Evaluation of Pleistocene groundwater flow through ...

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Online Supplement to Chemical Geology Manuscript

Evaluation of Pleistocene groundwater flow through fractured tuffs using a U‐series disequilibrium approach, Pahute Mesa, Nevada, USA 1*

2

James B. Paces , Paul J. Nichols , Leonid A Neymark3, Harihar Rajaram4 1

U.S. Geological Survey, Geology and Environmental Change Science Center, Denver Federal Center, Denver CO 80225, [email protected] 2

Department of Civil, Environmental and Architectural Engineering, University of Colorado, Boulder, Colorado, [email protected] 3

U.S. Geological Survey, Mineral and Environmental Resources Science Center, Denver Federal Center, Denver CO 80225, [email protected] 4

Department of Civil, Environmental and Architectural Engineering, University of Colorado, Boulder, Colorado, [email protected] *To whom inquiries should be addressed: This supplement contains a number of figures and tables referenced in the published paper. They provide additional information supporting the discussion and conclusions described in the main text.

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Sample Descriptions Table S1. Descriptions of sampled core intervals. Description

Borehole

Interval

PM‐1

1990 – 1990.3

PM‐1

2366.4 – 2366.6

PM‐1

2820.5 – 2820.6

PM‐1

3140.5 – 3140.7

Fine‐grained, yellow/green/cream‐colored, altered tuff. Hard, coarse breccia fragments from broken zone. Minor secondary minerals on surfaces Creamy/pink‐colored, partially‐welded lithic tuff. Reasonable unfractured with low porosity White, partially‐welded tuff with coarse pumpice fragments. Unfractured with low porosity Light‐cream‐colored bedded tuff. Unfractured with low porosity

PM‐1

3456.4 – 3456.6

Light‐pink lithic tuff. Unfractured with low porosity

PM‐1

5597.5 – 5597.7

PM‐1

5779.6 – 5779.9

PM‐1

5996.5 – 5996.8

PM‐1

6079 – 6079.2

PM‐1

6084 – 6084.3

PM‐1

6614 – 6614.2

UE‐19fS

2553.9 – 2554.2

UE‐19fS

3375 – 3375.3

UE‐19fS

3552.1 – 3552.5

UE‐19fS

4303.1 – 4303.5

UE‐19fS

4913.3 – 4913.7

UE‐19fS

5211.4 – 5212

UE‐19fS

5214.5 – 5214.7

UE‐19fS

5516.6 – 5516.8

UE‐19fS

5815.6 – 5815.9

UE‐19gS

2136 – 2136.6

UE‐19gS

4054 – 4057

UE‐19gS

4657.5 – 4657.9

Dark‐pink welded tuff. Large core fragment is bounded by intersecting fractures with thin secondary clay and Mn‐oxide mineral coatings present on surfaces Maroon welded tuff. Large core fragment has sub‐vertical fracture with red clay coating Maroon welded tuff. 2‐cm‐thick sliver of core is bounded by high angle fractures. Surfaces have a thin coating of dark reddish minerals (possibly clay?) Maroon welded tuff with abundant fractures. Sample consists of coarse breccia fragments. Minor secondary minerals present on fracture surfaces Dark maroon welded tuff with abundant fractures. Sample consists of coarse breccia fragments with thin secondary mineral coatings (Mn‐oxides and reddish clay?) Brick‐red, densely welded tuff. Largely intact sample with little to no fractures Creamy‐red lithic tuff. Longitudinal fractures with Mn Ox mineralization Purple/red welded tuff. Large fragment bounded by horizontal and vertical fractures with minor secondary minerals Purple/red welded tuff with high angle fractures. 2.5‐cm‐thick sliver bounded by fractures with no secondary mineralization Purple welded tuff. Vertical fractures lined with Mn Ox Grey welded tuff with small pumpice fragments. Sliver bounded by high angle fractures with minor clay minerals Purple/red welded tuff. 2‐cm‐thick sliver bounded by verticle fractures coated with secondary mineralization Purple/red welded tuff. 2.5‐cm‐thick sliver bounded by high angle fractures with abundant MnOx and white clays Welded lithic tuff, highly altered to bright green chlorite(?). Small breccia fragments Highly altered sperulitic tuff or volcanic breccia with red and green mottled appearance. Breccia fragments include surfaces with thin secondary mineral coatings Dark colored welded tuff with abundant 1‐ to 5‐mm pores. Highly altered tabular breccia fragments typically 0.5‐cm thick Green/tan altered highly brecciated tuff. Interval has very low recovery. Clay minerals present on fracture surfaces Dark altered tuff. Large fragments from broken zone. Fracture surfaces

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have secondary clay minerals present. Bright‐green welded tuff with abundant Fe‐Mn oxides. Physically intact with very low permeability. Grey welded tuff with small white pumpice. Sample consists of thumb‐ sized breccia fragments from a broken zone within an otherwise intact interval Zeolitized lithic tuff. Fist‐sized core with vertical longitudinal fracture. Little to no minerals on fracture surfaces Green/brown, hard (welded/altered?) tuff. 5‐cm‐thick fragment contains vertical fractures with minor secondary minerals

