Aitik mill as hub for a satellite minePreliminary development plan of a satellite copper deposit

Melissa Markesteijn BTA/RE/14-06

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Aitik mill as hub for a satellite mine

Preliminary development plan of a satellite copper deposit

by Melissa Markesteijn

In partial fulfillment of the requirements for the degree of

Bachelor of Sciencein Applied Earth Sciences

at the Delft University of Technology.

First Supervisor: Dr. ir. J. BenndorfSecond Supervisor: Dr. ir. D.J.M. Ngan-TillardSupervisor at Boliden: A. Renström

An electronic version of this thesis is available at http://repository.tudelft.nl/.

ABSTRACT

The copper grade in the Aitik mine in northern Sweden is decreasing, therefore other deposits areinvestigated. One of these deposits is the satellite deposit discussed in this thesis. The grade of thisdeposit is higher than in Aitik and could thus be used to increase the copper production at the Aitikmine site.

The goal of this thesis is to establish a preliminary development plan for a satellite copper deposit,which will be processed at the Aitik processing plant.

A literature study showed that the geology of the Aitik mine is the same as that of the satellitemine. Therefore the same design properties could be used as in the Aitik mine.

Because of the small surface operation and a steeply dipping ore, the best surface method for thesatellite mine is an open-pit operation. The mine design will slightly differ from the Aitik design, theoverall slope angle will be higher which results in less waste and thus less extracting costs. The overallslope could be made higher by a smaller bench width.

Different cut-off values and elevations of the pit bottom are tried. The best result was obtainedwith an elevation of the pit bottom of 400 meters. This means that the pit will be 85 meters deep,since the average surface elevation is 485 meters. For the cut-off value is found that the best cut-offvalue is 55 SEK. This would result in a maximum profit.

The fragmentation of the ore could best be done using a finer blasting schedule, instead of usingan in-pit crusher. The costs of finer blasting is less than that of an in-pit crusher.

The production schedule shows that the surface operation of this satellite mine will be from the1st of January 2018 to the 29th of May 2024, this means that the open-pit mine will produce for justunder 6,5 years. These dates are hypothetical and depend on the real starting date. After that a un-derground operation is considered. When this production schedule is used the Net Present Value ofthe project will be 59,9 MSEK.

Therefore this project is economically profitable, although the profit is fairly low. However, theprospects of a high-grade underground mine are promising. Therefore this will be a profitable project.

It is recommended for this project to do a more thorough research. The accuracy of grade inthe ore body is not very high, so this should be evaluated by drilling more boreholes. More modelsshould be evaluated, different cut-off values could be used, but also different production times couldbe considered to mine the ore quicker and start earlier with the underground operation.

Also, a leaching plant at the Aitik processing site should be considered. More and more gold andsilver is extracted from the Aitik area, but the recovery of these metals is fairly low, this could be in-creased by a leaching operation.

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CONTENTS

Abstract ii

List of Figures iii

List of Tables iv

Preface v

1 Introduction 11.1 Relevance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.2 Goal and methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.3 Report overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

2 The Aitik mine and its region 32.1 Geological Setting of the region . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32.2 The Aitik mine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

3 Processing the copper ore 63.1 Crushing the ore . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73.2 Grinding and milling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73.3 Flotation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73.4 Limitations of the processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

4 The satellite mine 94.1 Analysis of the satellite mine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94.2 Fragmentation of the ore . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

5 Production schedule and economic evaluation 155.1 Production schedule . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155.2 Economic evaluation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

6 Conclusions 19

7 Recommendations 20

Bibliography 21

Appendix A: Calculations for the satellite mine 23A.1 Waste Reduction when using a 2 degrees steeper slope . . . . . . . . . . . . . . . . . . . 23A.2 Different elevations cut-off of 55 SEK and 124 SEK . . . . . . . . . . . . . . . . . . . . . 24A.3 Kuz-ram models for blasting to 300 and 1200 millimeters . . . . . . . . . . . . . . . . . 25

Appendix B: Production Schedule 26B.1 Summary of the stage 1 production. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26B.2 Summary of the stage 2 production. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27B.3 Total production overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Appendix C: Economic Evaluation 30C.1 Calculation of the Net Present Value . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

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LIST OF FIGURES

1.1 Expected copper grades at the Aitik mine . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

2.1 The location of the Aitik mine and its region in the northern part of Sweden (McGimpsey,2010). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2.2 Geology of Northern Sweden (Wanhainen et al., 2012) . . . . . . . . . . . . . . . . . . . . 42.3 Schematic west-east vertical section through the Gällivare area . . . . . . . . . . . . . . . 5

3.1 The processing process at the Aitik processing site . . . . . . . . . . . . . . . . . . . . . . 63.2 The Mills at Aitik . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73.3 Principle of flotation (Kawatra, 2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

4.1 A simple model of the ore at the satellite mine . . . . . . . . . . . . . . . . . . . . . . . . . 94.2 Cross section of the block model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94.3 The bench design of the satellite mine. Note that this drawing is hypothetical and not

to scale. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

5.1 The outline of the satellite mine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

A.1 The Kuz-ram model for blasting to 300 mm . . . . . . . . . . . . . . . . . . . . . . . . . . . 25A.2 The Kuz-ram model for blasting to 1200 mm . . . . . . . . . . . . . . . . . . . . . . . . . . 25

B.3 Production Schedule Summary per bench . . . . . . . . . . . . . . . . . . . . . . . . . . . 27B.4 The gold and silver grades in the satellite mine . . . . . . . . . . . . . . . . . . . . . . . . . 28

iii

LIST OF TABLES

2.1 Rock properties in the Aitik mine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

4.1 The amount of ore in the satellite mine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104.2 The waste reduction if a steeper slope is used . . . . . . . . . . . . . . . . . . . . . . . . . 114.3 Cut-off calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124.4 Properties of the emulsion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134.5 Costs for the drilling and blasting with an Atlas Copco SmartROC D65 . . . . . . . . . . . 134.6 The variables used for the blasting to 300 mm . . . . . . . . . . . . . . . . . . . . . . . . . 14

