Magmatic-hydrothermal silver deposits, argentiferous provinces and the main controlling factors of formation

Magmatic-hydrothermal silver deposits (MHSD) mainly include silver-only and silver-base metal deposits (generally average Ag grade > 100g/t) associated with magmatic-hydrothermal activities. MHSD are the major source of silver. In this contribution, more than 80 typical large and super-large MHSD all over the world are sorted and summarized, which are mainly classified into four types : epithermal (low-, intermediate-, and high-sulfidation) , porphyry, skarn and five-element deposits, among which the epithermal type is most important whereas porphyry and skarn types are subordinate. The large and super-large MHSD are mainly located in the East Pacific subduction zone and the eastern Central Asian orogenic belt, all of which are located on the continental basement, and the age is mainly in the Mesozoic and Cenozoic. The six silver metallogenic provinces are the China XingMeng argentiferous province, the United States Western Basin Ridge argentiferous province, Northwest Mexico argentiferous province, the Central Peru argentiferous-polymetallic province, the Bolivia silver-tin argentiferous province, and Russia Far East silver-tin argentiferous province. The argentiferous provinces are genetically related to large-scale acidic to intermediate-acidic magmatism, such as the silicic large igneous provinces with massive rhyolite ignimbrite, or the highly evolved magmatic rocks characterized by tin-rich rhyolite, topaz rhyolite, and quartz porphyry. These large-scale magmatic-hydrothermal activities are formed during tectonic transitions, such as from compression to extension or extension to compression. Relatively silver-rich hydrous continental lower crustal source, large-scale highly evolved magma, relatively weak preferentially partition of silver into sulfides and magnetite, high salinity fluids, focused fluid flow and efficient precipitation are important controlling factors for large-scale silver mineralization. The studies for silver are far behind that of copper and gold, and there are still many questions about magmatic-hydrothermal silver deposits, for instance, the linkage between argentiferous provinces and silicic large igneous provinces, the formation of silver mineralization related to molybdenum and tin system, the control of silver mineralization by magmatic evolution, and the exploration for silver prospects.