Results of Chemical and 

Stable Isotopic Analyses 

of Water Samples 

Collected in the Patagonia 

Mountains, southern 

Arizona 

by Richard B. Wanty1, Wayne C. Shanks III1, Paul Lamothe1, Al Meier1, 

Fred Lichte1

, Paul H. Briggs1, and Byron R. Berger1

Open-File Report 01-463 

2001 

This report is preliminary and has not been reviewed for conformity with U.S. Geological 

Survey editorial standards or with the North American Stratigraphic Code. Any use of trade, 

firm, or product names is for descriptive purposes only and does not imply endorsement by 

the U.S. Government. 
U.S. DEPARTMENT OF THE INTERIOR 

U.S. GEOLOGICAL SURVEY 

1

Denver, Colorado 

 Page 2
Results of Chemical and Stable Isotopic Analyses of Water Samples Collected in the 

Patagonia Mountains, southern Arizona 

by Richard B. Wanty, Wayne C. Shanks III, Paul Lamothe, Al Meier, Fred Lichte, Paul 

H. Briggs, and Byron R. Berger 

Abstract 

Water samples were collected in the Patagonia Mountains in February, 1997. Most of the 

samples were collected from portals of abandoned mines, or from stream drainages 

immediately downstream from abandoned mines. Most of the samples have low pH (<4) and 

high total dissolved solids (> 1000 mg/L). Anion composition of the water samples is 

dominated by sulfate, while cation compositions range from calcium-dominated to mixed 

calcium-magnesium or calcium-sodium-dominated waters. Metals such as iron, manganese, 

copper, zinc, and aluminum contribute a significant portion (>10%) of the cation content to 

the water samples. Because of the low pH’s, protons contribute up to several percent of the 

cation character of the waters in some of the samples. The data are presented in tabular and 

graphical formats, with descriptions of data quality and brief descriptions of results. 

Introduction 

The Patagonia Mountains are located in southern Arizona, between Tucson and Nogales 

(fig. 1). This area has a history of mining activity that extends back at least 100 years 

(Schrader, 1915). Primary production has included copper, lead, and zinc, with gold and 

silver produced from epithermal vein systems. Most of the mines in the area have been 

inactive and abandoned for many decades, but some continue to produce acidic, metal-rich 

drainage waters from mine portals or possibly from discharge of ground water that has 

passed through the mine workings. Drainage from these mines is mostly ephemeral. 

The climate in southern Arizona is characterized by semiarid to arid conditions, with 

monsoon rains producing most of the average annual rainfall during the summer months. 

Only 25% of the average annual precipitation is historically experienced during the winter 

months. 

 Page 3
Tucson

Nogales

Bisbee

Arizona

United States

Mexico

Patagonia

Mountain

s

Figure 1- location map for this study. 

 Page 4
Field Methods 

Field sampling was conducted over a period of three days in February, 1997. During that 

time, air temperatures were 40-50oF (approx. 5-15oC). Rain fell during the third day of 

sampling, at the time that samples 14 through 17 were being collected. 

Samples were collected using established methods (cf. Ficklin and Mosier, 1999, for a 

thorough review). Field analyses were performed for pH, temperature, dissolved oxygen, 

and electrical conductivity. The pH measurements were made at each site following a 

calibration using three known buffer solutions. Because the samples generally had low pH 

values, buffers from a similar pH range were used; usually pH 1.68, 3.00 or 4.00, and 7.00 

(25°C values). The pH meter had an automatic temperature compensation device so that the 

pH calibrations and measurements are corrected for the listed water temperatures. 

Temperature was measured using a calibrated digital thermometer. Electrical conductivity 

was measured as equivalent total dissolved solids expressed as NaCl. At each site except 

97AZ-13, a visual estimate of discharge was made; these are approximations only. Sample 

locations and results of field analyses are shown in Table 1. Other data shown in Table 1 

include latitude, longitude, and elevation. These were determined after completion of field 

work from locations plotted on the USGS 1:24,000 scale topographic sheets for the Cumero 

Canyon and Harshaw quadrangles. The distribution of sample locations is shown in figure 2. 