5.1 The total amount of days to mine the two stages and its start and end date . . . . . . . . 165.2 Summary of the production per year . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165.3 The production of the trace elements gold and silver . . . . . . . . . . . . . . . . . . . . . 165.4 The long-term prices of copper, gold and silver . . . . . . . . . . . . . . . . . . . . . . . . 175.5 NPV Model for different NSR values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175.6 NPV Model for different capacities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

A.1 Waste Reduction Calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23A.2 Optimum pit depth calculated for two cut-off values . . . . . . . . . . . . . . . . . . . . . 24

B.1 Summary of the production per month for stage 1 . . . . . . . . . . . . . . . . . . . . . . 26B.2 Summary of the production per year for stage 2 . . . . . . . . . . . . . . . . . . . . . . . . 27

C.1 The overall NPV Calculation of the project . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

iv

PREFACE

This report is written as a Bachelor thesis at the end of the Applied Earth Sciences Bachelor’s programof the TU Delft in The Netherlands. The project is done for the company Boliden, with locations inScandinavia and Ireland. This report focuses on the Aitik mine in Sweden, in particular on a satellitemine which will be located 15 kilometers away from the Aitik mine site. This thesis is part of a pre-feasibility study.

I want to thank a few people who did help me to do this project. First of all, I want to thank Dr. ir.J.Benndorf and Dr. ir. D.J.M. Ngan-Tillard for their support and supervision from the TU Delft. Andof course I want to thank Arne Renström from Boliden, without whom I wouldn’t have been able towork on this project. I also want to thank Boliden for providing all the necessary data to work with.

This report would not have been possible without the support of all the employees of Boliden, atthe office and at the Aitik mine site.

Melissa Markesteijn

Delft, June 2014

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1INTRODUCTION

In this first chapter the main objective of this research is presented. The chapter closes with a shortoutline of each chapter.

1.1. RELEVANCE

The Aitik mine in northern Sweden is one of the biggest open pit copper mines in Europe. The minehas produced copper since 1968. However, over the years the copper grade has drastically decreased.The copper grade will decrease further in the next decade (Figure 1.1).

Figure 1.1: Expected copper grades at the Aitik mine

Around this Aitik mine, there are different other satellite deposits which are rich in copper. Oneof them is located just 15 kilometers from the Aitik mine. The copper grade in this deposit is muchhigher than in the Aitik mine, however it will be a much smaller operation. At the moment the aimis to have a surface mine, which can produce ore for about 5 years. After this 5 years undergroundmining is necessary. The plan is to open this surface mine in or before year X. From Figure 1.1 is clearthat the copper grade of the Aitik mine has a big decrease in that year. The copper from this satellitemine could then be used to have a higher copper production.

This study will investigate the possibility of a surface mine at a satellite deposit, 15 kilometersfrom the Aitik mine. This satellite mine will be implemented in the current processing at Aitik.

1.2. GOAL AND METHODS

The goal of this thesis can be summarized as follows:

"Establish a preliminary development plan for a satellite copper deposit with processing at the Aitikplant"

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1.3. REPORT OVERVIEW 2

To be able to reach the goal of the thesis, the following is done:

• Literature study of the geology of the area: can the assumption that the subsurface is the sameas in Aitik be validated?

• Obtain information about the current mining methods and design of the Aitik mine in order todetermine if this could be used for this satellite mine.

• Determine the best option for the fragmentation of the ore by finding an optimized blastingschedule.

• Create a production schedule for the copper ore.

• Do a basic economic evaluation of the satellite mine operations.

• Derive recommendations for mining the satellite mine.

In this studies, all economics are given in Swedish krona or SEK. In May 2014 the exchange rate is(CNN (2014)):

Swedish krona Euro American dollar1 0,11 0,15

1.3. REPORT OVERVIEW

This thesis is structured as follows. In chapter 1 the general framework and objectives of this thesisare discussed. Chapter 2 will go deeper into the region of the Aitik mine and the Aitik mine itself.Chapter 3 will be about the processing at Aitik and its limitations. Chapter 4 will cover the satellitemine with its data, assumptions and decisions. Chapter 5 will be about the production scheduleand the economic evaluation, this chapter will evaluate if the project is profitable or not. Finally, inchapter 6 conclusions are presented and in chapter 7 the recommendations are set out.

2THE AITIK MINE AND ITS REGION

This chapter will go deeper into the geology of Aitik and its surrounding and it will present somecurrent data from the Aitik mine and processing site.

The Aitik mine and its region is located in the northern part of Sweden. The location is shown onthe map of figure 2.1.

Figure 2.1: The location of the Aitik mine and its region in the northern part of Sweden (McGimpsey, 2010).

2.1. GEOLOGICAL SETTING OF THE REGION

The bedrock geology in northern Sweden is the result of a complex geodynamic evolution includingrepeated extensional and compressional tectonic regimes and associated magmatic and metamor-phic events (Wanhainen et al., 2012). The deformation in the northern Norrbotten ore provinces,the province in which the Aitik mine and its satellite mines are located, varies both regionally andon a local scale from a strong penetrative foliation to texturally and structurally well preserved rocks.The ductile deformation includes at least two phases of folding, with axial surface traces to the foldsmainly trending NW-SE and N-S. The age relationship between these two phases is not clear.

A highly saline(38 wt.% NaCl) aqueous magmatic fluid was released at about 300 degrees Centi-grade and a pressure of nearly 3 kbar, forming disseminated and vein-type ore of mainly chalcopyriteand pyrite within the intrusion and in the surrounding volcanoclastic rocks. At ca. 1.88 Ga this in-trusive and mineralising event was followed by metamorphism and deformation, resulting in foldingand foliation of the rocks. Extensive deformation and redistribution of metals occured at ca. 1.78 Ga.

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2.1. GEOLOGICAL SETTING OF THE REGION 4

The Aitik Cu–Au–Ag deposit represents a Palaeoproterozoic, strongly metamorphosed porphyry typedeposit. The complex geology is shown in figure 2.2

PORPHYRY DEPOSITS

A porphyry type deposit is a hydrothermal ore deposit (Voncken and Wolf, 2011). They are depositsthat are related to intrusions that have risen to a high level in the crust. These intrusions are subvol-canic. Aqueous fluids exsolve and collect in the apical part of the intrusion. Retrograde boiling canoccur in poryphyry deposits.

