0
~
0
~
Volcanic Gases and Geothermal Waters
63
Or-----------------------------------~------------_,
-50
-100
Wairakei--~
LarderellO+------- 0 S
The Geysers-.... -------------Q-::._0 H kl
Iceland--'---------------e a
. /
NiI7-e-----------(5Q--------------~----QtJ'--e---0--(J0Q0-----Lassen Park
/
/.--~8----- Steamboat Springs
6018 (%0)
Fig. 26. Observed isotopic variations in near-neutral chloride type geothermal waters and in geothermal steam .• : local meteoric waters or slightly heated nearsurface ground waters; .: hot springs or geothermal water; 0: high temperature,
high pressure, geothermal steam. Niland = Salton Sea Geothermal Area. (After
CRAIG, 1963)
In volcanic emanations and probably in primary magmatic gases,
CO2 is the next largest component after H20. From material balance
calculations (Section C, X) and from comparison with isotopic data of
carbonatites and diamonds, it may be postulated that this CO2 has a
b 13 C-value around - 7%0. However, as may be seen from Fig. 27, the
mean b I3 C-value of CO2 from geothermal areas varies between - 3 and
- 5%0. On the other hand attempts to sample CO2 from liquid lavas
(NAUGHTON and TERADA, 1954; WASSER BURG et aI., 1963) yield a wide
range in b 13 C between -14 and - 28%0 (see also HOEFS, 1972). The
reasons for these discrepancies are not well understood. On the one hand
it is possible that the CO2 is influenced through isotopic exchange with
sedimentary carbonates (CRAIG, 1963), on the other differences of physico-chemical conditions of the primary magma could also be responsible
(OHMOTO,1972).
In addition to CO2 , CH4 and CO have been identified in fumaroles.
The CH4 content rarely exceeds 1 % of the total gas content. The isotopic
composition of CO2 and CH4 in hot springs have been determined by
CRAIG (1953,1963) and HULSTON and MCCABE (1962) (see Fig. 27).
~
0
~
Volcanic Gases and Geothermal Waters
63
Or-----------------------------------~------------_,
-50
-100
Wairakei--~
LarderellO+------- 0 S
The Geysers-.... -------------Q-::._0 H kl
Iceland--'---------------e a
. /
NiI7-e-----------(5Q--------------~----QtJ'--e---0--(J0Q0-----Lassen Park
/
/.--~8----- Steamboat Springs
6018 (%0)
Fig. 26. Observed isotopic variations in near-neutral chloride type geothermal waters and in geothermal steam .• : local meteoric waters or slightly heated nearsurface ground waters; .: hot springs or geothermal water; 0: high temperature,
high pressure, geothermal steam. Niland = Salton Sea Geothermal Area. (After
CRAIG, 1963)
In volcanic emanations and probably in primary magmatic gases,
CO2 is the next largest component after H20. From material balance
calculations (Section C, X) and from comparison with isotopic data of
carbonatites and diamonds, it may be postulated that this CO2 has a
b 13 C-value around - 7%0. However, as may be seen from Fig. 27, the
mean b I3 C-value of CO2 from geothermal areas varies between - 3 and
- 5%0. On the other hand attempts to sample CO2 from liquid lavas
(NAUGHTON and TERADA, 1954; WASSER BURG et aI., 1963) yield a wide
range in b 13 C between -14 and - 28%0 (see also HOEFS, 1972). The
reasons for these discrepancies are not well understood. On the one hand
it is possible that the CO2 is influenced through isotopic exchange with
sedimentary carbonates (CRAIG, 1963), on the other differences of physico-chemical conditions of the primary magma could also be responsible
(OHMOTO,1972).
In addition to CO2 , CH4 and CO have been identified in fumaroles.
The CH4 content rarely exceeds 1 % of the total gas content. The isotopic
composition of CO2 and CH4 in hot springs have been determined by
CRAIG (1953,1963) and HULSTON and MCCABE (1962) (see Fig. 27).