Regional geologic setting and metallogenesis of central Inner Mongolia, China: Guides for exploration of mesothermal gold deposits

The central Inner Mongolia district forms one of the most important metallogenic provinces in China, because the district has been influenced by repeated distinct tectonomagmatic activity. The genetic relationships and spatial-temporal evolution of ancient tectonism and associated geologic structures and metallogeny are discussed in this paper. An integrated genetic model for gold metallogeny is proposed. During the late Archean to Paleozoic, repeated north-southward accretional tectonics between the Paleo-Mongolia Oceanic Plate and the North China Paleoplate led to the formation of not only the E-W-trending deep crustal faults but also a series of sedimentary, volcanic and metamorphic events. Numerous stratiform, Fe, Cu (Au), Pb-Zn and REE ores formed in association with sedimentation and volcanism within the platform environments at this time. During the late Paleozoic to early Mesozoic, the central Inner Mongolia district was largely influenced by northwestward subduction of the Circum-Pacific Plate beneath the Eurasia Plate. A series of NE-SW-trending faults, together with S-type granitoid intrusions, formed as a result of this subduction. Mesothermal-type gold deposits (e.g., the Saiyingwusu, Laoyanghao, Shibaqin, Wulashan and Donghuofang deposits) formed during the Permian to Jurassic (158.5 to 275.4 Ma), preferentially at or near the intersections between NE-SW-trending and E-W-trending fault systems. At these intersections, the areas of not only late Paleozoic to early Mesozic granitoids but also late Archean to early Proterozoic metamorphic rocks (especially the gold-rich, Seertengshan, Wulashan and Bayan Obo group rocks) may be promising exploration targets for mesothermal gold deposits.