Jökull - 01.12.1987, Side 11

Fig. 3. Anomaly map of mercury in soil
and radon in soil air in the Hrafntin-
nusker area. Contours show values
above background. Shaded areas in-
dicte >3 and >4 times background val-
ues for mercury and radon, respective-
ly. For mercury background values
range from 33.9 to 46.8 ppb. Squares
indicate hot springs/fumaroles. — Kort
sem sýnir kvikasilfur og radon íjarðvegi
a svœði við Hrafntinnusker. Línur af-
marka svœði sem hafa hœrri gildi en
nemur bakgrunni. Bakgrunnsgildi fyrir
kvikasilfur liggja á bilinu 33.9-46.8
Ppb. Ferningar tákna hveri og gufu-
augu.
N
RADON
er compositional features of the sodium-chloride waters
are similar to those of geothermal waters in basaltic
terrain.
Fumarole steam at Torfajökull contains generally
0.2-0.4% total gas by volume. C02 is always the dom-
inant gas constituent (>70%) but H2S and H2 amount to
2-8% and 0-10%, respectively. The gas compositions
are comparable with those found in some other high-
temperature fields in Iceland located in basaltic forma-
tions indicating that the same secondary mineral as-
semblages control the gas compositions despite the dif-
ference in rock composition.
The chemical composition of hot springs at Land-
mannalaugar indicates subsurface temperatures as high
as 265°C (Arnórsson 1985). Gas chemistry indicates
even higher temperatures (>300°C) for this and other
parts of the geothermal field.
Helium isotope ratios as high as 23.4 times atmo-
spheric have been observed in fumarole steam at Torfa-
jökull (Poreda et al. 1984). These high ratios are taken to
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