Upon retrograde boiling, the fluids escape by hydro fracturing of the country rock. Crystallizationof remaining silicate accelerated. Magmatic hydrothermal solutions contain dissolved metals and arerich in potassium. In this kind of deposit different sulfides can be expected, including:

• Chalcocite Cu2S

• Chalcopyrite CuFeS2

• Bornite Cu5FeS4

• Molybdenite MoS2

• Zinc may form sphalerite Z nS

• Excess Fe forms pyrite FeS2

Figure 2.2: Geology of Northern Sweden (Wanhainen et al., 2012)

2.2. THE AITIK MINE 5

GEOLOGY OF THE SATELLITE MINE

Because of the early stage in the feasibility study, no real geological investigation has been done, i.e.no rock mechanics results are available. However, there are some references from earlier studies thatsuggest that the geology in Aitik and the satellite mine are the same. A geological study of ’GeologicalSurvey of Sweden (SGU)’ mentioned that the ore body extended all the way to the place of the satellitemine (Danielson, 1987).

The data from figure 2.3 suggest indeed that the two ore bodies are on the same side of the faultzones. This could suggest that the two locations do indeed have the same subsurface.

Figure 2.3: Schematic west-east vertical section through Gällivare area. The Aitik ore body is not to scale. NDZ = NautanenDeformation Zone, KADZ = Karesuando Arjeplog Deformation Zone. Red = younger intrusive rock. Green = volcanoclasticrocks(Wanhainen et al., 2012).

Based on these two studies from Danielson (1987) and Wanhainen et al. (2012) the assumptionthat the geology at the satellite mine is the same as in Aitik is validated. That means that the datafrom Aitik can be used in this pre-feasibility study.

2.2. THE AITIK MINE

The Aitik mine is located in the northern part of Sweden, near the town of Gällivare. Aitik is the largestcopper mine in the world. The deposit consists of pyrite and chalcopyrite yielding copper, gold andsilver. The open pit is about 3 kilometers long, over 1 kilometer wide and 450 meters deep. Thedeposit was discovered in the beginning of the 1930’s, but its exploitation began in the 1960’s. Themining capacity is gradually tuned up since the large expansion in 2010 (Boliden, 2014).

Around the Aitik mine different small deposits have been found. These satellite deposits are notfar from the Aitik mine, so they could possibly be processed at the Aitik processing plant. One of thesedeposits is the one used for this study.

Because the same rock type in the satellite mine is found, data from the Aitik mine could be used.Some basic rock properties are listed in table 2.1.

Some discontinuities are found in Aitik and could also be expected at this satellite mine. In Aitikpegmatite dikes are found, these dikes are harder than the surrounding rock and it is therefore harderto drill, which can cause delays during the drilling and blasting of the rock.

Table 2.1: Rock properties in the Aitik mine

Rock Specific Gravity 2,8Elastic Modulus 60 GPa

UCS 100 MPa

3PROCESSING THE COPPER ORE

This chapter will cover the processing steps at the processing plant at the Aitik mine site. Before theore gets into the processing sequence, drilling and blasting have to be done, as well as loading the oreand transporting it to the processing site.

The process at the Aitik processing site is displayed in figure 3.1. The same processing site will beused for the processing of the ore of the satellite mine.

Figure 3.1: The processing process at the Aitik processing site

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3.1. CRUSHING THE ORE 7

3.1. CRUSHING THE ORE

The ore of Aitik is pre-crushed in the Aitik mine itself. Afterwards a cone crusher is used as secondarycrusher. Crushing is based on impact rather than on pressure. Cone crushers have a wide crushingcone with a side angle of 30◦C.

The crushing action is continuous. An eccentric cone is rotated in a funnel shaped opening. Start-ing the crusher with a full crushing chamber and a choke feed is possible. The feed can be directlydumped from a mine truck (Chaigneau, 2011). After crushing, the ore is transported 7 kilometers byconveyor belt to the ore storage.

3.2. GRINDING AND MILLING

There are two milling lines with a primary and a secundary mill. The capacity for each line is 2200tonnes per hour, which leads to a total of 36 million tonnes per year. The primary mills are 12 metersin diameter and 14 meters long. The motor in the primary mills has a capacity of 22.5 MW. The sec-ondary mills are 11,4 meters in diameter and 12 meters long. The motor in the secondary mill is 10MW. The feed fractions are between 25 and 100 mm and the discharge is 44 mesh(0.36 millimeters)(Metso, 2006).

The grinding circuits are fully autogenous. They are so-called because they self-grind the ore.A rotating drum throws larger rocks of ore in a cascading motion which causes impact breakage oflarger rocks and compressive grinding of finer particles. A picture of the grinding circuits is shown infigure 3.2.

Figure 3.2: The Mills at Aitik

3.3. FLOTATION

In Aitik froth flotation is used. This is a method for physically separating particles based on differ-ences in the ability of air bubbles to selectively adhere to specific mineral surfaces. When these par-ticles are attached to the bubbles, they will be brought to the surface. These bubbles with its particles

3.4. LIMITATIONS OF THE PROCESSING 8

are then removed from the flotation tank (Kawatra, 2009). This principle of flotation is given in figure3.3.

Figure 3.3: Principle of flotation (Kawatra, 2009)

In Aitik there are 52 flotation cells with a total volume of 5340 m3 of flotation cells. To achievebetter grades re-floating is required in one (cleaner) or more (recleaner) additional stages (Miskovic,2011). In Aitik there are different flotation tanks, the ore is enriched further and further in these tanks.

FURTHER PROCESSING

After these processing steps the concentrate is dried and stored. The concentrate will now have atarget of 60% copper. The concentrate will then be transported to the trains, which will transportthem to Boliden’s smelter in Rönnskar, a smelter near the city of Skellefteå.

3.4. LIMITATIONS OF THE PROCESSING

In order to implement the operation of the satellite deposit at the Aitik processing site, knowing thelimitations of the crusher are important. The only limitation is the fragmentation, the ore needs tobe fine enough to be processed at the Aitik site. The crusher in Aitik can take big boulders if nec-essary. However, for the trucks it is better to not have these boulders. The aim should be to get thefragmentation under 300 mm. Therefore either fine blasting should be considered or the ore shouldbe pre-crushed at the mine site. The evaluation of both options will be discussed in section 4.2.

