragm e nts of oceanic crust and implying an association of MORBtype ophiolite and an ancient ocean basin between the Qinling-Dabie and Yangtze plates during the Midd le Paleo zoic—Early Mesozoic. The second group consists of metabasalts belonging t o the initial ocean crust type. The third group is composed of islandarc volcanic rocks incl uding th oleiitic basalts and a large amount of calcalkaline intermediateacidic volca n ic rock assemblage. This indicates that the Mianlüe limited ocean basin underwent a complete process of development, evolution and then vanished fro m late Palaeozoic to early Mesozoic; and Qinling-Dabie had become an inde pendent lithospheric microplate during that period.