Jökull - 01.12.1965, Page 21

TABLE 2.
mg/1 1. 2. 3. 4.
Si02 512.0 170.0 171.0 15.2
Na 242.0 64.4 406.0 10.0
K 32.0 1.5 29.0 0.9
Ca 1.0 1.6 136.0 8.5
Mg- 0.1 0.5 32.0 2.5
C1 267.0 28.4 84.0 6.0
F 2.1 1.0 2.2 0.25
SO4 57.3 18.7 38.0 10.2
HCO3 9.8 47.6
CO3 48.6 50.4
OH 23.5
Diss. solids 1221.0 340.0 1660.0 76.0
T°C 100.0* 100.0** 41.0
P" 9.75 9.4 6.4 7.35
1. Hveragerði, drillhole G-8, 3. 1. 1963.
2. Reykjavík, drillhole G-4, 21. 7. 1960.
3. Lýsuhóll, carbonated spring, 30. 9. 1958.
4. Múlakvísl, glacier river, 1. 10. 1963.
*) Base temperature 230° C.
**) Base temperature 146° C.
calcium, magnesium and bicarbonate are more
similar in amount to waters of carbonated
springs.
The only component of the analysis in Table
1 which might be looked upon as magmatic in
origin is bicarbonate (i. e. COo). During the
jökulhlaups, however, considerable amounts of
SOo and H^S are released, but the amounts is
not known. Sorne of the sulfate in the water is
probably oxidized SO2 or H2S, but the amount
is linrited by the amount of oxvgen present in
the ice. The presence of sulphur dioxide lias
not been proven analytically, but its distinct
smell is a relatively good indicator. Ellis (1959)
nrade theoretical calculations on the composi-
tion of gasmixtures similar in molecular conr-
position to volcanic and geothernral gases, at
various temperatures and pressures. At low to
medium pressures SOo is the dominant sulphur
component at high temperatures, but the
amount of H2S increases with lower tempera-
tures. The theoretically predicted compositions
compare well with actually nreasured gasmix-
tures such as the volcanic gases from Surtsey,
where SO2 is the dominant sulphur conrponent
at 1100° C. (Sigvaldason and Elísson 1966). In
the Icelandic geothermal areas, SO2 has never
been found and here the highest measured
tenrperatures are 230° C. (Böðvarsson and
Pálmason 1961). The presence of SOo in the
gases from Grínrsvötn would therefore indicate
higher temperatures than found in otlrer high
temperature areas in Icalend.
An interesting aspect of this phenomenon is
the buildup of the chemical concentration in
the lake water during a known length of time.
The concentration of the Sept. 6th sample is
in some aspects conrparable to low temperature
thermal waters in Icelancl, which are believed
to be in equilibrium with the wallrock at depth,
at a temperature of 150 to 170° C. The base
temperature in the Grímsvötn area is probably
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