At each site, samples were collected for later laboratory analyses. These included 

samples for anions, cations, ferrous iron (for most samples), and for stable isotopes values of 

δD, δ18O, and δ34S in water and in dissolved SO4. The anion samples were filtered through a 

0.45 μm nominal pore size cellulose acetate filter and stored in low-density polyethylene 

bottles. Cation samples were similarly filtered and acidified with concentrated Ultrex-grade 

nitric acid from J.T. Baker Chemical Company (0.5 mL acid per 30 ml sample) and stored in 

low-density polyethylene bottles. The ferrous iron samples were filtered and acidified with 

reagent grade hydrochloric acid (1 mL acid per 100 mL sample) and kept in amber (opaque) 

high-density polyethylene bottles to avoid photo-oxidation of iron. Anion and ferrous iron 

samples were kept on ice in a cooler from the time of sampling, then stored in a refrigerator 

in the laboratory until the time of analysis. 

 Page 5
Table 1- Field analyses, locations and descriptive data for samples collected in the Patagonia 

Mountains, southern Arizona, in February, 1997. Elevations are given in feet above mean 

sea level (FAMSL) as determined from 1:24,000-scale topographic maps. Flow estimates 

were not made for samples 97AZ-13 or 97AZ-17. 

Sample No. description 

97AZ-1 flowing well in Humboldt Canyon 

97AZ-2 Humboldt Canyon, approx. 100m upstream of mine 

97AZ-3 mouth of World's Fair mine 

97AZ-4 World's Fair mine at base of tailings dump 

97AZ-5 50 m downstream of site #4 

97AZ-6 approximately 200 m downstream of site #5 

97AZ-7 approximately 1 km downstream from W.F. mine in Alum Gulch 

97AZ-8 approximately 500 m downstream of Three-R mine 

97AZ-9 approximately 800 m downstream from site #8 

97AZ-10 Ventura Mine mouth 

97AZ-11 approx. 150 m downstream from European Mine 

97AZ-12 flowing well down hill from European Mine

97AZ-13 Paymaster Spring

97AZ-14 Alum Gulch approx. 150 m downstream from Humboldt Canyon 

97AZ-15 Same as site #7 

97AZ-16 approx. 1 km downstream from site #15 

97AZ-17 Alum gulch near Exposed Reef Mine 

Sample No. Latitude Longitude elevation 

FAMSL 

flow, visual 

estimate 

pH T°C TDS, as

NaCl 

97AZ-1 31.4647 -110.7447 5150 30 gpm 3.45 19.3 160

97AZ-2 31.4686 -110.7331 4860 .1 - .3 gpm 2.89 9.6 650 

97AZ-3 31.4797 -110.7377 4800 10 gpm 3.07 12.5 1300

97AZ-4 31.4802 -110.7363 4650 5 gpm 2.92 6.4 1300

97AZ-5 31.4812 -110.7363 4640 5 gpm 3.15 11.7 1860

97AZ-6 31.4831 -110.7367 4575 5 gpm 2.97 10.0 1820

97AZ-7 31.4857 -110.7373 4500 5 gpm 3.41 7.3 1750

97AZ-8 31.4767 -110.7729 4520 1-2 gpm 3.12 7.2 660

97AZ-9 31.4763 -110.7769 4390 <.5 gpm 3.05 8.6 680

97AZ-10 31.4572 -110.7640 5320 .1 gpm 2.89 9.7 1620

97AZ-11 31.4648 -110.7703 4800 0.02 - .04 gpm 2.88 7.6 1020 

97AZ-12 31.4697 -110.7813 4415 .1 - .3 gpm 7.61 14.3 820 

97AZ-13 31.4111 -110.7052 5500 6.86 7.3 140

97AZ-14 31.4766 -110.7327 4775 10 -20 gpm 3.8 7.6 1770 

97AZ-15 31.4857 -110.7373 4500 25 gpm 3.45 7.1 1750

97AZ-16 31.4895 -110.7449 4390 5 gpm 3.77 9.6 1710

97AZ-17 31.4937 -110.7477 4350 3.47 9.0 1510

 Page 6
Figure 2- Base map of the Patagonia study area. Sample locations are indicated with a “+,” 

and numbers correspond to sample numbers in the tables, each of which has the prefix, 

“97AZ-.” Surface-water drainages are shown by the thin black lines. Roads are shown with 

double lines, dashed where not maintained. 

 Page 7
Laboratory Methods 

Ferrous iron determinations were made using Hach Accuvac® ampoules with a Hach DR2000 spectrophotometer. The method involves drawing the sample into an evacuated 

ampoule that contains a proprietary reagent, then measuring the color development. The 

method is based on the 1,10 phenanthroline method as outlined in Standard Methods for the 

Examination of Water and Wastewater (Clesceri and others, 1998). 

