Ore deposits and metallogeny of Finland
Field Trip Report
April 29th to May 14th, 2016
SEG Student Chapter
Laval University – INRS-ETE
Student chapter
Rapakivi granite texture
Editors : Pierre-Hugues Lamirande, Cynthia Lee, Marc-Antoine Vanier
Contributors : Philippe Drouin, Gaelle D’Hiver, Marika Labbé, Thierry-Karl Gélinas, Loraine
Tremblay, Marie-Pier Bédard
www.finlande.segulaval.ca
Table of content
Table of content..................................................................................................................... i
Introduction ..........................................................................................................................1
List of participants ...................................................................................................................... 1
Goals .......................................................................................................................................... 1
Pre-departure activities and financing ....................................................................................1
Field trip day-by-day ..............................................................................................................3
Summary .................................................................................................................................... 3
April 29th – Flight to Helsinki ....................................................................................................... 5
April 30th – Introduction to geology and metallogeny of Finland ................................................ 5
May 1st – Rapakivis granites ..................................................................................................... 10
May 2nd – Rapakivis granites and spectrolite gems quarry ........................................................ 12
May 3rd – Luumaki beryl pegmatite quarry ............................................................................... 14
May 4th – Diamond tests pits (kimberlites) ............................................................................... 16
May 5th – Public holiday in Kupio .............................................................................................. 18
May 6th – Silinjärvi apatite mine ............................................................................................... 19
May 8th – Rokua geopark .......................................................................................................... 22
May 9th – Otanmäki Fe-Ti-V mine ............................................................................................. 28
May 10th – Rompas gold and uranium prospect ........................................................................ 34
May 11th – Day off at Skibotn Fjord .......................................................................................... 37
May 12th – Kittilä gold mine ...................................................................................................... 38
May 13th – Kevitsa Ni-Cu mine .............................................................................................. 41
May 14th – Flight back to Quebec .......................................................................................... 45
Socializing events ................................................................................................................. 45
Acknowledgments ............................................................................................................... 45
Financial partners ................................................................................................................ 46
i
Introduction
Since 2001, the ULaval-INRS organizes annual field trips in order to create a network of students
in economic geology and geologists from the industry, government and academia. The 2016
Finland trip is part of this tradition.
List of participants
All participants are students from Université Laval in Québec, Canada:
Name
Pierre-Hugues Lamirande
Marie-Pier Bédard
Philippe Drouin
Marc-Antoine Vanier
Marie-Christine Lauzon
Cynthia Lee
Gaëlle St-Louis
Loraine Tremblay
Marika Labbé
Thierry Karl Gélinas
E-mail
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
Grade
M. Sc.
M. Sc.
M. Sc.
B. Sc.
B. Sc.
B. Sc.
B. Sc.
B. Sc.
B. Sc.
B. Sc.
Goals
• To gain first-hand knowledge about economic geology of the host country, through meetings
with local industry and academic personnel as well as guided visits of key outcrops linked to
exploration;
• To visit mining districts that have led to the development of descriptive and genetic models
used in mineral exploration;
• To visit mines in order to learn about new exploration and mining methods as well as different
types of mining infrastructure and the machinery used;
• To compare work health and safety procedures and regulations;
• To learn methods of mining waste management and environmental rehabilitation techniques
used on the site after mine closures.
Pre-departure activities and financing
Each participant was designated a leader for a particular day. As the leader of a day, he or she
had to research documentation (publications, field trip guidebooks, etc.) related to the
geological background related to the activity of that day, whether it was a mine, outcrop or
other feature. On the day of the fieldtrip, that participant presented their findings to the group
directly on the field.
1
In order to finance the excursion, all participants were asked to contact companies,
organizations and others of their network in order to obtain sponsorships. A web site was made
to explain the purpose of this fieldtrip : www.finlande.segulaval.ca. We organized several
fundraisers to pay for the field trip's expenses, listed in Table 1. The cost for the flight ticket is
estimated at 850.00$ per participant. The expenses listed do not include food and other
personal expenses.
Table 1 : Table of expenses
Expenses
Flight ticket (for 10 participants)
Transportation in Finland
Lodging
Other logistics
Total
Amount ($ CAD)
8500.00
4014.64
1667.81
176.62
14 349.07
The funds raised by fundraising activities and sponsorships from organizations and companies
are presented in Table 2.
