Rit (Vísindafélag Íslendinga) - 01.06.1976, Page 36
and
öo(D) — Ömd) — 4.63
( t»
\100
)
50(o18) = öL(o18) -0.975
(— - 1
Vioo
)
In high temperature areas where the base temperature is higher
than 200°C, the correction to he added to the measured ðD-value of
the surface water is of significance. The borehole H - 14 in Krísuvík
is an example of such a case. The water in H — 14 has a hase tem-
perature of approximately 230° C. The deuterium content of the
water phase collected at the outflow of H — 14 has ÖL(D) = — 45%0
The corrected value of the original water in the hole is 80(D) =
-51%o-
In low-temperature areas in Iceland, (these are areas with base
temperature lower than 150°C), the correction to be added to the
measured 8D-value is less than — 2%0.
From the above discussion it can be concluded that where the
base temperature is known the original deuterium content of geo-
thermal water in its circulation base can be found by measuring
the deuterium content of hot spring water collected at the surface.
For low-temperature areas in Iceland, the correction to be made is
usually very small and without importance. For high-temperature
areas, however, it is necessary to make such corrections.
In many geothermal areas where drilling has been performed
and direct temperature measurements have been made in the drill
holes, the base temperature is well known. In other areas, where
no such drillings have been performed and no direct measurements
of the base temperature are available, the only information avail-
able is obtained by using indirect methods.
One such method, which uses the silicate content of thermal
water, is treated in detail by Arnórsson (1970 and 1973). This
method has proved to be sucessful in cases such as drill holes and
hot springs, where a considerable amount of water flows rapidly
up to the surface. It is questionable, however, whether the method
is applicable for open hot springs discharging small amounts of
water. Another method uses the Na+, K+ and Ca++ content of the
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