This is a cartoon 3D viewer of an active VMS black smoker developing on the oceanic crust on the seafloor (good rock crusher). As you can see they are scattered all around the world, but I’m going to talk a little bit about the distribution later on. Here’s a bunch of the better-known deposits you may have heard of. VMS deposits have been forming throughout geological history and they still are forming on the seafloor today. In spite of that, they really are economically significant with 27% of Canada’s copper production and almost 50% of its historical zinc production, and 20% of the Pb having come from this group of deposits. There are only a few big enough or high enough grade to be economic. The deposits are pretty common although, as with any deposit type. If the heat chamber is long-lived you may get flat lenses of massive sulphide, each fed from the same fault, beginning successively younger as you go up through the stratigraphy. VMS deposits often form as clusters over a large intrusive heat source. VMS is basically mushroom shaped, Streamer zone tends to be copper rather than zinc rich. The deposits consist of a massive sulphide cap that formed on the seafloor and sort of lies parallel between two stratigraphy and an underlying feeder zone or streamer zone as it is usually called. VMS deposits are dominated by copper and zinc, but there are a number of other minor minerals, including: lead, silver, gold, cobalt, tin, selenium, magnesium, cadmium and a whole host of other ones that are associated with them. You’ll remember this cross section from reads on both porphyry deposits and epithermal, in the case of VMS deposit, we are basically looking at a submarine high sulfidation epithermal deposit venting from an underlying hot chamber into the sea. VMS will emit black plume of hot water venting from one of the chimneys. Most dikes and sills associated with ore are of intermediate composition.If we start with VMS Volcanogenic Massive Sulphide Ore Deposits and their Mineralization we see from this image shows some of the sulphide chimneys associated with the model black smoker VMS deposit. Dike injection is predominantly pre-ore, with lamprophyres and diabase apparently closely related in time to mineralization. Magmatic segregations commonly take the form of dikes and sills, and other gradational relationships between ore and igneous rock are occasionally noted. Post-ore injections may seriously dilute ore deposits, or may by heat action effect changes in mineral composition and distribution.Genetic relationships between dikes, sills, and ore are not well understood. Primary features of dikes and sills, such as permeability, width, and configuration are sometimes important in localizing ore.Contemporaneous and post-ore dikes and sills in a few cases are important as indicators of the factors controlling movements of ore solutions. Intersections of dikes and sills with fault zones, formation contacts, and other planar structures provide excellent sites for ore deposition. Fracturing at dike contacts also creates channelways and loci for deposition the nature of this fracturing is variable, and depends on relative competency and on the nature and direction of differential stress at the contact. Incompetent dikes and sills serve as dams, ponding ore solutions at their contacts. Dikes and sills commonly are competent, brecciated bodies that act as host rocks or as channelways for ore solutions. Most significant are the structural controls by pre-ore dikes on ore localization. A review of geologic literature shows many important relationships between ore deposits and associated dikes and sills.
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