N. Gulec, GEOCHEMISTRY OF THERMAL WATERS AND ITS RELATION TO THE VOLCANISM IN THE KIZILCAHAMAM (ANKARA) AREA, TURKEY, Journal of volcanology and geothermal research, 59(4), 1994, pp. 295-312
Thermal waters issuing through the Tertiary aged volcanics in the Kizi
lcahamam (Ankara) area are all alkali-bicarbonate waters with temperat
ures ranging from 28-degrees-C to 86-degrees-C. The waters from the to
wn center (MTA-1 and KHD-1 drilling wells, Big Bath and Small Bath) ha
ve the highest temperature and an intermediate TDS content, in compari
son to the waters sampled from the localities outside the town center
(Mineral Water Spring and Sey Bath). The Mineral Water Spring is chara
cterized by the lowest temperature and the highest TDS content. The wa
ters from the Sey Bath have an intermediate temperature and the lowest
TDS content. The variations in the temperature and the chemical compo
sition of the waters can be accounted for by a combination of processe
s including mixing between cold-shallow and hot-deep waters, boiling e
ither before or after mixing, steam heating and conductive cooling. Th
e chemical geothermometers, silica-enthalpy and enthalpy-chloride mixi
ng models suggest a reservoir temperature of 124-190-degrees-C for the
Kizilcahamam region, and a maximum of 71 % deep, hot component for th
e thermal waters. Within the framework of water-rock interaction, the
volume of volcanic rocks necessary to supply the annual water output h
as been estimated as 16.5 x 10(6) m3 a-1; the volume of the volcanic r
ocks necessary to supply the annual chemical output of the thermal wat
ers has been estimated, on the basis of cation contents, as 16,785 m3
a-1. This suggests that, for the thermal waters to obtain their chemic
al composition, only 0.1 % of the volcanics is required to have underg
one leaching. As this amount is rather low, the waters seem to have ob
tained their cation contents almost totally from the volcanics nearby.
On the other hand, the bicarbonate enrichment in the Kizilcahamam wat
ers points to the fact that groundwaters dissolve CO2 arising, probabl
y, from a magmatic body solidifying at depth, which can also account f
or the heat source of the Kizilcahamam geothermal system.