YGS Miscellaneous Report 19

Assessment of the thermo-hydraulic properties of rock samples near Takhini Hot Springs and in the Tintina fault zone, Yukon

H. Langevin Institut de la recherche scientifique, Québec T.A. Fraser Yukon Geological Survey J. Raymond Institut de la recherche scientifique, Québec Published under the authority of the Department of Energy, Mines and Resources, Government of Yukon http://www.emr.gov.yk.ca. Printed in Whitehorse, Yukon, 2020.

Publié avec l’autorisation du Ministères de l’Énergie, des Mines et des Ressources du gouvernement du Yukon, http://www.emr.gov.yk.ca. Imprimé à Whitehorse (Yukon) en 2020.

© Department of Energy, Mines and Resources, Government of Yukon

This, and other Yukon Geological Survey publications, may be obtained from: Yukon Geological Survey 102-300 Main Street Box 2703 (K-102) Whitehorse, Yukon, Canada Y1A 2C6 email [email protected] Visit the Yukon Geological Survey website at http://data.geology.gov.yk.ca

In referring to this publication, please use the following citation: Langevin, H., Fraser, T.A. and Raymond, J., 2020. Assessment of the thermo-hydraulic properties of rock samples near Takhini Hot Springs and in the Tintina fault zone, Yukon. Yukon Geological Survey, Miscellaneous Report 19, 30 p.

Cover photo: Geothermal drilling of the well at the Takhini drill site; located on Ta’an Kwächän Council Settlement Lands, 2 km from the Takhini Hot Springs. Table of Contents Abstract ...... 1 Introduction ...... 2 Project background ...... 2 Geological setting ...... 3 Lithology ...... 4 Methodology ...... 5 Sampling ...... 5 Thermal conductivity and diffusivity ...... 8 Relationship between thermal conductivity and temperature ...... 9 Radiogenic heat production ...... 10 Hydraulic conductivity ...... 10 Consolidated rocks ...... 10 Hydraulic conductivity of unconsolidated/brecciated rocks ...... 11 Fractured rocks ...... 11 Takhini geological cross sections ...... 12 Results ...... 14 Takhini area ...... 14 Thermal properties in YGS-17-01 (well samples) ...... 14 Thermal properties in outcrop samples ...... 14 Hydraulic conductivity ...... 17 Relationship between thermal conductivity and temperature of rocks ...... 19 Tintina well (YGS-18-01) ...... 19 Thermal properties ...... 19 Hydraulic conductivity ...... 19 Geological cross sections ...... 22 Discussion ...... 22 Heat transfer and groundwater flow ...... 22 Takhini well (YGS-17-01) ...... 22 Tintina well (YGS-18-01) ...... 24 Geothermal setting ...... 25 Takhini Hot Springs region ...... 25 Tintina well region ...... 26

YGS Miscellaneous Report 19 Thermo-hydraulic properties – Takhini Hot Springs and Tintina fault zone Conclusions ...... 26 Acknowledgements ...... 28 References ...... 28 Appendices ...... 30

Thermo-hydraulic properties – Takhini Hot Springs and Tintina fault zone YGS Miscellaneous Report 19 Abstract As part of an emerging program to understand ground temperature and geothermal heat potential in Yukon, the Yukon Geological Survey drilled two temperature gradient wells in south-central Yukon: one near the Takhini Hot Springs in 2017, and a second in the Tintina Trench in 2018. This study presents the thermo-hydraulic properties of drill core from these wells and from selected outcrops, to evaluate heat transfer mechanisms in the subsurface and provide a heat flow model to characterize the geothermal potential of these regions. Thermo-hydraulic properties of the rocks in the Takhini well have a moderate thermal conductivity (average of ~3 W m-1 K-1) and a low matrix hydraulic conductivity for consolidated rocks (on the order of 10-9 m s-1), corresponding to a linear geothermal gradient of 16°C km-1 in the upper part of the well and suggesting conductive heat transfer between 50 and 450 m depth. Hydraulic conductivity of fractured and brecciated rocks on the order of 10-5 m s-1 (assuming a moderate fracture size of 100 µm), and topographic contrasts affecting the hydrostatic pressure driving groundwater flow in the area suggest that forced convective heat transfer in the bottom of the Takhini well is responsible for the strong geothermal gradient of 250°C km-1 observed between 450 and 500 m depth. The rocks in the Tintina well have low thermal conductivity (average of ~2 W m-1 K-1) and hydraulic conductivity ranging from 10-5 to 10-3 m s-1. The linear geothermal gradient (30°C km-1) indicates conductive heat transfer even though the rocks are permeable. The proximity of the well to a mountain range suggests a shallow groundwater path in the Tintina well area, with no evidence of surface hot springs. The location of steep faults appears to be a key pathway for deep groundwater to seep to surface and can explain the geothermal context near the Takhini well. Such a framework is a typical geothermal play type in orogenic belts. Although the Tintina well is found in a similar setting, this study does not identify potential for deep forced convective groundwater flow movements because hydraulic head difference along the faults may not be enough for the deep groundwater to rise since the faults are expected to be subvertical. This research, therefore, helps to characterize the subsurface and provides critical information needed for a successful exploration of geothermal energy resources.

YGS Miscellaneous Report 19 Thermo-hydraulic properties – Takhini Hot Springs and Tintina fault zone 1 Introduction with the Da Daghay Development Corporation, the economic arm of the TKC. The second well, YGS- Project background 18-01, is located in southeastern Yukon, ~15 km southwest of the village of Ross River, in the crustal- As part of the Yukon government’s initiative to find scale, strike-slip Tintina fault zone (Fig. 1). This well green energy solutions, the Yukon Geological Survey was drilled on a section of the highway right-of-way (YGS) began a geothermal research program in on the South Canol road, in the traditional territory 2016. Following regional assessments of geothermal of the Kaska Dena Nation, in partnership with the potential, including mapping the depth to the Curie Ross River Dena Council and the Dena Nezziddi point (Witter and Miller, 2017), and calculation of Development Corporation. Drilling program details radiogenic heat generative potential (Friend and and results are summarized in Fraser et al. (2018). Colpron, 2017), YGS drilled two 500 m temperature Stabilized downhole temperature was measured gradient (TG) wells to characterize the geothermal in the Takhini well at intervals of 50 m. This well gradient in specific study locations. The first well, has a variable geothermal gradient with depth YGS-17-01, was drilled in the Takhini River area, (Fig. 2a): 16.5°C km-1 is found in the upper 450 m northwest of the city of Whitehorse, ~2 km from of the well while 250°C km-1 is present at the bottom a hot spring having a surface water temperature 50 m (Fraser et al., 2018). In the Tintina well, measuring 46°C. The well was drilled on land owned stabilized downhole temperatures were measured at by the Ta’an Kwäch’än Council (TKC) First Nation, intervals of 20 m indicating an equilibrium geothermal and the project was advanced in collaboration gradient of ~31°C km-1 (Fig. 2b).

140° 130° 120° ° N ° N 0 0 7 .! hot springs hitehorse trough 7 Primary Highway Terranes Secondary Highway parautochthonous drill location allochthonous Major faults

& dextral strike-slip pine rcu Po $ sinistral strike-slip

( thrust n Yuko

rdill Co era f n tern li o d eas mit ef

° N o

T rm ° N 5 i

n 5 6 t a in t 6 a io n

D en a li

T e s l in T in ti na ° N ° N 0 0 6 6 Figure 1. Simplified terrane map of Yukon illustrating locations of major faults, hot 0 100 200 300 springs, and the Whitehorse km trough (Fraser et al., 2018).

140° 130°

2 Thermo-hydraulic properties – Takhini Hot Springs and Tintina fault zone YGS Miscellaneous Report 19 a temperature (°C) YGS and Institut national de la recherche scientifique - 1 1 3 (INRS) initiated a collaboration in 2019 to analyze rock samples from the YGS’ geothermal research thermistor program at the Laboratoire ouverte de géothermie temperature profile (LOG), in Québec. This paper reports on the findings 1 of this collaboration. The study investigates heat transfer mechanisms present in YGS’ temperature 1 gradient wells in order to provide a better 1.°C km understanding of the geothermal potential of these regions. Data collection involved analysis of rock thermal and hydraulic properties on core samples,

depth (m) as well as on outcrop samples in the Takhini region. 3 -1 This study provides quantitative measures of 3 thermal conductivity and diffusivity, radiogenic heat production and hydraulic conductivity values of the rock samples analyzed. °C km -1 Geological setting Yukon, in northwestern Canada, comprises rocks of the North American Cordillera, which record more temperature (°C) b - 1 1 3 than 1.8 b.y. of Earth history and the evolution of western North America (Nelson et al., 2013). thermistor Two main geological domains occur in Yukon temperature profile (Fig. 1): 1) Proterozoic to Triassic platformal and 1 basinal sedimentary strata deposited on the North American continental margin to the northeast 1 (parautochthonous terrane); and 2) Late Paleozoic

and younger allochthonous island arc and ocean terranes that accreted to the North American margin,

to the southwest, beginning in the Late Paleozoic. In Yukon, the dividing line between the two domains

depth (m) 3 is for the most part the Tintina fault, a dextral 3.°C km 3 strike-slip fault that has ~430 km of early Cenozoic displacement (Gabrielse et al., 2006). Near Ross River and the location of the Tintina well, the fault -1 zone is ~10 km wide and consists of six prominent subparallel fault strands linked by a series of high- angle synthetic faults (Mira Geoscience, 2017; Figure 2. Downhole temperature data and Yukon Geological Survey, 2018a). calculated geothermal gradient in the (a) Takhini well (YS-17-01) and (b) Tintina well (YGS-18-01; after Fraser et al., 2018).

YGS Miscellaneous Report 19 Thermo-hydraulic properties – Takhini Hot Springs and Tintina fault zone 3 The Takhini well was drilled in sedimentary Quaternary Quaternary 2.6 rocks of the Whitehorse trough (Fig. 3), an 33.9 Priabonian elongated northwest-trending Mesozoic 37.8 Bartonian sedimentary basin that extends 650 km from 41.2 unconformity Lutetian northern British Columbia to central Yukon 47.8 Eocene

(Fig. 1; Colpron et al., 2015). In the vicinity Ypresian c complex Flat Creek pluton of the well, Jurassic sedimentary rocks lie 56.0 Annie Ned batholith - Thanetian 59.2 unconformably upon Upper Triassic marine Selandian 61.6 cene

Pale o Danian sedimentary, volcanic and volcaniclastic 66.0

163.5 Coast pluton i rocks (Hart, 1997) and unconformably below Callovian 166.1 Upper Jurassic to Cretaceous non-marine unconformity conglomerate and sandstone deposited in Bathonian 168.3 intermontane settings (Long, 2015). Middle Bajocian

Jurassic to Paleogene granitoid plutons intruded Middle Jurassic 170.3 Whitehorse trough and older strata, including Aalenian 174.1 Richthofen an Eocene granitoid pluton ~2 km west of the Toarcian formation

drill site (Hart, 1997; Yukon Geological Survey, akhini well

182.7 T 2018a). Pliensbachian NordenskiöldNordenskiöld Based on desktop studies (e.g., depth to Curie

190.8 Laberge Group hitehorse trough

point mapping; radiogenic heat potential from Lower Jurassi c Sinemurian granite; see Fraser et al., 2018) and its proximity 199.3 to the ‘Pacific Ring of Fire’, the southwestern Hettangian unconformity 201.3 Mandanna part of Yukon is expected to have the highest Rhaetian mb Hancock mb geothermal heat potential. Hot springs occur 208.5 in various locations in the territory, although Norian exclusively south of 65°N (Fig. 1). riassic

