The source and relative age of non-thermal and up to 90°C ground waters in the Skagafjoerdur tholeiite flood basalt province, N-Iceland

摘要

Combined data on hydrogeology and the natural tracers δ~2H, δ~(18)O, ~3H, Cl and B have been used to identify the origin and relative age of ground waters and < 90°C geothermal waters in the basalt province of the Skagafjoerdur valley system in N-Iceland and to delineate flow directions. Ground waters and thermal waters in the relatively permeable Quaternary formations in the interior highlands are of local origin and a few years to a few decades old. Ground waters in the less permeable Mid-Tertiary flood basalts north of the highlands are older. Under the steep mountains on the east side of the Skagafjordur valley they represent precipitation that has fallen on high ground in these mountains and are 100's to 1000's of years old. On the west side of the Skagafjoerdur valley the geothermal waters are a mixture of recent local precipitation and a Pre-Holocene precipitation.