Anion determinations were made using a Dionex DX-500 ion chromatography (IC) 

system. Standard running conditions used an AS-4 chromatography column, with a mixed 

carbonate/bicarbonate eluent. With this method, fluoride and chloride determinations were 

made. Minor amounts of bromide were detected in most samples, and nitrate was detected in 

two samples. Sulfate analyses also were performed using the IC method, but the results of 

sulfate analyses from the ICP-AES are considered to be more reliable because of an 

analytical problem with the IC system. In the normal sequence of IC analyses, each sample 

was run, diluted with an equal volume of deionized water. This first sample run provided 

reliable analytical results for fluoride, chloride, bromide, and nitrate, but sulfate results were 

always much greater than the linear working range (all samples had SO4

2- concentrations 

greater than 100 mg/L as SO4

2-; the instrument is calibrated to 15 mg/L). Subsequently a 

greater dilution was run (usually 1:100, 1:200, or 1:500 v:v) for sulfate. However, a problem

was discovered recently wherein there is a carryover effect following the injection of highsulfate samples into the IC, so the sulfate numbers produced by the IC were spuriously high. 

Thus, the IC sulfate numbers are not reported herein, but rather, sulfate analytical results are 

reported from the ICP/AES. Further method development work with the IC has shown that 

dilution of samples with eluent, rather than deionized water, prevents this carryover effect in 

all but the most sulfate-rich samples. 

Cations were determined by inductively coupled plasma / atomic emission spectroscopy 

(ICP/AES) and inductively coupled plasma / mass spectroscopy (ICP/MS). The ICP/AES 

method produces preferred values for major cations such as alkali metals and alkaline earths, 

as well as for some of the trace elements, including iron, aluminum, and manganese. The 

ICP/MS method has the advantage of greatly increased sensitivity, and is capable of 

detecting a greater number of elements, so most of the trace element values and rare-earth 

element analyses were determined by the ICP/MS method (Briggs and Fey, 1996; Lamothe 

and others, 1999). 

Samples for isotopic determinations were placed in 20 mL glass scintillation vials, tightly 

capped, and returned to the USGS laboratories in Denver for analyses by isotope ratio mass 

spectrometry. Water samples were prepared for hydrogen isotopic analyses using the Zn 

reduction technique (Coleman et al., 1982) and for oxygen isotope analyses using an 

automated CO2 equilibration technique. Values of δ18O and δD are relative to the VSMOW

standard and have reproducibility of approximately 1.0 and 0.7 ‰, respectively. Dissolved 

sulfate was precipitated in the laboratory as BaSO4, filtered, dried, and reacted with BrF5 to 

produce CO2 for δ18O analysis (Clayton and Mayeda, 1963) on a Finnigan 252 isotope ratio 

mass spectrometer. δ18O error is estimated to be ±1‰. A split of each BaSO4 precipitate 

 Page 8
was analyzed for δ34S using an automated elemental analyzer interfaced to a Micromass 

Optima isotope ratio mass spectrometer. δ34S error is estimated to be ±0.2‰. 

Results and Discussion 

General results 

Results of field analyses were given in Table 1. Ferrous iron determinations are shown in 

Table 2 for a subset of the samples collected. Anion results by ion chromatography (except 

sulfate) are shown in Table 3. Cation analyses were performed by ICP/AES on the same

subset of samples for which ferrous analyses were performed. Those results are shown in 

Table 4. Cation analyses for the full suite of samples are shown in Table 5. Rare earth 

element analyses for the ferrous-iron subset are shown in Table 6. Results for stable isotopic 

analyses are shown in Table 7. 

Data Quality 

The primary test of the overall quality of the chemical data is indicated by the charge 

balance calculations, which are shown in Table 8. In all cases, charge balances are within 

±8%. The analyses that contribute to the overall charge balances include, field (pH) and 

laboratory (anions by IC, cations plus sulfate by ICP/AES) methods. The results of cationanion balances are in excellent agreement, indicating that the analytical results are reliable. 

A second test of data quality is found in running field and laboratory blanks, using 

deionized or distilled water. A field blank was prepared using distilled water that was 

carried to a field site and treated as though it were a sample. Field-blank samples were run 

for anions (by IC) and cations (by ICP/MS) and in both cases, showed below-detection 

values for all components. This result demonstrates that the likelihood of sample 

contamination is very low. 