T Casca ~227 member Aksala formation Lithology Upper Carnian Lewes River Group The Takhini well was drilled in the Richthofen Povoas formation formation and Nordenskiöld facies of the ~237 Whitehorse trough sedimentary basin (Fig. 3). Twelve distinct lithological units were riassic encountered (Fig. 4), which are fully described in T Ladinian unconformity Langevin et al. (2020). Highly fractured intervals Middle indicated by unconsolidated/brecciated rock Stikinia depositional basement occur between ~290 and 350 m depth. Felsic, intermediate and mafic dikes crosscut basinal or Takhini volcaniclastic sedimentary rocks. assemblage and older

Outcrops examined in the vicinity of the Takhini Carboniferous well include Carboniferous to Paleocene Figure 3. Geological units in the Takhini well area rocks: 1) variably deformed greenstone of the (modified from Colpron et al., 2015). Mississippian (or older) Takhini assemblage; 2) Upper Triassic volcanic and sedimentary rocks of the Lewes River Group, including

4 Thermo-hydraulic properties – Takhini Hot Springs and Tintina fault zone YGS Miscellaneous Report 19 basalt of the Povoas formation, and volcaniclastic Methodology sandstone (Casca member), limestone/marble (Hancock member), and maroon sandstone and Sampling shale (Mandanna member) of the Aksala formation; The primary focus for this study was the Takhini well and 3) clastic sedimentary rocks of the Laberge and nearby outcrops. Forty-one core samples were Group, including shale and sandstone of the collected from depths between 55 and 500 m, and Richthofen formation and minor volcaniclastic rocks represent all 12 lithological units encountered in of the Nordenskiöld facies. Paleocene intrusive the well (Fig. 4). An additional 41 outcrop samples rocks include granite and granodiorite of the Flat from near the well supplement the sample set Creek pluton and Annie Ned batholith (Hart, 1997; (Fig. 7). This additional sampling was undertaken Ruby Range suite of Colpron et al., 2016). to improve understanding of the distribution of the Six sedimentary units were encountered in the thermal and hydraulic properties in the region and at Tintina well, ranging from clay to pebble/cobble depth, and to characterize additional geological units conglomerate (Fig. 5). General lithological not intercepted in the well that may affect regional descriptions are provided in Fraser et al. (2018). groundwater flow and hot springs generation. As the well was drilled in a major fault zone, the core A secondary focus was given to 11 samples collected is overall poorly consolidated and rocks are difficult from the Tintina well to provide thermal and hydraulic to assign to any formation or age (Fig. 6). properties required for future heat flow assessments (Fig. 5).

0 m 100 m 200 m 300 m 400 m H1 H1 G TG T1

T G T

1 C e (m) T D 1 B fa c 25 m 125 m 325 m T1 425 m T G H e 225 m 2 no H1 samples T1 w su r G T G

o 1 es per met r

H1 actu r T1 epth bel T H D 50 m 150 m TG T G 250 m 350 m 450 m T umber of f r G G n T1G G H1 G T 1 G T H G H 1 1 T 1 H 1 T T 1 1 H1

A T1 T T1 H1 G T 75 m T 175 m 275 m 375 m G 475 m 1 G H1 T1G F H1 H G G T1 G 1 T1 H1 T1 T 1 T H T G 1 1 T1 H1 100 m 200 m G 400 m 500 m 300 m T1 G H <5 55 <5 <5 <5 <5 5 - 10 5 - 10 5 - 10 5 - 10 5 - 10 10 - 15 10 - 15 10 - 15 10 - 15 10 - 15

pebbly mafic dike volcaniclastic sandstone, volcaniclastic sandstone minor interbedded siltstone/shale - HN hydraulic conductivity sample(s) volcaniclastic intermediate carbonate altered sandstone T - thermal conductivity sample(s) sandstone and tuff dike to pebbly sandstone N G - geochemistry sample shale/ felsic dike interbedded fine sandstone shale and sandstone faulted interval deformed sandstone/ pebbly volcaniclastic fault/breccia - lithostratigraphic unit shale sandstone A F

Figure 4. Lithostratigraphy of the Takhini well (YGS-17-01) including fracture density, and locations of samples for thermal and hydraulic conductivity measurements and lithogeochemistry.

YGS Miscellaneous Report 19 Thermo-hydraulic properties – Takhini Hot Springs and Tintina fault zone 5 0 m 100 m 200 m 300 m 400 m

T1H1 T2

25 m 125 m 225 m 325 m 425 m

core begins

e (m) 144 m 150 m 250 m 350 m 450 m

fa c 50 m

T2 w su r o T1H1 epth bel

d 75 m 175 m 275 m 375 m 475 m T1 T T1H1 1

100 m 200 m 300 m T1 300 m 500 m T1H1

pebble-cobble gravel/ T - thermal conductivity sample conglomerate fine sandstone N silty fine diamict HN - hydraulic conductivity sample sandstone-siltstone coarse sandstone silty clay/shale N - number of samples

Figure 5. Lithostratigraphy of the Tintina well (YGS-18-01) including locations of samples for thermal and hydraulic conductivity measurements.

6 Thermo-hydraulic properties – Takhini Hot Springs and Tintina fault zone YGS Miscellaneous Report 19 Figure 6. Typical condition of core in the Tintina well (YGS-18-01).

a b

Figure 7. Outcrop sampling of (a) Upper Triassic Aksala formation (Mandanna member) sandstone near the Takhini drill site and (b) Eocene Flat Creek pluton (granodiorite) west of the Takhini drill site near the end of the Takhini River road.

YGS Miscellaneous Report 19 Thermo-hydraulic properties – Takhini Hot Springs and Tintina fault zone 7 Thermal conductivity and diffusivity The Lippmann and Rauen thermal conductivity scanner (TCScan; Fig. 8b) was used for consolidated Thermal conductivity measures the amount of samples. The scanner measures temperature energy required to transfer a unit of heat through variations of a sample over time; the sample is a unit distance of solid material (SI unit W m-1 K-1). heated using a focussed, continuous heat source This property affects the geothermal gradient when in combination with infrared temperature sensors conduction is the dominant heat transfer mechanism. (Popov et al., 2020). Thermal conductivity values Transient thermal conductivity is measured when of studied samples are compared to temperatures the temperature within a material varies over obtained in standard samples with known thermal time, whereas steady state thermal conductivity is conductivity values. Thermal conductivity values are measured when the temperature within a material is provided for in situ conditions at ambient temperature stable. Thermal diffusivity is a property characterizing and have a relative error of ± 5%. The TCScan was the thermal inertia of a material at a given temperature used for all consolidated samples from the Tintina (SI unit m2 s-1), which is essentially quantifying the and Takhini wells, and Takhini outcrop samples speed of dispersion of heat within a material from hot (number of samples = 6, 41 and 39, respectively). to cold. This property affects the geothermal gradient because it characterizes the propagation of thermal Measurements of steady-state (i.e., set temperature) disturbances over time such as the effect of past thermal conductivity were conducted on a small subset glaciations. of consolidated samples using the FOX50 guarded heat flow meter (Fig. 8c). Based on Fourier’s Law, Thermal conductivity measurements on well and the FOX50 measures heat flux, sample thickness, outcrop samples were collected using three different and temperature differences across the sample to instruments. The K2D Pro TR-1 needle probe determine thermal conductivity at set temperatures was used for unconsolidated samples (Fig. 8a). ranging from -10 to 190°C for in situ and water The needle probe is inserted into a sample under saturated conditions (Lasercomp-TA Instruments, ambient conditions, and then is heated at a constant 2020). For this study, measurements were only made input. Temperature change of the sensor over time, for in situ conditions as sample porosity was low, and surface area of the needle, and heat input are used thermal conductivity was evaluated at temperatures to calculate the thermal conductivity of the sample between 20 and 160°C. Conductive thermal pads (Decagon Devices, 2012). These parameters are were placed on each side of the sample to guarantee used to calculate transient thermal conductivity for thermal contact between the plates and the sample. both in situ and water saturated conditions according FOX50 measurements have a relative error of ± 10% to the ASTM 5334 standard procedure for soil and with thermal pads. This instrument was used for soft rocks. Only values for saturated conditions are one or two representative consolidated samples presented in this report as rocks under evaluation for each geological unit in the vicinity of the Takhini are below the groundwater level; however, both well (n = 15) and one from a felsic plutonic rock in in situ and saturated measurements are provided in the well at a depth of 370.3–370.5 m, to determine Appendix A3. This instrument has a relative error of exponential expressions relating thermal conductivity 10%. This method was used for five unconsolidated/ and temperature. brecciated samples from the Tintina well, two from the ‘breccia’ unit from Takhini well, and three from Thermal diffusivity was measured on consolidated Quaternary outcrops near the Takhini well. well (Tintina = 6; Takhini = 41) and outcrop (Takhini region = 39) samples using the TCScan. An additional infrared temperature sensor, located 7 mm from the heated scan line, allows for the measurement of heat dispersion through the sample at the same time as

8 Thermo-hydraulic properties – Takhini Hot Springs and Tintina fault zone YGS Miscellaneous Report 19 a b c

sample sample sample heat/cold source heat/cold source heat/cold source

temperature sensor temperature sensor temperature sensor

insulation

Figure 8. Schematic diagrams of instruments used to measure thermal conductivity. Heat propogration is shown by the red arrows. (a) the K2D Pro TR-1 needle probe for unconsolidated rocks (Decagon Devices Inc., 2012), (b) the Lippmann and Rauen TCScan for consolidated samples (Popov et al., 2020) and (c) the FOX50 heat flow meter for consolidated samples (Lasercomp-TA instruments, 2020).

it records temperature for thermal conductivity. The The relationship between thermal conductivity sensors, 7 mm apart, measure temperature of the and temperature is expressed as an exponential sample at given points both on and off the heated equation:

scanline to determine of heat dispersion (thermal 0 (1) diffusivity) as proposed by the equation of Popov et aT al. (2020). Thermal conductivity and diffusivity values whereλ(T)= λλ(T) e is the thermal conductivity at temperature -1 -1 in this study are reported as a range of ± 2 standard T (W m K ), λ0 is the thermal conductivity at 0°C deviations (σ) within a ~95% level of confidence (W m-1 K-1), a is the decay rate of thermal conductivity around the lithological unit averages, and units with (°C-1) and T is the temperature (°C). Relationships a single sample have an error of ± 10% (Appendix were compared to well-known empirical equations A4). All raw thermal conductivity and diffusivity data from Vosteen and Schellschmidt (2003) describing are tabulated in Appendices A1 to A3. the decay rate for igneous, metamorphic and sedimentary rocks (Fig. 9). Equations of Vosteen Relationship between thermal and Schellschmidt (2003) are λ(T) = 2.3e0,0009T where conductivity and temperature a ranges from -0.0040 to 0.0024 for igneous rocks; 0,0010T Thermal conductivity of rocks varies with depth due λ(T) = 2.6e where a ranges from -0.0060 to 0,0020T to temperature changes and lithospheric pressure 0.0031 for metamorphic rocks; and λ(T) = 2.9e (Sass et al., 1992; Vosteen and Schellschmidt, 2003; where a ranges from -0.0050 to 0.0012 for Langevin et al., 2019). The relationships between sedimentary rocks. thermal conductivity and temperature for geological units were determined for outcrop samples in the Takhini area.

