PERMAFROST AT LUPIN

REPORT OF

PHASE 1 Timo Ruskeeniemi, Markku Paananen, Lasse Ahonen, Juha Kaija, Aimo Kuivamäki Geological Survey of Finland Shaun Frape University of Waterloo, Canada Lena Moren SKB, Sweden Paul Degnan Nirex Ltd, UK PERMAFROST PROJECT GTK-SKB-POSIVA-NIREX-OPG September 2002

Abstract Timo Ruskeeniemi, Markku Paananen, Lasse Ahonen, Juha Kaija, Aimo Kuivamäki, Shaun Frape, Lena Moren, Paul Degnan, 2002. Permafrost at Lupin: Report of Phase I. Geological Survey of Finland, Nuclear Waste Disposal Research. Report YST-112, 59 pages, 36 figures, 3 appendices. ISBN 951-690-846-2, ISSN 0783-3555. The aim of the project is to study the conditions and processes occurring in permanently frozen crystalline bedrock, with a special reference to deep (i.e., several hundreds of meters) bedrock conditions. The target of the study is the Lupin mine in Nunavut Territory, Northern Canada. The results may be utilized in assessing the long-term performance of deep underground constructions (e.g., nuclear waste repositories) in cooling climatic conditions. Phase I activities of the project include gathering of background information on climatic conditions, both local and regional. Geological information of the site was compiled, and facilities and infrastructure of the site are described. Five research expeditions to the site were carried out, and groundwater samples as well as rock samples were collected from the mine. Seismic survey was also carried out in the vicinity of the mine. Satellite images were utilized in structural interpretation as well as in study of thermal conditions. The results are presented in this report. The mining company provided geological and other structural information. Based on available data, a three dimensional structural model of the mine was created. The model was used in planning of the drilling and groundwater sampling of the second phase of the project. Processes related to permafrost are shortly discussed and the possibilities to study them in Lupin are evaluated. Keywords: permafrost, crystalline bedrock, groundwater composition, gas composition, fracturing

Tiivistelmä Timo Ruskeeniemi, Markku Paananen, Lasse Ahonen, Juha Kaija, Aimo Kuivamäki, Shaun Frape, Lena Moren, Paul Degnan, 2002. Lupinin ikirouta: Raportti I tutkimusvaiheesta. Geologian tutkimuskeskus, Ydinjätteiden sijoitustutkimukset. Tiedonanto YST-112, 59 sivua, 36 kuvaa, 3 liitettä. ISBN 951-690-846-2, ISSN 0783-3555. Hankkeen tarkoituksena on tutkia pysyvästi jäätyneenä olevan kallioperän olosuhteita ja siinä tapahtuvia prosesseja, erityisesti syvän kallioperän olosuhteissa (s.o. useiden satojen metrien syvyydessä). Tutkimuksen kohteena on Lupinin kaivos Nunavutin Territoriossa Pohjois-Kanadassa. Tuloksia voitaneen hyödyntää arvioitaessa syvien maanalaisten tilojen pitkäaikaiskäyttäytymistä (esim. ydinjätteen loppusijoitustilat) kylmenevissä ilmasto-oloissa. Hankkeen I vaiheessa on koottu tiedot ilmasto-oloista, sekä paikallisista että alueellisista. On koostettu geologiset tiedot tutkimuspaikasta, sekä kuvataan tutkimuspaikan tukipalvelut, välineistö ja infrastruktuuri. Tutkimusalueelle tehtiin viisi tutkimusmatkaa, keräten kaivosalueelta sekä vesinäytteitä että kivinäytteitä. Kaivoksen läheisyydessä tehtiin seisminen tutkimus. Satelliittikuvia hyödynnettiin rakennetulkinnassa samoin kuin termisessä tutkimuksessa. Tulokset esitetään tässä raportissa. Kaivosyhtiöltä saatiin geologista ja muuta rakenneinformaatiota, jonka pohjalta luotiin kolmiulotteinen rakennemalli kaivoksesta. Mallia on käytetty kairausten ja vesinäytteenoton suunnittelussa hankkeen toista vaihetta varten. Raportissa tarkastellaan lyhyesti ikiroutaan liittyviä prosesseja sekä arvioidaan mahdollisuuksia tutkia niitä Lupinissa. Avainsanat: ikirouta, kiteinen kallioperä, pohjaveden koostumus, kaasun koostumus rakoilu

Preface The permafrost project at the Lupin gold mine in northern Canada is a jointly funded international project with participants from Finland (Geological Survey of Finland and Posiva), Sweden (Svensk Kärnbränslehantering, SKB), Great Britain (Nirex Ltd) and Canada (Ontario Power Generation and University of Waterloo). This Phase I Report is the first in the series of “Permafrost at Lupin”. The continuously up-dated Geochemical Database has the status of an internal document till the completion of the research at Lupin. After that the partners will jointly make the decision on the release of the data. In parallel to the research described in this report a project on freezing experiments was carried out in the University of Waterloo. This work was supported by Ontario Power Generation and it will be reported separately. The Lupin mine is operated by Echo Bay Mines Ltd. The company has, not only provided the access to their property, but has also been extremely collaborative and has shown great hospitality towards the Permafrost project. In this respect the Mine Manager Bill Danyluk and the Loss Control Manager Hugh Ducasse have been in key role. Numerous persons have contributed to our work at the practical level: Doug Bencharski, Phil Geusebroek, Wayne Grudzinski, Quinton Hamilton, Andy Hureau, Dave Hohnstein, Barry Lowe, Graham McNally, Richard McPherson, Bruce Penner and many others.

Contents

Abstract

Tiivistelmä

Preface

1. Introduction ................................................................................................................... 1

Permafrost project ......................................................................................................... 1 Permafrost...................................................................................................................... 1 Needs for performance assessment ............................................................................... 2

2. General site description ................................................................................................. 5

2.1 The Lupin site.......................................................................................................... 5 2.2 The Lupin mine ....................................................................................................... 7 2.3 Climate and vegetation ............................................................................................ 9

3. Permafrost conditions.................................................................................................. 10

3.1 Permafrost in Canada ............................................................................................ 10 3.2 Permafrost at Lupin ............................................................................................... 11 3.2 The active layer ..................................................................................................... 14 3.3 The issue of taliks .................................................................................................. 16

4. Quaternary features and bedrock geology ................................................................... 18

4.1 Morphology and Quaternary Formations .............................................................. 18 4.2 Geology ................................................................................................................. 21

4.2.1 The main lithologies and their geochemistry ................................................. 21 4.2.2 Deformation and fracturing ............................................................................ 24 4.2.3 Fracture infillings ........................................................................................... 26 4.2.4 Petrophysical properties of the rocks ............................................................. 27

5. Hydrology and hydrogeochemistry ............................................................................. 29

5.1 Surface hydrology ................................................................................................. 29 5.2 Hydrology of the mine........................................................................................... 29 5.3 Groundwater hydrogeochemistry .......................................................................... 30

5.3.1 Sampling......................................................................................................... 30 5.3.2 Surface water .................................................................................................. 33 5.3.3 Waters in permafrost (0-540 m) ..................................................................... 34 5.3.4 Waters below permafrost (540-1130 m)......................................................... 35 5.3.5 Ice samples ..................................................................................................... 37 5.3.6 Stable isotopes ................................................................................................ 38 5.3.7 Salt in flushing water...................................................................................... 40 5.3.8 Salt precipitates .............................................................................................. 40 5.3.9 Gases in the mine............................................................................................ 41

5.3.9.1 General .................................................................................................... 41 5.3.9.2 Gas sampling and analytical results ........................................................ 42

5.3.10 Concluding remarks...................................................................................... 44

6. The structural implications for the conceptual model ................................................. 46

6.1 Methods ................................................................................................................. 46 6.2 Structural observations .......................................................................................... 46

Fracture zone V1 ................................................................................................. 48 Fracture zone V2, “Ramp fault” .......................................................................... 51 Fracture zone V3 ................................................................................................. 51 Indications from the seismic survey .................................................................... 52 Indications from the borehole video survey ........................................................ 53

7. Interpretation of the regional topographic lineaments................................................. 54

8. Discussion.................................................................................................................... 56

REFERENCES................................................................................................................ 58

APPENDIX 1, Seismic survey

APPENDIX 2, Regional lineament interpretation

APPENDIX 3, Table of Chemistry (Delivered separately)

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1. Introduction Permafrost project The main purpose of the project is to investigate subsurface conditions at the mine in order to improve the scientific understanding of processes occurring in crystalline bedrock under permafrost conditions. The main focus of the project is subsurface hydraulic and chemical processes, but thermal and mechanical processes as well as biosphere conditions are also of interest. Although the wide areal spread of permafrost in the Northern hemisphere, there are only a very few sites, which can provide the opportunity to investigate permafrost in crystalline rocks. It soon became evident that the most promising candidate would be the Lupin gold mine in the Arctic Canada. After receiving a positive signal from the mining company, Echo Bay Mines Ltd., a recognisance field trip was carried out to Lupin in October 2000 to evaluate the feasibility of the site. Major focus was on hydrogeochemical sampling and the identification of the existing data. The outcome was so promising that it was decided to continue the permafrost research at the mine and, consequently, the Permafrost project was established. The Phase 1 was launched in August 2001. The first field trip of the project took place in August-September 2001. The target of the fieldwork was to collect geological and structural information from the site to locate potential water-conducting fracture zones for future hydrogeochemical sampling. A seismic survey at the surface and review of the various sources of information was performed. An important task was the acquisition of the necessary databases from the mining company to construct the 3D model of the mine. Information on the surrounding Quaternary formations and morphological features was collected as well. The second field trip in November 2001 focused on the video survey of boreholes providing access to the potential, water-conducting fracture zones. Their location and orientation was of major interest. This work was continued in new boreholes during the last field trip in February 2002. Additionally, major efforts were made to sample gases from the boreholes. The hydrogeochemical database has been continuously supplemented by new samplings during all trips. This report aims to give a description of the Lupin site to provide a basis for the evaluation of the feasibility of the site for the research of the various phenomena related to the permafrost. Permafrost Permafrost is by definition ground that remains at or below 0°C for at least two consecutive years. Today permafrost occurs at high latitudes and/or altitudes. There is a general relation between the annual mean temperature in air and the temperature in the ground. The ground temperature increases with depth due to heat input from the interior of the earth. At the surface heat exchange with the atmosphere takes place. In areas with permafrost, the energy exchange at the surface is very complex. The complex heat exchange has among other things to do with freezing/thawing and the fact that the thermal conductivity of the ground is affected by its water content and by whether it is frozen or not. Examples of factors that influence the heat exchange are: • Precipitation – both form (snow, rain) and the season during which the precipitation falls are

of importance, affecting both water content and albedo.

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• Wind – moves snow and soil and affect evaporation. • Vegetation – affects albedo, the quantity of snow that reaches the ground, how much the

wind can move snow and soil, and evaporation. • Topography – occurrence of heights and hollows and their compass orientation. • Properties of soil and rock – water content, albedo, thermal conductivity and heat capacity. • Sea, lakes and watercourses – distance to (and occurrence of) major bodies of water. These factors are of great importance in relatively warm climates where the permafrost is sporadic. In areas with very cold climate, the thermal properties of the soil and rock mass are as a whole of the greatest importance for the development of permafrost. Permafrost is normally classified as continuous or discontinuous. In areas with continuous permafrost, permafrost occurs everywhere beneath the exposed land surface and bodies of unfrozen ground – taliks – only occur beneath large lakes, rivers and arms of the sea. In areas with discontinuous permafrost, areas of unfrozen ground separate bodies of permafrost. In the transition towards boreal conditions, the occurrence of permafrost becomes increasingly sporadic. The uppermost layer of the ground thaws and refreezes annually. The layer of ground that is subject to annual thawing and freezing is called the active layer. The permafrost and the annually frozen active layer restrict infiltration and groundwater recharge. Most of the annual precipitation contributes to surface runoff, and stream flow rates vary widely over the year. During the winter, the limited runoff is supplied by groundwater discharge from unfrozen ground. The snow and ice melt takes place during the span of a few weeks in the spring, causing peak runoff and stream flow rates. The active layer thaws. Due to the low temperature, evaporation is low. Meltwater cannot infiltrate through the frozen ground, and despite the low precipitation, large areas are waterlogged during the short summer. In Fennoscandia the geological evidences of permafrost are sparse, and there are currently no known geological traces of past permafrost depths. Based on present day observations permafrost starts to develop if the mean annual temperature is –1oC or below. In areas with an annual mean temperature of between –1 and –4ºC, the permafrost is limited to exposed areas. At annual mean temperatures below –4ºC, the permafrost becomes increasingly widespread. The limit to continuous permafrost runs where the annual mean temperature is between –6 and –8ºC. In a long time perspective such climate conditions may very well occur in large parts of the countries participating in the permafrost project. Needs for performance assessment During at least 2 million years, glaciations have taken place at the Northern hemisphere. According to different authors, alternating glacial and warmer interglacial periods have occurred in cycles of about 100 000 years during about the last 400 000 – 900 000 years (Holmgren & Karlen 1998, Ahonen et al. 2002, Peltier 2002). Nowadays, a major part of the area to the north of the latitude 60o N is under permafrost conditions, while Fennoscandia at the same latitudes belongs to the temperate zone. The main theory explaining the climatic variations is the Milankovich theory, according to which cold periods are due to variations of the Earth’s orbital parameters. Later, the model has been tuned to match the deep-sea sediment record (Imbrie and Imbrie 1980, ACLIN-model by Kukla et al. 1981). Figure 1 shows the future climatic scenarios derived from these models for the next one hundred thousand years. The models predict a cold period after 60 000 years.

3

-5

5

-40 -20 0 20 40 60 80 100 120

time (ky)

Forcing

Imbrie

ACLIN

Warm

Cold

Figure 1. Predictions of the future climate according to the Milankovich forcing, Imbrie & Imbrie model, and ACLIN-model (Ahonen 2001). Näslund et al. (2002) modelled the evolution of the Fennoscandian ice sheet during the last glacial period, the Weichselian. The model has been calibrated against geological evidences of warm periods (interstadials). During periods when the ice sheet covered only part of Fennoscandia, periglacial conditions and development of permafrost may have occurred in ice-free areas. New data of recent years (Ukkonen et al. 1999) indicate that, at least in southern Finland, ice-free period of Middle Weichselian has been longer than estimated earlier. Peltier (2002) modelled the behaviour of Laurentidian ice sheet. The developed coupled energy model is based on a number of well-known physical processes, but also relies on the geological evidence of the past climatic variations. Purpose of the work was to rationalize a Design Basis Glacier Scenario for the Performance assessment. An important aspect of Peltier’s work is also the discussion on the predictability of the future cyclic glaciation periods. Cold, dry periods favour the formation of periglacial conditions and development of deep permafrost. In a long time perspective permafrost is expected to occur in northern and central Europe and northern America and, consequently, evaluation of the effects of permafrost must be included in the performance assessments. The objective of performance and safety assessments is to demonstrate the long-term safety of a repository for long-lived radioactive waste. For a repository in fractured hard rock the preliminary question is; Do permafrost cause subsurface changes that may affect the integrity of the engineered barriers? Secondly – in case of leaking canisters – will permafrost affect the repository’s ability to retard and retain radionuclides. The latter evaluation besides subsurface effects includes surface conditions that are of importance for the dose rate of radioactivity to man.

