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Unusual mixed silica–carbonate deposits from magmatic–hydrothermal hot springs, Savo, Solomon Islands

Smith, D.J.; Jenkins, G.R.T.; Petterson, M.G.; Naden, J.; Fielder, S.; Toba, T.; Chenery, S.R.N.. 2011 Unusual mixed silica–carbonate deposits from magmatic–hydrothermal hot springs, Savo, Solomon Islands. Journal of the Geological Society, 168 (6). 1297-1310. 10.1144/0016-76492011-003

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Abstract/Summary

The volcanic island of Savo, Solomon Islands, hosts an active hydrothermal system discharging unusual alkaline (pH 7–8) sulphate-rich, chloride-poor fluid, with variable admixtures of Ca–Mg–HCO3- rich fluid. Hot springs and their outflow streams precipitate a variety of deposits, including travertine, silica sinter and unusual mixed silica–carbonate rocks. Travertine fabrics are dominated by ray-crystal calcite, associated with rapid abiotic precipitation from a supersaturated solution. Sinter is produced by evaporation of thermal waters, and downstream samples contain preserved traces of micro-organisms, which potentially acted as templates for precipitation. Trace element chemistry of sinters and travertines includes anomalously high levels of Te, indicating a magmatic origin for a component fluid in the hydrothermal system. Springs are close to or at saturation with both calcite and amorphous silica. Increased contributions from the Ca–Mg–HCO3 end-member favours calcite formation; this fluid is of low-temperature origin, and as such is favoured by high rainfall. Mixed samples show cyclical changes between silica and carbonate precipitation, potentially as a result of seasonal variation in rainfall.

Item Type: Publication - Article
Digital Object Identifier (DOI): 10.1144/0016-76492011-003
Programmes: BGS Programmes 2010 > Minerals and waste
ISSN: 0016-7649
Additional Keywords: hydrothermal fluids, geothermal systems
NORA Subject Terms: Earth Sciences
Date made live: 09 Nov 2011 13:17
URI: http://nora.nerc.ac.uk/id/eprint/15797

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