| one publication added to basket [9089] | Hydrothermal mineralization in the Red Sea
Scholten, J.C.; Stoffers, P.; Garbe-Schönberg, D.; Moammar, M. (2000). Hydrothermal mineralization in the Red Sea, in: Cronan, D.S. (Ed.) Handbook of marine mineral deposits. CRC Marine Science Series, 17: pp. 369-395
In: Cronan, D.S. (Ed.) (2000). Handbook of marine mineral deposits. CRC Marine Science Series, 17. CRC Press: Boca Raton. ISBN 0-8493-8429-X. 406 pp., more
In: Kennish, M.J.; Lutz, P.L. (Ed.) CRC Marine Science Series., more
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| Authors | | Top |
- Scholten, J.C.
- Stoffers, P.
- Garbe-Schönberg, D.
- Moammar, M.
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| Abstract |
Hydrothermal activity in the Red Sea is linked to the divergent movement of the African and Arabian continental plates and the subsequent formation of new oceanic crost. The formation of hydrothermal deposits is facilitated in the Red Sea for two reasons: (1) The development of new oceanic crost is focused in relatively small areas, i.e., isolated deeps. (2) The occurrence of high saline brines in these deeps favors the preservation of the hydrothermal fluids and deposits. As a result, iron,manganese, sulfate, and sulfide sediment facies can be observed in the Red Sea deeps. The most concentrated deposits occur in the brine-filled Atlantis-II-Deep, an area which has been extensively investigated during the past 40 years. The Atlantis-II-Deep is thus one of the few locations in marine geoscience where the time variability of a hydrothermal system can be investigated. Between 1965 and 1997 a temperature increase of the lower brine in the Atlantis-II-Deep from 55.9°C to 67.2°C has been observed, suggesting an increase of hydrothermal activity there. In the same time period, concentrations of dissolved Mn and Fe in the brine increased slightly, whereas the concentrations of Cu decreased. Although active vents have never been observed, there are strong indications that hydrothermal fluids discharge in the SW-basin of the Atlantis-II-Deep. Based on the paragenesis of authigenic minerals in the sediments, formation temperatures of the hydrothermal precipitates between 110°C and <450°C have been estimated. Apart from in the Atlantis-II-Deep, hydrothermal deposits have been found in the Thetis, Nereus, Vema, and Gypsum deeps, but in these deeps ore concentrations are lower. Massive sulfides from the brine-filled Kebrit Deep are another type of hydrothermal mineralization in the Red Sea. lts porous and fragile sulfides, which are sometimes impregnated with tar, consist of two types: the first type (type I) is characterized by a mineral assemblage of pyrite, marcasite, bravoite, sphalerite, digenite, chalcocite, jarosite, and minor amounts of galena, with relatively high Zn and Pb concentrations. The second type (type II) of massive sulfide consists almost exclusively of pyrite with low trace metal contents. The lack of significant Cu enrichments in any of the sulfides and their mineral structure suggests a low formation temperature. Lead isotope data on the sulfides indicate that the metals may have derived from mixing between a basaltic and a more radiogenic end member source. Age estimates of the sulfides suggest that the type II deposits formed between 20,000 and 28,000 years ago, whereas type I sulfides are much younger (<5,000 years). Periods of hydrothermal activity with obviously different chemical composition of the hydrothermal fluids have also been observed in the Thetis Deep. To what extent periods of hydrothermal activity in the Red Sea deeps are connected to each other by, e.g., tectonic activity, is a matter of speculation and needs forther investigation. |
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