Notes: Not all ore deposits will contain secondary minerals. The epigenetic (different times) and syngenetic (at the same time) is based on the time frame for the formation of the host rock and the ore. Some ores cab be classified as both syngenetic and epigenetic.
Secondary: Platinum, Uranium, Silver, diamonds
Host: magmatic basalt
Process: Magmatic intrusion and later transported by fluids
Examples: Gold Rush (India and any country river or flowing water)
Syngenetic and Epigenetic
Process: Chemical and physical weathering due to erosion
Examples: in the tropical areas
Other: Kimberlite Indicator Minerals (KIM)
Process: Formed in depths over 100 km under the temperature of 900 – 1200 C and high pressure. Ideal conditions are in the old, cold, thick Archean (>2.5 Ga). Rapid igneous intrusions known as Kimberlite pipes.
Examples: Ekati, Diavik and Snap Lake (unusual kim. sill), Canada
Mafic Igneous Intrusion Associated Deposits
Secondary: Gold, Copper, Molybdenum, (PEG)
Host: mafic and ultramafic magma and the type of rock depends on the degree of melting and the type of country rock.
Process: Magmatic intrusions result in partitioning of elements and contamination of the melt by assimilation of the host rock. Gravitation segregation of sulphur result in sulphide ore to form at the bottom of the melt. It is also possible to produce this type of ore through the meteorite impacts, rift/continental flood basalt-associated sills and dykes, volcanic flows and troctolite intrusions.
Examples: Sudbury (meteorite impact-unusual), Voisey’s Bay and Thompson, Canada
Greenstone Related Quartz Veins
Other: Chlorite, Actinolite, Amphiboles
Host: quartz vein
Process: Intrusion of epithermal fluids and regional metamorphism. Usually associated with areas of wide spread regional metamorphism.
Examples: Abitibi Greenstone Belt
Epigenetic and Syngenetic
Secondary: Molybdenum and Gold
Other: Chalcopyrite, Bornite, Chalcocite
Host: magmatic rocks, stockwork (veins and breccias)
Process: Intrusion of heavy mineral rich fluids in subduction zones (leading to hydrothermal alterations). Stockwork texture, veins amd breccia are typical types of rocks. If the formation is caused due to hydrothermal alternation, then the ore is classified as an epigenetic formation.
Examples: El Teniente, Chile
Volcanogenic Massive Sulphide (VMS) Deposits
Primary: Zinc, Copper, Gold, Silver, Lead
Secondary: Cobalt, Tin, Barium, Manganese, Cadmium, Selenium, etc
Host: stockwork sulphides and ophiolite
Process: Magmatic process which result in geothermal fluids (“black smokers”)
Examples: Since they form in tectonic settings, it has an age range between the modern seafloor materials to as far as 3.4 Ga. Therefore, the deposits are globally distributed along old and young spreading centers.
Sedimentry Exhalative Deposits (SedEx)
Primary: lead, zinc, silver
Secondary: barite, gold, copper, tungsten
Host: Underwater sedimentary rocks
Process: Mid-Ocean Ridge (MOE) hydrothermal fluids (“black smokers”)
Examples: Sullivan, Canada
Mississipi Valley Type Deposit (MVT)
Primary: zinc, lead
Host: carbonate hosted sulphides
Process: precipitation from circulating groundwater at relatively low temperature (brines transported)
Examples: edges of the sedimentry basin in Canada.
Unconformity Associated Deposit
Secondary: lead, radium, cadmium, thorium and REE
Process: Unconformities in the basins, but there are 14 different types have been identified. In Canada, they are usually found in unconformities between Proterozoic silliclastic basins and metamorphic basement.
Examples: Athabasca Basin, Canada