4THE SATELLITE MINE

There have been mining operations before on this location. The copper deposit was found in the late19th century. In the early 20th century mining started. The community grew quickly, but soon enoughthe mining company went bankrupt, leaving the location to what it is today. Now you can see the oldfoundations of storages and some remnants of the copper mine of the early 1900s.

The satellite mine is located about 15 kilometers from the Aitik mine. Because of the relativelysmall deposit, a surface mine is being investigated as an alternative to bring forward the mining ofthe ore on top of an underground mine. The ore will be transported to the Aitik concentrator.

In this chapter an analysis of the satellite mine will be done, including mining methods and amine design. It will also include a comparison between blasting and pre-crushing of the ore.

4.1. ANALYSIS OF THE SATELLITE MINE

Figure 4.1: A simple model of the ore at the satellitemine

Figure 4.2: Cross section of the block model

The ore deposit of the satellite mine is a narrow, steeply dipping ore as is visible in the figures 4.1and 4.2 (Boliden Technology, 2014). This means production costs fastly increase with depth, becausethere will be more waste production. Investigation of the boreholes at the site are focused on thehigh-grade deep zone, leaving only one borehole directly adjacent to the surface mine. This meansthat there is a high uncertainty, mainly around the boundaries of the surface mine and the marginalore.

The amount of ore from the satellite mine is determined in Boliden’s Ideastudy using a blockmodel (Boliden Technology, 2014). The ore data can be found in table 4.1.

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4.1. ANALYSIS OF THE SATELLITE MINE 10

Table 4.1: The amount of ore in the satellite mine

ORE FROM PIT

Ore (kton) 5233

Ore Cu (%) 0.5

Ore Au (g/ton) 0.2

Ore Ag(g/ton) 1.3

Ore NSR 170

MINING METHOD

To start, a mining method has to be chosen. There are several options, having an underground mineor a surface mine. Research has been done and because of the narrow, steeply dipping formation itwould be beneficial to start with a surface mine. This surface mine should be fairly shallow, becausethe deeper this mine is, the more waste it will produce. The costs therefore fastly increase with depth.

There are four common surface mining methods (Darling, 2011):

• Open-pit mining

• Quarrying

• Strip mining

• Auger mining

Strip mining and open-pit mining are the two most dominant types of surface mining methods inthe world, accounting for approximately 90% of the surface mineral tonnage. Strip mining is used forlarge, tabular, flat lying ore bodies for mineral seams, that are relatively close to the surface. Open-pitmining is typically applied to disseminated ore bodies for steeply dipping veins or seams where themining advance is toward increasing depth. Quarrying is a special type of open-pit mining used toproduce aggregates and dimension stone products. The last method, auger mining, is primarily usedto remove coal from under a final highway.

This means that for the satellite mine an open-pit mine is preferred. The ore body is steeply dip-ping and therefore the open-pit is a good option. This option is also preferred, since the assumptionis that the ore is the same as in Aitik. This means the methods from the Aitik mine could be used atthis satellite mine site, i.e. it would cost less because a lot of knowledge is already there.

MINE DESIGN

To have an optimized open pit design, alternative depths of the open pit have been analyzed by Boli-den Technology (2014). The open pit mine is relatively shallow, the depth varies from 120 meters inthe south end to 60 meters toward the north end. Optimization has been done by testing a number ofalternative open pit bottoms from Z355 to Z435 with a simplified design, Z355 stands for 355 metersabove sealevel and is according to the Swedish coordinate system. The optimization did also con-sider different cut-off grades, that is: values of 55 SEK and 124 SEK. The calculations can be found inappendix A.2. The optimum pit-bottom height is Z400 for a cut-off of 55 SEK and Z435 for a cut-offvalue of 124 SEK.

The same design criteria are used for embankments as used in the Aitik mine, but the design isslightly adjusted. The total slope will be 2 degrees steeper than in the Aitik mine. This can be done,because of the shallow open pit. A steeper slope is beneficial, because it reduces the volume of the

4.1. ANALYSIS OF THE SATELLITE MINE 11

Table 4.2: The waste reduction if a steeper slope is used

WASTE

Waste original design(kton) 10.717

Reduced waste rock with a steeper slope of 2 degrees (kton) - 1.169

Waste steep design (kton) 9.549

waste rock. The total reduction of waste rock is shown in table 4.2. This would mean that the bencheswould be smaller, this is possible because of the smaller equipment that is used.The total table with its assumption can be found in appendix A.1.

The maximum slope for the rock itself will be 72◦, this is the same slope as in Aitik. The bench widthwill be between 16 and 18 meters. This leads to an overall slope of 54◦.The bench heights of 10 and 15 meters have been considered. The bench height of 10 meters is cho-sen.The total mine design is shown in figure 4.3.

Figure 4.3: The bench design of the satellite mine. Note that this drawing is hypothetical and not to scale.

CUT-OFF VALUE

The cut-off value for the NSR in the open pit mine will differ from the final cut-off grade that will beused in underground mining. There is a difference, because all the ore and waste from the open pitmine have to be transported to the pits edges. The waste rock will later be used as backfill, to fill theopen pit mine. The waste rock will be stored close to the edges of the open pit mine.There are a few cut-off options (Boliden Technology, 2014):

• A cut-off of NSR 124 SEK/ton gives 2.1 million tonnes of ore with an average NSR of approxi-mately 400 SEK and a copper grade of 1.0%

• A cut-off of NSR 55 SEK/ton gives 5.2 million tonnes of ore with an average NSR of approxi-mately 200 SEK and a copper grade of 0.5%

4.2. FRAGMENTATION OF THE ORE 12

Table 4.3: Cut-off calculations

Cutoff Open pit Satellite mine

SEK/ton

Mining − Assumes that the rock willbe mined whether its ore orwaste rock.