UE‐19gS

4814.3 – 4814.5

UE‐19gS

4907.8 – 4908

UE‐19gS

5302.5 – 5302.8

UE‐19gS

5641 – 5641.4

UE‐19gS

6279 – 6279.3

UE‐19i

2419 – 2419.2

UE‐19i

2890.5 – 2809.6

UE‐19i

3407 – 3407.2

UE‐19i

3533 – 3533.3

UE‐20f

2626.15 – 2626.4

UE‐20f

2845.4 – 2845.6

UE‐20f

2848.7 – 2849

UE‐20f

3030.4 – 3030.6

UE‐20f

3607.3 – 3607.4

Maroon highly altered tuff. Mn Ox and clay/zeolites present throughout sample Welded tuff with multiple fractures containing thin coatings of secondary minerals Tan‐colored welded tuff. Longitudinal fracture contains thin surface coating of secondary minerals and a thin bleached zone 2.5‐cm‐thick slab of light‐greenish tan‐colored partially welded tuff. Strongly zeolitized. Secondary minerals are present on both fracture surfaces along with thin bleached zones Welded tuff. Sample consists of breccia fragements with variable amounts of secondary minerals on fracture surfaces Black vitrophyre with sub‐horizontal partings. Core is cut by longitudinal fracture with minor secondary mineral coating

UE‐20f

3704.4 – 3704.7

1.3‐cm‐thick slab of pink/tan‐colored welded tuff bounded by fractures with white, clay‐like mineralization on surfaces

UE‐20f

3904.2 – 3904.3

UE‐20f

4159.8 – 4160

Partially‐welded lithic tuff with light to moderate zeolitization. Relatively unfractured White, bedded tuff with little or no fractures

UE‐20f

4740.7 – 4741

Pink, welded tuff. Sample consists of coarse breccia fracgments. One fracture surface has noteable coating of white clay‐like minerals

UE‐20f

5290.7 – 5291

Densely welded tuff containing a longitudinal fracture but no obvious secondary mineralization

Purple welded tuff. Large breccia fragments from broken zone. Minor secondary minals on fracture surfaces White bedded tuff with low permeability Cream/white, very fine‐grained welded Tuff. Core fragment bounded by verticle and horizontal fractures with Mn oxides on fracture surfaces Maroon brecciated tuff. Large, breccia fragments from broken zone. Minor Mn oxides and clay present on fracture surfaces

Examples of Pahute Mesa core classified by sample type Figure S1 shows photographs of core which were sampled to represent three different types of material including intact core interiors (a, b, and c), brecciated core that was broken by natural rather than drilling processes as evidenced by altered and thinly coated outer surfaces of breccia fragments (d, e, and f), and discrete fracture surfaces (g, h, and i). Each core box is approximately 0.8 m in length. Arrows point to where samples were taken.

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Figure S1 1: Photograp phs of core classified d by sample tyype. Intact core interiors a) PM‐‐1: 6614.0–66 614.2’ 19gS: 4814.3––4814.5’ b) UE‐1 c) UE‐2 20f: 4159.8–4 4160.0’

Brecciateed core d) PM‐‐1: 6079.0–60 079.2’ 6084.0–6084.3’ e) UE‐1 19gS: 6279.0––6279.3’ f) UE‐2 20f: 3030.4–3 3030.6’

Discrete fractures g) UE19fS: 3552.1––3552.5’ h) UE‐1 19fS: 4303.1––4303.5’ i) UE‐1 19fS: 4913.3––4913.7’ 5211.4––5212.0’ Page 4 of 16


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Examples of Discrete Fracture Surface Minerals Figure S2 shows scanning electron microscope images of a selected number of discrete fracture surfaces from Pahute Mesa core. (a) Secondary electron image of core PM‐1, 5597.5‐5597.7’ fracture surface dominated by illite and smectite; (b) Secondary electron image of core PM‐1, 5996.5‐5996.8’ fracture surface dominated by botryoidal silica (opal/quartz/cristobalite), and small platelets of kaolinite, illite, and Mn‐smectite; (c) Secondary electron image of core PM‐1, 6084.0‐6084.3’ fracture surface dominated by feathery smectite on left side of image, and bumpy chlorite + silica on right side of image; (d) Secondary electron image of core UE‐19fS, 4913.3‐4913.7’ fracture surface dominated by tabular books of kaolinite; (e) Secondary electron image of core UE‐fS, 5211.4‐5212.0’ consisting entirely of kaolinite; (f) Backscatter electron image of core UE‐19gS, 4657.5‐4657.9’ showing relatively unmineralized surface with irregular tablets of quartz and feldspar with a fibrous clusters of secondary chlorite (light‐colored phase) and clusters of granular illite between grains constituting substrate, (g) Secondary electron image of core UE‐20f, 2848.7‐2849.0’ fracture surface dominated by fibrous mordenite with flecks of equigranular ilite/smectite. Figure S2 (following page): Scanning electron microscope images of discrete fracture surfaces from Pahute Mesa core