YGS Miscellaneous Report 19 Thermo-hydraulic properties – Takhini Hot Springs and Tintina fault zone 9 a b

Figure 9. Relationships between thermal conductivity and temperature from Vosteen and Schellschmidt (2003): (a) igneous and metamorphic rocks and (b) sedimentary rocks.

Radiogenic heat production Hydraulic conductivity Radiogenic heat production is a parameter Hydraulic conductivity is the ability of a material characterizing the internal energy produced by to transmit fluid through pore spaces or fractures radioactive decay in a cubic meter of material (SI unit under a hydraulic gradient, expressed as a distance W m-3). Thirty-three samples from the Takhini well over a given period of time (SI units m s-1). For this and outcrops were sent to ALS labs in Vancouver study, three different methods to evaluate hydraulic for whole rock geochemical analysis to determine conductivity were used, depending upon the sample’s concentrations of U, Th, and K, the primary state of consolidation and fracture. radioactive elements present in rocks. Additionally, geochemical data from four Povoas formation basalt Consolidated rocks samples from Bordet et al. (2019) were added to Air permeability of consolidated core plugs was the data set. Concentrations were converted to evaluated using a transient gas permeameter (Core -3 radiogenic heat production A (μW m ) using the Lab Instruments, 2016; measured in milliDarcies or Rybach (1981) method: mD). This instrument forces compressed air through (2) a 4 cm diameter by 8 cm long core, and measures -5 the pressure decay as the air infiltrates the rock -3), [U] is the uranium whereA= 10 ρ ∙ ρ ∙ (9.52[U] + 2.56[Th] + 3.48[K])is the rock density (kg m (Fig. 10). Recorded pressures are then plotted as concentration (ppm), [Th] is the thorium concentration a function of time to calculate air permeability. (ppm), and [K] is the potassium concentration (%). Permeability values were converted to hydraulic Values are reported as ranges of ± 2 standard conductivity using a factor of 1 mD = 9.6 × 10-9 m s-1 deviations (σ) within a ~95% level of confidence (Duggal and Soni, 1996), assuming water density around the lithological unit averages (µ). Radiogenic and viscosity at ambient temperature. The transient heat production values in this study are reported gas permeameter was used to analyze 21 cores as a range of ± 2 standard deviations (σ) within a from the Takhini well and 16 samples from outcrops ~95% level of confidence around the lithological unit near Takhini Hot Springs. From two to four runs were averages, and units with a single sample have an made on each sample and the average hydraulic error of ± 10% (Appendix B3). All raw geochemistry conductivity of the runs assigned to each sample, data are provided in Appendix B1, and individual except in instances where there was a misrun due sample heat production values are provided in to gas leakage. The instrument has a permeability Appendix B2. measurement range of 0.01 to 5000 mD (9.6 × 10-11 to 4.8 × 10-5 m s-1) under ideal operating conditions.

10 Thermo-hydraulic properties – Takhini Hot Springs and Tintina fault zone YGS Miscellaneous Report 19 Beyer (1966) using the grain size distribution of the rock (Alvarado Blohm et al., 2016): g 500 v log (3) -4 2 10 whereK = ∙ 6 × 10g is the∙ gravitational d 60 ⁄d 10 acceleration∙ d (m s-2); ν is the kinematic( viscosity[ of water]) (10-6 m2 s-1); and d10 and d60 are the diameters (m) of the 10% and 60% passing particle size. The method assumes that the hydraulic conductivity of unconsolidated rocks is related to grain size distribution affecting pore connections, where smaller grains can fill voids between larger grains. The hydraulic conductivity values reported from this method represent bulk values.

Fractured rocks sample gas Depending on the degree of deformation and pressure sensor inherent mechanical properties, rocks can be highly fractured at depth, providing preferential paths for Figure 10. Schematic of the transient groundwater flow. Fracture aperture and spacing gas permeameter which is used to can be used to calculate hydraulic conductivity measure and record pressure decay as K (m s-1) using the Cubic law, which is associated the air infiltrates consolidated rocks to calculate air permeability. with secondary porosity (Witherspoon et al., 1979):

3 (4) ρ ∙ g ∙ (b) ∙ N K = -3 where ρ12 ∙ μ is the density of the rock matrix (kg m ); g is the gravitational acceleration (m s-2); b is the However, measurements in the range of 1 to 2 mD width of the fracture (m); N is the total number of -9 -8 -1 (9.6 × 10 to 1.9 × 10 m s ) were assigned a fractures per metre (m-1); and μ is the dynamic -9 -1 value <1 mD (< 9.6 × 10 m s ) due to difficulties in viscosity of water (10-3 kg s-1 m-1). keeping rock surfaces pressurized. The hydraulic conductivity evaluated for plugs analyzed by the This method requires a manual count of natural gas permeameter are related to primary porosity, or fractures per unit distance (N) on cores and an porosity that existed when the rock was originally estimation of fracture aperture (b; Fig. 11). Care formed. must be taken not to count fractures that have occurred during or post drilling. Each open fracture Hydraulic conductivity of unconsolidated/ having mineralization observed in the Takhini core brecciated rocks (e.g., calcite, pyrite or chlorite precipitate) was assumed to be natural (Fig. 12). Fracture aperture Hydraulic conductivity was evaluated on two was not measured in core, as the measurements unconsolidated rock samples from a major breccia/ would not reflect in situ conditions. Instead, aperture fault zone in the Takhini well at a depth of 345 to was assigned a constant value for the entire well bore 346 m. Four samples from the Tintina well were also and the calculations were made for three aperture evaluated for hydraulic conductivity, at depths of types: superfine, fine, or moderate-large. Superfine 161.0, 174.3, 199.3, and 405.8 m. assigned apertures range from 0.2 to 4 µm; fine The hydraulic conductivity K (m s-1) for an assigned apertures from 4 to 100 µm; and moderate to unconsolidated and/or strongly brecciated sample large are assigned a range of 100 to 3000 µm, based was calculated based on the empirical equation of

YGS Miscellaneous Report 19 Thermo-hydraulic properties – Takhini Hot Springs and Tintina fault zone 11 on studies by Witherspoon et al. (1979). Hydraulic conductivity values (m s-1) therefore are reported as ranges for each aperture type, with the number of fractures per unit distance (N), the only variable in the equation (Fig. 11). Further, this method assumes N =n /L that fractures are interconnected and groundwater is L1 K1 1 1 1 flowing in every fracture observed. This method of determining hydraulic conductivity was evaluated for the entire Takhini well core (55–500 m depth).

Takhini geological cross sections Two geological cross sections were drawn through the Takhini well bore to help understand groundwater flow and heat transfer in the Takhini area. Cross sections were made using data from existing geological maps (Yukon Geological Survey, 2018a,b), and core from the Takhini well and N =n /L selected outcrop samples. The cross section extents L2 K2 2 2 2 were determined by the position of strategic water bodies such as the Takhini River, Takhini Hot Springs, Lake Laberge and Kusawa Lake as they represent flow boundaries (Fig. 13). Thermo-hydraulic properties measured from samples in the well and from outcrops were used to define potential regional Figure 11. Measured parametersb for calculating ranges of values. All data were interpreted to define hydraulic conductivity on fractured rocks using a hydrothermal conceptual model of the region. the Cubic law where ‘n’ is the number of fractures, ‘L’ is length of the geological unit (m), ‘N’ is the number of fractures per unit metre (m-1), and ‘b’ is the fracture width (m).

Figure 12. Volcaniclastic coarse sandstone in the Takhini well (YGS-17-01; 487m) crosscut by a calcite vein (upper core) and shale crosscut by an open fracture lined with calcite and chlorite precipitates (lower core; 489 m).

12 Thermo-hydraulic properties – Takhini Hot Springs and Tintina fault zone YGS Miscellaneous Report 19 & &

& &

& 136°00’ 135°30’ (!& 135°00’ & (! 61°20’ N (! & & N

Lake Laberge &

61°00’ N A B 61°00’ N

Takhini River A

60°40’ N

60°40’ N

B 0 10 20 40 Yukon governmentkm

136°00’ 135°30’ 135°00’

LGND Layered rocks Cenooic Paleooic Quaternary Pennsylvanian volcanics and older roads Takhini assemblage well location Mesooic Upper Devonian Upper Cretaceous sampled outcrop and older Carmacks Gp volcanics Snowcap assemblage cross section Upper Jurassic – Lower Cretaceous waterbody Tantalus Fm Plutonic rocks fault Jurassic Paleocene–Eocene Richthofen fm Late Cretaceous Nordenskiold fm Triassic Early Cretaceous Mandanna mbr Middle Jurassic Hancock mbr Early Jurassic Casca mbr Triassic Povoas fm

Figure 13. Geological map in the vicinity of the Takhini well (YGS-17-01), and location of cross sections shown in Figure 19. Geology from Yukon Geological Survey (2018a).

YGS Miscellaneous Report 19 Thermo-hydraulic properties – Takhini Hot Springs and Tintina fault zone 13 Results data for the ‘pebbly volcaniclastic sandstone and tuff’ and ‘volcaniclastic sandstone and mafic tuff’ Takhini area units, as the rock properties were deemed similar to the ‘volcaniclastic sandstone, minor interbedded Thermal properties in YGS-17-01 (well samples) siltstone and shale’ unit and the ‘pebbly volcaniclastic Average and ranges of thermal conductivity, sandstone’ of which 14 and 3 samples were taken, radiogenic heat production, and thermal diffusivity respectively. The breccia unit was not analyzed as for the Takhini well are shown in Table 1. Complete the rock was incompetent and could not be used on raw and average/range data sets of the thermal the TCScan. conductivity/diffusivity and radiogenic heat Thermal properties in outcrop samples production are in Appendices A and B, respectively. Average and range for thermal conductivity, Average thermal conductivity values (± 2σ or 10%) radiogenic heat production, and thermal diffusivity per lithological unit in the well range from 0.59 to for outcrops in the Takhini area are shown in Table 2. 4.19 W m-1 K-1; the highest average value is in the Complete data sets of the thermal conductivity/ deformed sandstone and shale unit (3.81 W m-1 K-1), diffusivity and radiogenic heat production are in and the lowest average value is in the fault/breccia Appendices A and B, respectively. unit (0.97 W m-1 K-1). Generally, average values are similar in the well and range between 3.0 and Average thermal conductivity values (± 2σ or 10%) 4.0 W m-1 K-1, except for the mafic dike and the fault/ per lithological unit for outcrop samples range from breccia units, which have values ≤2.4 W m-1 K-1. 0.73 to 4.14 W m-1 K-1; the highest average value Note that there are no data for the ‘pebbly is in the Hancock unit (3.18 W m-1 K-1), and the volcaniclastic sandstone and tuff’ and ‘volcaniclastic lowest average value is in the Quaternary silt unit sandstone and mafic tuff’ units, as the rock properties (1.07 W m-1 K-1). Average values of pre-Quaternary were deemed similar to the ‘volcaniclastic sandstone, rocks range between 2.0 and 3.5 W m-1 K-1. minor interbedded siltstone and shale’ and ‘pebbly Radiogenic heat production values (± 2σ or 10%) per volcaniclastic sandstone’ units of which 14 and lithological unit for Takhini outcrop samples ranges 3 samples were taken, respectively. from 0.00 to 3.46 µW m-3, the highest average value Average radiogenic heat production values (± 2σ is in the Flat creek pluton (3.00 µW m-3), and the or 10%) per lithological unit in the well range from lowest average value is in the Takhini assemblage 0.39 to 3.60 µW m-3; the highest average value is in (0.11 µW m-3). All average values are <1 µW m-3, the ‘felsic dike’ unit (2.94 µW m-3), and the lowest except for igneous rocks of the Ruby Range suite average value is in the ‘mafic dike’ unit (0.63 µW m-3). (Annie Ned batholith and Flat Creek pluton). Generally, average values are <1 µW m-3, except for Thermal diffusivity values (± 2σ or 10%) per the felsic dike unit. Note that there are no data for lithological unit for Takhini outcrop samples ranges the ‘deformed sandstone and shale’, ‘interbedded from 0.50 to 2.62 mm2 s-1; the highest average shale and sandstone’ and breccia units, as these value is in the limestone of the Hancock member units occur in insignificant proportions in the well. (1.56 mm2 s-1), and the lowest average value is in the Average thermal diffusivity values (± 2σ or 10%) Takhini assemblage metasediments (0.89 mm2 s-1). per lithological unit in the well range from 0.96 to Generally, average values range between 1.0 and 2.98 mm2 s-1; the highest average value is in the 1.6 mm2 s-1. interbedded shale and sandstone unit (2.07 mm2 s-1), and the lowest average value is in the mafic dike unit (1.08 mm2 s-1). Generally, average values are between 1 and 2 mm2 s-1. Note that there are no