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Safety case – the total amount of knowledge required for acceptance - must rest on scientifically sound descriptions of the main processes affecting the performed evaluations and conclusions. To evaluate the performance of the repository against safety criteria some kind of quantification of the possible effects of permafrost is often required. The objectives of this project are to deepen the scientific basis for performance assessment and to deliver permafrost scenarios including quantifications of possible changes. The following topics concerning permafrost are of interest for performance and safety assessments of deep geological repositories for spent nuclear fuel: • Occurrence and depth of permafrost

− Existence/extension of continuos/discontinuous permafrost regimes under different climate conditions.

− Geological evidences of permafrost. • Hydraulic conditions – groundwater flow

− Formation and importance of taliks. − Permafrost around major structures (fracture zones). − Role of active layer. − In case of leaking canisters – risk of concentration/accumulation of

radionuclides. • Chemical conditions

− Changes in groundwater composition − Salinity-increase due to out-freezing (formation of cryopegs). − Distribution of crypegs: As inclusions in the frozen rock vs. beneath it as a saline

front − Role of small-scale (grain-boundary) salinity − Occurrence of chlathrates (=methane hydrates).

• Mechanical impact of permafrost − Effects for flow conditions. − Effects of freezing/thawing on rock and soil stability.

• Biosphere conditions − Risk of concentration/accumulation of radionuclides. − Surface hydrology. − Dominating ecosystem processes.

The Lupin mine project can contribute to knowledge in many these areas, but the main objectives of the project are to study subsurface hydrological and chemical processes.

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2. General site description 2.1 The Lupin site The Lupin Mine is located in the Nunavut Territory (eastern part of the former Northwest Territory) about 1300 km north from Edmonton, Canada, and some 80 km south from the Arctic Circle. The distance to the White Sea in the north is about 300 km. The site is within the continuous permafrost zone (Figure 2.). The southern limit of the continuous permafrost corresponds roughly with a mean annual air temperature of -6° to -8°C (it is -11°C at Lupin), with the southern discontinuous limit at about -1°C. Most of the year the only access to the site is by air from the Echo Bay Hangar located at Edmonton International Airport. Both personnel (Monday) and freight (Thursday) are shuttled once a week. From early January to late March a winter road from Yellowknife provides a connection for heavy trucks. Telecommunications are facilitated by satellite-supported telephone and Internet connections. Currently a planning and licensing phase is going on for the construction of a road to Bathurst in the north. Accordingly, comprehensive environmental information is being gathered in order to estimate the possible effects of the road on this sensitive region. Some of this work might benefit the Permafrost project, but it is not clear when the data will become public.

Figure 2. Distribution of permafrost within the territory of Canada. Lupin (L) is located in the zone of continuous permafrost.

L .

6

Figure 3. Topographical map of the Lupin area. The mine (L) is located in the low middle. Curved lines towards the SE along the Lake Contwoyto indicate the routes of the winter road. Contour lines are presented with 10-m intervals.

L

Lake Contwoyto

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2.2 The Lupin mine The Lupin gold mine is operated by Echo Bay Mines Ltd. After a 20-month construction period the mining activities started in 1982. In January 1998 mining was suspended due to low gold prices. The cost structure, operating practises and the ore reserves were reviewed. As a result of these considerations the mine was re-opened in April 2000. Currently the reserves are estimated down to 1900-m depth. The ore zone is getting narrow with depth. However, if the price of gold remains about the present level, the mine can operate beyond 2007. During the fall of 2001, the company launched preparations to start mining again between levels 170 and 250 m. By March 2002 much of the mining at these levels was completed. Within the next six months (as of April 2002) the activities will be directed to the next section, i.e. 250-330 m. Among other things, new drifting towards the south at the 330 m level will be performed. According to the present state of knowledge these, developments will not disturb the areas the permafrost project is interested in. The contamination due to the mining activities is expected to be limited to the near vicinity of the ore zone. Also the access to the exploration drifts remains. At any given time about 200 employees will be at the site. Most employees work on either 2-week in/2-week out or 1-week in/1-week out rotation. The working day is composed of two 11-hour shifts and the mine is run 7 days a week and 365 days a year. The Lupin camp comprises two principal clusters of buildings: the industrial complex and the residential complex. The residential complex is capable of accommodating about 440 people in single rooms. Figure 4. Plan of the mining area showing the main buildings, roads and the projection of the ore zone (magenta). The grid in the figure is local, differing 30° from the true north. Grid line spacing is 200 m.

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All the mining activities at Lupin are operated underground. The roughly N-shaped, tightly folded mineralisation (with an almost vertical fold axes) is composed of three zones: West Zone (WZ), Centre Zone (CS) and East Zone (EZ). The total strike length of the mined zones is more than 900 m. The width of the ore zones varies from 1 m to 12 m. The access into the mine is facilitated by a main shaft, which extends down to the 1210 m level. The shaft allows the movement of both personnel and material. Access to the shaft is from levels at 87 m, 170 m, 250 m, 330 m, 490 m, 570 m, 650 m, 890 m and 1105 m. The mine is also serviced by a spiral-shaped ramp extending to the 1340 m level. The ramp provides the route for heavy vehicles to operate at all levels in the mine and also allows the movement of heavy or large units not transportable through the shaft

Figure 5. 3D-model of the mine. The long exploration drifts extending southwards are located at 250, 490 and 890-m levels. The ore and the workings are plunging to the NNE with a dip of c. 80˚.

1130 m

890 m

490 m 250 m

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2.3 Climate and vegetation The region is located in the continental sub-arctic climate zone well above the timberline. The vegetation is typical for tundra: grass and low-growing shrub species and dwarf birch. Blueberry and lingonberry can be identified from dryer terrains, while various grasses, marsh tea and cloudberry are found in wet lowlands. The mean annual air temperature is –11°C, and the annual extreme values range from –49°C to +31°C (Figure 6). According to the long-term average temperature records since 1982, positive diurnal temperatures are experienced from the first of June to the last week of September. During mid-winter the mean temperature drops to about –30°C. Quick and dramatic changes in the weather, especially in the temperature, are typical for the area. Temperatures can vary by more than 20°C within a couple days. The annual mean precipitation is low, about 270 mm (Figure 6). The major part of this is obtained between July and September; after Mid-September until Mid-May as snow. The snow cover is thin, but with strong wind, thick drifts can form at suitable spots.

Figure 6. Temperatures and precipitation at the Lupin Mine. The annual mean temperature in the period 1983 to 2001 is –11oC. Records were provided by the Lupin Mine Weather Station.

Mean temperatures 1983-2001

-40

-30

-20

-10

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10

20

1 2 3 4 5 6 7 8 9 10 11 12

Month

Mea

n Te

mpe

ratu

re Monthly MeanMaxMinYearly MeanMaxMin

Precipitation 1983-2001

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ipita

tion

(mm

)

Monthly meanMaxMinYearly MeanMaxMin

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3. Permafrost conditions 3.1 Permafrost in Canada The review below is provided by the web page: http://www.socc.uwaterloo.ca/permafrost. It is based on the publication by Smith, S.L., Burgess, M.M., and Heginbottom, J.A., (in press). Permafrost in Canada, a challenge to northern development; in A Synthesis of Geological Hazards in Canada, (ed.) G.R. Brooks; Geological Survey of Canada, Bulletin 548.

Permafrost is a thermal condition and therefore its occurrence is dependent on climate. Climate, however, is not constant and historically has undergone significant changes detectable at time scales from decades or centuries to millennia. During periods of cooling, permafrost may increase in both areal extent and thickness, while a warmer climate may cause an increase in active layer thickness, permafrost thinning, and in some cases, disappearance. Not all permafrost present today is in equilibrium with the current climate. Thick permafrost beneath the Beaufort Shelf is a relic of periods of lower sea level associated with the last glaciation. During this time, large areas of the continental shelf were above sea level and exposed to the intense cold of a full glacial climate. This allowed the formation of permafrost up to 700 metres in thickness. During interglacial periods and in postglacial time, these areas have been covered by Arctic Ocean water with a mean annual temperature 10 to 15°C higher than air temperatures during glacial periods. The thermal regime of the subsea permafrost is thus in disequilibrium with the present marine environment. The sediments therefore are warming gradually, causing the permafrost to slowly degrade. A general warm period followed the disappearance of glacial ice with temperatures peaking during the middle Holocene between 6000 and 9000 years ago. Macrofossil analysis and radiocarbon dating of peat cores has been used to reconstruct the permafrost distribution in western Canada 6000 years ago. The results of this analysis suggest that mean annual temperatures were about 5°C warmer than present and the southern limit of permafrost was 300 to 500 km northward of its current position. Much of the present discontinuous permafrost zone may have been free of permafrost. Where permafrost did exist during this time, active layer thickness was probably greater than at present. Many thermokarst lakes also developed in the Mackenzie Delta during this time. Cooler conditions followed the mid-Holocene warm period and permafrost became more extensive. Permafrost was probably established in northwestern Alberta by 3700 years ago and the climate at this time probably resembled the present climate regime. In the Mackenzie Delta region, permafrost aggradation (growth) and pingo development occurred in response to the deterioration in climate that began about 5000 BP. Frozen peatlands occur today in the southern fringe of the discontinuous permafrost zone at relatively warm ground temperatures (> 0.5°C). Permafrost likely formed when slightly colder climatic conditions prevailed in the northern hemisphere during the Little Ice Age. Between 1550 and 1850 AD, global temperatures were about 1°C cooler than present and permafrost occurred farther south than it does today. Much of this permafrost has generally degraded in response to warming but has been preserved in some areas due to the insulating properties of the thick peat cover.

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Evidence also exists for climate-induced changes to permafrost response during the last several decades to a century. During the last 100 years, air temperatures in the Mackenzie District (western Arctic) have warmed by about 1.5°C. This warming has caused an increase in permafrost temperatures in the Yukon and western N.W.T. In Manitoba, permafrost continues to degrade in the southern fringe of the permafrost region especially where there is no surface peat layer. In the eastern Arctic, however, recent cooling and aggradation (growth) of permafrost has occurred. Air temperature records for northern Quebec, show a decrease in temperature between 1947 and 1992 ranging from 0.02 to 0.03°C per year which has been accompanied by a cooling of the upper 20 m of permafrost between 1988-1993.

Figure 7. Depth distribution of permafrost in the territory of Canada. (National Permafrost Database, GSC, http://sts.gsc.nrcan.gc.ca/tsdweb/geoserv_permafrost.asp). 3.2 Permafrost at Lupin Today the depth of the permafrost in the area extends to about 400–500 m. The temperature measurements conducted in the shaft of the mine in 1989 indicated that permafrost persisted down to the 541 m level where 0°C was recorded (Fig. 8). The thermistores were installed to a depth of 1.2 m in brine-filled boreholes (Sandhu et al., 1996). The lowest values were recorded at 87 m depth (–6.8°C) and at 170 m depth (–5.8°C). The upper-most measurement was from the 27 m level with a value of –3°C. This temperature is rather high compared to the local mean annual air temperature (–11°C), and it is probable that ventilation or other mining activities have

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affected (increased) the value to some extent. Temperature measurements in a nearby esker gave values slightly below –6 ºC for the underlying bedrock (see Fig. 10). Presently it is not possible to comment on the reliability of the other temperature measurements. The main shaft has been open down to 370 m since 1982 and down to 780 m from 1984-86 onwards. The 1210 m level was reached during 1988–90. Hence, it may be logical to conclude that the true ambient temperatures still may be still lower compared to the reported ones. After the first visit of our team in October 2000 a thermistor was installed in the southern exploration drift at 490-m level. The thermistor is in a horizontal borehole reaching a depth of 12 m from the wall of the drift. Four readings are recorded (Table 1). The first row indicates the air temperature in the drift and the following rows show the temperatures at 2 m, 4 m, 7 m and 12 m in the rock. The ventilation of the drift has been turned off for a long time, which is shown by the abundant fragile frost flakes on the walls. The readings were taken in April, May and August 2001. The increasing surface temperature during the summer is slightly, but still clearly, reflected by the air temperature in the drift. However, the bedrock temperatures at the furthest measuring point show constant values, – 0.66º C.

Figure 8. Temperature versus depth, Lupin Mine. The measurements have been done in the main shaft in 1989 (open squares) and at level 490 m in 2001 (black square).

-8 -6 -4 -2 0 2

Temperature (°C)

-600

-500

-400

-300

-200

-100

0

Vertical depth (m)

Boundary of permafrost

Measured in 1989 Measured in 2001

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Table 1. Bedrock temperatures at 490-m level. The measurements are made by a calibrated thermistor (type YSI 44007) and are based on the temperature dependent resistance differences. The installation and the readings are provided by the personnel of EBM Ltd.

Depth (m) 13.4.2001 26.5.2001 31.8.2001 air - 0.27 0.0 - 0.08 2 - 0.46 - 0.45 - 0.51 4 - 0.53 - 0.52 - 0.54 7 - 0.60 - 0.59 - 0.60 12 - 0.66 - 0.66 - 0.67

The two set of measurement are in fairly good agreement with each other. The measuring point at 490-m level is about 150 m away from the shaft and other workings conducting warm air. Operations in the drift were suspended years ago and the ventilation has been sparse as mentioned above. Thus the conclusion that the limit of permafrost close to the mine is only slightly below 500 m, maybe around 540 m as suggested by the measurements from the shaft, seems to be justified. It is difficult to identify more precise location, since to our knowledge there are no drifts or boreholes at these levels providing access to undisturbed bedrock. For comparison, Figure 7 shows the depth distribution of permafrost elsewhere in Canada. The depth of the base of the permafrost at Lupin may vary somewhat due to several reasons. It is known that certain features at the surface (soil type, moisture, snow cover) may affect the thickness of the active layer, but it is not likely that they could have any significant influence down to 500 m depth. Important exceptions are the major watercourses, which may support underlying talik structures. The differences in porosity and heat conductivity of the main rock types are the main factors, which can cause fluctuation to the depth of the base of the permafrost. High porosity and consequent high water content retards the advance of permafrost, because the water has to be transformed to ice before the freezing front can proceed deeper. Regardless of the rock type the effective porosities of the intact rocks at Lupin are below 0.53% (Table 3) being too low to have any significant role. However, the case is different, if wide fracture zones are considered. In addition to the high water content, the potentially increasing groundwater salinity within the structure may generate unfrozen gaps extending above the surrounding base of the permafrost. Furthermore, flowing groundwater along a fracture zone transports heat and might have a local effect on permafrost depth. There is not yet enough information on the fracture zones to know whether this is the case at Lupin. The heat conductivity of amphibolitic rocks (iron formation) is higher than that for felsic rocks providing a route for deeper penetration of permafrost. Since the amphibolites form relatively narrow horizons at Lupin, the lithological control is believed to be limited, too. The thermal gradient in Lupin is about 16 mK/m, which is very close to the typical gradients in the Finnish bedrock. Figure 9 shows the relation between mean air temperature and near-surface temperature in rock. It is compiled from observations in Lupin and observations made by Kukkonen 1986. According to the Figure, formation permafrost starts when the annual mean air temperature is less than about -3oC.