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Analytical Methods Porosity: Porosity measurements were made by standard point counting methods using polished petrographic thin sections (30 µm thick) that were vacuum‐impregnated with blue‐stained epoxy prior to mounting. Measurements were made by visual inspection under a petrographic microscope using a magnification of 200x. A mechanical stage was used to provide a rectilinear grid with 1 mm x 1 mm point spacing. A total of 1,000 counts were made for each thin section sample. Each point was classified either as “void”, corresponding to pore space if the distinctive blue coloration was observed, or “solid”, corresponding to crystalline matrix if no blue coloration was present. Uncertainties for porosity measurements are estimated at 20% of the value reported. Rock digestion: Approximately 80 to 140 mg of powdered material were digested for chemical and U‐series isotope analyses. Digestion methods followed those given by Weis et al. (2006). Aliquots were weighed in PFA Teflon™ beakers and combined with approximately 0.5 ml of 15 N HNO3 and 3.0 ml of concentrated HF, capped tightly, cooked overnight on a 135°C hotplate. After drying, salts were treated with 0.5 ml 15 N HNO3 plus 0.5 ml 9 N HCl, capped, and heated at 135°C for several hours prior to drying a second time. Remaining salts were dissolved in 5 ml of 6 N HCl and allowed to equilibrate on a 130°C hotplate overnight. Solutions were transferred into 15 ml tubes and centrifuged at 10,000 rpm. Any residual gel was further digested with 9 N HCl and 15 N HNO3 , redissolved in 6N HCl, and added to the initial solution. After complete digestion, gravimetric solutions of 6 N HCl were split into two separate aliquots for chemical analyses by inductively coupled plasma mass spectrometry (ICPMS) and isotope analysis by thermal‐ionization mass spectrometry (TIMS). The aliquot for TIMS was weighed and spiked with approximately 0.04 grams of a mixed 236U/229Th tracer solution and allowed to equilibrate overnight on a hot plate. After the HCl was evaporated, the sample was redissolved in 1 ml of 7 N HNO3. Rare Earth Element analysis: Concentrations of rare earth elements (REE) were determined on splits of the digested rock powders described in the preceding paragraph using a PlasmaQuad‐III inductively coupled plasma mass spectrometer (ICPMS) at U.S. Geological Laboratories in Denver, Colorado, USA. The external precision and accuracy of the REE concentrations are routinely evaluated by analyzing the USGS rock standards BCR‐1 and G‐2. Resulting concentration for rock standards typically were within 10% of the accepted values. Analyses of unknown samples yield smooth, chondrite‐normalized REE patterns that are similar to previously published data from the same units (Broxton et al., 1989). Chemical separation and purification: U and Th were separated and purified using standard ion chromatography methods and AG 1‐×8 (200‐400 mesh) resin. Digested samples were loaded onto 7 N‐ HNO3‐equilibrated columns and washed with 3 column volumes of acid to remove most of the matrix. Th was then captured and U cleaned by switching to 6 N HCl. Purified U was then eluted using 0.05 N HNO3. Typically, Th would require a second round using smaller amounts of resin to obtain an adequately purified product. Total‐chemistry process blanks for this digestion and purification procedure are approximately 50 pg of U and 100 pg of Th, which typically constitute less than 0.05% of the U and Th present in the sample. Mass spectrometry: Purified U salts were loaded onto rhenium ribbons making up the evaporation side of double filament assemblies. Ratios of 234U/235U, 236U/235U, 230Th/229Th, and 232Th/229Th were measured using a single electron multiplier operating in a peak jumping mode on a Thermo Finnigan Triton™ mass spectrometer equipped with a retarding potential quadrupole (RPQ) filter that increases abundance sensitivity to ~20 ppb at mass 237. Ratios were corrected for spike addition as well as mass fractionation, and blank subtraction. A NIST U standard (SRM 4321B) was used to correct for instrument drift by normalizing values measured for unknowns by the same factor derived from analyses of SRM