A third test of data quality is given by running standards as though they are samples, and 

comparing the analytical results with most probable values given for the standards. For the 

IC, ICP/MS, and ICP/AES, at least 10% of the analyses were performed on standards run as 

unknowns. This test allows a check of analytical precision and accuracy through the data set. 

In addition, a minimum of 10% sample duplicates was run for the IC and ICP/AES as a 

further check of analytical precision. 

 Page 9
Table 2- Summary of analytical results for ferrous and total iron. Sampling, preservation, 

and analytical methods are described above. All concentrations are given in milligrams per 

liter (mg/L). The Fe2+/Fetot ratio is dimensionless. 

Fe

2+ total Fe Fe2+/Fetot

(colorimetric) (ICP/AES)

97AZ-1 0.26 0.74 35%

97AZ-2 0.18 3.1 5.8%

97AZ-3 130 130 99%

97AZ-4 21 93 22%

97AZ-5 0.94 11 8.5%

97AZ-6 0.31 6.0 5.2%

97AZ-7 0.38 1.0 38%

97AZ-8 0.02 1.5 1.3%

97AZ-10 210 240 88%

97AZ-11 1.5 47 3.2%

97AZ-17 0.67 1.3 54%

 Page 10
Table 3- Results of anion analyses by ion chromatography (IC). Sampling, preservation, and 

analytical methods are described in the text. Nitrate is give as milligrams per liter as NO3. 

To convert to milligrams per liter as N, multiply the result given by 0.23. A dash indicates 

no detectable quantity. 

Sample F Cl Br NO3

Number mg/L mg/L mg/L mg/L as NO3

97AZ-1 0.35 4.7 - -

97AZ-2 0.15 9.9 0.4 -

97AZ-3 1.8 10. - -

97AZ-4 2.0 13 - -

97AZ-5 0.95 16. 0.2 -

97AZ-6 0.85 16. 0.1 -

97AZ-7 1.1 17. 0.2 -

97AZ-8 0.2 9.9 0.7 -

97AZ-9 0.33 13. 0.68 2.2

97AZ-10 0.33 22. 0.5 -

97AZ-11 0.6 14. 0.3 -

97AZ-12 0.61 7.4 - -

97AZ-13 0.21 5 - -

97AZ-14 0.83 17 0.6 0.6

97AZ-15 1 17 0.1 -

97AZ-16 2.1 17 0.1 -

97AZ-17 2.2 18. 0.2 -

 Page 11
Table 4- Results of cation analyses by ICP/AES. Values are given in the units indicated in 

each column. The following elements were reported as being below the lower limit of 

detection for all samples: Ag, Cr (< 10 μg/L); Mo (< 20 μg/L); and As, P, and Sb (all < 100 

μg/L). 

Field No Ca mg/L Mg mg/L Na mg/L K mg/L SO4 mg/L Si mg/L Fe mg/L

97AZ-1 5.7 3.0 4.3 1.9 110 13. 0.74

97AZ-2 12. 9.8 8.5 3.0 680 29. 3.1

97AZ-3 170 100 11. 27. 1700 40. 140

97AZ-4 180 110 12. 24. 1700 40. 93.

97AZ-5 380 210 40. 7.3 2500 35. 11.

97AZ-6 390 210 40. 6.3 2500 35. 6.0

97AZ-7 400 200 41. 5.1 2500 34. 1.0

97AZ-8 15 8.5 22. 11. 730 49. 1.5

97AZ-10 260 130 60. 7.2 2500 37. 240

97AZ-11 90. 48. 36. 3.5 1200 51. 47.

97AZ-17 420 180 48. 4.4 2500 31. 1.3

Field No Li μg/L Be μg/L B μg/L Al mg/L V μg/L Mn mg/L Co μg/L 

97AZ-1 < 10 < 10 18. 12. < 10 .33 26. 