14

Figure 9. Near-surface temperature in rock as a function of mean air temperature. From the deeper levels of the mine only indirect temperature data is available. When measuring the water temperatures in pools and flowing boreholes, temperatures around 5°C were recorded at 890 m depth and 10°C at 1130 m depth. This value is lower than might be expected for Shield areas, where temperature gradients range in 15 – 45 mK/m. If the measured temperatures are representative, the cooling effect of the severe climate extends much lower than the distribution of permafrost indicates. However, the low water temperatures may also indicate vertical flow from upper levels facilitated by the leaking boreholes, which disturb the natural hydraulic balance. 3.2 The active layer The active layer is the part of the soil cover (or bedrock) susceptible to annual thawing and freezing. In addition to the air temperature the depth of this layer is related to the grain size and the moisture content of the soil. High water content and subsequent formation of ice tends to hinder the advance of thawing. A peat layer has a similar effect due to it’s insulation properties, either arising from the water saturation or the high air content (palsas etc.). Peat changes thermal conductivity during the year, becoming a particularly good insulator (low heat conductivity) in the summer when it is dry, and a good conductor in the fall/winter when it is wet/frozen. This characteristic enables permafrost beneath to be preserved. There is only a limited amount of information concerning the thickness of the active layer at Lupin. The period of positive mean air temperature is experienced from June to late September. During the field trip in August 2001 it was noticed that till-like soil in lowlands was quite moist and it was unfrozen to at least one metre depth. A large number of surface boreholes were surveyed and they were rather uniformly frozen at 2-2.5 m vertical depth. It is likely that due to the heat conductivity of the casing the thawing has been promoted in the holes and the true limit of the base of the active layer is somewhere between one and two metres. This is confirmed by the seismic survey, in which the depth of the active layer was interpreted at c. 1.5 metres, varying between 1.2 – 1.8 metres (see Appendix 1).

-10

-8

-6

-4

-2

0

2

4

6

8

-14 -12 -10 -8 -6 -4 -2 0 2 4 6

Air temperature

Gro

und

tem

pera

ture

Ground temperature as a function of air temperature

(Source: Kukkonen 1986)

(Source: Lupin)

15

The mining company has installed several thermistores in the surroundings of the tailing ponds and one is installed in an esker about 10 km to the south of the mine. The data from the tailing area is not available and in any case it is also less interesting due to the effect of inflow of warm process waters. However, the data from the esker shows nicely the influence of moisture in the formation of the active layer (Fig. 10). The esker is composed of fine- to medium-grained sand with some pebbles. This coarse material is not able to hold moisture between the grains and, consequently, the thermistore hole is dry down to the bottom (14 m). This is readily seen in the annual temperature record. The wide variation in the temperature regime well above the 10 m depth indicates the influence of the air temperatures down to this depth. Due to the incorrect installation depth of the thermistor and lack of readings close to the surface, it is not possible to locate the exact thawing depth in the borehole. It is seen that during summer months the temperature is well above zero at 0.3 m, but is always negative already at 1.3 m. The lower most measuring point represents the local bedrock temperature.

Figure 10. Temperature vs. depth in an esker showing the annual temperature variation in a 12 m-thick sand formation. The lowest value is recorded from the bedrock (the deviating value from 11.11.2000 is probably due to a reading error). Installation of the thermistor (YSI 440007) and the readings are provided by EBM Ltd.

16

3.3 The issue of taliks Talik is an unfrozen section of ground within permafrost. Three different situations can be distinguished: open talik (open to ground surface, but otherwise surrounded by permafrost), closed talik (all within permafrost) and through talik (open to the ground surface and to an area of unfrozen ground beneath it. Permafrost encases it along the sides). There are several reasons and mechanisms responsible for their formation. A zone of unfrozen ground within the continuous permafrost layer can be formed by the presence of thermal sources like volcanoes (hydrothermal taliks), by the presence of a nearby unfrozen water basin or by depression of the freezing point using high salinity water (hydrochemical taliks), (Williams and Smith. 1995) Burn (2001) has studied the taliks below the lakes on Richards Island, Northwest Territories. The site is located on the coast of the Beaufort Sea in the Mackenzie delta. The depth of permafrost in the island varies from shallow to more than 125 m. Near-surface ground temperatures on Richards Island range between -6º and -9ºC, so the relatively warm lake-bottom temperatures cause considerable disturbance to the thermal regime of permafrost. Water and lake-bottom temperatures, the configuration of permafrost, active-layer thickness, and frost heave were measured at a tundra lake between 1992 and 1997. The lake is ovate, 1.6 km long, 800 m wide, and up to 13 m deep. Sandy terraces, covered by less than a metre of water, extend over 100 m from the shore. The terraces are underlain by permafrost, which terminates at their edge in a near-vertical wall. The lake is well mixed in summer, but thermally stratified when ice covered. The active layer in the terraces was uniformly 1.4 m deep. A geothermal model of talik configuration indicates that there is no permafrost beneath the central pool of the lake. The model suggests that, at equilibrium, 30 to 40% of the lakes on Richards Island have taliks that penetrate permafrost. The Lupin site has a great potential for the study of taliks and their influence on the hydrosphere. If a postglacial origin of the permafrost is adopted, it is possible that Lake Contwoyto supports a through talik beneath the surface waters. The water body in the lake is large enough to insulate the underlying bedrock from the cold air. The lake is more than 100 km long and the width close to Lupin varies from 2 to 5 km. Unfortunately the depth log of the lake has not yet been made available for the project. However, currently there is no solid information to support this hypothesis. To the knowledge of the present mining personnel no drilling has been carried out below the lake. Some information has been obtained from other mine sites, where excavations have extended below lakes or large peat bogs. The experience from mines like Discovery and Tundra shows that there is no permafrost present under large watercourses. Correspondingly, when a lake was drained at Ekati to allow open pit mining the bedrock was seen to be unfrozen and large amounts of water have to be continuously pumped out from the pit. All these mines are located 100 km or more southwards from Lupin, obviously closer to or within the zone of discontinuous permafrost. However, this information provides some background for the talik discussion. So far no written source has been located to confirm this information obtained from the mining companies. The currently anticipated efforts that the Permafrost project intends to carry out, in order to obtain more information about this aspect at Lupin, are related to geophysical surveys and interpretation of satellite images. The electromagnetic SAMPO method will be tested at the site in June 2002. Applicability of this method is based on the assumption that advancing permafrost will generate a saline front just below the frozen rock. This electrically more conductive zone, if

17

present, will be used as a marker horizon and its lateral behaviour is of major interest. Some of the profiles to be measured will be positioned to run across islands or peninsulas to see if the permafrost gets thinner or even disappears below the lake. It is assumed that the permafrost will extend below the lake for some distance beyond the shoreline and disappear only below the deep part of the basin. The preliminary analysis of the thermal channels of five Landsat 7 images, taken at different times of the year, revealed different types of temperature anomalies on land (Fig. 35). Some of the positive anomalies can be attributed to exposed bedrock areas with higher capacity to store heat provided by the sun. Others may be related to lowlands with higher moisture content and more flourishing vegetation. In some cases a correlation with structural features can be inferred. However, in general, the interpretation would demand fieldwork to establish suitable reference points to identify the various reasons for the temperature differences. Some temperature variations were observed in Lake Contwoyto as well. In some images the shoreline of the lake appears cold relative to land and the shallow waters. As expected the shallow waters are warmer than the waters in the deeper part. The temperature of water is very sensitive to the winds and currents. Hard winds tend to mix the temperature layering in the basin making it very difficult to observe possible temperature anomalies related to taliks or groundwater discharge. However, it is worth some additional effort to analyse those anomalies, which can be related to structural features or to their possible continuations below the lake. Probably the only way to definitely solve the talik problem is to drill an inclined borehole below the lake and obtain a temperature profile. A permanent installation of a temperature probe would be required, because it is not possible to prevent the freezing of the upper part of the hole without considerable extra costs.

18

4. Quaternary features and bedrock geology 4.1 Morphology and Quaternary Formations The Lupin area is situated about 450 m above sea level and has been dry land for a long time before the Quaternary. The landscape is relatively flat with a height variation in the range of 30–40 m. (Figs 11, 12 and13). The highest locations (elevation over 479 m) are 3.5 – 5 kilometers to the NW, W or SW from the mine. The topography is characterised by low eskers and/or delta formations and flat boulder fields or outcrops (Fig 14). The soil cover in the vicinity of the mine is usually rather thin, 1-5 m, according to the surface boreholes and the seismic survey. This is supported by the fact that the bedrock is generally well exposed. However, the seismic survey revealed some locations, where the overburden thickness exceeds 10 meters (Figs 2 and 3 in Appendix 1). Sometimes they are related to a low bedrock velocity, indicating a possible fracture zone. These features are not obvious when observing the local surface topography. The Quaternary deposits are effectively smoothing the landscape and making the lineament interpretations difficult in large areas. In topographic lows the typical soil type is till. It contains abundant fine-grained silt and, unlike typical Fennoscandian tills, usually well-rounded pebbles. The latter feature indicates that the soil material has been subjected to glacial reworking processes and during the last glacial retreat gravel has been mixed with the debris worn-out from the bedrock. Weakly-sorted gravel forms mantels around outcrops or 2-3 m high ridges and terraces. Most of the linear features observed in the aerial photograph are due to these terraces and outcrops (Fig. 15). Whether they reflect bedrock structures below or purely Quaternary features is difficult to say without additional information. Figure 11. A topographical model of the near surroundings of Lupin Mine. Lake Contwoyto is located at the blue area in the upper right corner. The straight feature in the middle is the airstrip and the thin, zigzaging line is the pipe line from the mine to the tailing ponds. The white line shows the location of the profile presented in Fig 12.

Mine

3.2 km

N (local)

19

Figure 12. A SW-NE trending elevation profile across the Lupin Mine. The location of the profile is shown in Figure 11.

Figure 13. The regional topography and the main watercourses in the surroundings of Lupin. The area of the map is c. 19 km x 13 km.

Elevation m.a.s.l.

> 479 469 - 479 459 - 469 449 - 459 449 (Lake Contwoyto)

Mine

Elevation profile 1, vertical exaggeration 7

Mine Sewage Ponds

Lake Contwoyto

m.a.s.l.

Lake Contwoyto water level

20

In wet depressions thin peat and other organic layers can be detected. From what we have seen, they hardly ever exceed 20 cm in thickness. Only in one location were a few palsas observed. These are one-meter high 1.5x1.5 m2 peat hills. They are formed when an ice lens under the insulating peat cover survives through the summer and grows in size year after year. An interesting observation from the outcrops was the presence of strong striations caused by the moving ice cover during a glacial event. This is evidence for the dynamic nature of the ice cover and for warm-based conditions of the local glacier or ice sheet. This may provide a piece of evidence for the post-glacial nature of the permafrost, if the striations can be shown to be related to the last stage of the previous glacial event. It can be argued that the preservation of permafrost under warm-based glaciers is limited. The mean direction of the striations is 158°. The outcrops at Lupin have been preserved relatively well compared to the common situation in northernmost parts of Fennoscandia, where most outcrops are fragmented down to a few meters depth due to the freezing-thawing process. Only here and there repeated freezing has lifted some blocks up from the surface. The most outstanding periglacial features in the region are boulder pots and boulder fields. In the former large, usually rounded, boulders are gathered in the form of a round aggregate. In most cases both the well-rounded shape and the rock types indicate that the boulders have been deposited at the site after transport. All fine-grained material is absent between the boulders. This kind of segregation is typically the result of a cyclic freeze-thaw process. Freezing of water has gradually lifted the boulders upwards towards the surface and left the finer material behind. A similar explanation is valid for the boulder fields (rock garlands), which cover wider, usually elongated areas (Fig. 14). In these formations the boulders are angular and are probably derived from the underlying bedrock. In both texture types a localised source of water is needed to facilitate the process. The most probable explanation is that an underlying impermeable soil layer collects and stores melting water from the thawing surface, which is then frozen during the winter months.

Figure 14. Typical flat scenery NEE from the mine. Irregular boulder fields or rock garlands are characteristic periglacial features in the area.

21

One major SEE-NWW trending esker formation is located about 10 km southwest from the mine. It forms a chain of smooth highlands, but it is not as out-standing as typical eskers in Scandinavia. The esker is composed of well-sorted medium to coarse- grained sand with rather few pebbles (φ << 10 cm). The mining company has exposed a wide area of the formation by removing the vegetation and the thin organic cover. They are exploiting the sand for construction purposes.

Figure 15. Aerial photograph of the site (2,6x2,6 km2). The nearest shore of Lake Contwoyto is 1300 m to the northeast from the mining facilities. Two small ponds in the south are used as sewage and waste water pools. Light areas outside the mine proper are outcrops, gravel or bolder fields (1). Dark grey, irregular areas are indicative of more pronounced vegetation and humid areas (2). Most of the linear features indicate the slopes of bedrock or gravel terraces or combination of these (3). 4.2 Geology 4.2.1 The main lithologies and their geochemistry The Lupin gold deposit is located in an Archean metaturbidite sequence (Bullis et al., 1994). The formation has been subjected to regional and contact metamorphism. The peak of metamorphism is dated to 2.5 Ga. Amphibolite facies metamorphism (low Pressure, high Temperature) has partly destroyed the primary sedimentary structures and produced crystalline rock types, phyllite and quartz-feldspar gneiss, which are the major lithological units at the site. However, their sedimentary counterparts mudstone and graywacke/quartzite are locally preserved and

1

1

2

2

2

3

2

22

recognisable. The gold ore is hosted by an amphibolitic iron formation (Fig. 16), where sulphide –poor and sulphide-rich varieties can be distinguished. Metagraywacke occurs primarily in the footwall (in the stratigraphy below the ore horizon) of the Lupin Unit (Gardiner, 1986). The rock is massive, light grey and homogenous. The larger clastic grains, which typically account for 30% of the rock are usually quartz or feldspar and the smaller, granoblastic, quarts grains account for 30-40% of the rock. Metagreywacke may contain as much as 90% of quartz and then the term quartzite is used. The micaceous matrix is predominantly composed of very fine-grained muscovite. Occasionally chlorite or biotite occur as major minerals as well. Ore minerals and epidote are typical accessories (< 5%). Phyllite and mudstone, collectively called argillite, are black, fine grained and generally more schistose than the metagreywackes (Gardiner, 1986). Argillites are the dominant lithology in the hanging wall (in the stratigraphy above the ore horizon). Quartz accounts for 40-65% of the lithology. Chlorite and muscovite or biotite are the other major minerals. The most common accessories are garnet, zircon, tourmaline, graphite and ore minerals. Well-laminated iron formation is characterised by alternating amphibole and chert (SiO2) bands. The amphibolite has been subjected to intense folding and deformation and it is frequently crosscut by quartz veins. Variably chloritised thin garnet amphibolite horizons are encountered with the iron formations. Quartz occurs in three forms and accounts for up to 65% of the rock. Two types of amphiboles are encountered in the iron formation: hornblende (Ca-Fe-Mg amphibole) and grunerite (Fe-Mg amphibole) the former being the dominating species. Quartz and grunerite form the lighter coloured bands, and hornblende forms the darker green bands in the rock. Chlorite and sulphides (pyrrhotite and arsenopyrite), and sometimes pyroxene and garnet occur as major minerals. Graphite, epidote, ilmenite, sphene and ore minerals are typical accessories. Table 2 shows the average chemical composition of the main rock types.

