geothermal resource potential of the safford-san simon basin, arizona

Bowie Area
Introduction
At least 20 irrigation wells in the area surrounding Bowie pump 30 to
37°C water from depths of 183 to 610 m (Table 1, Figure 1). Chemical quality
of the thermal water is good; TDS of these waters ranges mostly between 250
and 500 mg/l (Table 2). Fluoride concentrations are generally less than 3.0
mg/l; although a few wells produce water with fluoride over 7.0 mg/l.
These
thermal waters are useful for irrigation and a few are suitable for drinking
because their fluoride contents are less than 1.4 mg/l.
Geochemistry
A wide variation of dissolved constituents occurs in the thermal waters
at Bowie.
Most of these waters are either sodium bicarbonate or sodium chloridesulfate
chemistry, and they have no readily distinguishable correlation among
chemical type and measured temperature.
This may indicate that the variability
in compositions is due to contact of these waters with different kinds of rock
in shallow «600 m)
aquifers.
Chemical geothermometer calculations are also highly variable; thermal
waters which have very low calcium and magnesium concentrations have the highest
Na-K-Ca geothermometer temperatures (Table 3).
Waters with relatively very
low magnesium concentrations are frequently associated with the higher temperature
zones of known geothermal systems (Ellis and Mahon, 1977).
The
sodium bicarbonate chemistry of these waters suggests that the reservoir is
contained in basement rock composed of either fractured volcanic or felsic
crystalline rocks.
A deep reservoir temperature of l24°C is inferred by the
Na-K-Ca geothermometer.
In other waters, all of which have relatively high
calcium concentration and which are trending toward sodium chloride-sulfate
o
chemistry, the calculated Na-K-Ca temperatures are all below 95 C.
The Na-K-Ca
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