Water Resources of the Basin and Range Carbonate-Rock Aquifer System, White Pine County, Nevada, and Adjacent Areas in Nevada and Utah - Draft Report

Welch, Alan H.; Bright, Daniel J.

doi:10.3133/ofr20071156

Cited by 22 publications

(17 citation statements)

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“…The range of measured permeability variations of basin fill and carbonate aquifers within the Basin and Range varies between about 10 )9 and 10 )14 m 2 (Blankennagel & Weir 1973;Winograd & Thordarson 1975;Plume & Carlton 1988;Dettinger et al 1995;Maurer et al 1996;Prudic & Herman 1996;Welch & Bright 2007). On the basis of grain size, we estimated that confining unit's permeability varied between about 10 )16 and 10 )18 m 2 (Neuzil 1994).…”

Section: Hydrostratigraphy and Fault Permeabilitymentioning

confidence: 80%

Analytical and numerical models of hydrothermal fluid flow at fault intersections

Person¹,

Hofstra²,

Sweetkind³

et al. 2012

Geofluids

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Fault intersections are the locus of hot spring activity and Carlin‐type gold mineralization within the Basin and Range, USA. Analytical and numerical solutions to Stokes equation suggest that peak fluid velocities at fault intersections increase between 20% and 47% when fracture apertures have identical widths but increase by only about 1% and 8% when aperture widths vary by a factor of 2. This suggests that fault zone intersections must have enlarged apertures. Three‐dimensional finite element models that consider intersecting 10‐ to 20‐m wide fault planes resulted in hot spring activity being preferentially located at fault zone intersections when fault zones were assigned identical permeabilities. We found that the onset of convection at the intersections of the fault zones occurred in our hydrothermal model over a narrow permeability range between 5 × 10−13 and 7 × 10−13 m2. Relatively high vertical fluid velocities (0.3–3 m year−1) extended away from the fault intersections for about 0.5–1.5 km. For the boundary conditions and fault plane dimensions used, peak discharge temperatures of 112°C at the water table occurred with an intermediate fault zone permeability of 5 × 10−13 m2. When fault plane permeability differed by a factor of 2 or more, the locus of hot spring activity shifted away from the intersections. However, increasing the permeability at the core of the fault plane intersection by 40% shifted the discharge back to the intersections. When aquifer units were assigned a permeability value equal to those of the fault planes, convective rolls developed that extend about 3 km laterally along the fault plane and into the adjacent aquifer.

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Section: Hydrostratigraphy and Fault Permeabilitymentioning

confidence: 80%

Analytical and numerical models of hydrothermal fluid flow at fault intersections

Person¹,

Hofstra²,

Sweetkind³

et al. 2012

Geofluids

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“…Most agricultural related hydrogeological studies have focused on characterizing shallow fl ow conditions (<500 m) within alluvial aquifers (e.g., Prudic and Herman, 1996). Municipal water supply, mine dewatering, and nuclear waste isolation studies have considered groundwater fl ow conditions within the deeper (>2 km) Paleozoic carbonate aquifer system (Welch and Bright, 2007;Maurer et al, 1996;Belcher, 2004). Plume and Carlton (1988) indicated that important aquifers of the Great Basin include shallow alluvial aquifers of Quaternary-Tertiary age (to 400 m thick), and Paleozoic carbonate rock aquifers (to 5 km thick).…”

Section: Great Basin Hydrogeology Flow Systems Faults and Heat Flomentioning

confidence: 99%

“…Regional springs are characterized by (1) high discharge rates, >~550 m 3 /day, at relatively constant volumes (Harrill et al, 1988); (2) elevated temperatures, >27 °C, assumed to be indicative of deep circulation (Miffl in, 1968); and (3) by water-chemistry indicative of fl ow through consolidated carbonate rock (Miffl in, 1968;Steinkampf and Werrell, 2001). Regional groundwater fl ow in the deeper carbonate aquifer system results in signifi cant interbasin fl uid transfer (Harrill and Prudic, 1998;Nichols, 2000;Welch and Bright, 2007). These regional fl ow systems are responsible for signifi cant lateral transport of heat, but probably do not account for the occurrence of modern geothermal features such as Dixie Valley or Beowawe, which appear to require the addition of magmatic heat or fl uid circulation along deep-seated faults .…”

Section: Explanation Geologic Unitsmentioning

confidence: 99%

Hydrologic models of modern and fossil geothermal systems in the Great Basin: Genetic implications for epithermal Au-Ag and Carlin-type gold deposits

