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The source of metals and mineralizing solutions for SEDEX deposits is deep formational saline waters and brines that leach metals from clastic sedimentary rocks and the underlying basement. The fluids derived their salinity from the evaporation of seawater and may have been mixed with meteoric water and pore water squeezed out of the sediments.
World-wide distribution of MVT deposits (red), clastic sediment-hosted (green), and unclassified (blue) lead-zinc deposits. Source: USGS. Carbonate-hosted lead-zinc ore deposits are important and highly valuable concentrations of lead and zinc sulfide ores hosted within carbonate (limestone, marl, dolomite) formations and which share a common genetic origin.
Volcanogenic massive sulfide ore deposits, also known as VMS ore deposits, are a type of metal sulfide ore deposit, mainly copper-zinc which are associated with and produced by volcanic-associated hydrothermal vents in submarine environments. [2] [3] [4] These deposits are also sometimes called volcanic-hosted massive sulfide (VHMS) deposits
Sources of hydrothermal solutions include seawater and meteoric water circulating through fractured rock, formational brines (water trapped within sediments at deposition), and metamorphic fluids created by dehydration of hydrous minerals during metamorphism. Metal sources may include a plethora of rocks.
The hydrothermal fluid leaches metals as it descends and precipitates minerals as it rises. Sedimentary exhalative deposits, also called sedex deposits, are lead-zinc sulfide deposits formed in intracratonic sedimentary basins by the submarine venting of hydrothermal fluids. These deposits are typically hosted in shale.
Massive sulfide deposits are ore deposits that have significant stratiform ore bodies consisting mainly of sulfide minerals.Most massive sulfide ore deposits have other portions that are not massive, including stringer or feeder zones beneath the massive parts that mostly consist of crosscutting veins and veinlets of sulfides in a matrix of pervasively altered host rock and gangue.
In both cases fluids and metals formed from volcanic and sedimentary products in tectonic processes, but also show differences in the origin of the source and the processes involved. [26] This model is associated with fluid ascent from devolatilization of a subducting slab and overlying sediment wedge. [26]
Carlin–type gold deposits are sediment-hosted disseminated gold deposits. These deposits are characterized by invisible (typically microscopic and/or dissolved) gold in arsenic rich pyrite and arsenopyrite. [2] This dissolved kind of gold is called "invisible gold", as it can only be found through chemical analysis. [3]