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Metals in deep liquid of the Reykjanes geothermal system, southwest Iceland; implications for the composition of seafloor black smoker fluids

V. Hardardottir, K. L. Brown, T. Fridriksson, J. W. Hedenquist, M. D. Hannington and S. Thorhallsson
Metals in deep liquid of the Reykjanes geothermal system, southwest Iceland; implications for the composition of seafloor black smoker fluids
Geology (Boulder) (December 2009) 37 (12): 1103-1106

Abstract

Seafloor hydrothermal systems precipitate Cu, Zn, and Fe sulfides at and below black smoker vents on the seafloor; as a result, the metal concentrations in the vent fluids are minimum values. We sampled deep, unboiled liquids from the Reykjanes geothermal reservoir, Iceland, and measured the metal concentrations. This active, seawater-dominated system, situated on the Mid-Atlantic Ridge, is the subaerial equivalent to mid-ocean-ridge hydro thermal systems. The liquids, collected at 1350-1500 m depth and 284-295 degrees C, contain 154-2431 mu M Fe (9-140 ppm), 207-261 mu M Cu (14-17 ppm), 79-393 mu M Zn (5-27 ppm), 0.6-1.4 mu M Pb (120-290 ppb), 6-31 nM Au (1-6 ppb), and 250-960 nM Ag (28-107 ppb). Fluids discharged at surface from the same wells have orders of magnitude lower metal concentrations due to precipitation caused by boiling and vapor loss during depressurization. The concentrations of Cu, Zn, and Pb in the high-temperature reservoir liquids at Reykjanes are similar to those in the highest-temperature black smoker discharges, whereas Au and Ag concentrations are one to two orders of magnitude higher at Reykjanes; lower-temperature seafloor fluids have lower metal contents, suggesting subseafloor deposition before discharge. The Reykjanes heat flux of 130 MW requires a liquid flux of approximately 100 kg/s; over 10 (super 4) yr, the minimum life of the system, 0.5 Mt each of Cu and Zn may have precipitated at depth.


ISSN: 0091-7613
EISSN: 1943-2682
Coden: GLGYBA
Serial Title: Geology (Boulder)
Serial Volume: 37
Serial Issue: 12
Title: Metals in deep liquid of the Reykjanes geothermal system, southwest Iceland; implications for the composition of seafloor black smoker fluids
Affiliation: University of Ottawa, Department of Earth Sciences, Ottawa, ON, Canada
Pages: 1103-1106
Published: 200912
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 29
Accession Number: 2010-007900
Categories: HydrochemistryEconomic geology, geology of energy sources
Document Type: Serial
Bibliographic Level: Analytic
Annotation: With GSA Data Repository Item 2009273
Illustration Description: illus. incl. 1 table, sketch map
N63°46'60" - N63°49'60", W22°49'60" - W22°40'00"
Secondary Affiliation: GEOKEM, NZL, New ZealandIceland GeoSurvey, ISL, Iceland
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201005
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