Gases of Icelandic hydrothermae

Gas contents associated with hydrothermal systems in Iceland were investigated and four types of hydrothermae identified. A spatial distribution is recognized in which the nitrogenous thermae are restricted to the areas of pre-Quaternary and Early Quaternary volcanism, the CO₂ hydrothermae to the Snaefellsnes Peninsula, the nitrogenous-CO₂ types to the areas of pre-Holocene volcanic activity of the median zone, and the hydrogenous types to the area of active volcanism in the median zone. Reasons for this distribution are proposed in terms of the origin of the gases. -R.E.B.