97AZ-2 16. < 10 15. 98. < 10 5.2 130

97AZ-3 110 19. 24. 50. < 10 150 360

97AZ-4 101 19. 29. 52. < 10 160 360

97AZ-5 120 12. 31. 75. < 10 140 260

97AZ-6 120 15. 27. 73. < 10 140 280

97AZ-7 110 14. 24. 73. < 10 140. 270

97AZ-8 37. < 10 16. 83. < 10 2.0 180

97AZ-10 88. 15. 21. 130 23. 41. 430

97AZ-11 56. < 10 16. 84. < 10 19. 240

97AZ-17 110 15. 22. 86. < 10 110 280

Field No Ni μg/L Cu μg/L Zn μg/L Sr μg/L Cd μg/L Ba μg/L Pb μg/L 

97AZ-1 22. 510 410 24. < 5 24. < 50 

97AZ-2 110 4,200 7,400 59. 52. 18. < 50

97AZ-3 310 96. 48,000 42. 29. 12. < 50

97AZ-4 320 110 49,000 44. 29. 11. < 50

97AZ-5 380 2,300 69,000 430 220 7.2 < 50

97AZ-6 370 2,300 70,000 440 220 14. 170

97AZ-7 360 2,600 68,000 460 230 11. 250

97AZ-8 91. 77,000 2,900 61. 130 16. 67.

97AZ-10 290 21,000 18,000 93. 62. 9.3 < 50

97AZ-11 58. 12,000 8,000 85. 39. 9.5 < 50

97AZ-17 360 2,600 59,000 550 220 13. < 50

 Page 12
Table 5- Results of cation analyses by ICP/MS. All values are shown in μg/L. The 

following results are not shown: Au (all <0.01 μg/L);Bi (all <0.05 μg/L); Nb (all <0.1 μg/L); 

Ge (all < 0.2 μg/l, except 97AZ-12, which was 1 μg/L); Sn (all <1 μg/L); Se (all < 5μg/L); 

Sc (all <10 μg/L); P (all < 100 μg/L); 

Sample Number Ca Mg Na K SiO2 Fe Mn

detection limit 100 5. 100 100 500 500 10.

