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

trending 1.5 km 2 closures with soil mercury exceeding 350 ppb Hg occur in the
anomalous areas (Figure 22).
zone is trending northwest.
The general configuration of the anomalous
This northwest trend corresponds with the geophysically
defined extent of the basin-bounding fault zone and the trend of
identified Pleistocene fault scarps to the north and south of the surveyed
area.
The superposed east-northeast trending mercury anomalies are on strike
with shear zones, mapped by Thorman (in press), in the Pinaleno Mountains to
the west.
The mercury anomalies may indicate a geothermal system in a basement
structural intersection and may indicate the southern closure of the hign
estimated temperature gradients at Artesia.
Ground Water Geochemistry and Geothermometry
Ground water in the Cactus Flat-Artesia area is one of three types of
chemistry.
Shallow non-artesian wells penetrating unconsolidated sand and
gravel nearest the Pinaleno Mountains are sodium bicarbonate water, while
deeper wells tapping confined aquifers and unconfined aquifers adjacent or
east of U.S. Highway 666 discharge sodium chloride-sulfate water.
The sodium
bicarbonate waters have the lowest temperatures, total dissolved solids (TDS)
and fluoride contents; conversely, the sodium chloride-sulfate waters show
temperatures up to 46 o C, TDS is between 1,000 milligrams per liter (mg/l) and
9,000 mg/l, and fluoride contents range between 1.0 and 14 mg/l. A third type
of water discharges from some shallow artesian wells and has an intermediate
sodium sulfate-bicarbonate-chloride composition with TDS
o
Temperatures of the latter type water range from 28 to 34 C.
less than 2,000 mg/l.
A possible mechanism for the intermediate composition water is mixing
of sodium bicarbonate water with sodium chloride-sulfate water; however,
mixing may not be a dominant mechanism because intermediate composition
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