The Mesoproterozoic volcanic activities took place in the Langsh an Mountains— Zh arta i Mountains region along the northwestern margin of the North China Craton. The produc ts of the volcanic activities are a suite of mafic volcanic rocks. The mafic vol canic rocks are present in the Mesoproterozoic Zhartai Group. Thes e maf ic volcanic rocks were metamorphosed into the greenschists and plagioamphibolites in the end of the Mesoproterozoic. Our studies indicate that they belong to t he normal mafic rock series. The petrochemical and geochemical data suggest that the suite of the volcanic rocks be low and mediumK basalt and analogous to oc e anic tholeiite. It is suggested that the volcanic activities should have occurre d durin g the intensive depressing stage of the north and south rift troughs in Langshan Mts.—Zhartai Mts. The isotope, REE and trace element data on the rocks, or e and min e rals indicate that the formation of the large and superlarge copperpolymetalli c deposits in the area is closely related to the Mesoproterozoic magmatic act ivities.