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4231B run in the same magazine (typically within analytical uncertainty of the certified value). Measured 234U/235U and 230Th/229Th atomic ratios were converted to 234U/238U AR and 230Th/238U AR using decay constants published by Cheng et al. (2000; 234=2.8262×10‐6 yr‐1; 230=9.158×10‐6 yr‐1) and Jaffey et al. (1971; 238=1.55125×10‐10 yr‐1), assuming that U has a 238U/235U composition of 137.88 (Steiger and Jäger, 1977). Analytical errors given for measured 234U/238U AR values are reported at the 95% confidence level and include within‐run uncertainties (counting statistics) plus uncertainties propagated from blank, spike, and mass fractionation corrections, as well as external error derived from multiple analyses of a U isotope standard (SRM 4321B). Replicate analyses of the NIST SRM 4321B U isotope standard (certified value of 234U/235U = 0.007294 ±0.000028) yielded a long‐term average value of 0.0072932 ±0.0000136 (2×standard deviation, or 2SD; N=136). Replicate analyses of a solution of 69‐million‐year U ore from the Schwartzwalder mine (Ludwig et al., 1985) that is assumed to be in radioactive secular equilibrium yielded a long‐term 234U/238U AR = 0.9982 ±0.0025 (±2×standard deviation, or 2SD; N=103) and 230 Th/238U AR = 0.9940 ±0.0094 (±2SD; N=83). Replicate analyses of IRMM‐036 Th isotope standard (certified 232Th/230Th atomic ratio = 321,230 ±8,050) yielded a long‐term average value of 322,080 ±3,020 (±2SD; N=35). Replicate analyses of USGS rock standard BCR‐1 processed using the same methods yielded long‐term concentrations values of 1.69 ±12 (2SD; N=6) for U and 5.77 ±0.44 (±2SD; N=6). Although these values are systematically lower than accepted values by approximately 3.5% (1.75±0.12 µg/g U and 5.98 ±0.06 µg/g Th; Gladney et al., 1990), Th/U concentration ratios are identical (3.417 for accepted values, 3.415 for mean measured values). Isotope ratios measured for the same BCR‐1 analyses yield mean values of 1.003±0.002 (±2SD) for 234U/238U AR and 1.010±0.009 (±2SD) for 230 Th/238U AR. An additional factor of 0.9% was added in quadrature to the overall uncertainty estimate for 230Th/238U AR to account for this external error. This increased the overall uncertainties from original estimates of approximately 0.6 to 1% for most determinations to values between 1 and 1.4%.

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Uranium characteristics of groundwater from Pahute Mesa and adjacent areas Uranium concentrations and isotopic compositions for groundwater samples from the Nevada National Security Site were determined at the USGS Denver Radiogenic Isotope Laboratory using the same methods described in the main text. Results from sites within the Pahute Mesa tributary flow system (Figure 7 of Fenelon et al., 2010) and closest to cored boreholes sampled in this study were used to derive the median 234U/238U AR value assigned as the composition of the input source in open‐system isotope‐evolution simulations (Table S2a). Samples from farther downgradient, or from other regional groundwater flow systems are included for comparison (Table 2b). Table S2a. U concentrations and 234U/238U activity ratios for groundwater samples from boreholes in close proximity to cored boreholes sampled for fracture/matrix studies (red symbols on Figure 1). Borehole ID