Crushing 5,0 Possible crushing

Transport to Aitik 17,5

Backfilling of waste rock to thepits

11,3 Back filling

Coverage −Enrichment 27,5

Theoretical cut-off Used in calculation

Cutoff NSR 39 55

Copper grade 0,11% 0,15%

The cut-off grade in the calculation as shown in table 4.3 is slightly higher than the theoreticalone, because it has to be a certainty that it would be profitable. From appendix A.2 is clear that themaximum result will be obtained with an elevation of Z400 for the pit bottom and a cut-off value of55 SEK. Therefore this value will be used further in this research.

4.2. FRAGMENTATION OF THE ORE

In order to process the ore at the Aitik crusher, the fragmentation should be taken into account. Thebiggest problem is not the crusher itself, but the transportation to the crusher. It’s not favourable if therocks are bigger than 300 mm, thus it should be either blasted to smaller particles or blasted to a biggersize and crushed at the mine site. The fragmentation of 300 mm could be accomplished by makinga finer blasting schedule, i.e. more emulsion in order to get the rocks finer fragmented. Anothermethod to get finer rocks is to have an in-pit crusher that pre-crushes the ore, however blasting stillneeds to be done. Both of these options are discussed.

DRILLING AND BLASTING

The ore and waste in the satellite mine will be drilled and blasted. The needed fragmentation sizedepends on the use of an in-pit crusher or not. The costs of both possibilities are evaluated.

For the drilling and blasting the Kuz-ram model is used. This is an empirical model that uses blastdesign and rock factors in an empirical equation to predict the fragmentation size distribution.For this analysis some factors have to be chosen, such as the burden and spacing. The burden is theminimal distance from the axis of a blasthole to the free space. The spacing is the distance betweenblastholes in the same row. These parameters depend upon the drilling diameters, the properties ofthe rock and explosives and the height of the bench (Jimeno et al., 1995).

From Hardygóra et al. (2004) the value u, which determines the size distribution curve, can becalculated by the following formula:

u = [2.2−14B/D]∗ [((1+S/B)/2)0.5]∗ [1−Ep /B ]∗ [|l f − lc |/l +0.1]0.1 ∗ l

H

in which D is the blasthole diameter in millimeters, B is the burden in meters, S is the spacing inmeters, l is the total charge length in meters, l f is the length of the bottom charge in meters, lc is the

4.2. FRAGMENTATION OF THE ORE 13

length of the column charge in meters, H is the bench height and Ep is the typical deviation due todrilling.

The same emulsion as in Aitik is used, this emulsion has the properties listed in table 4.4. Togetherwith the rock properties from section 2.2 it gives the fixed parameters of the calculation.

Table 4.4: Properties of the emulsion

Explosives

Density 1 SG

Relative Weight Strength 90% (% ANFO)

Nominal VOD 5500 m/s

Effective VOD 5500 m/s

Explosive Strength 0,9

In the block model a bench height of 10 meters is used. The stemming is usually around 70% ofthe burden according to National Park Service (1999). The stemming is the part of the borehole thatis not filled with explosives, but with a stemming material such as gravel or sand.

With the blasting the aim is to have 80% of the rocks smaller than 300 mm. Another alternative isto blast the rocks to 1200 mm and pre-crush it at the satellite mine site. Both of these options need tobe considered. The intention of this comparison is to find the most cost-efficient blasting plan.

Using Atlas Copco (2013) the different drills are found with their properties, the most importantproperty is the hole range. With this diameter the amount of emulsion could be evaluated to get asize distribution that could be used for the satellite mine.

A good option for drilling and blasting is the Atlas Copco SmartROC D65, a percussive drillingmachine. Other machines could be possible as well, however for this pre-feasibility study the D65 isused as a reference. This would be a typical sort of equipment that will be used in a small open-pitoperation. The maximum diameter it can drill is 203 mm. Based on this the Kuz-ram model is madeas shown in appendix A.3.

The costs are based on the known costs per meter from the Aitik mine, this is a total cost of 560SEK/m. The hole diameter of the Atlas Copco SmartROC D65 is smaller than in Aitik. Therefore thetotal costs will be an overestimate of the real costs. In table 4.5 two numbers are evaluated. First thecosts if 80% of the rocks is smaller than 300 mm and secondly the costs if 80% of the rocks is smallerthan 1200 mm.

Table 4.5: Costs for the drilling and blasting with an Atlas Copco SmartROC D65

Target size Hole diameter Charge Length Charge Density # holes Total costs

300 mm 203 mm 7,2 m 1,29 kg/m3 39723 160 MSEK

1200 mm 203 mm 7,2 m 0,97 kg/m3 29792 121 MSEK

The difference between these two fragmentation sizes is about 40 MSEK, this excludes the costsof the SmartROC D65 itself, but this will be the same for both. This means that blasting to 300 mm ismore expensive, because more drill holes are needed. However, if the rock is blasted to a size of 1200mm the rock needs to be pre-crushed by an in-pit crusher.

These costs do not include the Atlas Copco SmartROC D65 itself. The costs of this equipment willhave more or less the same price as the SmartROC D65 in Aitik, which will cost around 7 MSEK.The variables chosen for the blasting to 300 mm is given in table 4.6.

4.2. FRAGMENTATION OF THE ORE 14

Table 4.6: The variables used for the blasting to 300 mm

Hole Diameter 203 mm

Charge Length 7,2 m

Burden 4 m

Spacing 4,5 m

Drill Accuracy SD 0,1 m

Bench Height 10 m

USING AN IN-PIT CRUSHER

An in-pit crusher can be rented, so that means a fixed cost per ton is known for the operation. Thecosts for an in-pit crusher is 10 SEK/ton. Only the ore needs to be pre-crushed, the waste will bedumped on the edge of the mine, no matter what the size is. This means that about 5.2 Mton need tobe crushed. The total costs of this operation would be around 52 MSEK.

This means that the total costs for blasting to 1200 mm and then crushing it would be more expen-sive than blasting to 300 mm with direct transport to the Aitik processing site. Therefore the option toblast it to 300 mm is preferred.

5PRODUCTION SCHEDULE AND ECONOMIC

EVALUATION

With the information of the previous chapters, a production schedule can be made. When a produc-tion schedule is made, an economic evaluation could be done. In this economic evaluation comesforward if the mining of this satellite mine is profitable or not, in order to make a decision to gothrough with the project. This evaluation is done in this chapter.

