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

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waters occur in confined or artesian aquifers. Confined aquifers have limited hydrologic connection with underlying or overlying aquifers. Another mechanism is therefore preferred to explain th~ apparent continuum in ground water chemistry in the Cactus Flat-Artesia area. In order to further delineate ground water chemistry and test for mixing, milliequivalent ratios of anions are compared to lithium concentrations. Chloride, sulfate, and bicarbonate were selected because they represent major constituents in the Cactus Flat-Artesia ground waters; and they are not likely to be involved in ion exchange with clay. Lithium concentration is used as a comparison to the anion ratios because it is not likely to be involved in equilibria reactions due to its high solubility in the presence of chloride. While lithium may be acquired in ground waters by ion exchange, the reverse is unlikely due to its low electron negativity compared to similar-sized ions. The green clay facies and the evaporite facies are geologically inferred as the source of lithium, chloride, and sulfate due to the probable presence of evaporite minerals. Mixing of sodium bicarbonate water with sodium chloridesulfate water is possible; but it is tentatively ruled out because the correlation of high chloride-sulfate waters with high concentration lithium waters is not observed until the logarithmic concentrations are compared (Figure 23). Mixing generally shows a linear correlation instead of the observed exponential relationship. An exponential relationship suggests that equilibria or exchange reactions are responsible for the variation in ground water chemistry. Also, lithium and anion ratios show no correlation to temperature or TDS, which would be expected if mixing were occurring between a deep homogeneous sodium chloride-sulfate water and the shallow sodium bicarbonate water. Because differences in ground water chemistry due to equilibria or exchange reactions are indicated, Na-K-Ca geothermometry on these ground waters 63
may be erroneous. However, silica concentration is frequently used in geothermal exploration to infer deep geothermal reservoir temperatures with the assumption that silica concentration in shallow thermal wells and spring waters is derived from leakage of water out of a geothermal reservoir and that the silica concentration has not been diluted by mixing, or that if mixing has occurred, the mixing ratio can be determined in order to calculate silica concentration before mixing (Fournier and others, 1974; Fournier and Truesdell, 1974). The main requirements for silica geothermometry are that silica in solution is determined by temperature-dependent equilibrium with a solid form of silica in the reservoir and that no equilibration occurs after the thermal waters leak from the geothermal reservoir and cool. This latter requirement is reasonable because water flow or leakage rates probably exceed the kinetics of quartz equilibria in water at lower temperatures. Because Cactus Flat-Artesia thermal waters originate from confined aquifers which are apparently heated in a conductive heat regime, silica concentrations should be in temperature-dependent equilibrium with either quartz, chalcedony, or alpha-cristobalite. Silica concentrations for ground waters in the Cactus Flat-Artesia area are all supersaturated with respect to quartz at measured temperatures. In addition, inspection of the chemical analyses of Cactus Flat-Artesia ground waters listed in Table 2 shows relatively high concentrations of dissolved silica (up to 50 mg/l) in cold sodium bicarbonate ground waters, which have high bicarbonate concentrations and neutral pH. Several studies of low-temo perature «50 C) ground waters in contact with felsic rocks or sediment derived from these rocks have shown that silica concentration is a function of dissolved carbon dioxide concentration following the reaction in equation 1 (Garrels, 1967; Garrels and MacKenzie, 1967; Paces, 1972). 64