97AZ-1 4,500 3,000 3,600 1,900 16,000 250 280

97AZ-2 9,500 9,100 7,300 3,000 34,000 2,300 4500

97AZ-3 150,000 77,000 8,700 26,000 43,000 110,000 140,000

97AZ-4 150,000 80,000 9,000 24,000 44,000 78,000 150,000

97AZ-5 370,000 170,000 32,000 7,300 38,000 9,500 130,000

97AZ-6 380,000 170,000 32,000 6,400 39,000 4,900 130,000

97AZ-7 390,000 170,000 35,000 5,500 39,000 870 130,000

97AZ-8 11,000 7,100 18,000 11,000 56,000 900 1,300

97AZ-9 14,000 11,000 24,000 12,000 57,000 700 2400

97AZ-10 240,000 100,000 48,000 7,200 39,000 210,000 37,000

97AZ-11 77,000 38,000 31,000 3,600 64,000 40,000 17,000

97AZ-12 210,000 36,000 100,000 12,000 8,000 350 380

97AZ-13 28,000 4,500 15,000 4,000 29,000 80 34

97AZ-14 430,000 200,000 40,000 5,800 32,000 160 110,000

97AZ-15 400,000 170,000 35,000 5,500 39,000 930 130,000

97AZ-16 430,000 150,000 35,000 4,100 35,000 430 110,000

97AZ-17 420,000 150,000 39,000 4,500 34,000 860 100,000

Sample Number Li Be Al Ti V Cr Co 

detection limit 0.30 0.20 1.0 2. 10. 10. 0.50 

97AZ-1 4 <0.2 9,800 <2 <10 <10 21 

97AZ-2 16 3 81,000 3 <10 <10 100 

97AZ-3 99 17 37,000 <2 <10 10 280 

97AZ-4 100 18 39,000 <2 <10 <10 290

97AZ-5 120 11 57,000 <2 <10 <10 230

97AZ-6 120 15 56,000 2 <10 <10 240

97AZ-7 120 14 57,000 <2 <10 <10 240

97AZ-8 38 3 64,000 <2 <10 <10 130

97AZ-9 50 6 60,000 <2 <10 <10 110

97AZ-10 88 14 97,000 <2 24 15 330

97AZ-11 59 9 69,000 2 <10 <10 200

97AZ-12 260 <0.2 3 2 <10 11 <0.5

97AZ-13 53 <0.2 17 2 <10 10 <0.5

97AZ-14 99 4 36,000 <2 <10 <10 130

97AZ-15 120 14 58,000 2 <10 <10 240

97AZ-16 100 14 60,000 <2 <10 <10 230

97AZ-17 98 14 66,000 <2 <10 <10 240

 Page 13
Sample Number Ni Cu Zn Ga As Rb Sr

detection limit 1.0 0.50 0.50 0.50 0.50 0.10 0.10 

97AZ-1 19 450 350 <0.5 2.1 10 20

97AZ-2 91 3,800 5,700 1 <0.5 16 55

97AZ-3 240 100 39,000 1 0.5 170 42

97AZ-4 240 120 41,000 1 0.6 180 43

97AZ-5 290 1,900 57,000 1 6.5 44 430

97AZ-6 290 1,900 58,000 1 0.8 36 450

97AZ-7 290 2,300 58,000 1 <0.5 21 500

97AZ-8 63 140,000 1,600 <0.5 <0.5 44 52

97AZ-9 69 90,000 1,700 <0.5 <0.5 58 49

97AZ-10 230 21,000 13,000 3 1.6 87 91

97AZ-11 41 12,000 6,100 1 0.7 40 81

97AZ-12 <1 1 2 <0.5 61. 43 650

97AZ-13 1 2 20 <0.5 8.9 7 94

97AZ-14 260 1,800 58,000 1 <0.5 18 640

97AZ-15 300 2,300 59,000 1 <0.5 20 500

97AZ-16 270 2,100 53,000 1 <0.5 11 600

97AZ-17 280 2,100 50,000 1 <0.5 12 580

Sample Number Zr Mo Ag Cd In Sb Te

detection limit 0.10 0.10 0.05 0.10 0.05 0.05 0.5

97AZ-1 <0.10 <0.10 0.05 2.8 <0.05 0.12 <0.5

97AZ-2 0.9 <0.10 <0.05 47. 0.33 0.22 <0.5

97AZ-3 <0.10 <0.10 <0.05 28. <0.05 0.58 <0.5

97AZ-4 <0.10 <0.10 <0.05 30. <0.05 0.36 <0.5

97AZ-5 0.1 <0.10 0.11 210 0.06 1.5 <0.5

97AZ-6 0.1 <0.10 0.35 220 0.08 1.7 <0.5

97AZ-7 0.1 <0.10 0.25 220 0.09 1.4 <0.5

97AZ-8 1.2 <0.10 <0.05 110 0.09 0.13 <0.5

97AZ-9 0.6 <0.10 <0.05 52. 0.07 0.08 <0.5

97AZ-10 0.2 <0.10 0.05 60. 0.45 0.40 2.0

97AZ-11 0.3 <0.10 <0.05 37. 0.18 0.16 <0.5

97AZ-12 <0.10 2.4 <0.05 <0.1 <0.05 0.86 <0.5

97AZ-13 <0.10 0.3 0.12 0.2 <0.05 0.38 <0.5

97AZ-14 0.1 <0.10 0.10 220 <0.05 0.25 <0.5

97AZ-15 0.1 <0.10 0.21 230 0.10 1.4 <0.5

97AZ-16 0.2 <0.10 0.18 220 <0.05 0.30 <0.5

97AZ-17 0.2 <0.10 0.15 210 <0.05 0.30 <0.5

 Page 14
Sample Number Cs Ba Ta W Re Tl Pb 

detection limit 0.05 0.05 0.05 0.05 0.05 0.10 0.05

97AZ-1 0.34 9.1 <0.05 <0.05 0.29 0.39 2.1

97AZ-2 0.36 6.4 0.09 <0.05 0.72 0.19 0.26

97AZ-3 7.7 0.63 0.22 <0.05 0.34 0.46 8.7

97AZ-4 8.3 0.45 0.21 <0.05 0.34 0.46 14.

97AZ-5 1.5 1.2 0.34 <0.05 0.53 0.25 42.

97AZ-6 1.1 1.9 0.22 <0.05 0.54 0.24 210

97AZ-7 0.41 4.3 0.30 <0.05 0.55 0.20 270

97AZ-8 2.2 5.6 0.09 0.18 1.9 0.44 0.47

97AZ-9 3.0 4.5 0.07 0.06 0.93 0.58 0.32

97AZ-10 6.9 0.06 0.43 <0.05 1.1 1.9 0.40

97AZ-11 3.4 0.21 0.14 <0.05 0.19 0.51 1.2

97AZ-12 24. 7.8 0.09 30. <0.05 <0.1 0.17

97AZ-13 1.2 36. <0.05 <0.05 <0.05 <0.1 0.49

97AZ-14 0.13 5.1 0.15 <0.05 0.49 0.14 61.