Latitude (° N), NAD83

UE-19h ER-20-6#1

Mean values U 234U/238U conc., AR µg/L

Longitude (°), NAD83

Date collected

37.342751

-116.374447

12/12/1999

21.0

0.08

6.718

0.022

37.260151

-116.421661

12/17/1996

3.09

0.02

4.221

0.010

ER-20-6#1

37.260151

-116.421661

8/27/1997

3.04

0.02

4.431

0.019

ER-20-6#1

37.260151

-116.421661

5/14/1998

3.09

0.02

4.395

0.012

ER-20-6#2

37.259881

-116.422055

11/27/1996

3.11

0.02

4.542

0.013

ER-20-6#3

37.259137

-116.422425

12/16/1996

2.45

0.02

4.647

0.012

ER-20-6#3

37.259137

-116.422425

5/13/1998

2.57

0.03

4.867

0.060

U-20 WW

37.251357

-116.430171

11/5/1997

2.31

0.02

4.773

UE-20bh 1

37.244910

-116.410058

12/8/1999

0.896

0.004

U-20n, upper zone

37.242582

-116.421101

7/27/1998

2.65

0.02

U-20n, lower zone

37.242582

-116.421101

9/21/1998

2.40

0.02

ER-20-7

37.212988

-116.479999

9/24/2010

8.14

0.04

3.046

0.004

ER-EC-1

37.206256

-116.530633

2/1/2000

9.22

0.03

3.487

0.010

ER-EC-1

37.206256

-116.530633

6/3/2003

9.26

0.02

3.503

0.006

ER-EC-1

37.206256

-116.530633

4/2/2009

9.21

0.10

3.498

0.005

ER-EC-11

37.197491

-116.495651

5/18/2010

1.76

0.12

4.041

0.007

ER-20-4

37.195349

-116.441162

9/20/2011

1.72

0.02

5.355

0.009

1.72

5.355

ER-20-8-2

37.192969

-116.475021

12/17/2009

2.52

0.02

3.875

0.006

2.52

3.875

ER-20-8

37.193032

-116.474867

6/27/2011

2.71

0.02

3.669

0.004

2.73

3.85

ER-20-8

37.193032

-116.474867

8/8/2011

2.76

0.02

4.039

0.006

ER-EC-6

37.188716

-116.497574

2/10/2000

5.58

0.02

3.698

0.009

ER-EC-6

37.188716

-116.497574

6/10/2003

5.30

0.02

3.676

0.007

5.41

3.68

ER-EC-6

37.188716

-116.497574

4/9/2009

5.34

0.06

3.667

0.080

ER-EC-12, upper zone

37.173236

-116.492882

11/27/2011

2.40

0.02

6.392

0.010

2.40

6.392

0.0012

3.951

0.010

0.01

3.951

0.10

4.060

0.006

6.86

4.060

2.52

4.04

U conc. ( µg/L), ±2σ

ER-EC-12, lower zone

37.173236

-116.492882

3/26/2012

0.0104

ER-EC-13, upper zone

37.169313

-116.549195

7/12/2012

6.86

Median

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234

U/238U AR, ±2σ

20.97

6.718

3.07

4.35

3.11

4.542

2.51

4.76

0.012

2.31

4.773

3.682

0.027

0.90

3.682

4.036

0.013

2.52

3.52

3.009

0.008 8.14

3.046

9.23

3.50

1.76

4.041


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Table S2b. U concentrations and 234U/238U activity ratios for groundwater samples from boreholes not in close proximity to those sampled for fracture/matrix studies (green symbols on Figure 1). Location/Borehole

Latitude (° N), NAD83

Tolicha Peak Well, USAF

Longitude (°), NAD83

Date collected

37.308353

-116.782067

11/12/1997

U-12s

37.228287

-116.216690

8/22/2006

0.986

0.053

ER-12-4

37.219578

-116.184023

8/15/2005

0.0977

0.0004

ER-12-4

37.219578

-116.184023

4/25/2006

0.383

0.016

2.093

0.006

ER-12-4

37.219578

-116.184023

9/25/2008

0.343

0.002

2.039

0.004

ER-12-3

37.194968

-116.214996

7/6/2005

1.90

0.02

2.206

0.005

ER-12-3

37.194968

-116.214996

9/17/2008

1.92

0.03

2.152

0.003

ER-12-1

37.184856

-116.185093

12/8/2004

1.61

ER-12-2

37.171475

-116.123383

4/1/2003

0.0166

U conc. ( µg/L), ±2σ 2.53

0.01

234

U/238U AR, ±2σ

4.039

Mean values U 234U/238U conc., AR µg/L

0.016

2.53

4.039

2.204

0.006

0.99

2.204

2.125

0.011 0.2745

2.0859

1.91

2.18

0.02

7.054

0.024

1.61

7.054

0.0002

6.280

0.560

0.02

6.280

0.61

2.894

4.04

2.86

8.04

4.51

5.95

6.067

8.40

12.64

4.80

5.04

3.28

6.41

WW 8 (USGS HTH-8)

37.165536

-116.290033

11/4/1997

0.609

0.010

2.89

0.15

ER-EC-4

37.158805

-116.631953

8/17/2000

4.07

0.02

2.835

0.009

ER-EC-4

37.158805

-116.631953

6/24/2003

4.01

0.02

2.880

0.006

ER-EC-2A

37.144937

-116.568272

7/27/2000

9.16

0.04

4.034

0.021

ER-EC-2A

37.144937

-116.568272

7/8/2003

6.92

0.02

4.994

0.010

UE-18r

37.134701

-116.445596

12/9/1999

5.95

0.02

6.067

0.016

ER-18-2

37.103935

-116.373762

3/21/2000

8.35

0.03

12.655

0.036

ER-18-2

37.103935

-116.373762

6/17/2003

8.45

0.27

12.631

0.022

ER-EC-8

37.102789

-116.632176

7/12/2000

4.88

0.02

5.051

0.014

ER-EC-8

37.102789

-116.632176

7/1/2003

4.72

0.02

5.038

0.010

ER-EC-5

37.084493

-116.565453

5/25/2000

3.27

0.02

6.404

0.017

ER-EC-5

37.084493

-116.565453

7/15/2003

3.29

0.02

6.41

0.17

ER-OV-01

37.084383

-116.681175

11/8/1997

9.43

0.03

3.704

0.010

9.43

3.704

ER-OV-06A

37.084383

-116.681175

11/8/1997

5.24

0.02

3.254

0.009

5.24

3.254

3.28

4.04

Median

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Rare Earth Concentration Data Rare‐earth element concentrations were determined at U.S. Geological Survey Radiogenic Isotope Laboratory for several samples of intact‐ interior and brecciated core, as well as samples from three wafer profiles that include scraped fracture surfaces as well as subjacent matrix. Determinations were made by quadrapole ICP‐MS on the same rock digestions used to determine uranium‐series isotopes. Analytical uncertainties are estimated to be better than ±10% of the given values. Chondrite data are from Table 1 of Anders and Grevesse (1989). Table S3. Concentrations (in µg/g) of rare-earth elements from selected whole-rock samples of intact interior and brecciated core as well as samples from wafer profiles. Borehole

Depth interval (ft)