Table 2 : Table of revenue
Revenue
Amount ($ CAD)
Fundraising activities
--Social activity after QcMines at Les Voûtes de Napoléon
--Gala AEGGGUL
--Other found raising activities
Sponsorships
--PDAC
--AELIES
--Osisko Redevances Aurifères
--AESGUL
--Bureau de la vie Étudiante
--Agnico-Eagle
--Faculty of geology and geological engineering (Université Laval)
Total
2
1610.00
537.00
667.00
1250.00
250.00
1000.00
450.00
400.00
500.00
500.00
7164.00
Field trip day-by-day
Summary
Day
Date
Locality
Description
-
April 29
Helsinki
Arrival
1
April 30
Espo ( Helsinki )
Introduction to metallogeny of
Finland
2
May 1
Laajakoski
Rapakivis granite
3
May 2
Ylämaa
Rapakivis granite and spectrolite
quarry
4
May 3
Luumäki
Beryl pegmatite (gemstone quarry)
5
May 4
Lahtojoki
Kimberlite (diamond mine tests pits)
6
May 5
Kuopio
Public holiday
7
May 6
Siilinjärvi
Apatite mine
8
May 7
Siilinjärvi
Day off
9
May 8
Rokua
Rokua geopark (Quaternary)
10
May 9
Otanmäki
Fe-Ti-V oxydes deposit
11
May 10
Ylitornio (Rompas)
High-grade gold and uranium
mineralization prospect
12
May 11
Kittilä
Day off – Fjord of Skibotn (Norway)
13
May 12
Kittilä
Orogenic gold deposit
14
May 13
Kevitsa
Magmatic Ni-Cu deposit
-
May 15
Kittilä airport
Departure
3
Itinerary overview on Google Maps.
4
April 29th – Flight to Helsinki
All the participants took the plane either from Quebec City or Montreal and met in Helsinki
around noon (local time).
April 30th – Introduction to geology and metallogeny of
Finland
Geologian Tutkimuskeskus (GTK) is the Geological Survey of Finland. They offer various
geoscientific services. One of those is the production of reports and maps about the economic
potential of the bedrock in Finland. Our schedule only allowed us to visit their office on
Saturday, so their office was closed. Fortunately, senior geoscientist Pasi Eilu gave us a
presentation about mineral deposits in the the Fennoscandian shield. The following is an
overview of both the literature he provided us, as well as the presentation he gave us.
Finland is located in the Fennoscandian shield which is composed of Archean and Proterozoic
rocks. Each formation stage of the Fennoscandian Shield is associated with various
environments suitable for specific mineral deposits. The main objective of Pasi Eilu’s talk was to
present the geodynamic evolution of the Fennoscandian shield and its relation with various
mineral deposits.
The geological history of the Fennoscandian shield encompasses four supercontinent cycles, but
the rocks in Finland are only affected by the two oldest ones: Kenorland (2.75 to 2.6 Ga) and
Columbia (1.93 to 1.48 Ga). A supercontinent cycle consists of both the assemblage of
continental crust into one big continent and its dismemberment by the formation of rifts until a
new supercontinent is formed. A good understanding of the different stages is essential to
recognize geodynamic environments and their associated mineral deposits.
The Archean domain of the Fennoscandian shield is located in the northeastern part of Finland
(Figure 1). Two main stages are identified during the Archean period: pre-Kenorland and
Kenorland formation.
The first stage is the pre-Kenorland, from 3.6 to 2.75 Ga. Only few things are known from that
period. Two main lithological domains can be identified: the tonalite, trondjémite and
granodiorite (TTG) domain and the supracrustal belts. The TTG are mostly recognised to have a
crystallization age between 2.7 to 2.8 Ga. Nevertheless, there are regions older than 3.0 Ga. The
TTG represents most of the Archean basement which is largely migmatised and deformed to a
gneissic texture. There are only small occurrences of Mo and Ni found in these rocks. The
supracrustal belts are less important in terms of volume, but they contain most of the Archean
mineral deposits. Unlike other Archean cratons, there are few Ni-Cu mineralisations associated
with komatiite and no significant VMS or BIF mineralisation.