97AZ-15 0.39 4.1 0.20 <0.05 0.58 0.22 260

97AZ-16 1.1 5.0 0.17 <0.05 0.69 <0.1 16.

97AZ-17 0.60 4.4 0.15 <0.05 0.64 0.11 18.

Sample Number Th U

detection limit 0.05 0.02 

97AZ-1 <0.05 2.0

97AZ-2 1.9 10.

97AZ-3 0.09 8.6

97AZ-4 0.10 8.9

97AZ-5 0.10 11.

97AZ-6 0.21 12.

97AZ-7 0.15 11.

97AZ-8 30. 69.

97AZ-9 13. 59.

97AZ-10 6.7 67.

97AZ-11 7.6 52.

97AZ-12 <0.05 3.9

97AZ-13 <0.05 0.13

97AZ-14 0.05 3.6

97AZ-15 0.14 11.

97AZ-16 0.08 9.4

97AZ-17 0.11 8.7

 Page 15
Table 6- Results of analyses of rare earth elements and yttrium, lanthanum, and hafnium by 

ICP/MS. All values are given in μg/L. 

Sample Number Y La Ce Pr Nd Sm Eu Gd 

detection limit 0.10 0.05 0.05 0.05 0.05 0.05 0.05 0.05

97AZ-1 4.9 0.26 1.4 0.34 1.8 0.46 0.13 0.62

97AZ-2 24. 9.3 26. 3.7 16. 3.6 1.0 4.1

97AZ-3 120 13. 59. 13. 71. 21. 5.8 26.

97AZ-4 120 14. 61. 14. 73. 21. 6.2 27.

97AZ-5 150 40. 130 22. 110 27. 7.4 32.

97AZ-6 150 42. 130 22. 110 27. 7.4 31.

97AZ-7 150 49. 140 23. 110 27. 7.3 31.

97AZ-8 51. 32. 79. 10. 39. 9.3 1.1 9.6

97AZ-9 67. 32. 85. 12. 47. 12. 1.4 13.

97AZ-10 190 17. 72. 15. 79. 23. 5.8 30.

97AZ-11 130 34. 100 16. 69. 18. 3.0 20.

97AZ-12 <0.1 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05

97AZ-13 <0.1 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05

97AZ-14 99. 32. 81. 12. 52. 13. 3.5 16.

97AZ-15 160 48. 140. 23. 110 27. 7.3 31.

97AZ-16 190 99. 260. 37. 160 37. 9.5 40.

97AZ-17 200 96 260. 37. 160 38. 9.7 41.

Sample Number Tb Dy Ho Er Tm Yb Lu Hf

detection limit 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05

97AZ-1 0.13 0.87 0.16 0.50 0.06 0.41 0.06 <0.05

97AZ-2 0.69 4.3 0.76 2.1 0.30 1.8 0.25 <0.05

97AZ-3 3.9 21. 3.9 10. 1.3 7.1 0.94 <0.05

97AZ-4 4.0 22. 4.1 11. 1.3 7.3 0.95 <0.05

97AZ-5 4.8 27. 4.8 13. 1.6 8.8 1.1 <0.05

97AZ-6 4.8 27. 4.9 13. 1.6 8.8 1.1 <0.05

97AZ-7 4.8 27. 4.8 13. 1.6 8.7 1.1 <0.05

97AZ-8 1.7 10. 1.9 5.5 0.79 4.9 0.69 <0.05

97AZ-9 2.2 13. 2.4 6.8 1.0 6.3 0.91 <0.05

97AZ-10 5.2 32. 6.0 17. 2.4 14. 2.0 <0.05

97AZ-11 3.4 21. 4.1 13. 1.8 12. 1.8 <0.05

97AZ-12 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05

97AZ-13 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05

97AZ-14 2.7 15. 2.8 7.4 0.91 4.9 0.64 <0.05

97AZ-15 4.9 27. 4.9 13. 1.6 8.7 1.2 <0.05

97AZ-16 6.1 34. 5.9 15. 1.9 10. 1.3 <0.05

97AZ-17 6. 35. 6.2 16. 2.0 11. 1.3 <0.05

 Page 16
Table 7- Results of isotopic analyses of water samples. δ18O and δD are reported in permil 

deviation relative to standard mean ocean water (SMOW); δ34S is reported in permil 

deviation from Cañon Diablo troilite (CDT). 