Page 1:
GEOTHERMAL RESOURCE POTENTIAL OF TH
Page 5 and 6:
TABLE OF CONTENTS PAGE List Of Figu
Page 7 and 8:
FIGURES FIGURE 1 FIGURE 2 FIGURE 3
Page 9 and 10:
TABLES TABLE 1 TABLE 2 2A 2B 2C 2D
Page 11:
INTRODUCTION o In the Safford-San S
Page 14 and 15:
Land Status Figure 2 shows land own
Page 16 and 17:
asin are published in Andreasen and
Page 18 and 19:
114° 112° IIO O 108° 106° 104°
Page 20 and 21:
I.D ". ". '. ". ..... ",/" '. ~~~ ~
Page 22 and 23:
side of the mountains and coincide
Page 24 and 25: stress fields may dilate some of th
Page 26 and 27: I-' Ln !' .. "," "" ,,... P.c Tucso
Page 28 and 29: The upper basaltic andesite, overly
Page 30 and 31: over an inferred decollement in the
Page 32 and 33: attitudes of the thrust faults, rev
Page 34 and 35: gradation is observed only in certa
Page 36 and 37: to depth of 555 meters (Knechtel, 1
Page 38 and 39: asal conglomerate facies of the low
Page 40 and 41: Indian Hot Springs-Gila Valley Intr
Page 42 and 43: flow. A fault zone(s) is inferred t
Page 44 and 45: DWG. NO.-R.-IJ.-~ CALCULATED THICKN
Page 46 and 47: Geophysics, 1979). Nearby at Saffor
Page 48 and 49: Buena Vista Area Introduction More
Page 50 and 51: / I / / / / / / / / / / I / / / / /
Page 52 and 53: 33 34 31 T6S T7S
Page 54 and 55: GElEIEEOl'3,53IEEa3lljO Mile E] B R
Page 56 and 57: similar to the Precambrian granite
Page 58 and 59: 100 + + + + 300 + 500 ~ + + + + + +
Page 60 and 61: 500 m interval, while 1.2 HFU is re
Page 62 and 63: tN I \ 5 IOMiles \ ""1. EXPLANATION
Page 64 and 65: are interpreted as evidence of a ma
Page 66 and 67: LINE 7 RESISTIVITY N =2000 FEET, DI
Page 68 and 69: 100 200 0...---..."...-------------
Page 70 and 71: Artesia in D-8-26-32 and 33 have es
Page 72 and 73: trending 1.5 km 2 closures with soi
Page 76 and 77: Equation (1) Alumino-silicate + H 2
Page 78 and 79: Silica concentration in Figure 24 i
Page 80 and 81: San Simon Introduction The San Simo
Page 82 and 83: Geology Subsurface geology controls
Page 84 and 85: " " '"",.- ~--- ,....~, ~. 7 '1.v-~
Page 86 and 87: o 1 Mile '2, WATER LEVEL OF WELLS I
Page 88 and 89: Conclusion Geothermal potential at
Page 90 and 91: geothermometry for waters containin
Page 92 and 93: GRAVITY MODEL OF THE BOWIE AREA Mod
Page 94 and 95: TRANSVERSE TOPOGRAPHIC PROALES ACRO
Page 96 and 97: probably correlative with the "blue
Page 98 and 99: excellent chemical quality suitable
Page 100 and 101: Table 1 Wells With Measured Tempera
Page 102 and 103: Table 1 cont. Wells With Measured T
Page 104 and 105: Table 1 cant. Wells With Measured T
Page 106 and 107: Table 2A. Analyses of Gila Valley-I
Page 108 and 109: Table 2B. Analyses of Buena Vista a
Page 110 and 111: Table 2C. Analyses of Cactus Flat-A
Page 112 and 113: Tabl~ 2E. Analyses of Bowie area gr
Page 114 and 115: Table 3A Geothermometers for the Gi
Page 116 and 117: Table 3C. Geothermorneters for the
Page 118 and 119: Table 3E. Geothermometers for the B
Page 120 and 121: Table 4. Summary table showing aqui
Page 122 and 123: Summary of description of Core Lith
Page 124 and 125:
D-7-27-2cdb Driller's log Surface s
Page 126 and 127:
APPENDIX 2 pH Correction for the Si
Page 128 and 129:
By converting milligrams per liter
Page 130 and 131:
APPENDIX 3 Arizona Bureau of Mines
Page 132 and 133:
BIBLIOGRAPHY Aiken~ C. L. V., 1978,
Page 134 and 135:
-3- Davidson, E. S., and Cooley, M.
Page 136 and 137:
-5- Fournier, R. O. and Truesdell,
Page 138 and 139:
7 Marjaniemi, ,D. K., 1968, Geologi
Page 140 and 141:
-9- Scarborough, R. B., 1975, Chemi
Page 142:
Van Horn, W. L., 1958, Late Cenozoi
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