5.1. PRODUCTION SCHEDULE

The satellite mine will be mined in two stages, the division of the two stages is the green line in figure5.1 (Boliden Technology, 2014). The decision is made to mine in two stages because the mining wouldbe faster. Now it is possible to mine at two positions at once which will increase the production.

Figure 5.1: The outline of the satellite mine

Per stage one shovel will be used, for the calculation a capacity of 1000 tonnes per hour is used.If the first stage is finished, the shovel that is used for it will be used in the second stage. Thus itwill double the capacity in stage 2. However, the first blast of every bench can only use one shovel,because of the available space. The other blasts can be done simultaneously and thus the two shovels

15

5.1. PRODUCTION SCHEDULE 16

can be used. This all ends up in a production schedule, which is summarized in table 5.1. This wouldmean that the open-pit mine can produce for just under 6,5 years. A workweek of 2 shifts and 5 daysa week is assumed: this results in 12 hours of work a day, 5 days a week.

Table 5.1: The total amount of days to mine the two stages and its start and end date

Total duration(days) Start date End date

stage 1 815 01/01/2018 26/03/2020

stage 2 2340 01/01/2018 29/05/2024

In the production schedule a difference is made between the till, waste and ore. The till is mined first,followed by the waste and ore. The till is done first, because this is the soft soil which can be easilyextracted. The waste and ore have to be blasted, because the rock is a lot harder. In the block modelthe different parts are divided in either waste or ore, so that could be mined separately. With thisinformation the production can be summarized per year, as done in table 5.2.

Table 5.2: Summary of the production per year

Year Till (kton) Void+waste (kton) Ore (kton) Copper grade % Copper tonnes NSR

2018 1.654 1.346 127 0,4 467 170

2019 1.086 1.301 741 0,3 2.425 110

2020 349 1.932 718 0,5 3.284 140

2021 100 1.994 579 0,5 2.965 190

2022 0 2.109 956 0,4 4.165 170

2023 0 1.619 1.362 0,5 7.097 200

2024 0 415 750 0,7 4.954 260

Grand Total 3.191 10.717 5.233 0,5 25.356 170

The production per month for the first stage is given in appendix B.1. In appendix B.2 the productionper year is given for stage 2. An overal production per bench is given in appendix B.3.

TRACE ELEMENTSBesides copper, other trace elements are found in the ore. The ones that will be processed are silverand gold.

The amount of gold and silver during the two stages and the total amount of these trace elementsis given in table 5.3. The amount of silver and gold is given in figure B.4 for the entire production ofthe satellite mine.

Table 5.3: The production of the trace elements gold and silver

Stage Ore (kton) Ag (g/ton) Au (g/ton) Ag (kg) Au (kg)

Stage 1 1.105 1,0 0,1 1.091 144

Stage 2 4.129 1,4 0,2 5.924 976

Total 5.233 1,3 0,2 7.015 1120

The processing site in Aitik is not optimized for silver and gold, therefore the recovery is prettylow. Only about 50% of the gold is retrieved from the concentrate, for silver there’s a slightly higherpercentage of approximately 65% that is recovered.

5.2. ECONOMIC EVALUATION 17

5.2. ECONOMIC EVALUATION

Using the production schedule an NPV calculation could be done. To do this calculation the long-term metal prices are needed. The prices that Boliden uses are listed in Boliden Technology (2013)and given in table 5.4. A troy ounce is equal to 31.10 grams.

Table 5.4: The long-term prices of copper, gold and silver

metal prices

Cu $6600/ton

Au $1200/tr.oz

Ag $20/tr.oz

With all this data a net present value calculation can be done. The Net Present Value(NPV) of aproject is today’s cash equivalent of the cash flow that is expected to be generated by this project,assuming that money can be invested or borrowed at a specified discount rate (Rendu, 2014). Theformula for the NPV is:

N PV (i , N ) =N∑

t=0

Rt

(1+ i )t

in which N is the total number of years, Rt is the net cash flow, i is the discount rate and t is thetime of the cash flow.

The discount rate used in the NPV calculation is 10%. The enrichment at the Aitik processing sitecosts the same as for the Aitik ore. The mining costs, till extraction and mining and transport costs ofthe ore are based on historic knowledge of the costs in other mines, which was provided by Boliden.

An example of a NPV-calculation is given in appendix C.1. The NPV of this operation is 59,9 MSEK.

It is still an early stage in the feasibility study, but some sensibility calculations could be donebased on the NSR. The NSR of the ore depends on the long-term costs of copper, gold and silver.These prices could vary in the upcoming years. It turns out that the break-even point is around 152MSEK as shown in table 5.5.

Table 5.5: NPV Model for different NSR values

NSR NPV

150 -6.6 MSEK

151.93 0 MSEK

160 27.5 MSEK

170 61.6 MSEK

180 95.7 MSEK

190 129.8 MSEK

The project is also sensible for the exchange rate between the American dollar and the Swedishkrona. Everything in this studies is calculated in SEK, but the company gets paid in American dollars.The exchange rate could be either favourable or unfavourable and could be a factor in the economicevaluation. This calculation is not included in this studies.

An NPV model is made for different capacities. In table 5.6 the NPV is given for different capacities.If the capacity per hour is increased, the project time is decreased, and vice versa. The calculation isdone for a capacity of 500, 1000, 1500 and 2000 tonnes/hour.

5.2. ECONOMIC EVALUATION 18

Table 5.6: NPV Model for different capacities

capacity NPV

500 tonnes/hour 7.0 MSEK

1000 tonnes/hour 59.9 MSEK

1500 tonnes/hour 53.4 MSEK

2000 tonnes/hour 58.9 MSEK

From table 5.6 is clear that a capacity of 1000 tonnes/hour is the most favourable for this project.This is the capacity that is used for this studies.

6CONCLUSIONS

The objective of this project was to establish a preliminary development plan for for a satellite copperdeposit with processing at the Aitik plant.

As a result of this studies the following conclusions can be made.

• The geology of the satellite mine is found to be similar than in Aitik. Thus the same designproperties could be used as found in Aitik.

• An open-pit mine is the best surface mining option. A slightly steeper overall slope angle couldbe used and for the rock the same slope angle will be used as in Aitik.

