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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.
These deposits are also sometimes called volcanic-hosted massive sulfide (VHMS) deposits. The density generally is 4500 kg/m 3 . They are predominantly stratiform accumulations of sulfide minerals that precipitate from hydrothermal fluids on or below the seafloor in a wide range of ancient and modern geological settings.
The dispersal of hydrothermal fluids throughout the global ocean at active vent sites creates hydrothermal plumes. Hydrothermal deposits are rocks and mineral ore deposits formed by the action of hydrothermal vents. Hydrothermal vents exist because the Earth is both geologically active and has large amounts of water on its surface and within ...
Different mineral associations precipitate during the typical stages of mineralization that characterize the life span of such systems. [1] [2] [3] Minerals present in a hydrothermal system or a fossil volcanogenic massive sulfide deposit are deposited passively or reactively.
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.
Eventually a point is reached where the minerals start to crystallise out. [2] Minerals formed in this way are called primary, or hypogene, minerals. Sulfur is a common component of the fluids, and most of the common ore metals, lead, zinc, copper, silver, molybdenum and mercury, occur chiefly as sulfide and sulfosalt minerals. [3]
Sphalerite is amongst the most common sulfide minerals, and it is found worldwide and in a variety of deposit types. [8] The reason for the wide distribution of sphalerite is that it appears in many types of deposits; it is found in skarns , [ 25 ] hydrothermal deposits , [ 26 ] sedimentary beds, [ 27 ] volcanogenic massive sulfide deposits ...
The ore fluids of MVT deposits are typically low temperature (100 °C–150 °C) and have the composition of basinal brines (10–30 wt.% NaCl equivalent) with pH's of 4.5–5 (buffered by host carbonates). This hydrothermal fluid may or may not carry the required sulfur to form sulfide minerals.