The Chating Cu-Au ore deposit in the Xuancheng City of Anhui Province is a large deposit newly discovered in shallow overburden area of the Middle and Lower Yangtze River Valley Metallogenic Belt. It is located in the central uplift of Nanling-Xuancheng Meso-Cenozoic volcanic-sedimentary basin. The geological study of the deposit indicates that the ore bodies occur in the concealed quartz diorite porphyritic intrusion formed in Early Cretaceous. The strong mineralization keeps obviously with the cryptoexplosive breccia pipe and the range of the former is slightly larger than that of the latter. The alteration types are dominated by silication, potash-feldspathization, biotization, sericitization (muscovitization) , and pyritization, with obvious zoning characteristics, while skarnization, chlorinization and kaolinization scattered in the mineralization area as strip belts or gobbets. The ores have brecciated, veined, veinlet-stockwork, fine granular disseminated structures, and replacement remnant texture, exsolution texture, etc. Magnetite-hematite and skarn minerals grow in the brecciated and veined ores. Especially anhydrite develops in veins and even forms anhydrock. The metallic minerals in the ores are dominated by pyrite and chalcopyrite as well as a small amount of bornite, tetrahedrite, tennatite, etc. The breccia in cryptoexplosion breccia pipe is mainly composed of quartz diorite porphyrite, and the cementation mainly has two types : one is rock debris or rock powder which has similar composition with quartz diorite porphyrite; another is hydrothermal minerals mainly including quartz and anhydrite. Three types inclusions like aqueous, vapor-aqueous, and daughter mineral-bearing inclusions are found in the quartz of the ores, and the component of vapor phase in the inclusions is mainly water. The daughter mineral-bearing inclusions are mainly found in quartz paragenesis with pyrite which has crakes formed in the earlier stage, with homogenization temperature range from 360 degrees C to 420 degrees C and higher salinity and density. There two homogenization temperature rages, 270 similar to 300 degrees C and 190 similar to 220 degrees C were gained from the vapor-aqueous and aqueous inclusions developed at the main metallogenic stages of copper and gold, corresponding with lower salinity and density. The geochemical characteristics of H-O, C-O, S and Pb isotopes indicate that the ore-forming fluids, the ore-forming metal elements and the compound elements are mainly from magma or magmatic rocks, while sedimentary strata and atmospheric precipitation also contribute to mineralization, but play a relatively small role. The Re-Os age of pyrite is consistent with the U-Pb age of the zircon in quartz diorite porphyrite within the margin of error, indicating that its mineralization is closely related to the magmatic intrusion and hydrothermal activity of the metallogenic area in Late Yanshanian. Based on the comprehensive geological and geochemical characteristics of the deposit, comparing with the porphyry deposit and volcanic-subvolcanic (epithermal) deposit, it is considered that the Chating Cu-Au ore deposit in the Xuancheng City is a cryptoexplosive breccia type deposit related to the Early Cretaceous hypabyssal intrusive of quartz diorite porphyrite, which is a new type deposit in the Middle and Lower Yangtze River Valley Metallogenic Belt.