23

Figure 16. Bedrock geology of the Lupin Mine and its near surroundings. Data and geological interpretation provided by the Echo Bay Mines Ltd.

9000 N

9500 N

10000 N

10500 N

10000 E

10500 E

11000 E

SewageLake

30°

Quartz feldspar gneiss/PhylliteIron formation, sulphide poorIron formation, sulphide richDiabase

LUPIN MINEGeology

FaultEM conductor

0 100 200 300 400 500 m

MineComplex

24

Table 2. Average composition of iron formation and associated rock types in the Lake Contwoyto area (Lhotka and Nesbitt, 1988). Major elements in weight percent, trace element in ppm.

greywacke mudstone Iron formation mineralised iron formation

average (n) 4 4 7 8 SiO2 68.55 56.51 53.71 34.82 Al2O3 12.33 18.49 2.35 3.02 TiO2 0.56 0.70 0.11 0.09 Fe2O3 1) 6.90 9.27 38.29 42.19 FeO 2) - - 34.03 18.95 MgO 2.29 3.46 1.67 0.75 CaO 2.10 1.02 2.19 2.99 Na2O 2.46 1.80 0.06 0.07 K2O 1.79 3.56 0.09 0.05 MnO 0.08 0.07 0.08 0.04 P2O5 0.11 0.11 0.15 0.34 LOI 2.84 4.88 4.96 4.51 Total 99.98 100.08 100.13 97.91 Au 0.02 0.04 0.05 17.92 Ag 1 1 7 13 As 17 19 22 77770 Ba 461 1338 58 36 Bi 1 2 1 7 Ce 64 38 20 19 Co 20 27 19 42 Cr 152 197 35 59 Cu 73 14 26 397 La 35 20 5 5 Ni 47 81 19 5 Pb 16 16 6 10 Rb 82 125 5 6 S 3591 747 4084 97211 Sc 15 22 4 3 Sr 224 199 83 152 U 2 2 2 2 V 91 137 25 19 W 1 3 1 3 Y 19 21 13 14 Zn 73 75 22 38 Zr 173 122 30 27

1) All Fe expressed as Fe2O3 2) Non-sulphide portion of the Fe expressed as FeO

4.2.2 Deformation and fracturing Three major deformation phases have been identified. The interaction of these deformation events has created a complicated fold structure, which is characterised by interference patterns, i.e. large isoclinal folds are bent by younger folding resulting in distorted, semi-closed shapes. The mined part of the mineralisation is roughly trending N-S, while the southern limbs bend towards the SE. The lithological units are generally steeply dipping (80–85°).

25

Jointing is common and includes two vertical joint almost perpendicular to each sets that are other and one sub-horizontal set (dip direction/dip): 110/80°, 005/75° and 195/13°. The major fault movements have occurred along roughly N and NE trending structures that parallel the fold axial planes, typically resulting in well-developed slickenside structures (slide surfaces). Jointing is easily seen in the outcrops, but nevertheless the surfaces are relatively intact and no boulder-field development has occurred. Within the mine area there is a stoping providing a cross-section from the surface down to 27-m level. No increased fracturing can be observed close to the surface. Although most of the fractures seem to be tight, open fractures are present in all the six boreholes (levels 250 m, 890 m, 1105 m and 1130 m) surveyed with video camera. However, their distribution is irregular. There may be a short interval with a few open fractures and after that up to one hundred meters without any. Sometimes several fractures are located relatively close to each other, but nothing that could be termed as a fault or fracture zone was detected. Typically, the apertures are 1-2 mm wide while the largest apertures, around 5 mm, were seen in the borehole at level 890 m. A majority of the open fractures were interpreted to be parallel to schistosity. However, other directions occur, as well. Many fractures produce gas bubbles (Fig. 17). This was observed in all sub-permafrost holes. The major fault zones identified at the site are presented In Figure 16. Two of them coincide with the western and eastern limbs of the formation, and one is located behind the sewage pond. The western fault zone is a regional shear zone containing graphitic slickensides. The width of the zone varies, but is less than 10 m. There are only a few observations of week water flow in boreholes intersecting this structure. Furthermore, several minor and younger sub-vertical faults have been observed cutting the center and western zones. The displacement on these faults is commonly less than 3 metres (Bullis et al., 1994). Hydrogeologically the intersections of these faults and the regional ones may be important as they may form channels for groundwater flow.

Figure 17. An example of a borehole-video image showing an open fracture in borehole 890-188. The aperture is 1-2 mm. The gas bubbles emanating from the fracture are methane.

26

4.2.3 Fracture infillings In general fracture infillings are scarce. Most fracture surfaces are polished and may contain some chlorite and/or graphite. Thin calcite fillings are observed in rather few fractures. In some shear zones, complex, obviously hydrothermal, calcite-sulphide assemblages have been observed. Textural features indicate several reactivation episodes. Many of the most prominent occurrences are related to the sub-horizontal fracturing. One example is from the southern exploration drift at the level 890 m, where a gently dipping, 1-10 cm thick, calcite mineralisation is exposed on the wall of the drift (Figure 18). The zone contains a lenticular, 10x50x50 cm3, cavity filled with calcite crystals. At the surface there are tens of exploration drill cores stored unsheltered. A quick review of some of them revealed that rusty fractures are rather common down to about 40 m. The infilling material is probably composed of iron oxyhydroxides and clays. They indicate the depth of the oxidizing groundwater circulation in the upper part of the bedrock, most likely during the pre-permafrost conditions.

Figure 18. Calcite-sulphide filling in a gently dipping fracture system.

27

4.2.4 Petrophysical properties of the rocks The petrophysical properties of the Lupin rock types have been measured from six drill cores, two samples of each main rock type, in the Petrophysical Laboratory of GTK (Table 3). The properties examined were density, magnetic susceptibility, remanent magnetization, resistivity, P-wave velocity and effective porosity. Prior to the resistivity measurements, the samples were kept 48 hours in a water bath of ordinary tap water with a resistivity of 50 – 60 ohmm. For the porosity determinations, the samples were weighed both wet and dry, being placed in an oven for 48 hours at a temperature of c. 105° prior to the dry weighing. In Figures 19 and 20, susceptibility versus density and electric resistivity versus effective porosity are shown. According to the results, quartzites and phyllites are paramagnetic, whereas ore-bearing amphibolites are ferrimagnetic, indicating the occurrence of ferrimagnetic minerals (magnetite, sulphides). The amphibolite samples are also much denser than the felsic rocks due to the presence of dense mafic minerals such as amphibole and pyroxene as well as the occurrence of ore minerals (magnetite, pyrrhotite). For the same reason, measured P-wave velocities in the amphibolites are high, 6500 – 7130 m/s. The P-wave values for quartzite and phyllite (5060 – 5630 m/s) correspond rather well to the values gathered from the seismic survey at the ground surface. The resistivity of two amphibolite samples is anomalously low (from 51 to 410 ohmm, depending on the measuring frequency), indicating the occurrence of ore minerals (sulphides) in these samples. According to the porosity-resistivity diagram (Fig. 20), the samples can be divided into two categories. The phyllites and quartzites are resistive (over 10000 ohmm), and they do not seem to carry electrically conducting minerals. Their resistivity is dominated by porosity, as indicated by the reverse correlation between porosity and resistivity. The two amphibolites with low resistivity form a separate group. In these samples the resistivity is strongly affected by ore minerals, and the effect of porosity is probably insignificant (the reverse correlation between porosity and resistivity for the two samples is most likely a coincidence). Table 3. Petrophysical results from six drill core samples from Lupin. D = density, K = magnetic susceptibility, J = remanent magnetization, P = weight, Pe = effective porosity, R0.1 = electric resistivity with 0.1 Hz current, R10 = resistivity with 10 Hz current, R500 = resistivity with 500 Hz current, PV = seismic P-wave velocity.

SAMPLE Rock D (kg/m3)

K (uSI)

J (mA/m)

P (g)

Pe (%)

R0.1 (ohmm)

R10 (ohmm)

R500 (ohm)

PV (m/s)

1-LUP-01 Phyllite 2758 730 280 198.12 0.4 21600 20500 19000 5630 2-LUP-01 Phyllite 2982 1250 10 183.35 0.16 141479 141479 141479 6500 3-LUP-01 Amphibolite 3714 6410 1360 243.87 0.29 410 225 167 7130 4-LUP-01 Amphibolite 3756 2360 30 110.32 0.41 196 51 27.7 6590 311.6-LUP-01 Quartzite 2680 130 10 132.49 0.53 13400 12600 12200 5060 315.2-LUP-01 Quartzite 2775 300 20 127.84 0.28 17000 16200 15500 5120

28

Figure 19. Magnetic susceptibility versus density, 6 samples from Lupin.

Figure 20. Effective porosity versus electric resistivity, 6 samples from Lupin.

2600 2900 3200 3500 3800

DENSITY (kg/m3)

10

100

1000

10000

100000

SUSC

EPTI

BILI

TY (*

10-6

SI)

6 samples

PETROPHYSICS

QUARTZITE

PHYLLITE

LUPIN

AMPHIBOLITE

0 0.2 0.4 0.6 0.8

EFFECTIVE POROSITY (%)

100

1000

10000

100000

1000000

RESI

STIV

ITY

(OHM

M) 0

.1 H

z

6 samples

PETROPHYSICS

QUARTZITE

PHYLLITE

LUPIN

AMPHIBOLITE

29

5. Hydrology and hydrogeochemistry 5.1 Surface hydrology The main watercourse in the area is the long but narrow Lake Contwoyto (exceeding 100 km). The topography around the lake and its linear nature suggests an origin as a fault-valley type basin with possible deep fractured roots. From the shoreline the water depth increases slowly. A depth log from the lake has been performed, but the data has not been accessible to this project yet. According to unpublished information the deepest measured depth in the vicinity of the mine is 35 m. It is less than would be expected, but it is obvious that the Quaternary deposits have filled the basin and have flattened the topography. The Lupin Mine is located close to the SW corner of the lake, 1.3 kilometres from its shoreline (Fig. 3). Water in the lake is crystal clear, the amount of humic substances being insignificant. No bottom plants close to the shoreline could be seen. The lake bottom is covered by sand, gravel and/or boulders. According to a worker of a consulting company (Rescan Environmental Services Ltd.), the organic layer in the northern part of the lake is commonly only a few centimetres thick and sometimes it is difficult to find at all. He had no opinion concerning the thickness of the inorganic sediment, since it was not the target of his sampling. There are several small lakes and ponds in the area. It is noteworthy that they are located at variable topographic positions (Fig. 13). Due to the impermeable frozen soil, water is collected in any significant depression. Some of the lakes/ponds are interconnected forming complex waterways. Most of the lakes in the vicinity of the mine are discharging waters to Lake Contwoyto. A number of water divides can be established in the area. Two interconnected small lakes, a few hundred meters south from the camp, are used as sewage lagoons. Obviously they remain unfrozen throughout the winter due to continuous pumping from the camp and the mine. During the field trip in August 2001, two potential springs were located in the area 3-4 km to the east from the mine. In both cases water was flowing out from a bolder field close to a slope of a 2-4 m high terrace. The amount of out-flowing water was sufficiently large that it can’t be explained by rainfall or through-flow alone. Likewise the brooklets originating at the springs looked as though they never dry out during the summer season. Melting permafrost within the active layer is the most probable source of the water. These and some other surface waters will be sampled during next summer’s campaign (2002). The mine tailings are pumped from the mill to a pond system, which is dominantly composed of natural basins (lakes). This area is about 9 km south from the mine and has no obvious impact on the hydrogeology of the mine area. 5.2 Hydrology of the mine The mine is considered very dry, reflecting the low matrix permeability of the rocks and the tightness of the fracture system. The average inflow is 2.7-5.7 m3/h, which makes 24 000 - 50 000 m3/y. The amount is slowly increasing because the underground workings are expanding. In 1999, about 53 000 m3 was pumped out. This is a low amount compared to the volume of the underground workings, as these figures also include a proportion of water coming in via the pipelines to the mine. Most of the incoming water seeps into the mine from the unfrozen rock below the permafrost (below the 500 m level). The mine water is collected in four main sumps located at 170 m, 250 m, 890 m and 1105 m levels. An additional sump is in a drift at 1130 m,

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where groundwater from boreholes is dammed (Fountain of Youth). The excess discharge water is pumped up into the sewage lagoon. There are only some few locations where relatively large amounts of groundwaters have been observed to flow into the mine. Generally the amount has been small and the inflow has considerably diminished over time. However, some boreholes are known to be productive for several years. According to the experiences of the staff, all water-producing boreholes are drilled eastwards, indicating the existence of a hydraulically more conductive zone in that part of the bedrock. There are now reports of faults or fracture zones producing large amounts of water into the drifts. This indicates that the dominant water-conducting channels are located east from the mine and are probably trending roughly parallel with the underground workings, i.e. approximately N-S. It is tempting to think that the thick permafrost prevents completely the infiltration of surface water into the mine. There are three sources of meteoric waters: precipitation, melting snow during late spring and thawing permafrost during summer. The thawing active layer above the permafrost is able to reach the depth of a couple metres at most during the short summer and until late June it is very thin (tens of centimetres). Thus the spring flood is generated on frozen ground and the infiltration is effectively prevented. The amount of annual precipitation is small. Hence, the surface run-off into the lakes during the summer season is believed to account for all the meteoric water production. 5.3 Groundwater hydrogeochemistry Only a limited amount of previous hydrogeochemical information is available from the mine. Bottomley et al. (1994) published the analysis of one sample taken from the 1130 m level, but nothing is reported concerning groundwaters (ice) in the permafrost. Therefore, one of the major tasks during the recognisance visit in October 2000 was to collect water samples (also as ice) from the frozen part, as well as from the unfrozen zone below the permafrost. Since it was strongly suspected that the waters within the mined area might be contaminated by drilling brines, a sample was taken from a salt sack found underground to assess the nature of the possible contamination. The salt analysis is presented in the Chemistry Table, Appendix 3. 5.3.1 Sampling The research mission started from the 87 m level and continued along the ramp down to the 650 m level. This covered a large part of the permafrost zone and crossed the interface between the frozen and unfrozen bedrock. The deeper sections were not covered systematically but were visited as a rule when an inflow of water was known to occur at particular spot. The access to many levels, as well as, to the ramp was limited due to the mining activities and heavy traffic. Sampling of water was rather difficult in the permafrost. In the permafrost or at the permafrost/sub-permafrost interface, water dropped from fracture zone intersections in the ceiling of the ramp. This water was collected using large plastic sheets, and it could take up to one hour to get a 500 ml water sample. In a couple cases it was possible to leave behind a bottle or a sheet to collect water over one night or two nights. Traffic in the ramp usually prevented this kind of procedure. In total 25 water samples were collected in October 2000 (Lu/GTK/1, LU/GTK/3-26). This amount includes the lake water, the snow sample and six ice samples from the mine, either ice stalagmites or ice from the walls of the drifts. Additionally, two water samples were taken in August 2001 (LU/GTK/27 and 28), five samples in November 2001