14 Thermo-hydraulic properties – Takhini Hot Springs and Tintina fault zone YGS Miscellaneous Report 19 ) -1 s 2 low; high low; high (± 2σ or 10%; mm 1.35; 1.65 1.26; 1.82 1.02; 2.98 1.86; 2.28 1.12; 1.64 1.07; 1.91 1.25; 1.33 1.59 1.11; 0.96; 1.20 - - - standard standard deviation (σ) - 0.14 0.49 - 0.13 0.21 0.02 0.12 0.06 - - - ) -1 s 2 average average (mm 1.50 1.54 2.00 2.07 1.38 1.49 1.29 1.35 1.08 - - - number number of samples Thermal diffusivity 1 3 5 1 7 3 2 14 5 2 0 0

) -3 low; high low; high (± 2σ or 10%; (± 2σ or 10%; µWm 0.92; 1.08 2.28; 3.60 - 0.68; 1.92 0.76; 1.00 0.94; 1.14 0.52; 1.48 0.39; 0.87 - 0.66; 0.80 0.57; 1.25 - standard standard deviation (σ) 0.04 0.33 - 0.31 0.06 - 0.24 0.12 - 0.17 - ) -3 average average (µW m 1.00 2.94 - 1.30 0.88 1.04 1.00 0.63 - 0.73 0.91 - number number of samples Radiogenic heat production 2 4 0 3 3 1 5 3 0 1 2 0 ) -1 K -1 low; high low; high (± 2σ or 10%; Wm 3.05; 3.89 3.18; 3.58 3.43; 4.19 2.32; 4.00 3.02; 3.30 3.04; 3.08 2.64; 3.24 2.15; 2.63 0.63; 1.33 - - 2.95; 3.61 standard standard deviation (σ) 0.21 0.1 - 0.42 0.07 0.01 0.15 0.12 0.19 - - - ) -1 K -1 average average (Wm 3.47 3.38 3.81 3.16 3.16 3.06 2.94 2.39 0.98 - - 3.28 Thermal conductivity number number of samples 3 5 1 7 3 2 14 5 2 0 0 1 lithology lithology graphic

lithology descriptio n carbonate altered carbonate altered sandstone to pebbly sandstone felsic dike interbedded shale and sandstone shale and fine sandstone pebbly volcaniclastic sandstone intermediate dike volcaniclastic sandstone, minor interbedded siltstone and shale mafic dike fault/breccia pebbly volcaniclastic sandstone and tuff volcaniclastic sandstone and mafic tuff deformed sandstone and deformed sandstone and shale Thermal properties of the Takhini well (YGS-17-01). 1. Thermal properties of the Takhini Table

YGS Miscellaneous Report 19 Thermo-hydraulic properties – Takhini Hot Springs and Tintina fault zone 15 ) -1 s 2 low; high low; high (± 2σ or 10%; mm - 0.84; 1.64 0.82; 1.50 1.01; 1.53 1.09; 1.33 0.50; 2.62 1.03; 1.27 0.87; 1.31 0.76; 1.40 0.69; 1.09 standard standard deviation (σ) - 0.20 0.17 0.13 0.06 0.53 0.06 0.11 0.16 0.10 ) -1 s 2 Thermal diffusivity - 1.24 1.16 1.27 1.21 1.56 1.15 1.09 1.08 0.89 average average (mm 0 3 2 2 4 7 6 5 6 5 number number of samples ) -3 - 2.54; 3.46 1.49; 1.83 0.46; 1.26 0.66; 1.66 0.20; 0.24 0.53; 0.65 0.65; 0.79 0.00; 0.34 0.10; 0.12 low; high low; high (± 2σ or 10%; µW m - 0.23 ------standard standard deviation (σ) ) -3 - average average (µW m 3.00 1.66 - - 0.22 0.59 0.72 0.10 0.11 Radiogenic heat production 0 number number of samples 4 1 0 0 1 1 1 3 1 ) -1 K -1 0.73; 1.41 1.29; 3.77 1.93; 2.85 1.98; 3.62 2.60; 2.80 low; high low; high (± 2σ or 10%; Wm 2.22; 4.14 1.79; 3.19 1.89; 2.25 2.21; 2.89 1.93; 3.13 0.17 0.62 0.23 0.41 0.05 standard standard deviation (σ) 0.48 0.35 0.09 0.17 0.30 ) -1 K -1 Thermal conductivity 1.07 average average (W m 2.53 2.80 2.39 2.70 3.18 2.49 2.07 2.55 2.53 2 number number of samples 3 2 2 4 7 6 5 6 5 member Hancock Mandanna Casca Aksala Quaternary

Stratigraph y

formation Flat Creek pluton Nordenskiöld Annie Ned Batholith Richthofen Povoas

Range

Laberge River Lewes Ruby Ruby group Takhini assemblage Takhini Thermal properties of outcrop samples in the Takhini area. 2. Thermal properties of outcrop samples in the Takhini Table

16 Thermo-hydraulic properties – Takhini Hot Springs and Tintina fault zone YGS Miscellaneous Report 19 Hydraulic conductivity Table 3. Hydraulic conductivity of consolidated rock samples in (a) the Takhini well (YGS-17-01) and (b) outcrop samples Average hydraulic conductivity values for in the Takhini region. consolidated rock samples in the Takhini a well sample well depth well depth hydraulic lithological lithology from (m) to (m) conductivity well and from nearby outcrops are shown unit (m s-1)

in Tables 3a and 3b, respectively, with volcaniclastic sandstone 302.83 303.07 <9.6x10-9 a full data set and calculations provided volcaniclastic sandstone 325.16 325.34 <9.6x10-9 in Appendix C1. Gas permeameter -9 measurements indicate a hydraulic fine sandstone with shale 363.17 363.32 <9.6x10 conductivity <9.6 × 10-9 m s-1 for all but mafic intrusive 378.89 379.09 2.8x10-8 eight samples (four well and four outcrop fine sandstone with minor shale 401.86 402.08 <9.6x10-9 samples). The maximum average hydraulic mafic intrusive 423.03 423.18 <9.6x10-9

conductivity occurs in a mafic dike sample mafic intrusive 424.58 424.76 1.6x10-7 at a depth of ~424.6 m in the Takhini well, fine sandstone minor shale 439.86 440.00 7.1x10-8 with a value of 1.6 × 10-7 m s-1, which is an fine sandstone minor shale 455.00 455.25 <9.6x10-9 order of magnitude or more than all other samples (the rest are ≤9.3 × 10-8 m s-1). fine sandstone minor shale 459.43 459.27 <9.6x10-9 fine sandstone minor shale 461.44 461.59 2.1x10-8 Hydraulic conductivity values for two volcaniclastic sandstone 462.85 463.00 <9.6x10-9 brecciated rock samples at the 345–346 m depth in the well were evaluated at 8.3 × 10-4 volcaniclastic sandstone 467.00 467.15 <9.6x10-9 and 2.9 × 10-4 m s-1 (Table 4; Fig. 14), intermediate intrusive 470.39 470.59 <9.6x10-9 -4 -1 averaging 5.6 × 10 m s . Fracture spacing intermediate intrusive 475.00 475.28 <9.6x10-9

ranges from 2 to 52 fractures per metre fine sandstone with shale 480.38 480.52 <9.6x10-9 along the well, typical values are <10 (Fig. fine sandstone with shale 485.95 486.10 <9.6x10-9 4); values of fracture-related hydraulic volcaniclastic sandstone 493.10 493.25 <9.6x10-9 conductivity are shown in Figure 15. -9 Overall, hydraulic conductivity values are volcaniclastic sandstone 496.40 496.50 <9.6x10 on the order of 10-14 m s-1, 10-10 m s-1, and fine sandstone with minor shale 497.00 497.15 <9.6x10-9 -6 -1 -1 10 and 10 m s for superfine, fine and volcaniclastic sandstone 497.84 498.00 <9.6x10-9 moderate to large apertures, respectively.

sample hydraulic b latitude longitude lithology formation number conductivity (m s-1) 19-TF-01-2 60.89 -135.38 Volcaniclastic sandstone Nordenskiöld <9.6x10-9

19-TF-02-1 60.89 -135.41 Granite Flat creek pluton <9.6x10-9 19-TF-04-1 60.89 -135.37 Sandstone Aksala (Mandanna mbr) 9.3x10-8 19-TF-04-2 60.89 -135.37 Siltstone Aksala (Mandanna mbr) <9.6x10-9 19-TF-06-1 60.92 -135.22 Sandstone Richthofen <9.6x10-9 19-TF-06-3 60.92 -135.22 Sandstone Richthofen <9.6x10-9 19-TF-07-1 60.91 -135.52 Leucogranite Flat creek pluton 9.3x10-8 19-TF-08-1 60.88 -135.35 Fine sandstone Aksala (Casca mbr) <9.6x10-9 19-TF-08-2 60.88 -135.35 Fine sandstone Aksala (Casca mbr) <9.6x10-9 19-TF-09-1 60.81 -135.97 Granodiorite Annie Ned batholith <9.6x10-9 19-TF-10-3 60.84 -135.87 Green schist Takhini Assemblage <9.6x10-9 19-TF-11-1 60.82 -135.31 Sandstone Aksala (Mandanna mbr) <9.6x10-9 19-TF-GM-1 60.67 -134.90 Limestone Aksala (Hancock mbr) <9.6x10-9

15-EB-466-1 61.08 -134.89 Volcanoclastic sandstone Aksala (Hancock mbr) 7.9x10-8

15-EB-503-1 61.07 -134.95 Pyroclastic basalt Povoas <9.6x10-9 17-EB-214-1 61.37 -135.22 Pyroclastic basalt Povoas 5.1x10-8

YGS Miscellaneous Report 19 Thermo-hydraulic properties – Takhini Hot Springs and Tintina fault zone 17 Table 4. Hydraulic conductivity of the breccia unit in the Takhini well (YGS-17-01) and from selected samples in the Tintina well (YGS-18-01) using the size distribution of the rock (Alvarado Blohm et al., 2016).