• The best cut-off value is 55 SEK with a pit bottom of 400 meters and thus a pit depth of 85meters.

• It is more cost-efficient to blast the ore to 300 millimeters than to blast it to a bigger size of 1200millimeters and then pre-crush it at the satellite mine site.

• The production time of the open-pit operation is just under 6,5 years.

• The Net Present Value of the operation is 59,9 MSEK.

• An NPV model shows that the most favourable capacity for this project is 1000 tonnes/hour.

This open-pit operation is supposed to be followed by an underground operation. The ore gradein the lower part of the open-pit mine is higher than the upper part of the mine. Therefore the averagegrade of the underground operation would probably be higher than that of the surface mine. Thiscould mean that the underground operation is more profitable than the open-pit operation.

Since this open-pit operation has a positive Net Present Value of 60 MSEK with the prospect ofan even more profitable underground operation, the mining of this satellite deposit has a promisingperspective.

19

7RECOMMENDATIONS

This study suggests that the mining of the satellite deposit is a profitable operation. However, toget more accurate results and more certainty about the project, the following recommendations aremade:

1. Evaluate the ore body more accurately by drilling more holes

The ore body model is now made with only one borehole. That means that almost all the orein this investigation is a result of extrapolating the existing data from the deeper part of the orebody to the upper part. By drilling more holes the model of the shallower part could be mademore accurate.

2. Look into the archives to find information about the former mine in the 1920’s Since there was amine in the 1920’s it is possible that there is geological information available. This might givean indication about the deposit. It might be that there were some tests done at that time whichcould be used to make a better evaluation of the project.

3. More cut-off values could be considered

For this pre-feasibility study only the cut-offs of 55 SEK and 124 SEK are considered. For fu-ture research other cut-off grades could be considered to get the most profitable model for thisopen-pit operation.

4. Investigate the possibility of decreasing the production time of the open-pit part of the mine

The length of the operation by using two shovels with a capacity of 1000 tonnes/hour is 6,5years. The production could be faster by using longer working days, 3 shifts instead of 2 andworking all days of the week, instead of 2 shifts and working 5 days a week. Another option isto use more shovels and thus increase the capacity. However, it turns out that the increase ofcapacity is not profitable.

5. Consideration of a leaching plant as an extension of the current processing site

The recovery of gold and silver is relatively low. This recovery could be increased by using aseparate leaching plant to extract the gold and silver. Since the production of the Aitik mineitself increases, and there are also satellite mines that will increase production in the future, itmight be profitable to have a leaching plant on site to recover the silver and gold.

20

BIBLIOGRAPHY

Atlas Copco (2013). Blasthole Reference Book. Atlas Copco.

Boliden (2014). Aitik fact sheet. http://www.boliden.com/Documents/Press/Publications/Fact%20sheets/facts-aitik-en.pdf. Last checked: 28 April 2014.

Boliden Technology (2013). Annual Report 2013.

Boliden Technology (2014). Idéstudie 2014 Dagbrott.

Chaigneau, R. (2011). Physical Processing. TU Delft.

CNN (2014). Currency exchange rate. http://money.cnn.com/data/currencies/. Last checked:2 May 2014.

Danielson, S. (1987). Geologisk beskrivning över Nautanen - Aitik - Jårbokistråket i Gällivareområdet.Sveriges Geologiska Undersökning.

Darling, P. (2011). SME Mining Engineering Handbook. Society for mining, metallurgy and explo-ration, Inc., 3rd edition.

Hardygóra, M., Paszkowska, G., and Sikora, M. (2004). Mine Planning and Equipment Selection 2004.CRC Press.

Jimeno, E. L., Jimeno, C. L., and Carcedo, A. (1995). Drilling and blasting of rocks. Geomining Tech-nological Institute of Spain.

Kawatra, S. K. (2009). Froth Flotation. Michigan Technological University.

McGimpsey, I. (2010). Petrology and lithogeochemistry of the host rocks of the nautanen cu-au de-posit, gällivare area, northern sweden. Master’s thesis, Lund University.

Metso (2006). Service contract for swedish grinding mills. http://www.metso.com/miningandconstruction/webmagazine.nsf/WebWID/WTR0602132256BC7966?OpenDocument. Last checked: 8 May 2014.

Miskovic, S. (2011). An investigation of the gas dispersion properties of mechanical flotation cells: anin-situ approach. PhD thesis, Virginia Polytechnic Institute and State University.

National Park Service (1999). Handbook for the transportation, and use of explosives. National ParkService.

Rendu, J.-M. (2014). An introduction to cut-off grade estimation. Society for mining, metallurgy andexploration, Inc., 2nd edition.

Voncken, J. H. L. and Wolf, K. H. A. A. (2011). Economic Minerals and Rocks - An introduction to ores,ore minerals, industrial minerals, and coal. TU Delft.

Wanhainen, C., Broman, C., Martinsson, O., and Magnor, B. (2012). Modification of a palaeoprotero-zoic porphyry-like system: integration of structural, geochemical, petrographic, and fluid inclusiondata from the aitik cu-au-ag deposit, northern sweden. Ore Geology Reviews, 48:306–331.

21

Appendices

APPENDIX A: CALCULATIONS FOR THE

SATELLITE MINE

A.1. WASTE REDUCTION WHEN USING A 2 DEGREES STEEPER SLOPE

Table A.1: Waste Reduction Calculation

Calculation of waste that can be saved by having a steeper slope

Changing theslope from IRS50 to IRS 52saves X metersper pallet 3 m

Approximateopen pit depth 90 m

bench height 15 m

density 2,8

Production of waste per year

Length of open pit kton Y2018 Y2019 Y2020 Y2021 Y2022

Pall 1 437 m 110 100%

Pall 2 890 m 224 60% 40%

Pall 3 880 m 222 70% 30%

Pall 4 820 m 207 30% 70%

Pall 5 810 m 204 70% 30%

Pall 6 800 m 202 80% 20%

1.169 135 417 345 223 40

23

A.2. DIFFERENT ELEVATIONS CUT-OFF OF 55 SEK AND 124 SEK

Note that the average surface elevation at the satellite mine is 485 meters.