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(Lu/GTK/29-33), eight samples in February 2002 (Lu/GTK/34-41) and four samples in June 2002 (Lu/GTK/42-45). Some boreholes have been sampled several times to monitor possible changes in the chemistry. Supplementary water samples from the mine are taken at any opportunity when access is allowed to new areas. The mining personnel are asked to report all groundwater leakage from boreholes and faults. The water and snow samples collected and the analyses available are presented in Table 4. Comparable information of ice sampling is given in Table 5. The basic field measurements during the first field trip included pH, electrical conductivity and temperature. However, due to the poor quality of the field data, obviously due to the difficult conditions underground (low temperature, high air humidity) the field measurements were restricted to electrical conductivity only. The other parameters will be measured later from selected sampling points using flow–through cells. The discussion below refers to the laboratory measurements unless otherwise indicated. Samples taken for cation and REE determinations were preserved against bacterial growth, oxidation reactions and adsorption/precipitation of cations by adding HNO3 suprapure acid to the water sample until pH reached <2. Before acidification the water samples were filtered through a 0.45µm disposable sterile filter. Samples were taken for chemical analyses, environmental stable isotopes and tritium, and in some cases also for 14C and isotopes of Cl, Sr, B and Nd. All samples were analysed for the major and minor components in the Geolaboratory of GTK. The University of Waterloo has provided the analyses for oxygen and hydrogen isotopes and for tritium (Table 6). Analyses (Sr, B and Nd isotopes) performed in BRGM, France, were received in January 2002, but they are not reviewed in this report. The ion balance error in most of the samples is below 10 % and thus the results are acceptable. Figure 21 presents the trilinear diagram of the chemical composition of water and ice samples taken from the Lupin mine area. The whole chemistry is presented in Appendix 3, Table of Chemistry (not included in the public delivery). Figure 22 presents the sampling locations relative to the depth and the permafrost.

Figure 21. Trilinear diagram of the chemical composition of the snow, lake, water and ice samples from the Lupin Mine area. Permafrost refers to depth of 0-540 m.

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Table 4. Groundwater sampling localities, type of samples and analyses performed. Also the assumed structure is indicated (for definition see Chapter 6).

Lupin waters 26-28.10.2000 Code Level (m) Type structure chem. δ18O, D 3H Lu/Gtk/17 surface lake x x x Lu/Gtk/18 surface Snow x x x Lu/Gtk/1 250 Drips V2 x x x Lu/Gtk/21 290 Drips V2 x x Lu/Gtk/4 310 Drips V2 x Lu/Gtk/5 330 water from cable hole x x x Lu/Gtk/6 390 Drips V2 x Lu/Gtk/7 430 Drips V2 x x x Lu/Gtk/8 470 wet spot on floor V2 x Lu/Gtk/9 510 Drips V2 x Lu/Gtk/10 530 Drips V2 x x Lu/Gtk/11 570 Pool x x Lu/Gtk/12 590 Drips V2 x Lu/Gtk/13 630 Drips V2 x x x Lu/Gtk/14 650 Drips V2? x Lu/Gtk/20 890 borehole 890-188 V1 x x x Lu/Gtk/15 1130 Fountain of Youth −V1 x x Lu/Gtk/16 1130 borehole 1130-195 V1 x x x Lupin waters 30.8-1.9 2001 Lu/GTK/27 890 re-sampling of Lu/GTK/20 V1 x Lu/GTK/28 890 Drips V3 x Lupin waters 8.11-10.11 2001 Lu/GTK/31 890 borehole 890-216 x Lu/GTK/32 890 borehole 890-217 x Lu/GTK/33 890 borehole 890-220 x Lu/GTK/29 1105 borehole 1105-57 V3 x Lupin waters 10.2-18.2.2002 Lu/GTK/34 890 re-sampling of Lu/GTK/20 V1 x x x Lu/GTK/35 1105 re-sampling of Lu/GTK/29 V3 x Lu/GTK/36 1130 borehole 1130-197 V1 x x x Lu/GTK/37 1130 borehole 1130-192 V1 x x x Lu/GTK/38 1130 borehole 1130-181 V1 x x x Lu/GTK/39 1130 borehole 1130-175 deep x x x Lu/GTK/40 1130 borehole 1130-191 V1 x x x Lu/GTK/41 1130 borehole 1130-201 V1? x x x Lupin waters 10.6-24.6.2002 Lu/GTK/42 430 re-sampling of Lu/Gtk/7 V2 x Lu/GTK/43 1130 re-sampling of Lu/Gtk/38 V1 x Lu/GTK/44 1130 re-sampling of Lu/Gtk/40 V1 x Lu/GTK/45 1130 re-sampling of Lu/Gtk/37 V1 x

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Figure 22. Sample types and locations at Lupin. The rock temperatures are measured from the shaft (data provided by Echo Bay Mines Ltd.). The measurement at 1130 m is from a water pool. The temperatures of the borehole waters at this level are in the same order. 5.3.2 Surface water Based on one sample taken from Lake Contwoyto, the surface water is of very dilute Na-Ca-Mg-HCO3-SO4 -type, the amount of total dissolved solids is only 14.5 mg/L. It is interesting to note that the lake water is Na dominant like most of the mine waters. Probably due to erroneous field measurements there is a large difference between pH measured in field (8.8) and in laboratory (6.1). A similar difference is observed with the snow sample. δ18O and δD values in the lake water are -19 and -158, respectively (Fig. 25). The values plot slightly below the global meteoric waterline (GMWL) possibly indicating evaporation effects. The tritium content is 20.1 TU, which is about the average observed in the precipitation of the Nunavut Territory during the last decade (ISOHIS Database of IAEA, 2001).

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5.3.3 Waters in permafrost (0-540 m) The lower limit of the permafrost is tentatively placed at the 540-m level. All together 10 water samples were taken above this level, from the frozen part of the bedrock. All water samples were collected from the ramp, except Lu/GTK5, which was taken from a subvertical cable hole at 330-m level. Water was found to be dripping from a more fractured part of the rock. Obviously the same structure is repeatedly met at different depths in the ramp. The lowest sample was taken at the 630-m level. Besides drips the Ramp Fault (V2) is indicated by some deposition of a brownish mixture of organic slime and inorganic precipitates. The waters are typically sodium dominant Na-Cl or Na-Cl-SO4 type. In three samples Ca or Mg are also major components besides Na. The content of total dissolved solids (TDS) varies between 7.3 and 39.5 g/L and tends to show a decreasing trend with depth. The most saline waters are of the Na-Cl type. There is a large variation in the measured pH. Most measurements show values between 6.8 and 7.5. Two exceptionally low values, pH 3.2 at 310 m and pH 3.3 at 390 m, were recorded. These low pH values in a mine environment are typically related to the oxidation of sulphides. Indeed, these samples show SO4 concentrations at the high end of the range of permafrost waters. Also the contents of heavy metals are much higher in these two samples than generally in the permafrost waters (Fig. 23). Although acid generating reactions are slowed down at temperatures approaching 0 ΕC, they are obviously not completely hindered (cf. MEND report 1.61.1).

Figure 23. Variation of selected heavy metal concentrations (Co, Ni, Cu, Zn, Cd, Pb and As) in Lupin mine waters in relation to SO4 content.

0

5

10

15

20

25

30

1 10 100 1000 10000

SO4, mg/l

(Co+

Ni+

Cu+

Zn+

Cd+

Pb+A

s) m

g/l

PermafrostSubpermafrostIce

35

However, the relationship between pH and SO4 content is not straightforward. Despite stable pH highly variable SO4 is observed. SO4 increases with depth to 5000 mg/L at 390 m after which concentrations decline to 1439 mg/L at 530 m. NO3 concentrations in the Lupin permafrost waters are exceptionally high. They range from 423 to 2630 mg/L. The highest value is from the 250-m level, the concentrations drop rapidly to the 330 m level and after that, a concentration well below 1000 mg/L is reached. An explosive containing ammonium nitrate has been in common use at the mine and it is the most likely source for the elevated NO3 concentrations. Uranium shows anomalously high concentrations in the groundwater, with more than 100 µg/L observed in many samples from the permafrost. The highest value is from level 310 m, 590 µg/L. Comparable values are observed, for example, around the U-mineralisation at Palmottu. According to the whole rock analyses the U concentrations at Lupin are below 6 ppm (pers. com. Andy Hureau), which is very low compared to the Palmottu site (40- 4000 ppm). Currently, the reason for the uranium anomaly is not known.

There are some features in the REE patterns, which may help in the classification of waters. The REE contents show extremely large variations and the ΣREE ranges from 1,5 to 15150 µg/L. The extreme concentrations are recorded from level 390 m (Lu/GTK/6). In general, the LREEs (La, Ce and Nd) are strongly enriched over HREEs. La and Ce are the dominant elements. Nd is a minor component, but still anomalous compared to other REEs. The La/Ce ratio divides the waters in two groups: 1) samples from levels 250, 430, and 510 have La>Ce, while 2) samples from 310 and 390 show La<Ce. It is interesting to notice that the lake water is similar to the group 1, but in the main rock types the ratio is the opposite (Table 2).

The four samples taken for tritium analysis have values that vary between 12.2 and 28 TU indicating the mixing of recent meteoric waters (Table 6). Since recharge from the surface is assumed to be largely prevented due to permafrost, it is reasonable to conclude that any tritium present at depth is due to the water pumped down for the mining activity (drilling, washing etc.) The 28 TU value from the 430-m level is higher than that observed from Lake Contwoyto (20.1 TU), which is the source for all process water used in the mine. If the result is representative, it is a signal from earlier decades when the tritium in precipitation was much higher that at present (AECL, Canada). 5.3.4 Waters below permafrost (540-1130 m) In total 25 analyses from 18 locations are available from the water sampled below the permafrost (Table 4). Two of the samples (590 m and 630 m) are drips collected from the ramp (V2 structure), a sample from level 650 m is comparable, but collected from another structure close to the ramp. Three samples are from the southern displacement fault (V3), (LU/GTK/28, 29 and 35). The first one is a drip sample from level 890 m and the two others are from the same borehole at level 1105 m. Two samples were taken from clean water pools from levels 570 m and 1130 m. Finally, 17 samples are taken from boreholes at levels 890 m and 1130 m. Most of the borehole samples are assumed to represent the V1 structure. An exception is sample Lu/GTK/39, which is taken from a steeply dipping borehole drilled westwards. Borehole 1130-175 extends down to about level 2000 m, but it is not known where the water comes into the hole.

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The waters form two clearly different groups. Samples taken from the ramp or from its vicinity (Lu/GTK/11-14) have many features in common with the permafrost waters. They are Na-Cl, Na-Cl- SO4 or Na-Mg-Cl-SO4 waters. TDS is generally high 14,6-20.8 g/L, although lower than in permafrost waters, and pH varies from 6.3 to 7.6. NO3 and SO4 concentrations are still high, 516-1280 mg/L and 2360-3480 mg/L, respectively. The deep borehole waters representing groundwaters from the pristine area, east from the mine, differ distinctly from the previous group. Sample Lu/GTK/15 from the Fountain of Youth at level 1130 m belongs to the same category despite the slightly elevated NO3 and SO4 levels. These deep waters are predominantly of Na-Ca-Cl type except Ca dominant waters in four boreholes at level 1130 m (191,197, 201 and 219). There is also a wide variation in TDS of the deeper samples (levels 1105 m and 1130 m. TDS in three boreholes range from 19 to 30 g/L, while in the others it is 7-15 g/L. The variation in salinity does not correlate with water type or with the location of the holes. The samples from levels 890 m and 1050 m are more dilute, typically with TDS of 3-4 g/L. The recorded pH values for the deep waters, only slightly above pH 6, are surprisingly low for these depths and need to be confirmed with field measurements. It is noteworthy that the samples from level 890 m are collected from different spots about 500 m and 1000 m apart and they represent different fracture zones. Based on the uniform chemistry of these samples it seems that the groundwater at this depth is rather homogenous, in contrast to the situation deeper down. The SO4 and NO3 concentrations in the borehole waters are drastically lower than those observed in the upper levels. Sulphate content varies from less than 1 mg/L to 31 mg/L and nitrate contents are below detection limit. The trend from high-sulphate permafrost waters to low-sulphate deep borehole waters is clearly seen in Figure 24.

Figure 24. Variation in Ca/(Ca+Na) vs. SO4 in Lupin samples.

0,010

0,100

1,000

0,01 0,1 1 10 100SO4, mmol/l

Ca/

(Ca+

Na)

Lake ContwoytoPermafrostSubpermafrostIce

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Also in comparison to more shallow measurements U concentrations have dropped to insignificant levels. Ba, Br and Li are strongly enriched in the deep waters. Sr concentrations are high throughout, ranging from 7 mg/L at level 890 m to the maximum value of 147 mg/L at level 1130 m. REE concentrations are low with ΣREE 0.02-5.9 µg/L. Most samples have values well below 1µg/L. An exception is the sample from level 590 m, where ΣREE is 62 µg/L. LREEs La, Ce and Nd are the dominant elements. The La/Ce ratio is variable. There are still too few REE analyses to justify further comments. There are 13 tritium analyses from the sub-permafrost waters (one pool sample is not considered representative). Tritium values show a decreasing trend with depth. As would be expected recent meteoric waters are assumed to have no impact on the deep borehole waters. Most of the 12 tritium samples taken at the deepest levels have values that are below the detection limit, 0.8 TU. Four samples have values 1.1 – 1.64 TU. From some boreholes the samples were difficult to obtain, therefore air/air vapour contamination is the probable reason for the elevated values. There are indications of the diminishing role of meteoric waters already at level 630 m. The measured tritium value from a ramp sample is < 6 TU. The most probable explanation is that the increasing volumes of deep groundwaters gradually dilute the contaminating effect of surface waters pumped into the mine. 5.3.5 Ice samples Seven ice samples were collected from levels between 170 – 330 m (Table 5). Except for the ice stalagmite from the level 170 m, all samples were taken from ice lenses on the walls of drifts. Consequently, all the ice has formed after the excavation of the drifts in the early 1980’s. No fracture ice or anything comparable, i.e. which could be considered as primary permafrost ice, was detected. Ice was cleaved from the wall, it was melted at room temperature and, thereafter, treated in the same way as the water samples. Table 5. Ice sampling localities, type of samples and analyses performed.

