Volcanogenic Massive Sulfide Ore Deposit
Volcanogenic massive sulfide ore deposits (VMS ) are a type of metal sulfide ore deposit, mainly Cu-Zn-Pb which are associated with and created by volcanic-associated hydrothermal events in submarine environments.
These deposits are also sometimes called volcanic-hosted massive sulfide (VHMS) deposits. They are predominantly layered accumulations of sulfide minerals that precipitate from hydrothermal fluids on or below the seafloor in a wide range of ancient and modern geological settings. In modern oceans they are synonymous with sulfurous plumes called black smokers.
They occur within environments dominated by volcanic or volcanic-derived (e.g., volcano-sedimentary) rocks, and the deposits are contemporary and coincident with the formation of associated volcanic rocks. As a class, they represent a significant source of the world's Cu, Zn, Pb, Au, and Ag ores, with Co, Sn, Ba, S, Se, Mn, Cd, In, Bi, Te, Ga and Ge as mining by-products.
Volcanogenic massive sulfide deposits are forming today on the seafloor around undersea volcanoes along many mid ocean ridges, and within back-arc basins and forearc rifts. Mineral exploration companies are exploring for seafloor massive sulfide deposits; however, most exploration is concentrated in the search for land-based equivalents of these deposits.
The close association with volcanic rocks and eruptive centers sets VMS deposits apart from similar ore deposit types which share similar source, transport and trap processes. Some volcanogenic massive sulfide deposits are distinctive in that ore deposits are formed in close temporal association with submarine volcanism and are formed by hydrothermal circulation and exhalation of sulfides which are independent of sedimentary processes. This can set VMS deposits apart from sedimentary exhalative (SEDEX) deposits. Host rock assemblages, textural relationships in sulfide minerals and hydrothermal alteration mineralogy are the best tools for distinguishing SEDEX from VMS deposits (Robb, 2005).
There is a subclass of VMS deposits, the volcanic- and sediment-hosted massive sulfide (VSHMS) deposits, that do share characteristics that are hybrid between the VMS and SEDEX deposits. Notable examples of this class include the deposits of the Bathurst Camp, New Brunswick, Canada (e.g., Brunswick #12); the deposits of the Iberian Pyrite Belt, Portugal and Spain, and the Wolverine deposit, Yukon, Canada.
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