The d10 and d60 values indicate the grain size, which corresponds to 10% or 60% of the sample weight that is smaller than the indicated grain size.

sample depth sample depth hydraulic conductivity well name lithology d (m) d (m) from (m) to (m) 10 60 (m s-1)

345.32 345.52 breccia 0.0002 0.006 2.9 x 10-4 YGS-17-01 346.00 346.20 breccia 0.0003 0.004 8.3 x 10-4

161.00 161.16 fine sand 0.0001 0.0006 1.1 x 10-4

174.32 174.54 diamict 0.0007 0.004 5.6 x 10-3 YGS-18-01 199.31 199.56 coarse sand 0.00008 0.00018 8.8 x 10-5

405.83 406.15 silty clay 0.00025 0.002 6.6 x 10-4

100 90 80 346.0 - 346.2 m 345.3 - 345.5 m g 70 d

n 60 i 60 d s 60 s 50 a P

40

30 20 d10 10 0 0.01 0.1 1 10 100 Grain size (mm)

Figure 14. Grain size distribution of samples from the breccia unit in the Takhini well (YGS-17-01;

346–346.2 m and 345.3–345.5 m). The d10 and d60 values indicate the grain size, in millimetres, which corresponds to 10% or 60% of the sample weight that is smaller than the indicated grain size. For

example, a d10 value of 1 mm indicates that 10% of the sample passed through the 1mm sieve size, therefore 10% of the sample < 1mm, and 90% >1 mm.

18 Thermo-hydraulic properties – Takhini Hot Springs and Tintina fault zone YGS Miscellaneous Report 19 The highest value of hydraulic conductivity related a high of -0.004 for Richthofen formation sedimentary to fracture porosity in the Takhini well is found at a rocks to a low of -0.0008 for Povoas formation depth of 332–341 m in a ‘volcaniclastic sandstone volcanic rocks. The decay rate for plutonic rocks with minor interbedded siltstone and shale’ unit; ranges from -0.003 to -0.0008; -0.004 to -0.002 for 52 fractures per metre were observed (Fig. 4). sedimentary rocks; and the decay rate is 0.002 for Hydraulic conductivity for this interval is the metamorphic rocks of the Takhini assemblage. 3.4 × 10-13 m s-1; 2.7 × 10-9 m s-1; 4.3 × 10-5 and These ranges are comparable to those of Vosteen 1.1 × 100 m s-1 for superfine, fine and moderate to and Schellschmidt (2003; Fig. 17). large apertures, respectively (Fig. 15). The lowest fracture-related hydraulic conductivity occurs in Tintina well (YGS-18-01) the lower part of the well at a depth of 465 m in a Thermal properties ‘volcaniclastic sandstone with minor interbedded siltstone and shale’ unit (Fig. 4), where there are Thermal conductivity and diffusivity averages and 2.2 fractures per metre. Hydraulic conductivity ranges for each geological unit in the Tintina well values calculated for this interval are 1.4 × 10-14 m s-1, are presented in Table 5, and complete data sets 1.2 × 10-10 m s-1, and 1.8 × 10-6 and 4.9 × 10-2 m s-1 for provided in Appendix A. superfine, fine, and moderate to large apertures, Thermal conductivity values in the well (± 2σ or 10%) respectively (Fig. 15). per lithological unit range from 0.79 to 3.23 W m-1 K-1; with both values from the ‘coarse sand’ unit. The Relationship between thermal conductivity and temperature of rocks highest average value is in the ‘pebble gravel/ conglomerate’ unit (2.58 W m-1 K-1), and the lowest Relationships between thermal conductivity and average value is in the ‘fine sand’ unit (1.16 W m-1 K-1). temperature on Takhini outcrop samples are shown Thermal diffusivity (± 2σ or 10%) per lithological unit in Figure 16. The decay rate, or decrease in thermal in the well ranges from 0.94 to 1.49 mm2 s-1 from the conductivity with a rise in temperature, a ranges from ‘silty clay’ and ‘coarse sand’ units, respectively. The highest average value is in the ‘coarse sand’ unit Hydraulic conductivity (m s-1) (1.35 mm2 s-1), and the lowest average value is in the 10-14 10-12 10-10 10-8 10-6 10-4 10-2 100 ‘silty clay’ unit (1.04 mm2 s-1). 0 no samples 50 Hydraulic conductivity Grain size distribution for the Tintina well samples 100 Moderate are provided in Figure 18, and hydraulic conductivity 150 Superfine Fine to values are presented in Table 4. A complete set of Large grain size distribution and hydraulic conductivity 200 0.2–4 µm 4–100 µm 100–3000 µm calculations can be found in Appendix C2. Poorly

250 consolidated rocks define the Tintina well and hydraulic conductivity values range between

Depth (m) 300 8.8 × 10-5 and 5.6 × 10-3 m s-1. The highest value is fractures/m in the ‘diamict’ unit at a depth of 174.54–176.32 m 350 (5.6 × 10-3 m s-1), and the lowest value is in a

400 ‘coarse sand’ unit at a depth of 199.31–199.56 m (8.8 × 10-5 m s-1). 450 fractures/m

500

Figure 15. Hydraulic conductivity of fractured rocks in the Takhini well (YGS-17-01) analyzed for superfine, fine, and moderate-to-large fracture apertures.

YGS Miscellaneous Report 19 Thermo-hydraulic properties – Takhini Hot Springs and Tintina fault zone 19 Annie Ned batholith

a ) Felsic intrusion 1 - ) 3.5

1 3.5 - K 1 K 3 - 1

- 3 m 2.5

( m 2.5

(

t y

y 2

t 2 i v i t 1.5 c 1.5 u d

n 1 -0,003T 1 -0,001T conductiv i o λ(T) 2,31e λ(T) 3,03e c

l 0.5 0.5 a mal

m R 0,95

R 0,85 e r r 0 0 e T h h 0 50 100 150 200 0 50 100 150 200 T Temperature (°C) Temperature (°C)

Nordenskiöld Flat Creek pluton ) ) 3.5 3.5 1 1 - - K K 3

1 3 1 - - m m 2.5 2.5 ( (

2 y 2 t i vi t y v i t 1.5 1.5 c u

d 1 -0,002T n λ(T) 2,91e 1 -0,002T ond uc t i o λ(T) 2,32e c c

0.5 l 0.5 a R 0,89

m 0 R 0,06 r 0 e 0 50 100 150 200 h 0 50 100 150 200 Therm al T Temperature (°C) Temperature (°C) Povoas

) 2.5 1 - K 1 - 2 ( m 1.5 t y v i 1 λ(T) 1,99e-8E-04T

conduct i 0.5

mal R 0,19 0 e r 0 50 100 150 200 T h Temperature (°C)

) Casca

) Hancock 1 1 -

b - K K 3.5 3.5 1 1 - -

m 3 3 m

( ( 2.5 2.5 y t y t i i v v

i 2 2 t i t c

u 1.5

d 1.5 n ondu c o c

c -0,002T 1 1 -0,003T

l λ(T) 3,08e λ(T) 2,52e a l a 0.5 0.5 m r

e R 0,94 R 0,80

h 0 0 Ther m T 0 50 100 150 200 0 50 100 150 200 Temperature (°C) Temperature (°C)

Mandanna Richthofen ) ) 1 - 1 -

K 3.5 3.5 K 1 - 1 -

m 3 3

( ( m

2.5 2.5

y t i it y

v 2 i 2 t ti v c

u 1.5 1.5 d n ndu c o 1 -0,002T c 1 -0,004T c o

l λ(T) 2,36e λ(T) 2,92e a 0.5 0.5 m ma l r R 0,47 e R 0,91 h 0 0 T 0 50 100 150 200 The r 0 50 100 150 200 Temperature (°C) Temperature (°C)

c Takhini assemblage

) 3.5 1 -

K 3 1 - 2.5 m ( 2 it y 1.5 Figure 16. Relationship between thermal 1 λ(T) 1,90e-0,002T

conducti v conductivity and temperature for 0.5

mal R 0,69 0 (a) igneous, (b) sedimentary and

he r 0 50 100 150 200 T Temperature (°C) (c) metamorphic rocks in the Takhini area.

20 Thermo-hydraulic properties – Takhini Hot Springs and Tintina fault zone YGS Miscellaneous Report 19 Metamorphic rock - this study

Metamorphic range and average value

Sedimentary rocks - this study

Sedimentary range and average value

Igneous rocks - this study

Igneous range and average value

-0.008 -0.006 -0.004 -0.002 0 0.002 0.004 Decay rate a (°C-1)

Figure 17. Comparison between decay rates calculated in this study and those of Vosteen and Schellschmidt (2003) for igneous, sedimentary and metamorphic rocks in the vicinity of the Takhini well.

Table 5. Thermal properties of the Tintina well (YGS-18-01).

Thermal Conductivity Thermal Diffusivity lithology lithology number standard low; high number standard low; high average average description graphic of deviation (± 2σ or 10%; of deviation (± 2σ or 10%; (Wm-1K-1) (mm2 s-1) samples (σ) Wm-1K-1) samples (σ) mm2 s-1)

pebble gravel/ 2 2.58 0.04 2.50, 2.66 2 1.33 0.04 1.25; 1.41 conglomerate

diamict 2 2.21 0.19 1.83; 2.59 0 - - -

coarse sandstone 2 2.01 0.61 0.79; 3.23 1 1.35 - 1.22; 1.49

fine sandstone 1 1.16 - 1.04; 1.28 0 - - -

silty fine sandstone 2 2.22 0.39 1.44; 3.00 2 1.08 0.04 1.00; 1.16 - siltstone

silty Clay 2 1.85 0.48 0.89; 2.81 1 1.04 - 0.94; 1.14

YGS Miscellaneous Report 19 Thermo-hydraulic properties – Takhini Hot Springs and Tintina fault zone 21 100 100 YGS-18-01; 174.5 -176.3 m YGS-18-01; 161.2 - 161.4 m diamict unit fine sandstone unit 80 80

d60 60 60 d60

40 40 Passing Passing 20 d 20 10 d10

0 0 0.01 0.1 1.0 10 0.01 0.1 1 Grain size (mm) Grain size (mm)

100 100 YGS-18-01; 405.8 - 406.2 YGS-18-01; 199.3 - 199.6 m silty clay/shale coarse sandstone unit 80 80

d 60 60 60 d60

40 40 Passing Passing d 20 10 20 d10

0 0 0.01 0.1 1.0 10 0.01 0.1 1 Grain size (mm) Grain size (mm) Figure 18. Grain size distribution of Tintina well (YGS-18-01) rock units.

Geological cross sections Discussion Conceptual cross sections A-A’ and B-B’ (Figs. 13 Heat transfer and groundwater flow and 19) show the distribution of geological units influencing heat transfer and groundwater flow in Takhini well (YGS-17-01) the vicinity of the Takhini well. Basement rocks consist of variably deformed and metamorphosed Heat transfer mechanisms in the Takhini well include greenstone of the Takhini assemblage. Triassic to both conduction and forced convection. Conduction Jurassic sedimentary sequences and volcaniclastic refers to the process of heat transfer that takes strata overlie the Takhini assemblage. Steeply place between materials by direct contact, while dipping north-trending normal faults separate the convection refers to heat transfer driven by fluid flow. sedimentary basin into segments as a result of A distinction can be made between auto (natural) regional tectonic activity in pre-Late Cretaceous convective and forced convective heat transfer. The (Hart, 1997). Eocene granitoid plutons intruded former occurs in hot and permeable rocks such as Triassic to Jurassic sedimentary sequences and in an active volcanic environment where there are volcaniclastic strata (Hart, 1997). Fault extensions significant temperature contrasts in rocks with high and thickness of rock units at depth are interpretive hydraulic conductivity. The latter occurs in deep and due to the lack of geophysical or deep well data in confined aquifers with significant connectivity over this area. long distance with sufficient hydraulic gradient to induce fluid movements (Sass and Götz, 2012).

