Advances in the study of porphyry tungsten deposits

P Porphyry tungsten deposit is the third most important type in the world, but its research is weak and scattered. This paper systematically summarizes and analyzes the research results in recent years from our team and other scholars about porphyry tungsten deposits. The results show that porphyry tungsten deposits are widely distributed in the Circum-Pacific metallogenic belt and the Alps-Himalayan metallogenic belt, and occur in magmatic arc, intraplate, and continental collision settings. Most of them were formed in Mesozoic and a few in Paleozoic. Porphyry tungsten mineralization is closely related to weakly oxidized, highly fractionated I-type or A-type hypabyssal granitic rocks, which were mainly derived from re-melting of the ancient crust, contaminated with a small amount of juvenile crust and/or depleted mantle and/or marine sediments. The ore-forming metals and fluids were dominantly originated from related magmatic rocks, and the Ca²⁺, Fe²⁺, and Mn²⁺ needed for W mineralization could be provided by the strata and magmatic rocks through water-rock reaction. The initial ore-forming fluids of porphyry tungsten deposits in magma arc and intraplate settings belong to the NaCl-H₂O system with medium-high temperature, medium-high salinity and low CO₂ content, while those under continental collision setting belong to NaCl-H₂O-CO₂ system with medium-high temperature, medium-low salinity and high CO₂ content. W tends to be enriched in the coexisting fluid phase in the process of melt-fluid differentiation, and then migrates in the form of monomer tungstate, polytungstate, and fluorotungstate. The mechanisms of mineral precipitation mainly include fluid immiscibility/boiling/CO₂ escape ±fluid mixing and water- rock reaction. Scheelite and wolframite are the dominant W-bearing minerals in porphyry tungsten deposits, and their occurrence may be mainly controlled by the fluorine content in relevant magma-fluid system.