Sample type

La

Ce

Pr

Nd

Sm

Eu

Gd

Tb

Dy

Ho

Er

Tm

Yb

Lu

PM-1

2820.5 – 2820.6

Intact interior

36.1

75.1

9.26

31.7

7.00

0.33

6.21

1.00

6.12

1.20

3.51

0.54

3.61

0.54

PM-1

3140.5 – 3140.7

Intact interior

61.9

121

12.5

41.5

7.24

0.78

5.81

0.89

5.27

1.00

2.92

0.45

2.82

0.42

PM-1

3456.4 – 3456.6

Intact interior

53.4

109

12.9

45.3

9.20

0.21

7.88

1.36

8.23

1.67

4.91

0.75

4.89

0.74

PM-1

6614 – 6614.2

Intact interior

57.4

125

14.8

53.0

12.2

0.18

11.5

2.14

13.7

2.77

8.34

1.31

8.01

1.28

PM-1

6079 – 6079.2

UE-20f

3904.2 – 3904.3

UE-20f

4159.8 – 4160

UE-20f

3030.4 – 3030.6

PM-1 PM-1 PM-1 PM-1 PM-1 PM-1

6084 – 6084.3 6084 – 6084.3 6084 – 6084.3 6084 – 6084.3 6084 – 6084.3 6084 – 6084.3

UE-19fS UE-19fS UE-19fS UE-19fS UE-19fS UE-19fS UE-19fS UE-20f UE-20f UE-20f UE-20f UE-20f UE-20f UE-20f

Breccia

59.3

119

16.0

58.2

14.0

0.21

13.7

2.56

16.6

3.44

9.88

1.56

9.32

1.49

Intact interior

54.2

97.1

10.9

37.3

6.31

0.65

5.26

0.78

4.55

0.86

2.54

0.37

2.46

0.37

Intact interior

30.5

59.7

6.74

22.7

4.48

0.39

3.89

0.63

3.90

0.74

2.20

0.33

2.16

0.32

Breccia

30.9

62.7

7.19

24.6

4.94

0.31

4.29

0.67

4.11

0.81

2.39

0.37

2.43

0.36

Fracture surface Wafer 1 of 18 Wafer 2 of 18 Wafer 4 of 18 Wafer 9 of 18 Wafer 16 of 18

106.1 67.3 60.8 62.7 67.4 73.7

334.8 152.0 132.0 139.8 154.0 160.0

33.57 18.54 16.59 17.26 18.35 20.67

120.7 68.3 61.2 64.5 67.9 75.2

22.4 17.0 14.7 15.4 16.1 17.2

0.22 0.24 0.21 0.22 0.23 0.23

13.9 17.7 15.2 15.5 16.1 16.7

2.09 3.29 2.81 2.80 2.93 3.06

12.1 21.8 17.8 17.8 18.8 20.0

2.38 4.46 3.70 3.63 3.81 4.11

6.82 13.1 10.9 10.7 11.3 12.4

0.99 1.92 1.62 1.59 1.67 1.90

6.39 12.6 10.7 10.8 11.2 12.4

0.92 1.83 1.54 1.59 1.65 1.80

5211.4 – 5212 5211.4 – 5212 5211.4 – 5212 5211.4 – 5212 5211.4 – 5212 5211.4 – 5212 5211.4 – 5212

Fracture surface Wafer 1 of 6 Wafer 2 of 6 Wafer 3 of 6 Wafer 4 of 6 Wafer 5 of 6 Wafer 6 of 6

35.1 94.0 101.4 97.9 101.0 103.3 117.6

19.2 215 232 215 194 205 256

8.61 23.3 26.0 24.6 25.2 25.5 29.3

24.5 84.0 95.0 89.7 90.3 91.2 105.2

3.23 16.8 18.6 17.6 17.5 17.7 20.4

0.16 0.31 0.31 0.30 0.27 0.30 0.36

2.65 15.2 16.4 15.4 15.3 15.4 18.2

0.48 2.63 2.75 2.64 2.55 2.56 3.04

2.94 16.0 16.9 16.2 15.7 15.8 18.8

0.60 3.27 3.45 3.35 3.22 3.23 3.88

1.85 9.64 10.4 9.87 9.81 9.87 12.0

0.28 1.46 1.60 1.51 1.47 1.53 1.79

1.99 9.83 10.8 10.4 10.3 10.4 12.4

0.30 1.53 1.68 1.61 1.62 1.61 1.92

2848.7 – 2849 2848.7 – 2849 2848.7 – 2849 2848.7 – 2849 2848.7 – 2849 2848.7 – 2849 2848.7 – 2849

Fracture surface Wafer 1 of 12 Wafer 2 of 12 Wafer 3 of 12 Wafer 5 of 12 Wafer 6 of 12 Wafer 8 of 12

20.7 25.0 19.3 63.3 18.3 17.9 20.8

402 62.7 36.2 124 32.3 33.0 37.2

7.18 5.27 4.02 12.7 3.55 3.56 3.82

32.5 17.8 13.2 42.6 11.4 11.3 12.1

16.0 3.35 2.06 7.17 1.67 1.68 1.60

0.89 0.48 0.25 0.53 0.26 0.29 0.26

31.4 3.45 1.54 5.60 1.24 1.24 1.15

7.17 0.62 0.21 0.81 0.17 0.19 0.17

54.2 4.19 1.18 4.27 0.98 1.12 1.09

11.4 0.84 0.21 0.73 0.19 0.23 0.24

32.7 2.45 0.62 1.97 0.60 0.74 0.81

4.65 0.34 0.10 0.26 0.087 0.11 0.13

29.9 2.40 0.65 1.54 0.73 0.97 1.09

4.31 0.34 0.10 0.23 0.12 0.15 0.17

0.29

0.763

0.117

0.572

0.183

0.069

0.249

0.043

0.302

0.0693

0.198

0.03

0.2

0.03

Mean concentrations for C1 chondrites*

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Chondrite-normalized concentraon