22 Thermo-hydraulic properties – Takhini Hot Springs and Tintina fault zone YGS Miscellaneous Report 19 A Aʹ 2000 Legend Triassic Cenooic Lewes River Group Takhini 1500 Quaternary Aksala fm Hot drill sand, silt, gravel Hancock mbr: limestone Springs Takhini site 1000 Paleocene – Eocene Mandanna mbr: green River and red sandstone, mudstone, granitoid intrusions pebble conglomerate 500 Casca mbr: shale, siltstone Mesooic calcareous sandstone Jurassic Povoas fm Richthofen fm 0 basalt, gneiss, tuff Nordenskiöld facies: crystal tuff, marble, sandstone volcaniclastic sandstone

-500 turbiditic sandstone, siltstone, Paleooic shale Pennsylvanian and older Takhini assemblage -1000 greenstone Takhini well

fault -1500 0 5 10 normal fault km -2000 elevation (m) VE 3.9

B Bʹ 2000 Lake Kusawa drill Braeburn Laberge Lake site fault 1000

0

-1000

-2000

-3000 0 10 20 km -4000 elevation (m) VE 4.2 Figure 19. Schematic geological cross-sections A–A’ and B–B’ through the Takhini well (YGS-17-01). Location of cross sections are shown in Figure 13. Geology after Hart (1997), Colpron et al. (2015), and Yukon Geological Survey (2018a).

Temperature measurements and analysis of thermo- the whole well and surrounding outcrops (generally hydraulic properties in the Takhini well indicate that <9.6 × 10-9 m s-1). Instead, the temperature anomaly conduction is the main mechanism of heat transfer in in the lower part of the well is interpreted as forced- the well above 450 m. The low thermal conductivity convective heat transfer caused by deep, warmer variation between units (Table 1), no drastic change groundwater rising along fractures. Sass and Götz in the geothermal gradient, and a smooth and (2012) suggest that heat transfer in rocks transitions near-linear temperature profile above 450 m depth from forced convective to auto (natural) convective (Fig. 2a) are characteristic of heat conduction (Sass over a hydraulic conductivity increase from and Götz, 2012). 10-9 m s-1 to 10-5 m s-1 (Fig. 20). The matrix hydraulic conductivity of rock samples in the Takhini well and The high geothermal gradient of 250°C km-1 surrounding outcrops is generally <9.6 × 10-9 m s-1, observed below 450 m depth shows a drastic suggesting conductive heat transfer, however, the change in temperature of ~12.5°C over a depth of presence of fractured and unconsolidated rocks 50 m. This heat transfer cannot be explained by may provide a higher hydraulic conductivity to conduction as the thermal conductivity is similar for

YGS Miscellaneous Report 19 Thermo-hydraulic properties – Takhini Hot Springs and Tintina fault zone 23 Petrothermal systems Transitional systems Hydrothermal systems

Conductive- Forced Auto-convective – forced convective Auto-convective Conductive heat transfer convective convective heat transfer heat transfer heat transfer heat transfer

Superfine fracture Fine fracture oderate to large (0.2–4 μm) (4–100 μm) (100–3000 μm)

10-11 10-10 10-9 10-8 10-7 10-6 10-5 (hydraulic conductivity m s-1)

Figure 20. Classification of geothermal systems based on the dominant mechanism of heat transfer (convective vs. conductive; after Sass and Götz, 2012).

achieve convective heat transfer. Figure 15 shows high geothermal gradient at the bottom of this well that fine to large fracture apertures in the Takhini (>450 m). Despite these limitations, the thermal- well can provide adequate hydraulic conductivity hydraulic properties assessed in this study suggest (>10-9 m s-1) to allow forced convective to auto- the forced convective heat transfer hypothesis convective heat transfer. As auto convection only remains the most plausible for the temperature spike induces groundwater movement in rocks with in the bottom of the well. Assuming that faults and significant temperature contrasts and high hydraulic fractures are interconnected and have hydraulic conductivity, forced convection is most likely driving conductivity at least greater than 10-9 m s-1, regional groundwater movement in the Takhini region which groundwater flow can be directed toward the Takhini is controlled by the regional hydraulic gradient in an River and upflow can occur along faults, creating a aquifer system of moderate hydraulic conductivity. resurgence under the Takhini well near the river, a For example, this can occur where topographic major waterbody collecting groundwater. highs in a mountain range act as a recharge zone for water that discharges in lower altitude valleys Tintina well (YGS-18-01) provided there is adequate fracture connectivity in Heat transfer and groundwater flow in the Tintina the host rock. As fine and moderate to large fracture well can be similarly related to the Sass and Götz apertures and unconsolidated rocks in the Takhini (2012; Fig. 20) classification of geothermal systems. well have a hydraulic conductivity that is mostly The low thermal conductivity contrast and linear greater than 10-9 m s-1 (Fig. 15), forced convective geothermal gradient are characteristics of conductive heat transfer can occur and trigger the formation of a heat transfer in the well. Hydraulic conductivity hydrothermal system and hot springs, provided that estimations for unconsolidated/brecciated rocks fractures are interconnected. The Takhini well and of the Tintina well suggest permeable rocks, with the hot springs are located in a topographical trough hydraulic conductivity ranging from 10-5 to 10-3 m s-1 (Fig. 21), where the difference in elevation (~500 m (Table 5). These values fall within an auto-convective over ~15 km distance) can cause a strong hydraulic heat transfer realm, which could trigger the formation gradient. Data provided from one well is not enough of warm hydrothermal systems in the area, however, to evaluate fracture connectivity in this study, and it is no hot springs or surface seeps are known. difficult to correlate any permeable zones observed in the core samples of the Takhini well with the

24 Thermo-hydraulic properties – Takhini Hot Springs and Tintina fault zone YGS Miscellaneous Report 19 Geothermal setting tends to flow through permeable rocks. Several north-trending steep normal faults cut strata in Takhini Hot Springs region the Takhini area (Hart, 1997) including one that The geological setting in the Takhini area is typical crosscuts the center of the A–A’ cross section of an orogenic belt, where conductive and forced (Fig. 21). This major feature can affect the convective heat transfer can occur (Moeck, 2014). groundwater flow path as it is believed to be more Geological features, such as steeply dipping fractured and permeable than rocks outside the crustal faults, can favour forced convective heat fractured zone. Due to the hydraulic head difference transfer as they are preferential paths for rising between the top and the base of the fracture, deep warm groundwater. Figure 22 illustrates schematic water heated from the Takhini area’s local geothermal isotherms and water flow line interpretations based gradient can rise along the fault to create shallower on the main recharge areas and major faults in the isotherms. This can form hot springs like Takhini area. Groundwater recharge areas are commonly Hot Springs where well-connected fractures allow a associated with elevated mountainous regions and constant groundwater discharge (Fig. 22). the discharge dominantly occurs near the Takhini River. From recharge to discharge, groundwater

136°0 135°40 135°20 135°0

30 00

35 00 5000

50 00 Lake 4500 A Laberge 00 11 61°0N 1 00 0 0 3 1 15 1 1 0 0 3 0 1 6 1500 0 1 0 0 15 2 0 1 0 0 6 0 1 1 3 0 0 0 1 0 0 4 5 0 0 2 1 0 0 1 1 1 0 0 3 7 1 0 3 1300 2 0 0 5 0 9 0 0 1 1 0 0 0 0 61°0N 0 1 0 1 0 40 0 5 0 0 0 0 0 1 00 0 0 1 1 0 0 0 1 0 0 6 6 30 0 0 0 5 1 0 1 0 1 1 0 1 0 3 4

0 1 1 1 4 0 1 0 0 0 0 5 0 0 0 0 1 1 2

0 2 4 1 0 8 1 0 2 1 4 1 0 1 1 5 0 9 5 0 0 1 1 0 0 2 0 2 0 0 0 0 0 0 0 1 0 900 0 0 0 0 6 0 0 0 00 0 0 0 0 1 100 0 1 1 0 0 8 1 1 1 0 1 1 4 0 0 0 0 8 0 0 1 0 18 1 0 0 9 00 1 0 6 0 0 0 5 0 0 Yukon R. 0 0 YGS-17-01 1 0 0 0 8 0 0 1 1 0 1 0 7 0 6 0 0 3 0 9 0 1 0 0 0 5 0 River 1 0 5 8 00 1 Takhini Hot0 Springs 7 1 0

0 4 1 0 3 0 100 0 7 0 5 1 3 0 0 3 0 0 1 1 70 0 0 1100

1 60°50N 900 1

0 4 0 Alaska Highway 1000 0 1 0 0 0 0 8 0 9 0 0 5 0 0

0 1 0 8 0 2 0 0 1 1 0 1 0 6 60°50N 1 1 1 3 0 0 0 0 9 1 1 0 0 0 0 0 1 1 Takhini 0 8 0 0 0 6 4 0 2 0 40 0 0 0

0 0 1 1 9 0 0 1 4 0 0

0 0 0 0 1 7 0 7 1 0 1000 0 10 5 1 0 7

1 00 1 0 4 8 1 0 0 3 1 1 0 0 0 0 5 0 10 0

1 0 0 0 0 1 3 9 6 0 1200 1 0 0 0 1 0 0 8 0 0 1 5 00 00 1 0

5 0 0 16 14 6 6 0 1 1 0 1

0 0 0 1 2 0

0 1 1 A’ 0 6 0 00 1 1900 0 40 12 0 3 0 1 8 0 0 0 3 1 0 0 0 3 0 1 0 0 1 0 7 1 0 0 0 0 0 0 0 4 4 0 1 1 0 3 1 1 0 4 1 0 0 1 1 1 4 0 1 19 0 0 0 6 10 0 0 0 0 3 0 0 0 0 12 00 0 0 1 7 1 00 7 1 5 1 0 hitehorse 13 1 8 1 0 1 0 0 1 1 0 60 0 0 1 4 3 15 7 00 0 1 0 60°40N 00 km 0 0 0 3 15 0 0 0 0 90 1 5 0 0 0 0 0 6 10 1 20 1 11 1 0 0 170 0 4 1 20 14 1 0 0 800 0 400 3 0 2 0 1 60 1 0 0 1500 1700 1 0 0 1800 1200 60°40N

135°40 135°20 135°0 Figure 21. Topographic map of the Takhini well area, with locations of cross sections (A–A’) in Figure 22. Contour intervals in metres. Grey lines denote surface expression of faults (Yukon Geological Survey, 2018a).

YGS Miscellaneous Report 19 Thermo-hydraulic properties – Takhini Hot Springs and Tintina fault zone 25 Aʹ A main water recharge area main water recharge area 1500 m

Takhini 1200 m Hot Springs YGS-17-01 (46°C water) Takhini River

10°C 10°C

50°C 50°C Legend lithology contact schematic isotherm water flow line

normal fault 1 km

Figure 22. Conceptual hydrothermal system of the Takhini Hot Springs area according to geothermal play-types in orogenic belts; after Moeck (2014). Vertical axis is schematic and depth of isotherms approximated. Dotted vertical lines indicate where cross section line changes direction.

