Abstract: Quite a few gold deposits have been found recently in the southern Sonid Zuoqi, Inner Mongolia, such as the Bayan Bold, Bayan Har and others. The Bayan Bold gold deposit is located to the north of the Sonid Zuoqi ophiolitic melange belt, and the Bayan Har gold deposit is in the west of the belt, which is thought to be a part of the Sonid Zuoqi-Hegenshan suture zone between the southern margin of the Siberian plate and the northern margin of the North China plate. Based on a comprehensive study, the authors hold that there are two genetic types of gold deposits in Sonid Zuoqi. The Bayan Bold gold deposit, which is related to granite-porphyry formed in Early Paleozoic island arc environment, is of a mesothermal type. And the Bayan Har gold deposit, which is related to the granite-porphyry intruded in Sonid Zuoqi ophiolitic melange belt in the middle-late stage of the Late Paleozoic, is of an epithermal type.

Key words: gold, mesothermal type, epithermal type, Sonid Zuoqi, Inner Mongolia