Hydrothermal mineral deposit

Hydrothermal mineral deposits are accumulations of valuable minerals which formed from hot waters circulating in Earth's crust through fractures. They eventually produce metallic-rich fluids concentrated in a selected volume of rock, which become supersaturated and then precipitate ore minerals. In some occurrences, minerals can be extracted for a profit by mining. Discovery of mineral deposits consumes considerable time and resources and only about one in every one thousand prospects explored by companies are eventually developed into a mine.[1] A mineral deposit is any geologically significant concentration of an economically useful rock or mineral present in a specified area.[2] The presence of a known but unexploited mineral deposit implies a lack of evidence for profitable extraction.[2]

Hydrothermal mineral deposits are divided into six main subcategories: porphyry, skarn, volcanogenic massive sulfide (VMS), sedimentary exhalative (SEDEX), and epithermal and Mississippi Valley-type (MVT) deposits. Each hydrothermal mineral deposit has different distinct structures, ages, sizes, grades, geological formation, characteristics and, most importantly, value.[3] Their names derive from their formation, geographical location or distinctive features.[3]

Generally, porphyry-type mineral deposits form in hydrothermal fluid circulation systems developed around felsic to intermediate magma chambers and/or cooling plutons. However, they did not precipitate directly from the magma. While, a skarn deposit is an assemblage of ore and calc-silicate minerals, formed by metasomatic replacement of carbonate rocks in the contact aureole of a pluton.[4] Volcanogenic massive sulfide deposits form when mafic magma at depth, (perhaps a few kilometers beneath the surface), acts as a heat source, causing convective circulation of seawater through the oceanic crust.[5] 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. Hydrothermal epithermal deposits consist of geological veins or groups of closely spaced geological veins. Finally, Mississippi Valley-type (MVT) are hosted in limestone or dolomite that was deposited in a shallow marine environment in a tectonically stable intraplate environment. As expected in such an environment, volcanic rocks, folding and regional metamorphism are absent as a general rule. MVT deposits commonly lie in close proximity to evaporites.[6]

  1. ^ Wilkinson, Jamie J. (2013-10-13). "Triggers for the formation of porphyry ore deposits in magmatic arcs" (PDF). Nature Geoscience. 6 (11): 917–925. Bibcode:2013NatGe...6..917W. doi:10.1038/ngeo1940. hdl:10044/1/52216. ISSN 1752-0894.
  2. ^ a b Misra, Kula C. (2000), "Formation of Mineral Deposits", Understanding Mineral Deposits, Springer Netherlands, pp. 5–92, doi:10.1007/978-94-011-3925-0_2, ISBN 9789401057523
  3. ^ a b Deb, Mihir; Sarkar, Sanjib Chandra (2017), "Energy Resources", Minerals and Allied Natural Resources and their Sustainable Development, Springer Singapore, pp. 351–419, doi:10.1007/978-981-10-4564-6_6, ISBN 9789811045639
  4. ^ Peters, W.C. (1987-01-01). Exploration and mining geology. Second edition.
  5. ^ Sahlström, Fredrik; Troll, Valentin R.; Palinkaš, Sabina Strmić; Kooijman, Ellen; Zheng, Xin-Yuan (2022-08-29). "Iron isotopes constrain sub-seafloor hydrothermal processes at the Trans-Atlantic Geotraverse (TAG) active sulfide mound". Communications Earth & Environment. 3 (1): 193. Bibcode:2022ComEE...3..193S. doi:10.1038/s43247-022-00518-2. hdl:10037/26716. ISSN 2662-4435. S2CID 251893360.
  6. ^ Cite error: The named reference :0 was invoked but never defined (see the help page).