Medium-scale porphyry Cu-Mo-(Au-Ag) deposit, consisting of several parallel veins in an early Paleozoic granodiorite porphyry (U-Pb zircon isotopic age: 466 to 694 Ma) in a northern belt, and in greenschist at the contact to a porphyry in a southern belt. The host metamorphic rock (Bainaimiao Group) is intruded by porphyry and consists of Mesoproterozoic island arc volcanic and sedimentary rocka with a U-Pb zircon isotopic age of 1,130 Ma. These metamorphic rocks underwent Late Silurian intense shearing. The host granodiorite porphyry is controlled by east-west-trending ductile shear zones. The ore minerals occur in disseminations and veinlets. The deposit is closely related to silica alteration.

The Bainaimiao ore district encompasses the large Bainaimiao porphyry Cu-Au deposit, the middle Bainaimiao vein-type Au deposit, and several Cu and Au prospects. Strata ranging in age from the Cambrian to Quaternary are exposed within the ore district. The large Bainaimiao porphyry Cu-Au deposit contains 0.6 Mt of Cu, 20 t of Au, and associated Mo and Ag. The deposit is divided into two ore zones based on the characteristics of the ore bodies. The southern zone comprises the II, III, IV, V, VI, VII, X, and XI ore bodies. These ore bodies are observed in flattened and lenticular forms in metamorphic rocks (sub-groups III and V of Bainaimiao Group). Their occurrence is consistent with the direction of the regional tectonic trends and schistosity of host rocks. The metallic minerals in these ore bodies include pyrite, chalcopyrite, bornite, molybdenite, pyrrhotite, sphalerite, galena, and electrum. In the northern zone, the VIII, IX, XII, and XIII ore bodies are situated. These are found within the ore-related granodiorite porphyry and in contact with metamorphic rocks. Ore types primarily include veinlets, veins, and dissemination. Sulfides found in these ore bodies include chalcopyrite, pyrite, molybdenite, and bornite.
Event I primarily originates from the northern zone and deeper sections of ore bodies. There, the rocks exhibit minimal deformation and lack the preferential orientation of minerals. The samples analyzed to reflect Event II are largely derived from the southern zone, where the local geological conditions exhibit characteristics of Event II. The rocks of interest developed distinct schistosity, and minerals display a preferred orientation. Veins analyzed as part of Event III intersect both the granodiorite porphyry and metamorphic rocks.

Bainaimiao is an important deposit on the northern margin of NCC. Its mineralization characteristics display both porphyry-style alteration features and obvious signs of later orogenic modification. It is a polymetallic deposit dominated by copper with associated gold and molybdenum. Wall-rock alteration in the mining area is relatively well developed, dominated by K-feldspathization, biotitization, sericitization, silicification, chloritization, and epidotization, with subordinate carbonatization. Among these, K-feldspathization and silicification are closely related to mineralization, while carbonatization is largely unrelated and mainly represents a post-ore alteration. The southern and northern ore sections show distinct differences in alteration types. The northern ore section is characterized by the development of K-feldspathization, while biotitization is more developed in the southern ore section. Other alteration types occur in both ore sections. Mineralization is divided into three main stages: the early quartz-pyrite stage, the middle quartz-sulfide stage, and the late quartz-carbonate stage. In the early stage, the primary ore minerals are pyrite and pyrrhotite, with minor chalcopyrite. In the middle stage, the main ore minerals are chalcopyrite and molybdenite, with lesser amounts of pyrite, galena, and sphalerite. Late stage is characterized by thick quartz and calcite veins, with vein widths ranging from 5 to 10 cm.

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