Geochemistry of CO2-rich waters in Iceland

Autor: Stefán Arnórsson, D. Thomas, Dennis K. Bird, Kate Maher
Rok vydání: 2016
Předmět:
Zdroj: Chemical Geology. 444:158-179
ISSN: 0009-2541
DOI: 10.1016/j.chemgeo.2016.09.002
Popis: CO2-rich waters in Iceland from volcanic systems of the Mid-Atlantic Ridge and off-rift volcanic areas of Iceland provide insights into the interactions between CO2-rich fluids and basaltic crust. These waters, from the Snaefellsnes Peninsula, within the South Iceland Seismic Zone and on the margin of the Torfajokull central volcano, are chemically and isotopically distinct from surface waters, groundwaters and low and high-temperature geothermal fluids in Iceland. Our conceptual model for the evolution of thermal and non-thermal CO2-rich waters (~ 4–80 mmol/kg ΣCO2 (aq); 6.6–192 °C) suggests that lower subsurface temperatures during retrograde alteration and cooling of a geothermal system increase the aqueous solubility of CO2, which allows anomalously high aqueous CO2 concentrations. The elevated CO2 concentrations result in slightly acidic pH (average in situ pH of 6.40), which leads to increased dissolution of primary and hydrothermal silicate minerals. Equilibrium with respect to carbonate minerals, calculated using measured solute concentrations, suggests that carbonate mineral reactions control the water compositions in these systems more than in high-temperature systems, and that hydrothermally altered basalts are sufficiently reactive to promote carbonate mineralization during geologic CO2 sequestration (GCS). Water-rock interaction with previously hydrothermally altered basalts releases trace elements to the aqueous phase to levels above the World Health Organization drinking water limit. The elements of environmental concern include arsenic (
Databáze: OpenAIRE
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