Tintina well region hydraulic head is expected to remain similar along this major fault. Therefore, the discharge area is The Tintina well has a different hydrogeological mainly sourced by the cold water from the mountain setting compared to the Takhini well. Regional highs. The geological setting in the Tintina Trench is groundwater flow near the Tintina well is more likely typical of an orogenic belt, but the hydrogeological to come from a shallow aquifer due to the proximity context is not favourable for hot spring development. of high mountains (Figs. 23 and 24), explaining why the observed temperature profile does not appear to be affected by upwelling warm water even though Conclusions the rocks are fractured and appear to be permeable. This study has defined the thermo-hydraulic Groundwater can rise along major faults if there properties of rocks in, and within, the vicinity is a significant hydraulic head difference between of the Takhini temperature gradient well (YGS- the base and the top of faults, commonly caused 17-01) and in the Tintina well (YGS-18-01), in by fault orientation and topography with recharge southern Yukon. The new data, combined with the at mountain highs and discharge in valleys. Such temperature gradient measured in the wells, offers regional groundwater flow can exist in the Tintina explanations for heat transfer mechanisms. In Trench area where the main waterbody collector addition, hydrothermal conceptual models of the well is the Pelly River. However, the hydraulic head locations are presented. The thermal conductivity difference along the faults may not be enough for results show that conductive heat transfer the deep groundwater to rise since the Tintina fault dominates the Takhini well to a depth of 450 m, as is likely to be subvertical (Welford et al., 2001) and the temperature profile is near-linear and thermal

26 Thermo-hydraulic properties – Takhini Hot Springs and Tintina fault zone YGS Miscellaneous Report 19 133°20 133°0 132°40 132°20

3 0 3 0 5 0 0 3000 30 500 4 0 00 0 4 50 300 00 350 3 00 0 30 0 0 5 5 4 35 4 30 00 3 0 0 3000 3 00 0 0 2 0 4 0 4 0 0 0 0 3 5 5 0 0 0 3 0 0 4 0 0 5 0 elly 0 0 0 00 0 3 5 5 0 0 0 Robert Campbell5 Highway 0 0 0 2 3 0 3 2 3 5 5 4 0 4500 0 0 00 00 5 0 0 5 3 0 0 0 0 4 0 5 0 0 0 0 3 2 0 2 0 0 0 0 5 4 5 0 0 4 5 5 00 0 5 50 0 0 4 4 5 0 3 0 0 0 4 0 5 0 00 0 0 0 00 0 0 2 0 5 4 0 2 5 2 35 4 5 5 0

0 4 5 45 0 5 0 0 0 00 4 0 0 0 0 0 5 0 0 0 0 0 0 0 0 0 0 0 0 4 5 5 3 0 5 0 5 5

0 River 0 0 0 4 0 5 0 5 5 0 ʹ 0 C 0 0 5 3 30 3 4 0 4 0 0 0 0 5 0 5 0 0 0 0 0 4 0 0 0 55 0 5 0 3 3 0 0 0 0 0 0 0 0 0 0 5 0 0

0 4 5500 0 0 0

5 4 0 50 0 30 45 3 0 0 00 3 0 0 5000 00 4 00 400 5 55 3500 0 0 40 3 4500 00 0 0 0 25 0 4 00 00 00 5 5 0 0 0 00 0 0 0 4000 0 0 00 0 5 450 5 45 4 3 0 00 0 0 0 0 3 0 4000 25 0 0 0 5 0 4 5 0 3 0 2500 00 5000 5000 400 50 4000 4000 5000 3 0 0 3 40 0 4 0 4000 5000 0 5000 0 5 0 3000 5 5 5 0 0 450 4 0 0 5 5 3 2 00 62°0N 5 0 3 2 30 0 0 0 0 5 0 0 50 00 3 0 00 0 0 4 62°0N 0 0 0 0 0 0 5 0 0 0 00 5 0 5 5 0 4 4 0 3 3 6 5 4 5 50 0 3 3 3 0 0 0 5 0 0 5 0 0 0 0 5 5 0 0 0 0 0

0 4 4 3 0 0 0 5000 0 0 0 0 0 0 3 0 0 0 5 0 0 0 0 0 0 3 0 0 0 0 0 0

6 5 0 6 0 0 0 0 0 0 5 0 0 7 0 0 0 5 5 0 0 0 55 0 0 0 0 0 6 5 0 0 0 4 2 0 5 4 5 0 5 PLL 3 4 Ross 0 River 4 40 0 0 5 0 0 0 0 0 0 0 00 00 0 0 0 0 3 0 0 5 55 5 0 0 0 50 0 6 4 0

6 5 0 5 0 5 0 0 2

0 4 5 0 3 0 0 0 0 0 0 0 0 5 000 0 0 5 0 3 6 6 0 5 6 0 5 5 0 55 5 0 5 00 00 00 4 00 0 6 5 5 6000 0 5 0 6 0 5 0 2

0 5 5 0 0 5 0 0 0

0 0 0 5 0 0 0 0 5 0 0 5 350 0 0 5 7 00 0 0 0 500 00 7 6 6 5 0 0 30 5 0 0 5 0 0 0 0 0 5 0 0 5 0 5 3 0 6 4 0 5000 0 0 5 0 0 5 0 0 5 0 0 0 0 0 0 5 0 0 0 6 7 0 5 0 5 0 5 4 5 6 0 5 6 0

0 0 5 5 0 0 5000 0 30 6 0 5 0 0 5 00 6 0 0 00 3 5 6 0 0 0 0 30 0 5 0 0 0 0 5 0 0 5 0 0 4 0 0 0 0 0 5 0 0 0 00 3 0 6 5 0 5 0 3 5 0 0 0 0 50 0 3 00 4 4 0 0 00 3

0 5 00 50 4 0 0 3 0 0 550 0 3 00 0 0 0 5 GS-1-10 0 00 0

5 3 3 0 0 40 0 5 5 0 0 0 6 0 3 0 5 50 5 0 5 0 0 5 5 0 0 0 0 4 4 0 0 0 5 0 0 5 0 0 0 6 0 0 0 0 0 0 3 0 0 0 0 0 0 5 5 6 5 0 0 6 6 0 0 0 3 0 5 000 00 0 0 0 6 0 0 5 3 0 6 6 5 5 0 3 3 5 0 0 0 0 5 0 0 0 0 0 0 5 0 0 0 6 0 6000 0 0 0 3 0 500 0 6 0 5 0 0 5 0 6 0 5 0 5 0 5 0 0 0 0 0 0 5 5 0 5 0 6 0 5 0 5 0 5 5 5 30 0 0 0 0 0 0 5 6 0 0 4 0 0 0 55 0 0 0 5 0 3 0 0 00 0 0 0 7 0 00 0 0 0 0 00 0 0 45 7 5 5 0 0 5 6 0 6 0 0 61°50N 0 0 0 0 0 0 5 0 0 6 0 5 61°50N 5 5 4 5 0 3 0 0 5 5 6 5 0 6 0 0 0 0 5 65 6 0 0 0 0 0 0 0 5 0 0 5 500 MNTAINS 4 7 0 0 0 0 0 0 5 5 0 0 5 0 5 7 00 5 0 5 0 0 5 0 0 0 0 0 6 0 0 6 0 6 0 5 5 0 500 0 4 5 0 0 0 0 0 5 0 0 0 South Canol Road 0 5 0 0 7 6 0 000 0 45 50 0 40 0 7 0 0 0 0 0 5 6 0 0 50 3 35 6 0 0 0 500 5 0 0 0 50 5 65 00 0 0 0 00 00 0 7000 0 0 0 0 0 75 4 6 4 5 5 0 0 0 00 0 0 6 0 0 0 0 5 0 6 0 0 0 0 50 0 0 0 5 4 0 0 0 5 0 5 7 0 5 0 0 0 5 5 5 0 0 0 0 6 60 4 0 0 5 5 0 0 6 0 5 0 600 6 5 0 5 5 00 5 0 0 0 3 0 7 0 5 5 4 0 7 6 0 50 0 0 000 0 5 0 0 6 6 0 4 6 0 60 0 0 0 0 0 0 0 6 4 5 5 0 6 00 0 5 0 0 5 5 0 0 6 0 0 650 0 0 0 0 70 0 0

00 0 0 0 0 0 6 0 0 6500 6 0 5 5 6 0 5 0 0 6 0 5 00 0 0 0 0 0 6 3 0 5 0 6 5500 5 5 60 0 5 5 4 6 5 7 4 5 5 5 5 0 0 0 00 00 0 0 00 0 5 0 0 0 0 0 6 0 5 3 5 0 0 0 0 5 00 5000 5 0 6 5 0 00 0 0 0 65 6 0 0 0 0 6 0 5 0 0 0 0 6 6 5 0 5 0 0 6 0

0 5 0 0 6 0 5 0 0 5 0 0 0 6 6 0 0 0 6

0 6 0 0 0 0 0 0 0 0 0 0 0 5 0 0 00 5 0 5 6 0 5 0 0 5 0 0 0 4 0 00 5 5 0 6 0 6 0 0 5 0 6 5 0 0 0 0 6 5 0 5 6 6 0 0 5 0 5 0 4 6 5 0 0 0 6 00 4 4 0 0 0 6500 0 5 0 5 6 5 5 0 65 5000 5 0 0 0 3 0 0 0 0 55 6 0 0 6 4 0 6500 0 0 5 0 0 0 0 0 5 00 5 0 0 0 0 60 5 0 600 0 0 5 0 6 0 4500

0 5500 0 0 0 5 4 0 0 500 0 0 0 0 7 0 0 0 0 5 0 5 0 C 6 0 0 4 0 0 50 5 5 0 5 6 0 3 0 0 5 0 0 0 4 0 6 5 0 0 0 0 0 0 0 0

5 0 0 5 0 0 5 0 0 0 0 0 5 0 0 0 5 0 5 3 0 0 6 5 0 0 0 0 4 0 0

6 6 0 5 6 0 5 6 6000 0 5 6 0 5 0 0 0 0 0 50 0 50 0 6 0 6 0 0 4 00 4 5 5 0 0 5 0 0 0 5 0 0 6 5 0 6 5 0 7 0 0 00 0 0 6500 500 0 0 60 6 0 5 0 0 6 4 0 6 0 0 65 0 5 0 0 0 5 00 0 5 0 0 0 0 0 0 0 0 61°40N 0 0 0 0 4 0 0 5 50 6 0 6 6 0 5 0 0 0 6 5 5500 60 0 61°40N 6 0 6 00 0 5 0 0 550 0 0 50 6 0 0 6 0 4 0 4 0 6 0 0 0 0 0 000 5 0 0 0 6 0 5 0 5 5 0 0 km 5 60 55 0 0 5

0 0 6 0 0 0 5 4 5 0 0 0 0 0 5 0 5 0 0 50 0 0 0 5 6 0 5 5 0 00 0 5500 50 0 0 0 0 0 0 5 0 0 0 0 0 0 0 0 6 0 4 0 0 6 5 0 0 60 0

5 0 5 0 0 00 0 0 5 0 0 7 0 0 4 5 0 0 450 5 5 050 10 0 5 20 5 5 6 5 0 5500 0 4 0 5 0 6 4 5 4500

133°20 133°0 132°40 132°20 Figure 23. Topographic map of the Tintina trench well area with the location of cross section C–C’ in Figure 24. Contour intervals in feet. Grey lines denote surface expression of faults (Yukon Geological Survey, 2018a).

