Editing Hydrothermal circulation (section)

==Deep crust==
Hydrothermal also refers to the transport and circulation of water within the deep crust, in general from areas of hot rocks to areas of cooler rocks. The causes for this convection can be:
* Intrusion of magma into the crust
* Radioactive heat generated by cooled masses of granite
* Heat from the mantle
* Hydraulic head from mountain ranges, for example, the [[Great Artesian Basin]]
* Dewatering of metamorphic rocks, which liberates water
* Dewatering of deeply buried sediments

Hydrothermal circulation, in particular in the deep crust, is a primary cause of [[mineral]] deposit formation and a cornerstone of most theories on [[ore genesis]].

===Hydrothermal ore deposits===
During the early 1900s, various geologists worked to classify hydrothermal ore deposits that they assumed formed from upward-flowing aqueous solutions. [[Waldemar Lindgren]] (1860–1939) developed a classification based on interpreted decreasing temperature and pressure conditions of the depositing fluid. His terms: "hypothermal", "mesothermal", "epithermal" and "teleothermal", expressed decreasing temperature and increasing distance from a deep source.<ref>W. Lindgren, 1933, ''Mineral Deposits'', McGraw Hill, 4th ed.</ref> Recent studies retain only the ''epithermal'' label.  John Guilbert's 1985 revision of Lindgren's system for hydrothermal deposits includes the following:<ref>Guilbert, John M. and Charles F. Park, Jr., 1986, ''The Geology of Ore Deposits'', Freeman, p. 302 {{ISBN|0-7167-1456-6}}</ref>

* Ascending hydrothermal fluids, [[Magmatic water|magmatic]] or [[meteoric water]]
** [[Porphyry copper]] and other deposits, 200–800&nbsp;°C, moderate pressure
** Igneous metamorphic, 300–800&nbsp;°C, low to moderate pressure
** Cordilleran veins, intermediate to shallow depths
** Epithermal, shallow to intermediate, 50–300&nbsp;°C, low pressure
* Circulating heated meteoric solutions
** [[Carbonate hosted lead zinc ore deposits|Mississippi Valley-type deposits]], 25–200&nbsp;°C, low pressure
** [[Uranium ore deposits|Western US uranium]], 25–75&nbsp;°C, low pressure
* Circulating heated seawater
** [[Volcanogenic massive sulfide ore deposit|Oceanic ridge deposits]], 25–300&nbsp;°C, low pressure