Controls over the chloride concentration of submarine hydrothermal vent fluids; evidence from Sr/Ca and 87Sr/86Sr ratios

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doi: 10.1016/0012-821X(92)90072-4
Authors:Palmer, M. R.
Author Affiliations:Primary:
Bristol Univ., Dep. Geol., Bristol, United Kingdom
Volume Title:Earth and Planetary Science Letters
Source:Earth and Planetary Science Letters, 109(1-2), p.37-46. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0012-821X
Publication Date:1992
Note:In English. 29 refs.; illus. incl. 1 table
Summary:Sr and Ca are transported as chloride complexes in submarine hydrothermal vent waters with the Sr and Ca concentrations being controlled by equilibration with secondary mineral phases (mainly epidote and anorthite-albite). The relative proportions of albite and anorthite precipitated from hydrothermal fluids are also dependent on the Cl level of fluids due to sodium metasomatism of the oceanic crust. The Sr/Ca ratio of albite is higher than that of coexisting anorthite, hence the Sr/Ca ratios of the vent waters are also a function of Cl concentrations. The Sr isotope composition of hydrothermal fluids is determined by the mixture of sea-water Sr passing through the anhydrite precipitation zone and Sr leached from basalt. The proportion and absolute amount of sea- water Sr in the hydrothermal waters can be calculated from the 87Sr/86Sr ratio of sea-water, local basalt and the vent fluids themselves, and is also dependent on the Cl concentrations of the fluids. These two observations have been used to examine the factors controlling chloride concentration of submarine hydrothermal fluids. The data support precipitation of a Cl-rich mineral phase and hydration of oceanic crust as the major processes controlling Cl concentrations in intermediate-Cl vents. The Cl levels of vent fields with extreme-Cl concentrations appear to be controlled by supercritical brine condensation followed by mixing of the brine and vapour phases. [Author's abstract] [P.Br.]
Subjects:Alkaline earth metals; Calcium; Chloride ion; Chlorine; Geochemistry; Halogens; Hydrothermal conditions; Isotopes; Metals; Mid-ocean ridges; Sea water; Sr-87/Sr-86; Stable isotopes; Strontium; Vents; Atlantic Ocean; East Pacific; East Pacific Rise; Mid-Atlantic Ridge; Pacific Ocean; Ratios
Abstract Numbers:92M/4289
Record ID:1992023075
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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