World Library  
Flag as Inappropriate
Email this Article


Article Id: WHEBN0000286699
Reproduction Date:

Title: Hydrothermal  
Author: World Heritage Encyclopedia
Language: English
Subject: Gypsum, Breccia, Bastnäsite, Ozarks, Metasomatism, Volcanogenic massive sulfide ore deposit, Walter Barshai, Rare earth mineral
Publisher: World Heritage Encyclopedia


Hydrothermal circulation in its most general sense is the circulation of hot water; 'hydros' in the Greek meaning water and 'thermos' meaning heat. Hydrothermal circulation occurs most often in the vicinity of sources of heat within the Earth's crust. This generally occurs near volcanic activity, but can occur in the deep crust related to the intrusion of granite, or as the result of orogeny or metamorphism.

Seafloor hydrothermal circulation

Hydrothermal circulation in the oceans is the passage of the water through mid-oceanic ridge systems.

The term includes both the circulation of the well known, high temperature vent waters near the ridge crests, and the much lower temperature, diffuse flow of water through sediments and buried basalts further from the ridge crests. The former circulation type is sometimes termed "active", and the latter "passive". In both cases the principle is the same: cold dense seawater sinks into the basalt of the seafloor and is heated at depth whereupon it rises back to the rock-ocean water interface due to its lesser density. The heat source for the active vents is the newly formed basalt, and, for the highest temperature vents, the underlying magma chamber. The heat source for the passive vents is the still-cooling older basalts. Heat flow studies of the seafloor suggest that basalts within the oceanic crust take millions of years to completely cool as they continue to support passive hydrothermal circulation systems.

Hydrothermal vents are locations on the seafloor where hydrothermal fluids mix into the overlying ocean. Perhaps the best known vent forms are the naturally-occurring chimneys referred to as black smokers.

Volcanic and magma related hydrothermal circulation

Hydrothermal circulation is not limited to ocean ridge environments. The source water for hydrothermal explosions, geysers and hot springs is heated groundwater convecting below and lateral to the hot water vent. Hydrothermal circulating convection cells exist any place an anomalous source of heat, such as an intruding magma or volcanic vent, comes into contact with the groundwater system.

Deep crust

Hydrothermal also refers to the transport and circulation of water within the deep crust, generally 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, particularly 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 which were assumed to have formed from upward flowing aqueous solutions. Waldemar Lindgren developed a classification based on interpreted decreasing temperature and pressure conditions of the depositing fluid. His terms: hypothermal, mesothermal, epithermal and teleothermal were based on decreasing temperature and increasing distance from a deep source.[1] Only the epithermal has been used in recent works. John Guilbert's 1985 redo of Lindgren's system for hydrothermal deposits includes the following:[2]

  • Ascending hydrothermal fluids, magmatic or meteoric water
    • Porphyry copper and other deposits, 200 - 800 °C, moderate pressure
    • Igneous metamorphic, 300 - 800 °C, low - moderate pressure
    • Cordilleran veins, intermediate to shallow depths
    • Epithermal, shallow to intermediate, 50 - 300 °C, low pressure
  • Circulating heated meteoric solutions
    • Mississippi Valley type deposits, 25 - 200 °C, low pressure
    • Western US uranium, 25 - 75 °C, low pressure
  • Circulating heated seawater

See also


This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.

Copyright © World Library Foundation. All rights reserved. eBooks from World Library are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.