et al. 2008

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The Great Basin region in the western United States contains active geothermal systems, large epithermal Au-Ag deposits, and worldclass Carlin-type gold deposits. Temperature profi les, fl uid inclusion studies, and isotopic evidence suggest that modern and fossil hydrothermal systems associated with gold mineralization share many common features, including the absence of a clear magmatic fl uid source, discharge areas restricted to fault zones, and remarkably high temperatures (>200 °C) at shallow depths (200-1500 m). While the plumbing of these systems varies, geochemical and isotopic data collected at the Dixie Valley and Beowawe geothermal systems suggest that fl uid circulation along fault zones was relatively deep (>5 km) and comprised of relatively unexchanged Pleistocene meteoric water with small (<2.5‰) shifts from the meteoric water line (MWL). Many fossil ore-forming systems were also dominated by meteoric water, but usually exhibit δ 18 O fl uid-rock interactions with larger shifts of 5‰-20‰ from the MWL.Here we present a suite of two-dimensional regional (100 km) and local (40-50 km) scale hydrologic models that we have used to study the plumbing of modern and Tertiary hydrothermal systems of the Great Basin. Geologically and geophysically consistent cross sections were used to generate somewhat idealized hydrogeologic models for these systems that include the most important faults, aquifers, and confi ning units in their approximate confi gurations. Multiple constraints were used, including enthalpy, δ 18 O, silica compositions of fl uids and/or rocks, groundwater residence times, fl uid inclusion homogenization temperatures, and apatite fi ssion track anomalies.Our results suggest that these hydrothermal systems were driven by natural thermal convection along anisotropic, subvertical faults connected in many cases at depth by permeable aquifers within favorable lithostratigraphic horizons. Those with minimal fl uid δ 18 O shifts are restricted to high-permeability fault zones and relatively small-scale (~5 km), single-pass fl ow systems (e.g., Beowawe). Those with intermediate to large isotopic shifts (e.g., epithermal and Carlin-type Au) had larger-scale (~15 km) loop convection cells with a greater component of fl ow through marine sedimentary rocks at lower water/rock ratios and greater endowments of gold. Enthalpy calculations constrain the duration of Carlin-type gold systemsto probably <200 k.y. Shallow heat fl ow gradients and fl uid silica concentrations suggest that the duration of the modern Beowawe system is <5 k.y. However, fl uid fl ow at Beowawe during the Quaternary must have been episodic with a net duration of ~200 k.y. to account for the amount of silica in the sinter deposits.In the Carlin trend, fl uid circulation extended down into Paleozoic siliciclastic rocks, which afforded more mixing with isotopically enriched higher enthalpy fl uids. Computed fi ssion track ages along the Carlin trend included the convective effects, and ranged between 91.6 and 35.3 Ma. Older fi ssion tra...

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“…, 2007; Smith et al. , 2007; Welch and Bright, 2007) were based solely on estimates of mean annual ET, assuming that no other ground water sinks existed in the study area. While ground‐water ET as an overall water budget component has been estimated in other studies, including BARCAS, the estimates of sensitivity and uncertainty have not been analyzed systematically to the best of our knowledge.…”

Section: Introductionmentioning

confidence: 99%

“…In this study, we propose an approach to quantify the uncertainty and sensitivity of ground‐water discharge estimates. The basic ground‐water discharge model presented by Welch and Bright (2007) is described below and used to demonstrate the approach proposed in this study. However, the procedure to quantify uncertainty and sensitivity can be generalized to easily handle other, more complicated models involving large numbers of independent variables.…”

Section: Introductionmentioning

confidence: 99%

Sensitivity and Uncertainty of Ground‐Water Discharge Estimates for Semiarid Shrublands¹

Zhu

Young

2009

J American Water Resour Assoc

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We proposed a step‐by‐step approach to quantify the sensitivity of ground‐water discharge by evapotranspiration (ET) to three categories of independent input variables. To illustrate the approach, we adopt a basic ground‐water discharge estimation model, in which the volume of ground water lost to ET was computed as the product of the ground‐water discharge rate and the associated area. The ground‐water discharge rate was assumed to equal the ET rate minus local precipitation. The objective of this study is to outline a step‐by‐step procedure to quantify the contributions from individual independent variable uncertainties to the uncertainty of total ground‐water discharge estimates; the independent variables include ET rates of individual ET units, areas associated with the ET units, and precipitation in each subbasin. The specific goal is to guide future characterization efforts by better targeting data collection for those variables most responsible for uncertainty in ground‐water discharge estimates. The influential independent variables to be included in the sensitivity analysis are first selected based on the physical characteristics and model structure. Both regression coefficients and standardized regression coefficients for the selected independent variables are calculated using the results from sampling‐based Monte Carlo simulations. Results illustrate that, while as many as 630 independent variables potentially contribute to the calculation of the total annual ground‐water discharge for the case study area, a selection of seven independent variables could be used to develop an accurate regression model, accounting for more than 96% of the total variance in ground‐water discharge. Results indicate that the variability of ET rate for moderately dense desert shrubland contributes to about 75% of the variance in the total ground‐water discharge estimates. These results point to a need to better quantify ET rates for moderately dense shrubland to reduce overall uncertainty in estimates of ground‐water discharge. While the approach proposed here uses a basic ground‐water discharge model taken from an earlier study, the procedure of quantifying uncertainty and sensitivity can be generalized to handle other types of environmental models involving large numbers of independent variables.

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Water Resources of the Basin and Range Carbonate-Rock Aquifer System, White Pine County, Nevada, and Adjacent Areas in Nevada and Utah - Draft Report

Cited by 22 publications

References 0 publications

Analytical and numerical models of hydrothermal fluid flow at fault intersections

Analytical and numerical models of hydrothermal fluid flow at fault intersections

Hydrologic models of modern and fossil geothermal systems in the Great Basin: Genetic implications for epithermal Au-Ag and Carlin-type gold deposits

Sensitivity and Uncertainty of Ground‐Water Discharge Estimates for Semiarid Shrublands¹

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Water Resources of the Basin and Range Carbonate-Rock Aquifer System, White Pine County, Nevada, and Adjacent Areas in Nevada and Utah - Draft Report

Cited by 22 publications

References 0 publications

Analytical and numerical models of hydrothermal fluid flow at fault intersections

Analytical and numerical models of hydrothermal fluid flow at fault intersections

Hydrologic models of modern and fossil geothermal systems in the Great Basin: Genetic implications for epithermal Au-Ag and Carlin-type gold deposits

Sensitivity and Uncertainty of Ground‐Water Discharge Estimates for Semiarid Shrublands1

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Sensitivity and Uncertainty of Ground‐Water Discharge Estimates for Semiarid Shrublands¹