Hydrothermal silica chimney fields in the Galapagos Spreading Center at 86°W.
Herzig, Peter M., Becker, Klaus P., Stoffers, Peter, Bäcker, Harald and Blum, Norbert (1988) Hydrothermal silica chimney fields in the Galapagos Spreading Center at 86°W. Earth and Planetary Science Letters, 89 (3-4). pp. 261-272. DOI 10.1016/0012-821X(88)90115-X.
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Abstract
Silica chimneys were discovered in 1985 at 86°W in the rift valley of the Galapagos Spreading Center at 2600 m depth (“Cauliflower Garden”). The inactive chimneys lack any sulfides and consist almost entirely of amorphous silica (up to 96 wt.% SiO2, opal-A); Fe and Mn oxides are minor constituents. Oxygen isotope data show that formation of the silica chimneys took place at temperatures between 32°C (+29.9‰ δ18O) and 42°C (+27.8‰ δ18O).Th/Udating reveals a maximum age of 1440 ± 300y. Amorphous silica solubility relations indicate that the silica chimneys were formed by conductive cooling of pure hydrothermal fluids or by conductive cooling of a fluid/seawater mixture. Assuming equilibrium with quartz at 500 bars, initial fluid temperatures of more than 175°C (i.e., a concentration of > 182 ppm SiO2) were required to achieve sufficient supersaturation for the deposition of amorphous silica at 40°C and 260 bars. If the silica chimneys originate from the same or a similar fluid as higher-temperature ( < 300°C) sulfide-silica precipitates found nearby (i.e., 2.5 km away), then subsurface deposition of sulfides may have occurred.
Document Type: | Article |
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Keywords: | Geochemical cycle; Hydrothermal springs; Oxygen isotope ratio; Radiometric dating; Siliceous rocks; Silica chimney; Thorium isotopes; ISE, Galapagos Rift; GARIMAS, RV Sonne, SO32, SO39 |
Research affiliation: | Kiel University |
Refereed: | Yes |
Open Access Journal?: | No |
DOI etc.: | 10.1016/0012-821X(88)90115-X |
ISSN: | 0012-821X |
Projects: | GARIMAS |
Expeditions/Models/Experiments: | |
Date Deposited: | 18 May 2016 07:56 |
Last Modified: | 18 May 2016 07:59 |
URI: | http://oceanrep.geomar.de/id/eprint/32889 |
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