RESEARCH PROGRESS ON VOLCANOGENIC MASSIVE SULFIDE DEPOSIT

The VMS (Volcanogenic Massive Sulfide) deposits can be classified into four types, i.e. Kuroko-type, Cyprustype, Besshi-type and Sullivan-type, in respect to their tectonic settings and host lithology. There are commonly two major styles of footwall alteration associated with VMS deposits:footwall alteration pipes which occur immediately below the massive sulfides; and semiconformable or strata-bound footwall alteration which can be regionally extensive. As with footwall alteration, hanging-wall zone alterations vary from pipe shapes to semiconformable zones. There are two alternative sources which have been suggested for the metals in VMS deposits:leaching from the ore-bearing volcanic rocks and related basement rocks by heated seawater above a magmatic intrusion or a volcanic magma chamber; and direct input of a magmatic volatile phase from the magma chamber. The fluids involved are derived dominantly from seawater penetrating downward through the basement rocks. Fluid inclusion and stable isotope studies suggest that abundant magmatic fluid component may have been incorporated into the circulating fluid system. VMS deposits are characterized by well developed metal zonation patterns defined by a typical sequence from Fe to Fe-Cu to Cu-Pb-Zn to Pb-Zn-Ba in an upward and lateral sense and this zonation reflects the evolution of fluids and the growth mechanism of the massive sulfide mound with time. The four-stage model with the change of the fluid temperature through time can interpret the classic massive sulfide mound-type deposit well.