C main water recharge area C

water recharge area 5000 ft 1523 m YGS-18-01 5°C Pelly River 3500 ft 15°C 1067 m 5°C

15°C 25°C Tintina fault zone

25°C LGND 35°C schematic isotherms

water flow lines

35°C drill hole fault 1 km highly fractured zone Figure 24. Conceptual hydrothermal system of the Tintina well area according to geothermal play-types in orogenic belts; after Moeck, (2014). Vertical axis schematic and depth of isotherms approximated. Not all faults are indicated on the cross section which are on the map, for model simplicity.

YGS Miscellaneous Report 19 Thermo-hydraulic properties – Takhini Hot Springs and Tintina fault zone 27 conductivity contrasts between lithological units are provides more data to evaluate this potential around minor. The elevated geothermal gradient observed the hot springs. Further calculations and simulations at the bottom of the Takhini well (250°C km-1) and combined with the measurements obtained with this the thermal manifestations at Takhini Hot Springs study will bring a better comprehension of resources are likely caused by forced convective heat transfer to move towards an evaluation of the likelihood of associated with deep groundwater flow in permeable geothermal energy resources in this region. fractures generating a hydrothermal system typical of a geothermal play type in an orogenic belt Acknowledgements (Fig. 22). The ~2 km lateral distance between warm water at the bottom of the Takhini well and the Takhini The Takhini well (YGS-17-01) was drilled on Hot Springs can give an approximate estimate of the Category A land of the Ta’an Kwäch’än Council – we extent of this warm fluid ascending zone, assuming are grateful for their collaboration on this project, there is interconnectivity of fractures. This study and for providing access to outcrops in summer did not identify the heat source for the hot water at 2019. The Tintina well was drilled in the traditional Takhini, however, this would be a good future study, territory of the Liard First Nation, in partnership with specifically a focussed evaluation of the distribution the Ross River Dena Council. We are grateful for the and radioactive heat potential of igneous intrusions opportunity to collaborate with these First Nations in the vicinity to evaluate their role in the geothermal on these important ground temperature studies. system. This work was funded by a Discovery grant from the Natural Sciences and Engineering Research Council Thermo-hydraulic properties of rocks in the Tintina of Canada awarded to INRS and a scholarship well, including little thermal conductivity contrasts from the Armand-Frappier Foundation awarded to between rock units and a linear geothermal gradient, the first author. Maurice Colpron (YGS) provided suggest that conductive heat transfer dominates the field, technical, and GIS guidance for which we are well, and groundwater in the well is likely sourced appreciative. Liam Maw is acknowledged for thin from shallow aquifers. Unlike the Takhini setting, no section descriptions and Bailey Staffen (YGS) for GIS hot springs or seeps are known from this area. assistance. Carolyn Relf (YGS) is acknowledged for Assessment of the thermal conductivity can be used ongoing managerial and funding support of student with calculated radiogenic heat production values geoscience projects. from geological units in the region as a next step to evaluate heat flow and extrapolate temperature References at depth. Quantifying the natural amount of heat originating from the Earth’s interior and based on Alvarado Blohm F.J., 2016. Determination of Fourier’s Law, the heat flux density is needed to hydraulic conductivities through grain-size define boundary conditions of numerical groundwater analysis. MSc thesis, Boston College University flow and heat transfer models to quantitatively Libraries, Chestnut Hill, United States, 102 p. confirm the heat transfer hypotheses formulated in Beyer, W. 1966. Hydrogeological investigations in this work. Such an approach would be helpful to the deposition of water pollutants. Journal of improve understanding of the origin of the Takhini Hot Applied Geology, vol. 12, p. 599–606. Springs. Such a model can be used to reproduce the Bordet, E., Crowley, J.L. and Piercey, S.J., 2019. temperature measured in the Takhini well or at the Geology of the eastern Lake Laberge area hot springs to better explain the factors controlling (105E), south-central Yukon. Yukon Geological the formation of the hydrothermal system. Survey, Open File 2019-1, 120 p. The geological context of Yukon shows potential Colpron, M., Israel, S. and Friend, M., 2016. Yukon for geothermal energy with many hot springs like plutonic suites. Yukon Geological Survey, Open Takhini. Geothermal exploration done by the YGS File 2016-37, scale 1:750 000.

28 Thermo-hydraulic properties – Takhini Hot Springs and Tintina fault zone YGS Miscellaneous Report 19 Colpron, M., Crowley, J.L., Gehrels, G.E., Long, Langevin, H., Raymond, J., Comeau, F.-A., Malo, M. D.G.F., Murphy, D.C., Beranek, L.P. and and Molson, J., 2019. Évaluation des ressources Bickerton, L., 2015. Birth of the northern géothermiques des Îles-de-la-Madeleine. Cordilleran orogen, as recorded by detrital Conférence: XIVème Colloque International zircons in Jurassic synorogenic strata and Franco-Québécois en énergie, Baie St-Paul, regional exhumation in Yukon. Lithosphere, vol. 7, Canada, p. 6. p. 541–562. Langevin, H., Fraser, T. and Raymond J., 2020. Core Lab Instruments, 2016. PPP-250 Portable Assessment of thermo-hydraulic properties of probe permeameter operations manual. Core rock samples near Takhini Hot Springs, Yukon. Lab Instruments. Tulsa, United States, p. 6. In: Yukon Exploration and Geology 2019, K.E. MacFarlane (ed.), Yukon Geological Survey, Decagon Devices Inc., 2012. KD2 Pro Thermal p. 57–73. properties analyser: operator’s manual, version 12. Decagon Devices Inc. Pullman, United Lasercomp-TA Instruments, 2020. FOX 50. https:// States, 68 p. www.tainstruments.com/fox-50/. Duggal, K.N. and Soni, J.P., 1996. Elements of Water Long, D.G.F., 2015. Depositional and tectonic Resources Engineering. New Age International framework of braided and meandering gravel- (P) Limited, p. 270. bed river deposits and associated coal deposits in active intermontane basins: The Upper Fraser, T.A., Grasby, S.E., Witter, J.B., Colpron, Jurassic to mid-Cretaceous Tantalus Formation, M., Relf, C., 2018. Geothermal studies in Whitehorse trough, Yukon, Canada. Yukon Yukon-collaborative efforts to understand Geological Survey, Open File 2015-23, 80 p. ground temperature in Canadian North. GRC Transactions, vol. 42, 20 p. Mira Geoscience, 2017. Ross River geothermal exploration project: Review of the 2014 work Friend, M., and Colpron, M., 2017. Potential program. Miscellaneous Report, MR 18, Yukon radiogenic heat production from Cretaceous and Geological Survey, 141 p. younger granitoid plutons in southern Yukon. Yukon Geological Survey, Open File 2017-60, Moeck, I.S., 2014. Catalog of geothermal play types scale 1:1 000 000. based on geologic controls. Renewable and suitable energy reviews 37, Elsevier, p. 867– Gabrielse, H., Murphy, D.C. and Mortensen, J.K. 882, https://doi.org/10.1016/j.rser.2014.05.032. Cretaceous and Cenozoic dextral orogeny parallel displacements, magmatism and Nelson, J.L., Colpron, M., Israel, S, 2013. paleogeography, north-central Canadian Cordillera of British Columbia, Yukon, and Cordillera. In: Paleogeography of the North Alaska: Tectonics and Metallogeny. Society of American Cordillera: Evidence For and Against Economic Geologists Special Publication no. 17, Large-Scale Displacements, Haggart, J.W., p. 53–109. Monger, J.W.H. and Enkin, R.J. (eds.). Geological Popov, Y.A, Berezin, V.V. and Seminov, V.G., 1985. Association of Canada, Special Paper 46, Evaluating the thermal conductivity of anisotropic p. 255–276. minerals and rocks. Izvestiya, Physics of the Hart, C.J.R., 1997. A transect across northern Solid Earth, vol. 7, p. 565–570. Stikinia: Geology of the northern Whitehorse Popov, Y., Lippmann, E. and Rauen A., 2020. Thermal map area, southern Yukon Territory (105D/13- Conductivity (TC) and Thermal Diffusivity (TD) 16). Yukon Geological Survey, Bulletin 8, 112 p. Scanner-Manual version 9.3.2020, 62 p., http:// www.geophysik-dr-rauen.de/tcscan/downloads/ TCS-Manual.pdf.

YGS Miscellaneous Report 19 Thermo-hydraulic properties – Takhini Hot Springs and Tintina fault zone 29 Rybach, L., 1981. Geothermal systems, conductive Appendices heat flow, geothermal anomalies. In: Geothermal Appendices are only available as digital files. They systems: principles and case histories, L.J.P. are included in a .zip file that accompanies this Muffler and L. Rybach (eds), John Wiley & Sons, document and available from https://data.geology. New York, p. 3–36. gov.yk.ca. Sass, J.H., Lachenbruch, A.H., Moses Jr., T.H., and Thermal conductivity scanner Morgan, P., 1992. Heat flow from a scientific Appendix A. (1) measurements for consolidated rocks using a research well at Cajon Pass, California. Journal Lippman and Rauen thermal conductivity scanner of Geophysical Research, vol. 97, p. 5017–5030, (TCScan; Popov et al., 2020). Thermal https://doi.org/10.1029/91JB01504. (2) conductivity heat flow meter measurements Sass, I. and Götz, A.E., 2012. Geothermal reservoir for consolidated outcrop rocks with the FOX50 characterization: a thermofacies concept. (Lasercomp-TA Instruments, 2020). (3) Thermal Terra Nova, vol. 24, p. 142–147, https://doi. conductivity needle probe measurements for org/10.1111/j.1365-3121.2011.01048.x. unconsolidated rocks with the K2D Pro needle Vosteen, H.-D. and Schellschmidt, R., 2003. Influence probe (Decagon Devices Inc., 2012) of temperature on thermal conductivity, thermal Appendix B. (1) Whole rock geochemical data capacity and thermal diffusivity for different type (ALS labs). (2) Radiogenic heat production of rocks. Physics and Chemistry of the Earth, calculations (Rybach, 1981). vol. 28, p. 499–509. Appendix C. (1) Hydraulic conductivity Witherspoon, P.A., Wang, J.S.Y., Iwai, K. and Gale, measurements for consolidated rocks using a J.E., 1979. Validity of Cubic law for fluid flow transient gas permeameter (PPP-250; Core Lab in a deformable rock fracture. Department of Instruments, 2016). (2) Hydraulic conductivity Materials Science and Mineral Engineering, and measurements for unconsolidated rocks from the Lawrence Berkeley Laboratory, University of grain size distribution (Beyer, 1966). (3) Hydraulic California, Berkeley, 28 p. conductivity calculations for fractured rocks using Welford, J.K., Clowes, R.M., Ellis, R.M., Spence, the Cubic law (Whiterspoon et al., 1979). G.D., Asudeh, I. and Hajnal, Z., 2001. Lithospheric structure across the craton-Cordilleran transition of northeastern British Columbia. Canadian Journal of Earth sciences, vol.38. p. 1169–1189, https://doi.org/10.1139/cjes-38-9-1169. Witter, J.B. and Miller, C., 2017. Curie point depth mapping in Yukon. Yukon Geological Survey, Open File 2017-3, 38 p. Yukon Geological Survey, 2018a. Bedrock geology data set. Compilation. Yukon Geological Survey, http://data.geology.gov.yk.ca/Compilation/3. Yukon Geological Survey, 2018b. Surficial geology data set. Compilation. Yukon Geological Survey, http://data.geology.gov.yk.ca/Compilation/33.

30 Thermo-hydraulic properties – Takhini Hot Springs and Tintina fault zone YGS Miscellaneous Report 19