1000

a)

Online Supplement

100

10

Intact interior & brecciated core samples 1 1000

La Ce Pr Nd

UE-20f: 3904’ UE-20f: 4160’ UE-20f: 3030’

Sm Eu Gd Tb Dy Ho Er Tm Yb Lu

c)

Fracture surface Wafer 4/6 Wafer 1/6 Wafer 5/6 Wafer 2/6 Wafer 6/6 Wafer 3/6

100

10

1

b)

Fracture surface Wafer 1/18 Wafer 2/18 Wafer 4/18

100

10 Wafer 9/18 Wafer 16/18

1 1000

UE-19fS: 5211’ La Ce Pr Nd

08/17/2013

1000

PM-1: 2821’ PM-1: 3141’ PM-1: 3456’ PM-1: 6614’ PM-1: 6079’

Chondrite-normalized concentraon



PM-1: 6084’ La Ce Pr Nd

d)


Fracture surface Wafer 1/12 Wafer 2/12 Wafer 3/12

Wafer 5/12 Wafer 6/12 Wafer 8/12

100

10

1

UE-20f: 2849’ La Ce Pr Nd


Figure S3: Chondrite‐normalized rare‐earth element plots of rock matrix for intact interior and brecciated samples from boreholes PM‐1 and UE‐20f (a), and for fracture‐surfaces and associated subjacent matrix from three separate wafer profiles (b, c, and d). Data are from Tabl e S3 (online supplement) and normalized to concentrations in chondrite meteorites reported in Anders and Grevesse (1989). Grey fields represent range of values observed for whole‐rock compositions shown in (a).

Analytical Solutions to Open‐System Isotope Evolution Equations Differential equations describing the change in U‐series isotope activities with time are given in Section 4.3.2 of Dequincey et al. (2002) and Appendix B of Ma et al. (2010). These equations assume that U is mobile and can be added to or removed from the solid phase at constant rates through time. The equations are formulated to include a term that combines all processes leading to the input of U (F234 and F238 activity input rates, in atoms yr‐2), a term that combines all processes leading to the removal of U (k234 and k238 leaching rate constants, in yr‐1), and a term that accounts for radioactive decay of each isotope (238, 234, and 230 decay constants, in yr‐1). Th is considered geochemically immobile in the oxidizing groundwater that flows through the saturated zone beneath Pahute Mesa; therefore, terms for F230 or k230 are considered to be zero. Equations for the rate of change of each isotope were solved by hand and verified using MATLAB™ to derive the number of atoms at time t based on the number of atoms present in the system initially (238U0, 234U0, and 230Th0). The following solutions were derived:

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∙

∙

Online Supplement

∙

1

08/17/2013

∙

∙

∙

1

∙

∙ 1

where b238 = k238+238 and b234 = k234+234, and where Q238 and Q234 represent atomic input rates (F238/238 and F234/234, respectively). Atomic abundances can be converted to activity ratios by multiplying by the decay constants: ∙ ∙

∙ ∙

In practice, values for initial isotope abundances in the solid phase were assigned based on U concentrations observed in the rock and the assumed isotopic composition of the starting material (either 234U/238U AR = 230Th/238U AR = 1.0 for secular equilibrium or 234U/238U AR = 4.0 and 230Th/238U AR = 0.0 for newly formed fracture minerals). Values for input activities (F238 and F234) were then determined by adjusting groundwater U concentrations until the F238/(238U)0 reached values targeted in individual simulations, with F234 adjusted to the value required by the assumed input activity ratio (i.e., 4 for Pahute Mesa groundwater). In addition to F238/(238U)0, the leaching rate constant for 238U (i.e., k238) and amount of fractionation during leaching (i.e., k234/k238) were allowed to vary for any given simulation. Model results identical to those given by Dequincey et al. (2002) were obtained when the same input parameters were used.

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Simulations of Open‐System Uranium‐Series Isotope Evolution Results for a number of simulations involving open‐system evolution of U‐series isotopes are given in the main text and figures 6 and 7. The following figures show additional results intended to simulate transient behavior in some samples of discrete‐fracture and wafer‐profile samples.