Sample No. δ18O in H2O δD in H2O δ18O in SO4 δ34S in SO4

97AZ-1 -8.5 -59.4

97AZ-2 -8.1 -56.6 2.3 -6.2

97AZ-3 -8.9 -62.2 1.3 -5.2

97AZ-4 -4.5 -58.2 -1.0 -3.7

97AZ-5 -52 -0.4 -4.0

97AZ-6 -6.92 -50.4 0.0 -3.5

97AZ-7 -49.7 0.4 -3.5

97AZ-8 -55 -0.4 -3.3

97AZ-9 -64.2 0.3 -3.3

97AZ-10 -9.14 -59.3 0.9 -4.0

97AZ-11 -8.83 -64.6 1.2 -6.9

97AZ-12 -73.8 1.7 -1.3

97AZ-13 -8.32 -56.3 9.2 -2.4

97AZ-14 -7.53 -54 0.5 -2.8

97AZ-15 -6.81 -51.4 -0.2 -3.3

97AZ-16 -51.1 -0.2 -3.4

97AZ-17 -48.1 0.1 -3.1

 Page 17
Chemical character of the waters: 

The general chemical character of the waters can be depicted by a number of methods, 

including Piper diagrams, Durov plots, etc. (cf. Freeze and Cherry, 1979; Domenico and 

Schwartz, 1998). The data from Tables 3 and 4 are shown in a Piper diagram in figure 3. As 

seen in the figure, the cation composition of the waters ranges from Ca-dominated through a 

mix of Ca-Mg-Na+K dominated. The anion compositions, on the other hand, are nearly 

always sulfate dominated. The cation composition most likely varies as a result of the 

differences in the chemistry of the rocks with which the waters come into contact. The 

sulfate-dominated waters result from the oxidation of pyrite in the rocks, which produces 

sulfate. 

Stable isotope data indicate that all of the sampled waters are of meteoric origin. The 

waters from Alum Gulch, downstream from the World’s Fair mine drainage, are somewhat 

evaporated, as indicated by δD and δ18O enrichment. Sulfur isotope data for dissolved 

sulfate in mine drainage waters vary in δ34SSO4 from –6.9 to –2.8‰. These values are similar 

to δ34S values of primary sulfides in nearby ore deposits (Shanks and Lichte, 1996). Oxygen 

isotopes values of sulfate in mine drainage waters have δ18OSO4 from –1.0 to 2.3‰, about 8-

10‰ enriched relative to local meteoric water δ18O. These values would indicate isotopic 

equilibrium exchange between SO4 and H2O at a temperature of about 200oC (Mizutani and 

Rafter, 1969), which is unrealistically high. More likely dissolved SO4 that forms as a result 

of bacterial sulfide mineral oxidation in mine tailing and working has incorporated some

atmospheric oxygen, as demonstrated experimentally by Krouse et al. (1991). 

Conclusions 

Chemical analyses are presented for surface-water samples collected in 1997 in the 

Patagonia Mountains of southern Arizona. A full suite of inorganic chemical constituents is 

presented in this report. Data quality is assured by a variety of methods, which are oriented 

towards assuring accuracy and precision of the analytical results. 

Typical of acid mine drainage waters, the samples reported on here have low pH, and 

high concentrations of sulfate and metals. In most cases, sulfate constitutes >95% of the 

total anion composition, but the cation character of the samples is more variable. In some

cases, pH is sufficiently low that hydronium ion (H3O+

) figures significantly into the anioncation charge balance. 

Oxygen and hydrogen isotopes indicate that mine drainage exiting underground workings 

is meteoric water and becomes somewhat evaporated as it moves downstream significant 

distances in drainages. Sulfur and oxygen isotope values of sulfate in mine drainage waters 

indicate sulfur is derived from sulfides and some atmospheric oxygen may be incorporated. 

 Page 18
Ca Na + K ΣCO3 Cl

Mg SO4

(Ca,Mg)-CO3

(Ca,Mg)-(Cl-SO4)

(Na±K)-CO3

(Na±K)-(Cl-SO4)

Figure 3- Piper plot for the water samples collected in the Patagonia Mountains study area. 

 Page 19
 Page 20

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