On Wednesday March 7th, Stefán Arnórsson, professor emeritus in the Faculty of Earth Sciences, will give a lecture on progressive water-rock interaction of surface- and up to 100°C ground-water in the Skagafjördur Province, N-Iceland.
The subject of the lecture is partly based on a newly published book, yet more detailed, by the speaker (chapter 6), entitled Jarðhiti og jarðarauðlindir (geothermal energy and Earth´s resources). The lecture will be given in English.
Venue: Lecture Hall N-132, ground floor in Askja
Stefán Arnórsson is one of the foremost experts in the geochemistry of water rock interaction and has been active in research in that field for half a century. He has taught geochemistry and related fields to generations of geology students at the University of Iceland.
The origin and age of ground-water has been inferred from general hydrological considerations and data on the isotopes of water (deuterium, oxygen-18 and tritium) and the mobile components, Cl and B. In surface water (in soil, rivers and streams) aqueous Ti, Fe and Al concentrations are already controlled by precipitation of metastable oxides and hydroxides. The pH of these waters are controlled by supply to CO2 from the atmosphere and decaying organic matter.
Progressive reaction of the ground-water with the bedrock after it has become isolated from the atmosphere involves increase in pH to as much as 10, mainly as a consequence of dissolution of pyroxene but also olivine. The pH increase and progressive primary mineral dissolution help bring the water to saturation of secondary minerals. In non-thermal ground water, Mg, K, Ca are already controlled if pH rises to over ~9. The mobility og Si increases with increasing temperature and Na and SO4 possess the highest mobility of all major components of the basaltic rock.