Magmatic-Hydrothermal Vein Systems

Vein-type molybdenum (Mo) mineralization is concentrated in the Huaxiong block. It includes quartz veins, fluorite veins and carbonatite dykes, as represented by the Zhaiwa, Tumen and Huanglongpu deposits, which are introduced in this chapter. They yield pre-Yanshanian ages’ events and provide insights into pre-Yanshanian multistage Mo mineralization and enrichment. The Zhaiwa Mo-Cu-bearing quartz veins were formed by high-salinity magmatic fluids. It is an analog of the upper domain of a porphyry system in the continental arcs. The 1.76-Ga mineralization coevals with the eruption of the Xiong’er Group volcanic rocks that developed in a continental arc associated with the outgrowth of the Columbia supercontinent. The Tumen Mo-fluorite deposit is hosted by the Neoproterozoic Luanchuan Group dolostones. Four-stage hydrothermal mineralization progressed from early white fluorite veins, through purple fluorite-molybdenite-pyrite and sulfide-calcite veins, to late carbonate ones. The 0.85-Ga mineralization is synchronous with a syenite event. They are a prelude of the Rodinia supercontinent breakup occurring in the postcollisional extension setting. The Triassic Huanglongpu carbonatite dyke-hosted system is unique for both Mo- and HREE-enrichment. It was formed by the high-salinity CO₂-rich magmatic fluids. The carbonatite resulted from a low-degree partial melting of a refractory oceanic slab, likely due to the Triassic closure of the Paleo-Tethys Ocean or the Pangea supercontinent assembly.