Lupin ice samples 26-28.10.2000 Code Level Type chem. stb.isot. 3H Lu/Gtk/22 170 ice stalagmite x Lu/Gtk/23 210 ice on wall x Lu/Gtk/3 250 ice on wall x x Lu/Gtk/25 250 ice on wall x Lu/Gtk/24 290 ice on wall x x Lu/Gtk/19 330 ice curtain x Lu/Gtk/26 330 ice on wall x x x

It is known that the beautiful forest of ice stalagmites at level 170 m was formed after the summer of 2000 within a couple months. Ventilation during the summer months brought down warm air and moisture and warmed up the ceiling of the drifts. Within a short space of time the dripping water formed stalagmites up to one meter high on the cold floor of the drifts. It is more difficult to assess the water source for the other ice occurrences. Probably there are boreholes or fractures behind the thick ice lumps, but they were not visible. The typical shape of the ice

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plates, limited lateral extension and the growth towards the floor, tends to support a point-like source. Thus, these ice samples represent the frozen fraction of the water leaked from the bedrock, which is either natural or flushing water. Most of the samples were white or clear, but some were stained with iron (derived from steel bolts or tubes?). The ice is not formed from pure water as the TDS values 0,04- 1,24 g/L demonstrate. All waters, except one, are Ca dominant. They contain variable amounts of Na, Cl, SO4 and HCO3. The chemistry of the three deeper samples from levels 290 m and 330 m is more uniform. They are of Ca-SO4-(Cl) type. The tritium measurements from two ice samples indicate that the ice has formed from water with a sizeable meteoric component. The values 11,3 and 12,5 TU are much lower that recorded from the lake (20,1 TU). When comparing the drips and ice samples from the same levels, it is readily seen that the water drips are exclusively Na dominant while the ice is Ca dominant. Possibly this relationship is evidence for the fractionation of waters during freezing, with the Ca dominant fraction being frozen while Na (and Cl) dominant fluids continue to migrate downwards away from the freezing front. Additionally, sublimation of ice under cold conditions may further modify its composition. 5.3.6 Stable isotopes Currently the lake water, snow, permafrost and subpermafrost drips, one ice sample and two deep borehole waters have been analysed for stable isotopes (Table 6). All the water samples, including the lake water, plot in a line below the global meteoric water line (GMWL). The snow sample plots exactly on the line (Fig. 25). The drips from the upper levels tend to have lighter isotopic composition than the lake water, while the deeper drips are heavier. The deep waters are again distinctly lighter than the lake water. The heavy waters are from the ramp sampling points from levels 430 m (δ18O –9.86‰; δ2H –77.9‰) and 630 m (δ18O –17.47‰; δ2H –147.4‰). The sample from the level 430 m is among the three most concentrated waters so far sampled from the site (TDS 37. 4 g/L). However, the heavy isotope signature is not in common for these Na-Cl waters, since the two other samples from levels 250 m and 290 m have considerably lighter isotope compositions (δ18O: –21.09‰ and –20.57‰; δ2H: –171.4‰ and –167.9‰). The fractionation of oxygen and hydrogen isotopes during freezing leads towards lighter isotope composition in the residual water, since the heavier isotopes are preferentially incorporated into the ice. This seems to be the case at the level 330 m when the isotope signatures of the water and ice are compared. However, the samples are not consistent enough to justify this kind of interpretation.

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Figure 25. Stable isotope plot (δ2H and δ18O) for the Lupin mine water samples compared to the Global Meteoric Water Line (δ2H=8δ18O+10; Craig, 1961). Cambridge Bay and Yellowknife data are from the ISOHIS Database of IAEA (2001). Table 6. δ 18O , δ2H and tritium values of the Lupin samples. Analyses performed at the University of Waterloo.

Sample # Depth Type δ 18O (SMOW)δ2H (SMOW) 3H (TU) Lu/Gtk/17 0 lake -19,1 -157,9 20,1 Lu/Gtk/18 0 snow -25,7 -195,0 6,5 Lu/Gtk/1 250 drips -21,1 -171,4 17,3 Lu/Gtk/3 250 ice on wall -18,9 -153,1 11,3 Lu/Gtk/21 290 drips -20,6 -167,9 <6 Lu/Gtk/5 330 water, cable hole -22,6 -180,5 13,2 Lu/Gtk/19 330 ice on wall -18 -152,4 12,5 Lu/Gtk/7 430 drips -9,9 -77,9 28 Lu/Gtk/10 530 drips -20,4 -164 12,2 Lu/Gtk/11 570 pool -17,8 -153,8 13,5 Lu/Gtk/13 630 drips -17,5 -147,4 <6 Lu/Gtk/20 890 borehole 188 -22,4 -177,6 <0,8 Lu/Gtk/27 890 borehole 188 -22,1 -174.7 1,64 Lu/Gtk/34 890 borehole 188 -22,4 -179,5 <0,8 Lu/Gtk/28 890 drips -22,9 -176,8 <0,8 Lu/Gtk/15 1130 Fountain of Youth -24,1 -183,5 <0,8 Lu/Gtk/16 1130 borehole 195 -22,5 -175,6 <0,8 Lu/Gtk/36 1130 borehole 197 -22,8 -186,4 <0,8 Lu/Gtk/37 1130 borehole 192 -22,6 -181,3 <0,8 Lu/Gtk/38 1130 borehole 181 -23,5 -172,5 1,2 Lu/Gtk/39 1130 borehole 175 -22,6 -177,2 1,1 Lu/Gtk/40 1130 borehole 191 -23,2 -179,3 <0,8 Lu/Gtk/41 1130 borehole 201 -23,2 -177 1,2

-300

-250

-200

-150

-100

-50

-30 -25 -20 -15 -10

δ 18O ‰ V-SMOW

δ 2 H

‰ V

-SM

OW

Lupin snowLake ContwoytoIceCambridge Bay rain+snowYellowknife rain+snowPermafrostSubpermafrost

GMWL (δ2H=8δ18O+10 ‰V-SMOW)

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5.3.7 Salt in flushing water The mining company has used large amounts of salt solutions when operating within the permafrost. Both sodium and calcium chloride have been added to the flushing water to prevent freezing. The brines are used both for exploration drilling and production drilling. Calcium chloride was used only by way of a trial for a short time. There are no records to justify even rough estimates of the amounts or concentrations of these solutions. A common practice was to excavate a depression, fill it with the lake or other clean water and add a sufficient amount of salt. One of these sumps at the level 250 was accidentally drained during the night through a fracture zone. Consequently, tens of cubic metres of saltwater is currently seeping downwards along the fracture zone. Based on this information it is reasonable to suspect the quality and integrity of the water samples showing high TDS and mole ratios for Na/Cl around 1. This is the case with most of the samples collected from the ramp. The contamination is likely to last for a long time due to the paucity of flushing/diluting natural groundwaters. We have not been able to trace back the quality or the producer of the calcium chloride, but a sack containing sodium chloride was found from one drift. The salt is very pure NaCl. Any notable impurities are: Ca 270 ppm, SO4 517 ppm and Br 42,4 ppm. 5.3.8 Salt precipitates Small amounts of precipitates are found where ever water is leaking. Both inorganic and organic material is encountered. The organic material is generally brownish, yellowish or reddish slime accumulated around leaking holes or fractures. The populations are more abundant at depth, but they are also found at levels where the rock temperatures are below zero. Usually only small mineral deposits are detected. However, at 650 level precipitates cover a whole wall in the Electrical Shop (both rock surface and constructions, i.e. cables, steel nets etc.). The minerals are forming white icicles or a yellow and white crystalline mass (Fig. 26). The main components are gypsum (CaSO4) and halite (NaCl). Currently the wall is dry and the channel(s) for the fluids are unknown. In more typical cases small gypsum or halite stalagtites are hanging from the roof and dripping water. Occasionally, a small amount of calcite (CaCO3) occurs in some samples. Gypsum and halite are the very minerals expected to precipitate from the Na, Ca, Cl and SO4 –rich drips observed at the upper levels. Since not much attention was paid to the occurrence of precipitates, currently it is not possible to present any details about their distribution in the mine or whether they are derived from the natural groundwaters or as a result of the salt used in the mine.

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Figure 26. Bladed gypsum and cubic halite crystals on the surface of a precipitate icicle from level 650 m. 5.3.9 Gases in the mine 5.3.9.1 General Gases are observed in many of the Canadian mines located in permafrost areas (pers.comm. Wayne Grudsinski, Lupin Mine). For example, at Yellowknife they have even experienced methane explosions. There is only a little historic information about gases at Lupin. The personnel were able to recall only one proven occurrence of methane gas emanation from a freshly drilled borehole, most likely at level 890 m. Obviously, it was not considered very serious, since there are no reports on the incident. During our field trips we have already observed several signs of gases at levels 890 m, 1105 m and 1130 m. In borehole video surveys it was noticed that many open fractures produced gases. In borehole 1105-57 the gas was identified as methane using a TMX410 gas detector. This equipment is routinely used underground to monitor the quality of air. The alarm level, 5 vol-%, was exceeded at the collar of the hole, but not in the air of the drift. The water from the long boreholes at level 1130 m contains considerable amounts of gases as well. The gas flow tends to be cyclic so that gas bursts (increased bubbling) can be observed at regular intervals. In a near vertical borehole 1130-175 the cycle was 15 seconds of bubbling for every 5 minutes seeming to indicate a consistent flow and filling of a subsurface reservoir or consistent diffusion from the rock mass in contact with the borehole. In addition, the mine reported that the five newly drilled boreholes at the exploration drift at the 890 m level had to be cemented, because of methane outflow. After completion of the drilling, the ventilation was stopped at the dead-end drift. A week later, during mine inspection, high methane values were recorded. The levels were clearly below the explosive level (5-15 vol-%), but still high enough to motivate the sealing of the holes. Three of the five boreholes were water producing. Fortunately, we had the opportunity to sample them during the November field trip. However, since the drilling was still going on, it is possible that the flushing water had an impact on the quality of the samples.

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5.3.9.2 Gas sampling and analytical results During the February, 2002 field trip gas samples were taken from five boreholes located in the 1130 m exploration drift. Sampling conditions were not ideal as the boreholes were generally open in the case of the horizontal holes 191, 192 and 197 or situated in shallow standing pools of water in the case of the near vertical holes 175 and 176. The results of volume percent gases can be seen in Table 7, which also includes some examples from other Canadian and Fennoscandian sites (Sherwood-Lollar et al. 1989). Table 8 contains the preliminary carbon and hydrogen isotopic signatures of the bulk hydrocarbon gases (methane etc.) and Figure 27 modified from Sherwood-Lollar et al. (1989) shows where the Lupin methanes would plot isotopically compared to other Canadian and Finnish Shield sites. There are several observations to be made from this preliminary data. First the volume percent data clearly shows a large component of oxygen gas in the samples. This is particularly true in the horizontal boreholes where a large portion of the hole (100's meters) is open to the atmosphere. The oxygen is most likely atmospheric in origin and could be subtracted from the listed results along with an atmospheric proportion of nitrogen. If we do this calculation the proportion of methane in the gases from the boreholes would be almost 100 percent. The only way to secure none contaminated samples from these holes would be to packer off the hole, allow the fluids to flush the borehole over time and allow the borehole to re-pressurize over a long time period. However, the samples are useful in providing methane gas for isotopic analyses. The rate of flow from the boreholes and the strong evidence of rock degassing seen in the borehole video logs suggests that the methanes collected had only a very short residence time in the open borehole. Therefore, we feel that the isotopic numbers reported in Table 8 are representative of the site. The results both from the 1130 horizontal boreholes and the two deep boreholes plot in a very narrow range (Figure 27). Figure 27 also shows the fields for thermogenic and biogenic methanogenic gases. The Lupin gases plot in an area described by previous researchers (Sherwood-Lollar et al. 1989) as abiogenic. The majority of methane in these samples would have an origin that is thermogenic and therefore most likely have been formed during high temperature events in the past. It should also be noted that the closest Canadian Shield sites on the Figure such as Val D'or, Yellowknife and Timmins are also gold mines and also have a high temperature emplacement history. Additional compound specific analyses to determine the proportion of C1, C2, C3 and C4 gas and further isotopic analyses is ongoing. It may be worth while to pursue a limited gas sampling program in Phase II for several reasons. (1) Packering, flushing and pressurized sampling of the holes should resolve the

oxygen issue and test the reliability of the isotopic results. (2) Refined isotopic results for methane, nitrogen and rare gases (He isotopes) will

most likely show the gases are of a high temperature, thus hydrothermal rock origin and are extremely old, thus pointing to an old stable system at depth before mining activity opened the rock mass.

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Figure 27. Isotopic compositions of methanes from Lupin compared to selected Canadian and Finnish sites. Modified from Sherwood-Lollar et al. (1989). Table 7. Volume % of selected gases from several boreholes in the Lupin Mine, Canada and examples of gases from other Canadian and Finnish sites (Sherwood-Lollar et al. 1993). Site CH4 % N2 % O2 % CO2 % H2 % Ar % Lu 191 13.5 70.0 17.5* 0.20 - - 192 37.0 55.0 13.1* 0.68 - - 197 80.0 17.7 1.4* 1.14 - - 175 80.0 13.9 1.4* 1.25 - - 176 78.4 16.3 1.3* 1.20 - - Sudbury 12.5 77.2 - - - 3.9 Thompson 52.2 43.2 - - - 0.5 Matagami 87.6 8.5 - - - 0.1 Juuka 78.9 6.3 - - 12.8 < 0.1 Enonkoski 75.9 11.4 - - 0.4 < 0.1 * Note high O2 levels are most likely due to the borehole fluids being in contact with air

over a considerable length of the hole.

44

Table 8. Carbon and hydrogen isotopic signatures of methane samples from several boreholes in the Lupin Mine, Canada. Site 13CCH4 2HCH4 Lu 191 -43.5 -326.7 192 -42.1 -319.1 197 -46.6 -322.6 175 -40.9 -313.6 176 -43.8 -319.3 5.3.10 Concluding remarks

The Lupin waters plot into two distinct fields based on their Br/Cl-ratio (Figure 28). The high Na/Ca permafrost and subpermafrost waters sampled from the ramp form a uniform group of low Br/Cl-ratio, while the deep borehole waters and the lake water plot at the high-end of the diagram. The Br/Cl-ratios, exceeding 0,007, are high compared to the Finnish and Canadian saline groundwaters.

As discussed above, many features denote contamination of water samples taken in the proximity to the ramp due to the Na-Cl dosed-waters used in excavation and drilling through the permafrost. Consequently, the anomalously low Br/Cl ratios in Figure 28 can be explained by the contribution of salt solutions (lake water + NaCl salt). This relationship is evident from Figure 29, where two distinct dilution/mixing trends can be seen. The deep waters, enriched in bromide, plot in a straight line. The waters sampled from the ramp (both permafrost and subpermafrost) plot along a line trending towards the NaCl-salt used in the mine.

