S. Arnorsson | USGS Science

USGS2000

The boron isotope systematics of Icelandic geothermal waters: 1. Meteoric water charged systems

We have measured the boron isotope composition and boron and chloride concentrations of 27 Icelandic geothermal fluids from both high- and low-temperature systems. The δ 11 B values range from −6.7‰ in the Krafla system, to +25.0‰ in a warm spring from the Southern Lowlands. In addition, we have also determined the δ 11 B values of basaltic glass from Nesjavellir (−5.3 ± 1.4‰) and travertine from Snaefellsnes (−22 ± 0.5‰). The B isotope and Cl/B systematics of the high-temperature systems are dominated by the composition of the local basalts. The lower temperature systems show evidence for mixing with B and Cl of a marine origin, together with some uptake of B into secondary mineral phases. The data from the Snaefellsnes geothermal system indicate that the fluids have undergone interaction with basalts that have undergone significant low-temperature alteration by seawater.

Geochimica et Cosmochimica Acta↗

USGS1983

The nature of carbon dioxide waters in Snaefellsnes, western Iceland

Over 20 occurrences of thermal and non-thermal waters rich in carbon dioxide are known in the Snaefellsnes Peninsula of western Iceland. On the basis of the thermal, chemical and isotopic characteristics of these waters, and hydrological considerations, it is concluded that they represent meteoric waters which have seeped to variable depths into the bedrock. Ascending carbon dioxide gas originating from intrusions or the mantle mixes with the meteoric waters to produce carbon dioxide waters: at considerable depth in the case of the thermal carbon dioxide waters but close to the surface in the case of cold carbon dioxide waters. The occurrence of carbon dioxide waters cannot be regarded as evidence for underground geothermal reservoirs.

Geothermics↗