Jökull - 01.12.1984, Page 109
Figure 1. The Borgarfjördur region and its main tectonic features.
/. mynd. Yfirlilskort af Borgarfirði. Sýnd eru brotakerfi, megineldstöðvar, Hreðavatnsmislœgið og ás
Borgarnesandhverfunnar.
ture hot springs in Iceland has been estimated
about 1825 l/s with a weighted average tempera-
ture of 67°C (Gudmundsson and Pálmason 1981).
With 23% of the total discharge and 33% of the
total thermal output, the Reykholt thermal sys-
tem is the largest low temperature thermal sys-
tem in Iceland.
Fig. 2 shows the distribution of hot springs of
the Upper Borgarfjördur region. It also indicates
the temperature and discharge of the hot springs.
The three largest thermal fields are the Deildar-
tunga-Kleppjárnsreykir field with the discharge
253 1/s, whereof 180 1/s belong to the Deildar-
tunga hot spring and 70 1/s to the Klepp-
járnsreykir hot spring (Georgsson et al. 1978),
and the Hurdarbak-Sídumúli and Vellir fields
with 45 1/s and 32 1/s, respectively.
CHEMISTRY OF THE THERMAL
WATER
In Borgarfjördur four thermal systems can be
distinguished on the basis of chemistry and the
fifth has been proposed from the geographical
distribution of hot springs. Within each system
the concentration of each element shows fairly
regular distribution. Three thermal systems are
adjacent to the Reykholt thermal system. The
Baer system, to the west, can be distinguished
from the Reykholt system by slightly different
chemistry (higher salinity) and higher Cl/B ratio.
The Húsafell system, to the east, has different
chemical composition due to flow through acid
rock, associated with the extinct Húsafell central
volcano, and a different deuterium content. The
Brautartunga system, to the south, has a similar
chemical composition and deuterium content as
the Reykholt system but is separated from it
geographically. The fifth thermal system is the
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