Many of the geochemical trends at Lupin, such as increased salinity and sulphate concentrations, are proposed to be derived from contamination but could theoretically be induced by freezing processes as well. However, the lack of representative borehole waters, or any waters from other structures than the ramp fault, from the upper levels to date has prevented the establishment of the “baseline” hydrochemical situation in the permafrost. The available strong evidence pointing to contamination, e.g. low pH, high SO4 and NO3, Na/Cl mole ratios clustering around 1 and high tritium values, clearly suggests that permafrost areas close to the underground workings are not suitable for the kind of research planned for the project. Preferentially, efforts should be directed to investigating water-bearing fracture zones, which are not exposed in the mine, or, at least, to the extensions of the fracture zones outside the mined area.

45

Figure 28. Variation of Na/Ca ratio versus (Br/Cl)*1000

Figure 29. Bromide and chloride concentrations in Lupin mine waters and in NaCl-salt used for antifreeze purposes.

y = 0,0154x + 5,7501R2 = 0,9929

y = 0,0003x + 1,9071R2 = 0,6961

1

10

100

1000

1 10 100 1000 10000 100000 1000000

Cl, mg/l

Br,

mg/

l

Ramp watersDeep borehole watersSalt

0

2

4

6

8

10

12

14

16

18

20

0 1 2 3 4 5 6 7 8 9 10

(Br/Cl)*1000

Na/

Ca

Lupin snowLake ContwoytoPermafrostSubpermafrostIce

Deep samples (890-1130 m)

46

6. The structural implications for the conceptual model 6.1 Methods More than 20 000 underground boreholes have been drilled during the operational life of the mine. However, only some tens of these are longer, exploration boreholes. The geological reports are stored in the mines archive, but unfortunately, only nine drill cores have been preserved. The cores are stored unsheltered at the surface. The mining company has delivered the whole digitised borehole database containing the basic information of the holes for the permafrost project. In addition, a large number of surface boreholes were drilled during exploration in 1970’s. The cores are stored at the mine area, but the Geology Office has no information about the holes (location, reports), since another, presently suspended unit was responsible for the exploration work. It is the same case with the basic data from airborne and surface geophysical surveys. The material is not available at Lupin. However, a combined interpretation of the geophysical data as a digital presentation has been received from EBM.

The structural interpretation below combines the existing, written and oral, background information provided by the Echo Bay Mines Ltd (EBM) and the extensive research performed within the permafrost project. During the four field trips carried out to date structural information was obtained using various methods including: 1) drillcore logging, 2) a seismic survey in the most essential terrain (i.e. of greatest interest to the project) close to the mine, 3) borehole-video surveys and 4) structural observations in the mine. All the data is compiled in a 3D-model including all the underground workings and other facilities in the mine. The model is based on the database received from EBM and it is generated by use of Surpac Vision at GTK. Surpac Vision provides an effective tool for interpretation and visualisation of structural, geochemical etc. information.

6.2 Structural observations This section concentrates on the analysis of three structures considered most promising for future research, as targets for drilling. Major criteria in any selection are 1) water production, 2) “clarity” of the structure and 3) location relative to the underground workings. Strong weight is put on the first criterion due to the essential role of groundwater research in the permafrost project. The second item refers to the need that the target structure should be identifiable and predictable for some hundreds of meters, since conceptual extrapolation of the structure is needed due to the uneven availability of supporting information (boreholes, drifts). In the ideal case the structure should be traced from the surface, through the permafrost, down to the unfrozen bedrock. The third criterion has two-fold content. First, the contamination of the mine waters underlined the need to find a pristine bedrock block for hydrogeochemical studies. Thus, the assumed structure should preferentially be located outside the mine workings or, at least, should continue into pristine areas unaffected by mine activities. However, at the same time it should be possible to reach the target structure with a reasonable amount of diamond drilling effort. The most favourable locations for the drilling stations would be the southern exploration drifts at levels 250, 490 and 890 (cf. Fig. 5). They provide quiet space for prolonged

47

research installations (as they are not disturbed by the current mining activities) and sufficient scope for extension into pristine areas. Based on the information so far collected from the mine, three obviously vertical or subvertical structures seem suitable for detailed investigations in the permafrost project. Tentatively they are labelled as V1, V2 and V3 (Table 9). Projections of these structures relative to the underground workings at 890-m level are presented in Figure 30. The exact location and orientation of V1 is based on indirect observations and needs further research (see below). The location of V2 down to this level is an extrapolation based on observations between levels 250 and 650 m. Fracture zone V3 is observed at levels 890 and 1105 m, and it was possible to measure its orientation with reasonable accuracy. Table 9. Potential fracture zones and their characteristics at Lupin. The orientation of the structures is given by local grid referencing.

Indication Observed at dip direction/dip Note V1 water flow 890, 1130 tentatively 090/85 Flow from boreholes V2 drips several levels 100/75 Fractured zone in the ramp V3 drips 890, 1105, 250 (?) 010/65-83 0.5 –1 m thick shear zone

Figure 30. Location of structures V1, V2 and V3 at level 890 m.

V1

V2

V3

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Fracture zone V1 The fracture zone with the most potential for the project is V1, because it seems to support strong groundwater flow. The structure is intersected by boreholes at 890 m and 1130 m levels and possibly at 250 m level. At the lowest level three boreholes in the wall of a garage, the Mechanical Shop, produce water (Table 10). Two of the boreholes (1130-195 and 1130-197) are so generous that one is plugged and water is pumped directly from the other one. In the third hole (1130-219) the water flow is gentle. The outflow has continued since 1994 without showing any signs of diminishing. The three boreholes are drilled towards the SE with slightly different azimuths. They are all horizontal, and their length varies from 330 m to 580 m. It is evident that the holes conduct water to the drift, since no inflow was experienced before the drillings. Table 10. Water flow from some boreholes. The numbers should be considered as minimum values, since bypass in the order of 10-25% was inevitable in most boreholes. FB indicates sparingly fractured bedrock, i.e. discrete fracturing without any notable fracture zone.

Level Borehole Length (m) Date Flow L/min Structure 890 188 523 14.2.2002 7,7 V1 890 216 240 10.11.2001 0,5 FB? 890 217 193 10.11.2001 0,5 V3? 890 220 375 10.11.2001 1,0 ? 1105 57 482 8.11.2001 2,0 V3? 1130 181 495 16.2.2002 4,3 V1 1130 192 549 17.2.2002 6,4 V1 1130 197 574 16.2.2002 4,5 V1 1130 219 336 10.11.2001 << 0,5 FB

An exploration drift known as the Fountain of Youth is trending to the NNE from the NE corner of the Mechanical Shop (Fig. 32). The drift is grading two degrees. Thus the end of it is almost four meters higher than floor at the Mechanical Shop. A 10-m long and 1 m deep pool is embanked at the opening of the drift. Water is continuously pumped from this pool to lower levels for drilling and other purposes. Despite the heavy use, the reservoir does not appear to be reducing. There are numerous boreholes, which intersect the same fracture zones in the East as do the holes drilled from the Mechanical shop. All except one are plugged, but nevertheless water (and gas) is coming out from the holes. No leaking fracture zones have been observed in the drift. The most distinct outflow comes from boreholes 1130-181, 1130-191 and 1130-192 in the exploration drift. It has to be emphasised that apart from these observations, there are no other water-producing spots at this level. This tends to imply that the orientation of the structure is such that it doesn’t cut any underground workings. Roughly N-S trending zones would fulfil this condition. It is assumed that the same fracture zone is intersected at 890 m level as well. Borehole 890-188 is drilled in the same position as the boreholes 1130-194 and 1130-197 at the 1130 m-level. The borehole was closed with a double plug and, therefore, water was being forced out through fractures and cracks in the wall. The leaking water is collected in a sump and water is continuously pumped up to the surface to prevent flooding. The hole was opened in October 2001 by slashing down about 1 m from the wall to facilitate the video survey in the hole.

49

The similarities in chemistry and isotopic signatures in many of the water samples taken from levels 890 and 1130 give further support for the common origin (cf. above). The large and constant flow through the years suggests that the water reservoir must have significant lateral extensions, since permafrost prevents it being supplemented from surface. The low tritium values (<0.8 TU) further negate the possibility of the introduction of any significant amount of surface waters to these levels. Measuring the orientation of the structure was attempted with the down-hole video survey in three boreholes at levels 250 m, 890 m and 1130 m. Unfortunately, two of the holes (890-188 and 1130-192) have collapsed just before the assumed structure and it was not possible to measure the orientation or the width of the fracture zone. However, the location of the structure was established with a reasonable accuracy. The fracture zone (V1) is intersected at c. 494 m in borehole 890-188 and at c. 509 m in borehole 1130-192. The outcome from borehole 250-247 was much more uncertain due to poor visual conditions. No clear fracture zone or hole collapse was observed but intense fracturing was discovered at c. 351 m. Combining these three results gives an orientation of 332°/77° for a plane-like fracture zone. This orientation is geologically clearly discordant, and no similarly oriented structures have been observed in the area. Neither does it explain outflow from the boreholes 1130-181 and 1130-191 in the Fountain of the Youth. Furthermore, with this geometry the structure should hit excavated areas in the south. Clearly this is not the case. No significant water producing fracture zones have been observed in the drifts. Therefore the hypothesis of the discordant structure is abandoned and, instead, a roughly N-S trending, undulating or discontinuous fracture zone is assumed to be more probable (Fig. 33.). Correlation from 890 level with the seismic results on the ground surface and the flowing boreholes at 1130 level would give an approximate orientation of 090°/85° (dip direction/dip in degrees) for the structure (Fig. 31 – 33). However, between levels 890 m and 1130 m, the structure may be more steeply dipping. On the ground surface, the structure is outlined on the basis of seismic P-wave minima, and it has the same strike as the nearby diabase dyke swarm in the East, indicating one major direction of brittle deformation in the area. The calculated intersections of V1 in selected boreholes are presented In Table 11. Unfortunately it is not possible to follow the structure upwards, since there are no boreholes long enough or underground workings, which could extent to the structure between 890 and 250 levels. Table 11. Calculated borehole intersections of fracture zone V1.

Borehole Intersection depth (m) 1130-181 405 – 414 1130-191 438 – 441 1130-192 511 – 520 1130-195 571 – 579 1130-201 315 – 325 1130-217 430 – 437 250-247 480 – 489 890-188 488 – 518

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Figure 31. Possible location of structure V1 on the ground surface according to the seismic survey. Figure 32. The plan of the level 1130 and the boreholes potentially intersecting the structure V1. Boreholes 181, 191/217, 192, 195 and 197 are producing water and gas. Others holes are either dry or plugged.

9000 N

9500 N

10000 N

10500 N

10000 E

10500 E

11000 E

SewageLake

30°

Quartz feldspar gneiss/PhylliteIron formation, sulphide poorIron formation, sulphide richDiabase

LUPIN MINEGeology

FaultEM conductor

0 100 200 300 400 500 m

MineComplex

V1

V1

219

197

195 192

191 181 217

214

198

200

201203

51

Figure 33. A 3D view of fracture zone V1, > 200 m long boreholes and level plan 890 m, view from the South. Fracture zone V2, “Ramp fault” Fracture zone V2 intersects the spiral ramp. It is generally a 1-2 m wide zone showing more intense cross-cutting fracturing and it has clear continuation downwards from the 250-m level where it was observed. Probably, the structure extends up to the ground surface. V2 is not causing any notable stability problems and standard bolting is sufficient for support. The structure is more permeable than the surrounding bedrock. Water is sparsely dripping from the fractured sections and most of the water samples collected in 2000 were taken from this zone. The seeping water brings along salts and obviously supports microbial populations (slime) resulting in a patterned look. The trend of V2 is N-S and it is running across or close to the central part of the mine. As the hydrogeochemical results indicate, the location of the structure is not ideal for our purposes. Heavy drilling with brines in the frozen upper part of the bedrock and other mining activities have generated a contaminated waterfront, which is slowly moving downwards. However, the extensions to pristine areas, especially southwards, may deserve further consideration. Fracture zone V3 At the 890 level exploration drift, a sub-vertical fault is clearly discernible (Figure 34). Its thickness is less than 0.5 metres and it is dipping to the N with a dip > 65°. This structure is characterized by slickensides on fractures with calcite and graphite. The dextral displacement along this plane is about 10 m. Similarly trending, but sinistral faults can be observed also on the ground surface and at level 1105m. Extrapolation from ground surface to level 890 would give an orientation of 014°/86° (dip direction/dip). Extrapolation between the 890 m and 1105 m

52

levels gives a little bit gentler dip, 014°/72° - 74°. Direct correlation from the ground surface to level 1105 m results in an orientation of 014°/83° The measured dips at level 890 m are >65° and at level 1105 m 80°. Accordingly, the dextral fault zone at 890 m may not be same structure as the sinistral faults on the ground surface and at the 1105 m level or, alternatively, the present relationship is a result of complex movement history along the fault plane. V3 is located 200 m south of the shaft and about 400 m south of the active mining areas. Hence, the structure is located in an uncontaminated area. The water production from the zone is very sparse at level 890 m. However, it was possible to get a water sample by collecting drips on a plastic sheet. Deeper down, at level 1105 m, the water supply from the structure is more generous.

FormationExtrapolated downdip from surface and 250 m level

Fault 890 m level

200 m

400 m

600 m

400 m 600 m 800 m

Figure 34. Location of a cross-cutting fault zone (V3) at level 890 m. The green horizon is the amphipolite iron formation hosting the ore. Indications from the seismic survey The seismic survey revealed several locations where P-wave velocities less than 5000 m/s were recorded, indicating probable fracture zones (Fig. 1 in Appendix 1). Typically the strongest indications (Vp < 4500 m/s) are quite narrow (20 m or less), especially at profiles 1, 2 and 3. However, there are some wider indications with P-wave velocities between 4500 and 5000 m/s at profile 7, the western part of profile six and the northern part of profile 4. The velocity difference between the survey lines with different orientations indicates anisotropy in the survey area (the velocities at profiles 1 – 4 are usually higher than at profiles 6 and 7). This anisotropy may be related to roughly N-S trending geological structures (fracture zones and lithological contacts). Maybe the most clearly fractured area is near the crossing of survey lines 4 and 7 (Fig. 1 in Appendix 1), where the formation is clearly displaced, indicating the possible surface location of structure V3. Low velocity at the western end of profile 7 seems to be related to the eastern fault zone. The clear velocity minima at the central part of profile 6 may reflect the

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location of structure V1 on the ground surface. However, more accurate interpretation would require correlation with the borehole camera survey in some boreholes. The most potential holes for the correlation are located at upper levels 250 m and 490 m, e.g. boreholes 250-247, 250-356 and 490-195. Unfortunately the core is available only from the last one. Indications from the borehole video survey In November 2001 and in February 2002 a borehole video survey was performed at the site. The equipment is composed of a down-hole camera head (including mirror, camera and batteries), a cable and a digital video camera for recording. The camera head is operated in the hole using aluminium rods. The depth/length is determined with the measured marks on the cable and with the number of aluminium rods used (each 3 m long). The survey was performed in five subhorizontal boreholes at levels 250 m, 890 m, 1105 m and 1130 m. All together, almost 3000 m of borehole was recorded. The objective of the research was to locate the water-producing fractures and obtain information about their apertures and orientation. Therefore, all the surveyed sub-permafrost boreholes produce water. Since the exploration holes were not orientated and almost all the drill core has been thrown away, this method is the only way to get this kind of information. The major outcome was that discrete, open fractures are relatively common below 890 m. However, their distribution is irregular. There may be a short interval with a few open fractures and after that up to one hundred meters without any. Typically, the apertures are 1-3 mm, although a couple fractures with apertures around 5 mm were seen. In relation to water production, the borehole 890-188 has a key role. It produces 7-8 L of water per minute. The length of the hole is about 520 m. During the survey open fractures were observed every now and then within the first 490 m, but they can’t be responsible for all the outflow observed, even though the hydraulic pressure is equivalent to about a 400 m water column (measured from the limit of the permafrost). The survey had to be terminated at 494 m due to abundant rock fragments. Obviously the hole has collapsed due to the unstable rock conditions in the fracture zone. Strong flow through the blockage caused by the collapsed borehole wall is seen to transport gas bubbles and debris through the plug. A similar situation was faced in borehole 1130-192 at 509 m depth. These boreholes are the only ones currently available for the video survey. All other long boreholes at these levels are plugged. Consequently, it is was not possible to determine the orientation or width of the fracture zone, but its location in these boreholes could be determined with an accuracy of some tens of meters. In addition, it was learned that we are dealing with a distinct fracture zone and not with an evenly fractured bedrock. It is also note worthy that the bedrock is not totally intact at 1 km depth and minor fracturing is observed between major structures. However, these fractures are only able to produce small amounts of water. This was clearly observed at the level 1130 m, where one 330-m long borehole (1130-219) was surveyed. Scattered open fracturing was observed in the borehole. The hole produces very little water, while two other nearby, almost parallel, holes are very productive. The difference between these holes and hole 1130-219 is that they are almost 600 m long. It is concluded that the major hydraulic zone is somewhere out of the reach of borehole 1130-219, i.e 500 - 600m east from the drilling station.

