Mineralization and Its Controls

In Qinling Orogen, the Mo deposits occur in an orogenic area with thickened crust, especially in overriding slabs of A-type subduction. The most intensive Mo mineralization occurred in Yanshanian, associated with granitoids. Early Precambrian rocks and their derivative sediments have high Mo concentrations and host giant and large Mo deposits. Physicochemical features of country rocks control mineralization types, locations, and metal inventories. Ore-causative granitoids are usually porphyry stocks of high-K calc-alkaline to alkaline affinity. Magmatic or metamorphic hydrothermal mineralization generally includes four stages, with fluids evolving from magmatic/metamorphic, through boiling and mixing, to meteoric in nature. The PMDs (porphyry Mo deposits) show much stronger alterations of K-feldspar, fluorite, and carbonate, but weaker phyllic, propylitic, and argillic alterations than porphyry Cu deposits; and so do the Yanshanian PMDs relative to the pre-Yanshanian. The pure carbonic, carbonic-aqueous, and daughter mineral-bearing carbonic-aqueous inclusions are present in PMDs in continental rifts or collision belts, but absent in continental arcs, indicating that they result from CO₂-rich and CO₂-poor fluids, respectively. Carbonic-aqueous inclusions have high Mo contents. The Re content in molybdenite is a tracer of ore geneses and sources, with 50 ppm being the criteria between continental and oceanic crust or mantle.