Table A.2: Optimum pit depth calculated for two cut-off values

Low grade cutoff HG=125 LG=80 Mar=55

Avg. Pit depth (m): 100 50 85 130

Design criteria for corresponding slopes at Aitik

Pit bottom elevation (m): 385 435 400 355

Ore (million tonnes) 7,38 1,91 5,24 11,67

Cu% 0,4 0,6 0,5 0,4

NSR SEK/ton 170 240 190 160

Moraine (million tonnes) 4,34 1,54 3,19 6,43

Waste Rock (million tonnes) 16,01 4,01 10,72 28,59

Total ore, waste rock and moraine 27,72 7,45 19,16 46,70

Costs and Revenues in million SEK

Refractive Cost −693 −186 −479 −1167

Transport & Enrichment −369 −95 −262 −584

Recovery −80 −20 −54 −143

Ore revenue 1283 466 996 1864

Results 141 165 202 −30

High grade Cutoff = 124

100 50 85 130

Design criteria for corresponding slopes at Aitik

Pit bottom elevation (m): 385 435 400 355

Ore (million tonnes) 2,23 0,93 1,80 3,18

Cu% 1,01 1,04 1,02 0,98

NSR SEK/ton 410 430 420 400

Moraine (million tonnes) 4,34 1,54 3,19 6,43

Waste Rock (million tonnes) 21,15 4,98 14,16 37,08

Total ore, waste rock and moraine 27,72 7,45 19,16 46,70

Costs and Revenues in million SEK

Refractive Cost −693 −186 −479 −1167

Transport & Enrichment −112 −47 −90 −159

Recovery −106 −25 −71 −185

Ore revenue 922 398 754 1271

Results 11 140 114 −241

24

A.3. KUZ-RAM MODELS FOR BLASTING TO 300 AND 1200 MILLIMETERS

Figure A.1: The Kuz-ram model for blasting to 300 mm

Figure A.2: The Kuz-ram model for blasting to 1200 mm

25

APPENDIX B: PRODUCTION SCHEDULE

B.1. SUMMARY OF THE STAGE 1 PRODUCTION

Table B.1: Summary of the production per month for stage 1

Month Till (kton) Void+waste (kton) Ore (kton) Ag g/ton Au g/ton Cu %

jan-18 98 33 0 0,0 0,0 0,6

feb-18 98 22 0

mrt-18 130 0.6 2 3,3 0,5 1,1

apr-18 115 13 0 0,0 0,0 0,2

mei-18 22 110 0.8 3,3 0,5 1,1

jun-18 20 61 47 0,8 0,2 0,4

jul-18 71 61 44 0,5 0,1 0,1

aug-18 133

sep-18 55 74

okt-18 84 15 34 0,7 0,1 0,3

nov-18 107 17 5 0,6 0,1 0,2

dec-18 84 15 33 1,0 0,2 0,4

jan-19 73 60 0 0,7 0,1 0,2

feb-19 111 9 1,1 0,1 0,4

mrt-19 133 1,1 0,1 0,4

apr-19 31 33 64 1,0 0,2 0,4

mei-19 0 127 6 0,9 0,2 0,4

jun-19 12 116 1,0 0,1 0,3

jul-19 32 101 1,0 0,1 0,3

aug-19 101 22 10 0,7 0,1 0,17

sep-19 70 46 12 1,0 0,1 0,3

okt-19 2 8 122 1,0 0,1 0,3

nov-19 10 50 68 0,6 0,1 0,2

dec-19 82 51 1,1 0,1 0,3

jan-20 133 1,1 0,1 0,3

feb-20 0 76 48 1,1 0,1 0,3

mrt-20 110 1,1 0,1 0,3

Grand Total 1.340 1.051 1.105 1,0 0,1 0,3

26

B.2. SUMMARY OF THE STAGE 2 PRODUCTION

Table B.2: Summary of the production per year for stage 2

Year Till (kton) Void + Waste (kton) Ore (kton) Ag g/ton Au g/ton Cu %

2018 636 923 5 2,1 0,4 0,8

2019 765 750 49 1,7 0,3 0,6

2020 349 1.855 427 1,0 0,2 0,6

2021 100 1.993 579 1,4 0,3 0,5

2022 0 2.109 956 1,2 0,2 0,4

2023 0 1.619 1362 1,5 0,2 0,5

2024 0 415 750 1,9 0,3 0,7

Grand Total 1.851 9.667 4.129 1,4 0,2 0,5

B.3. TOTAL PRODUCTION OVERVIEW

Figure B.3: Production Schedule Summary per bench

27

Figure B.4: The gold and silver grades in the satellite mine

28

jan-18 sep-18 mei-19 jan-20 sep-20 jun-21 feb-22 okt-22 jun-23 feb-24

Stage 1

Stage 2

0

50000

100000

150000

200000

250000

300000

jan

.18

apr.

18

jul.1

8

okt

.18

jan

.19

apr.

19

jul.1

9

okt

.19

jan

.20

apr.

20

jul.2

0

okt

.20

jan

.21

apr.

21

jul.2

1

okt

.21

jan

.22

apr.

22

jul.2

2

okt

.22

jan

.23

apr.

23

jul.2

3

okt

.23

jan

.24

apr.

24

ton

ne

s

The total tonnage and ore production

Ore tonnes Total tonnes

0

50000

100000

150000

200000

250000

300000

jan

.18

apr.

18

jul.1

8

okt

.18

jan

.19

apr.

19

jul.1

9

okt

.19

jan

.20

apr.

20

jul.2

0

okt

.20

jan

.21

apr.

21

jul.2

1

okt

.21

jan

.22

apr.

22

jul.2

2

okt

.22

jan

.23

apr.

23

jul.2

3

okt

.23

jan

.24

apr.

24

Ton

ne

s

Amount of ore, waste and till

Ore Waste till

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

jan-18 mei-19 sep-20 feb-22 jun-23

g/t

on

Pe

rce

nta

ge

Copper and gold grade

Copper grade Gold grade

APPENDIX C: ECONOMIC EVALUATION

C.1. CALCULATION OF THE NET PRESENT VALUE

Table C.1: The overall NPV Calculation of the project

30