Temperature/flow statistics and thermomechanics of low-temperature geothermal systems in Iceland

A survey of low-temperature geothermal activity in Iceland shows that there is a strong positive correlation between the temperature and the mass flow of the systems. The relation is very clearly displayed by the thermal systems in Central Northern Iceland. Subdividing the temperature interval from 20/dgC to 100°C into 8 intervals of equal length and plotting the average system flow in each interval against the average temperature of the interval we find that the mass flow increases with the temperature. At the lower end this relation is the result of a conductive cooling of the thermal water as it ascends to the surface. At temperatures above 50°C convective effects appear to be the dominant cause. A very simple lumped element analysis of the low-temperature systems results in reasonable estimates of important flow parameters. The convective downward migration of fracture spaces along the walls of mafic dikes appears to be a dominant thermomechanical process in the development of the low-temperature systems in Northern Iceland.