VMS成矿系统定位预测与勘查OA

Volcanogenic massive sulfide(VMS)deposits,associated with submarine volcanic activity,constitute a metallogenic spectrum ranging from Cu,Cu-Zn,and Cu-Pb-Zn to Pb-Zn types.These deposits are significant sources of base and precious metals such as copper,zinc,lead,silver,and gold.Due to their high ore grades,diverse useful components,and high economic value,VMS deposits are globally important targets for mineral exploration.This paper systematically summarizes the classification,ore-forming environments,characteristics of the metallogenic system,and positioning prediction indicators of VMS deposits.We propose that VMS deposits are products of submarine volcanic hydrothermal systems in extensional tectonic settings,generally related to sodium-rich marine volcanic rocks.The VMS metallogenic system exhibits the following characteristics:① The ore mineral assemblage is dominated by pyrite,followed by pyrrhotite,chalcopyrite,sphalerite,and galena,often associated with gold and silver mineralization.② The deposits exhibit a classic"T-shaped"architecture with stratiform massive sulfides overlying a discordant mineralized-alteration stockwork(pipe);the massive orebodies form via submarine exhalative sedimentation,while the underlying pipe represents the hydrothermal conduit.③ A typical metal zoning sequence exists from the conduit toward the outer exhalative facies,following a Cu→Cu-Zn→Cu-Pb-Zn→Pb-Zn transition,with the Zn/Cu ratio systematically increasing outward,which can serve as an indicator to trace the exhalative center.④ Wall-rock alteration mainly occurs in the footwall,including two main types:alteration pipes and stratabound alteration.Residual hydrothermal fluids may also alter the hanging-wall rocks near the vents and/or form polymetallic veins.(5)Deposits may occur in clusters associated with multi-center mineralization.The massive sulfide orebody,mineralized-alteration pipe,and polymetallic veining serve as mutual prospecting indicators.Identifying volcanic eruptive centers(areas with volcanic breccia,agglomerates,and subvolcanic intrusions)and favorable ore-bearing horizons(containing gossan,pyritization,hydrothermal sedimentary rocks,etc.)is essential for"favorable horizon prospecting".During the optimization of geochemical anomalies,priority should be given to pathfinder elements such as Cd and Tl,as well as the"sodium depletion zone"in the footwall.Magnetic,gravity,induced polarization(IP),and transient electromagnetic(TEM)surveys are the most effective geophysical methods.Taking the VMS exploration in three volcanic-sedimentary basins(Hokuroku in Japan,Ashele in Xinjiang,China,and Shire in Ethiopia)as examples,this paper introduces successful exploration cases where prospecting breakthroughs were achieved by applying the VMS metallogenic system model,positioning prediction indicators,and geochemical-geophysical techniques.The aim is to provide references for scientifically formulating exploration plans and efficiently evaluating VMS deposits.