1

/ 238U AR

2 1

/ 238U AR

2

234U

0 4

1

2 1

k234/k238 = 4 k238 = 5×10-5 Q238 /(238U)0 = 1×10-5 Q238 /(238U)0 = 5×10-5 Q238 /(238U)0 = 1×10-4 Q238 /(238U)0 = 5×10-4 Q238 /(238U)0 = 1×10-3

0

1 230Th

2

3

4 7 10

F234/F238 = 4.0 k238 = 1×10 -5 -5 k238 =238 5×10 F238 (U)/0 = 1×10-7 -5 238 F238 /( U)0 = 5×10

3

0

3

0

1

2

0 4

k234/k238 = 4 k238 = 1×10-5 Q238 /(238U)0 = 1×10-6 Q238 /(238U)0 = 1×10-5 Q238 /(238U)0 = 5×10-5 Q238 /(238U)0 = 1×10-5 Q238 /(238U)0 = 5×10-4

3

/ 238U AR

1

2

234U

2

1

3

/ 238U AR

3

0 4

234U

4

k234/k238 = 4 k238 = 1×10-6 Q238 /(238U)0 = 1×10-6 Q238 /(238U)0 = 5×10-6 Q238 /(238U)0 = 1×10-5 Q238 /(238U)0 = 5×10-5 Q238 /(238U)0 = 1×10-4

234U

234U

/ 238U AR

4

1

2 7

0

4

F234/F238 = 2 .0 k238 = 5×10-5 F238 /(238U)0 = 5×10-5

1

2

3

230Th

/ 238U

AR

4

4

/ 238U AR

Figure S4. Simulations for open‐system U‐series isotope evolution for a solid phase starting at secular equilibrium (plots on left side) as well as the composition of newly formed mineral precipitated from groundwater (plots on right side), and then subjected to open‐system addition and removal of U using equations given in the previous section. Simulations shown on the left side used fixed values for fractionation of input and output processes (i.e., F234/F238 = k234/k238 = 4) and variable values for the intensity of input and removal (variable parameter is color coded to resulting evolution curve). Simulations shown on the right side used a fixed value for the leaching rate constant and intensity of atomic U input (k238 = Q238/(238U)0 = 5×10‐5 yr‐1) and allowed fractionation in the input term to vary (F234/F238 = 4 in upper plot and 2 in lower plot) along with fractionation in the output term (k238/k238 values from 1 to 10).

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234U

/ 238U AR

4 k234/k238 = 3.5 Q238 /(238U)0 = 1×10-5 k238 = 1×10-7 k238 = 1×10-6 k238 = 1×10-5 k238 = 2×10-5 k238 = 3×10-5 k238 = 5×10-5

3 2 1

k238 = 1×10-5 238 F238 (U)/0 = 1×10-7

/ 238U AR

2

234U

0 4

1

3

k234/k238 = 3.5 Q238 /(238U)0 = 1×10-6 k238 = 1×10-7 k238 = 1×10-6 k238 = 1×10-5 k238 = 2×10-5 k238 = 3×10-5

234U

/ 238U AR

0 4 3

k234/k238 = 3.5 Q238 /(238U)0 = 1×10-7 k238 = 1×10-7 k238 = 1×10-6 k238 = 1×10-5 k238 = 2×10-5

2 1 0

0

1 230Th

2

3

/ 238U AR

4

Figure S5. Simulations for open‐system U‐series isotope evolution for a solid phase starting at secular equilibrium that is subjected to open‐system addition and removal of U using equations given in the previous section. Simulations used fixed, nearly‐equal values for fractionation of input and output processes (i.e., F234/F238 = 4 and k234/k238 = 3.5) and allowed values for the intensity of input and removal to vary (variable parameter is color coded to resulting evolution curve).

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References Anders, E., Grevesse, N., 1989. Abundances of the elements: meteoric and solar. Geochim. Cosmochim. Acta 53, 197–214. Broxton, D.E., Warren, R.G., Byers, F.M., Scott, R.B., 1989, Chemical and Mineralogic Trends Within the Timber Mountain‐Oasis Valley Caldera Complex, Nevada: Evidence for Multiple Cycles of Chemical Evolution in a Long‐Lived Silicic Magma System. J. Geophys. Res. 94, 5961‐5985. Dequincey, O., Chabaux, F., Clauer, N., Sigmarsson, O., Liewig, N., Leprun, J.‐C., 2002. Chemical mobilizations in laterites: Evidence from trace elements and 238U‐234U‐230Th disequilibria. Geochim. Cosmochim. Acta, 66, 1197–1210. Gladney, E.S., Jones, E.A., Nickell, E.J., Roelandts, I., 1990, 1988 Compilation of elemental concentration data for USGS basalt BCR‐1. Geostandards Newsletter 14, 209–359. Fenelon, J.M., Sweetkind, D.S., Laczniak, R.J., 2010. Groundwater flow systems at the Nevada Test Site, Nevada: a synthesis of potentiometric contours, hydrostratigraphy, and geologic structures. U.S. Geol. Survey Prof. Paper, 1771, 54 p. Weis, D., Kieffer, B., Maerschalk, C., Barling, J., Williams, G.A., Hanano, D., Pretorius, W., Mattielli, N., Scoates, J.S., Goolaerts, A., Friedman, R.M., Mahoney, J.B., 2006. High‐Precision Isotopic Characterization of USGS reference materials by TIMS and MC‐ICP‐MS. Geochem., Geophys., Geosyst. (G‐cubed) 7, 30 p.

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