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

sidence that was created by ground water removal.
Additional leveling data
reported by Holzer (1980) show up to 1.25 m of subsidence since 1972 over
the graben, but no net uplift over the horst.
However, Holzer (1980) pointed
out that aerial photographs taken in 1935 over the Bowie area show many polygonal
earth fissures over the horst. No significant ground water withdrawal occurred
before 1935; therefore, these fissures may not be subsidence related.
As to
whether or not the 1935 earth fissures are definitely related to uplift of
the horst, it is speculative, because earth fissuring in many areas of southeastern
Arizona is reported by DuBois and Smith (1981) during the 1887 Sonoran
earthquake.
Therefore, the fissures seen in 1935 photographs may have originated
during the Sonoran earthquake and may not indicate local tectonism.
Conclusion
A spatial coincidence of wells, producing sodium bicarbonate water with
low magnesium, high Na-K-Ca geothermometers, and an apparent structural intersection,
which is inferred from ground water falls and gravity data, support
the hypothesis that a deep (>2 km)
moderate-temperature geothermal reservoir
o
(~124 C) occurs south of Bowie. Well D-13-28-l5DCC, which has the highest Na-
K-Ca temperature (124°C), is the most anomalous well from a temperature and
depth standpoint.
o
This well, 145 m deep, has a discharge temperature of 35 C
and an estimated average temperature gradient of l24°C/km.
All other wells in
the area have estimated temperature gradients between 30 and 80 o C/km and a mean
temperature gradient of 49 0 C/km.
Further studies are advised before drilling a deep test into this possible
deep reservoir.
Heat flow studies and geochemical modeling are needed to site
a deep hole.
A shallow «600 m) geothermal resource does exist at B~wie and it has a
reservoir temperature ranging between 35 and 45 0 C.
The geothermal water has
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