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7. Interpretation of the regional topographic lineaments A regional lineament interpretation was carried out to map the regional fracture zones around the Lupin mine. The interpretations were based on satellite image data and available topographic maps. The satellite images were provided by Landsat 5 and 7. The following images have been purchased for the Permafrost project:

Satellite Mapper Date of image Landsat 5 Thematic Mapper 1 May 1990 Landsat 7 Enhanced Thematic Mapper + 27 May 2000 Landsat 7 Enhanced Thematic Mapper + 18 October 2000 Landsat 7 Enhanced Thematic Mapper + 3 July 2001 Landsat 7 Enhanced Thematic Mapper + 3 September 2001

The best images for the lineament interpretation turned out to be the summer images (3 July and 3 September) of Landsat 7. The spectral range of ETM+ is as follows:

Spectral Band Bandwidth (µm)

Resolution (m)

Panchromatic 0.522-0.90 15

1 0.45-0.52 30

2 0.52-0.60 30

3 0.63-0.69 30

4 0.76-0.90 * 30

5 1.55-1.75 ** 30

6 10.4-12.5 *** 60

7 2.08-2.35 ** 30

* Near infrared; ** Mid Infrared; *** Thermal Infrared Landsat images were processed with the Ermapper 5.5 program to obtain the optimum band and colour combination for structural interpretation. The version shown in Figure 35 was selected as the base map for the lineament interpretation. Also the Thermal Infrared band was processed to reveal temperature differences around the Lupin mine (Fig. 36). The lineament interpretation of the Lupin region was carried out at scale 1: 20 000. To support Landsat data detailed topographic maps were used for the interpretation. The lineaments were classified into three groups intended to represent fracture zones of different size categories: The result of the lineament interpretation is shown in Appendix 2. Size category of fracture zone

Size of fracture zone

I Regional (length: tens – hundreds of kilometers) II Regional – Local (length: several – tens of kilometers) III Local (length : one to several kilometers)

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Figure 35. Base map for the lineament interpretation. Landsat 7 ETM+ image. Colour combination of bands 1, 2 and 3. Date of the image 03.09.2002.

Figure 36. Processed Landsat 7 Thermal IR image (band 6: 10.4 – 12.5 µm) of the Lupin mine area. Date of the image: 03.09.2002. Spectral colours from violet = cold to red = warm.

Lupin mine

Lupin mine

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8. Discussion The overall goal of the studies at the Lupin mine is to study permafrost features and processes, which could have relevance in assessing the performance and safety of nuclear waste disposal systems. Thus information obtained must be transferable from observations in Lupin mine to a generic nuclear waste repository in a similar geological environment. Figure 37 shows a general, conceptual model for possible features and processes to be studied in Lupin.

Figure 37. Conceptual model of a permafrost system. Following issues, supporting the nuclear waste disposal research, were identified as possible targets of study in Lupin:

• Freezing rate and depth extent of permafrost in crystalline bedrock • Cold saline water segregations (cryopegs) and their role in transport processes • Role of non-frozen areas (taliks) as pathways for groundwater flow • Long-term stability of the hydrogeological and hydrogeochemical conditions • Effects of freezing on bedrock stability • Aggregation of solid methane hydrates (chlatrates)

Deep permafrost in Canada has been formed during the Holocene, i.e. during less than the past 10 000 years. Due to the global climatic changes, the extent of permafrost has also changed considerably during that time (chapter 3.1). According to theoretical calculations, in low-porosity “dry” crystalline rocks, permafrost may propagate to the depth of 500 meters in a few

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thousand years (e.g., Ahonen 2001, Ahonen et al. 2002). The observed permafrost depth in Lupin is about 540 meters. That temperature gradient is about 16 mK/m (Figure 9), which corresponds very well to temperature gradients in Finnish bedrock (e.g. Kukkonen 1986). Near-surface temperature measured in a near-by esker (about -7 oC, Figure 11) is well in accordance with the mine observations. The depth of the permafrost is thus well justified by an apparent thermal equilibrium model. It was observed, that the annual mean air temperature in Lupin (-11 oC) is about 4 degrees colder than the near-surface temperature. This points out the importance of the active layer in temperature regulation. Identification of saline water segregations (cryopegs) and consequent precipitation of mineral phases was identified as one of the main targets of the study. Small amounts of slightly saline waters were observed to drip from walls of the tunnels in the frozen part of the bedrock. However, the contamination due to saline drilling (flushing) water could not be ruled out. Below the permafrost, in the deepest parts of the mine, saline waters were observed. They probably represent typical deep, stagnant waters, as indicated by the existence of e.g. methane. A general observation was that the mine is “dry”. Water-bearing fractures are few, and the total amount of water pumped out from the mine is relatively small. One of the main strategies adopted for further studies is to clarify the mode of occurrence of the salinity. What is the role of water-conducting fractures and the chemical composition of fracture waters. Another question is the speculated existence of a saline front below the permafrost. High groundwater salinity has been considered to be a negative factor for the performance of the engineered barriers using a bentonite back-fill. On the other hand, non-frozen saline segregations in fractures may serve as a transport pathway for radionuclides possibly released from the repository. The amount and mode (e.g. continuity) of saline water occurrences within the frozen bedrock are the key questions. Due to the warming effect of major lakes and rivers, the bedrock below them remains unfrozen (taliks). Detection and identification of taliks in areas surrounding the Lupin mine has been considered as one of the options for further studies. The possible role of major fracture zones in the formation of taliks can then be considered more properly. So far the observations in the Lupin mine have not shown any evidence of the effects of freezing on bedrock stability. Methane hydrates (clathrates) are a common feature in the northern gas fields of North Alaska and western Siberia. Amounts of methane are much less in shield areas, but some methane is often present in deep groundwaters, as was also observed in Lupin. At cold conditions and high pressure, methane forms solid compounds with water. It is thus possible that clathrates may be found also in Lupin. As long as the clathrates remain in the solid phase, their effects on the performance of nuclear waste is negligible. However, pressure release or temperature increase makes the hydrate structure unstable and vast amounts of methane may be released.

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REFERENCES Ahonen, L., 2001. Permafrost: occurrence and physicochemical processes. Posiva Oy,

report POSIVA 2001-05.

Ahonen, L., Luukkonen, A., Pitkänen, P. Rasilainen, K., Ruskeeniemi, T. 2002. Jääkaudet ja ydinjätteen loppusijoitus. Geological survey of Finland, report YST-110. (Ice ages and nuclear waste disposal, in Finnish with English abstract).

AECL. http://www.science.uottawa.ca/~eih/ch7/7tritium.htm

Bottomley, D.J., Gregoire, C.D. and Raven, K.G., 1994. Saline groundwaters and brines in the Canadian Shield: Geochemical and isotope evidence for a residual evaporite brine component. Geochimica et Cosmochimica Acta 58, 1483-1498.

Bullis, H.R., Hureau, R.A. and Penner, B.D., 1994. Distribution of gold and sulphides at Lupin, Northwest Territories. Economic Geology 89, 1217-1227.

Burn, C.R., 2001. Tundra lakes and permafrost, Richards Island, western Arctic coast, Canada (abstract). Annual Scientific Meeting of the Canadian Geophysical Union. May 14-17, 2001, University of Ottawa, Ottawa.

Echo Bay Mines Ltd., 2000. Lupin operation – General information. Internal report, 21 p.

Gardiner, J.J., 1986. Structural geology of the Lupin mine, Northwest Territories. Unpublished MSc-thesis, Wolfville, Nova Scottia, Acadia University, 206 p.

Graig, 1961. Isotopic variation in meteoric waters. Science 133, 1702 – 1703.

Holmgren K, Karlén W. 1998. Late Quaternary changes in climate. SKB Technical report TR-98-13.

Kukla, G., Berger, A., Lotti, R., Brown, J. 1981. Orbital signatures of interglacials. Nature 290, 295 - 300.

ISOHIS Database of IAEA, 2001. Isotope hydrology information system. http://isohis.iaea.org.

Imbrie, J. and Imrie, J. 1980. Modeling the climatic response to orbital variations. Science 207, 943 - 953.

Kukkonen, I., 1986. Menneisyyden ilmastomuutosten vaikutus kallion lämpötilaan ja lämpötilagradienttiin Suomessa. Geological survey of Finland, report YST-51. (Abstract: The effect of past climatic changes on bedrock temperatures and temperature gradients in Finland).

Kukkonen, I., 1986. Lämpötilamittauksia syvistä kairarei’istä. Geological survey of Finland, report YST-54. (Abstract: Temperature loggings in deep drill holes).

Lhotka, P.G. and Nesbitt, B.E., 1988. Evidence for epigenetic Au mineralzation in Archean silicate iron formation, Lupin mine, Slave province, Canada. Bicentennial Gold ’88,Geological Society of Australia, no. 23, Poster volume 1, 89-91.

MEND Report 1.61.1, 1997. Review and assessment of the roles of ice, in the water cover option, and permafrost in controlling acid generation from sulphide tailings. http://mend2000.nrcan.gc.ca/reports/1611es_e.htm.

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Näslund J O, Rodhe L., Fastook J L., Holmlund P., 2002. New methods of studying ice sheet flow and glacial erosion by computer modelling – examples from Fennoscandia. In press.

Peltier, W.R. 2002. A design basis glacier scenario. Report No: 06819-REP-01200-10069-R00, Ontario Power Generation, Nuclear Waste Management Division. Toronto.

Sandhu, M. and Tansey, C.M., 1996. Echo Bay Mines Ltd. Lupin Mine Design. Internal report, 31 p.

Sherwood Lollar, B., Frape, S. K., Fritz, P., Macko, S. A., Welhan, J. A. and Blomqvist, R., 1989. Gas geochemistry and its relationship to brines of the Canadian and Fennoscandian Shield. In: Geological Society of America 1989 Annual Meeting, St. Louis, Missouri, November 6-9, 1989. Geological Society of America. Abstracts with Programs 21 (6), A316.

Sherwood-Lollar, B., Frape, S. K., Weise, S. M., Fritz, P., Macko, S. A., Welhan, J. A., 1993. Abiogenic methanogenesis in crystalline rocks. Geochimica et Cosmochimica Acta 57, pp.23-24.

Ukkonen, P., Lunkka, J.P, Jungner, H., Donner, J., 1999. New radiocarbon dates from Finnish mammoths indicating large ice-free areas in Fennoscandia during the Middle Weichselian. Journal of Quaternary Science 14, 711 – 714.

Williams, P.J. and Smith. M.W., 1995. The frozen earth. Cambridge University press, Cambridge, p. 306.

APPENDIX 1, Seismic survey

Seismic survey at Lupin Mine A seismic refraction survey was carried out at Lupin between 20th and 24th August 2001. The purpose of the study was to locate fracture zones as well as overburden thickness, bedrock velocities and bedrock topography. Altogether six profiles with the total length of 2750 metres were measured. The locations of the profiles are shown in Figure 1 of this Appendix. The survey profiles were staked with Garmin 12XL GPS. The survey was done with 110 m geophone spreadings using 24 geophones with a spacing of 5 metres. As an exception, at both ends of each spreading the spacing of the first three geophones was 2.5 metres. The shot points were located at both ends and 55 metres beyond the ends of each spreading. The seismic waves were generated by emulsion explosive sticks with zero delay electric detonators. The seismic signals were recorded by 24-channel digital Bison 7000 seismograph. Interpretation A typical estimate for the error of interpreted overburden thickness is 10% of the real thickness or one meter for depths less than 10 meters. The accuracy of bedrock velocity determination depends on the quality of the data. The interpretation was done by software developed in the Geological Survey of Finland. The software calculates the depths of seismic boundaries at the spreading ends by intercept time method and under each geophone by delay time method. Results The main results are as follows: • The melted part of the overburden is about 1.5 meters deep, with variation from 1.2 to 1.8

meters (Fig. 2 and 3). The model velocity for this layer is 300 m/s. This is based on the measured data, although it’s not typical for wet soil. Some delay on the detonators may disturb this velocity, but it has only weekly affected the interpreted layer depth. The main reason for the low velocity is obviously cyclic freezing and thawing, which make the soil very loose. The same phenomenon with a layer thickness of half a meter has been observed in Finland, too.

• The frozen overburden can obviously be detected in many places. This layer might also

describe the uppermost fractured part of bedrock. The velocity of this layer varies from 3500 to 4000 m/s and the layer is certainly a hidden layer on some parts of profiles (It is too thin to create its own velocity line on the time-distance diagram, so the interpreted layer may be too thick). The total overburden thickness is less than 15 meters, usually only a few meters.

• Some lower velocity zones in bedrock can also be found. Typically the velocity drop is from

500 to 1000 m/s, probably indicating fracture zones. Bedrock can be regarded as fractured when the velocity is below 5000 m/s. Some velocity variation in bedrock is also obviously caused by variations in lithology.

Fig. 1. Seismic P-wave velocity along the survey lines and the location of the Lupin formation. Green and blue colours indicate low velocities and the locations of possible fracture zones.

1

2

3

4

6

7

Figure 2. Cross-sections of profiles 1 – 4 .

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Figure 3. Cross-sections of profiles 6 and 7.

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APPENDIX 2, Regional lineament interpretation

vhakkara

Text Box

67a

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APPENDIX 3, Table of Chemistry (Delivered separately)