The second stage corresponds to the formation of the Kenorland supercontinent between 2.75
and 2.6 Ga. It is an important period of crustal growth. The converging plates is a good
geological setting for the formation of orogenic gold deposit but there are only few such kinds of
mineralisation found in the Archean part of the Fennoscandian shield. The Pampalo mine is
actually mining orogenic gold, but the amount of gold mined in the Archean part of the
Fennoscandian shield is significantly lower than what has been mined in other Archean cratons
such as the Superior, in Canada and the United States. A 2.6 Ga carbonatite associated with an
anorogenic context represents an important deposit of apatite which is actually mined. Some
5
hypotheses are presented to explain the lack of Archean mineralisation. 1) There is no context
evidence for a subduction. 2) Erosion was more important in the Fennoscandian shield than in
other Archean domains in the world, removing most of the green schist and lower amphibolite
facies rock and exposing large areas of upper amphibolite to granulite facies rocks.
Figure 1: Map of the Fennoscandian Shield (Lahtinen et al., 2011)
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The Proterozoic Era is a very significative period in the Fennoscandian shield. An important
proportion of the Fennoscandian shield was formed during this era. The Proterozoic Era is
divided into three main stages: rifting, orogenic and late magmatism.
The initial breakup of the Fennoscandian part of Kenorland began in the northeastern part of
the present day Fennoscandian shield (Figure 2). Magmatic complexes were put in place
between 2.50 and 2.44 Ga. These are composed of layered gabbro-norite intrusions and plumerelated dyke swarms (Lahtinen et al., 2011). They contain some major mineralisation in Cr, Ni-Cu
and EGP (Figure 2), such as the world-class chromium deposit of Kemi. The rifting related
magmatic complexes seem to have formed continuous chains which were then fragmented by
younger tectonics events. This period is also associated with sediments of shallow and fluviatile
environments. The rifting process continued from 2.3 to 1.95 Ga and is associated with tholeiitic
dykes, sills and some volcanic mafic rocks. Oceanization occurred, as demonstrated by the
presence of MORB-like pillow basalts and turbiditic sedimentation (Lahtinen et al., 2011) (Figure
3). Major mineral deposit of Finland formed during this period, but their relation with the
tectonic setting is unclear for now. It is the case of the Kevitsa, a Ni, Cu, Au and EGP mine which
is hosted in a 2.05 Ga mafic intrusion. And the mafic intrusion-hosted Fe-Ti-V deposit of
Otanmäki is about the same age.
The final breakup of Kenorland occurred between 1.98 to 1.95 Ga. The sedimentary rift
environment has good potential for the formation of exhalative (SEDEX) type deposit. Some
major mineralisation in Finland could be associated to this environment. It is the case of the
Talvivaara nickel-cobalt-copper zinc deposit. The mineralisation is hosted in a Paleoproterozoic
black schist rift sequence. The metal content of the schist is strongly related to the reduction
potential of the deposition environment (Lahtinen et al. 2011). But the genesis of this mineral
deposit remains partly unknown. The oceanic crust formed at this time contains the Ottokumpu
Co-Cu-Zn-Ni mineralization. It appears to be a VMS formed in ultramafic oceanic crust which has
been later obducted as an ophiolite.
Figure 2: Rifting area during early Paloproterozoic. Purple dots indicate large Cr deposit, green dots Ni-Cu-PGE and
white dots V-Ti deposit. Mofified from Lahtinen et al., 2008.
7
Figure 3: Continued rifting during Paleoproterozoic and location of several large deposits. Mofified from Lahtinen
et al., 2008.
Two main Palaeoproterozoic orogens affected the Fennoscandian shield: the Lapland-Kola
orogen (1.94–1.86 Ga) and the composite Svecofennian orogen (1.92– 1.79 Ga). These orogens
occurred during the assemblage of the Columbia supercontinent. The Lapland-Kola orogen can
be compared to the Trans-Hudson orogen as they both involved the collision of two Archean
cratons, with only a small amount of juvenile material formed or preserved. At the other end of
the spectrum, the Svecofennian orogen is associated with a significant volume of newly formed
crust due to the formation of juvenile arcs (2.02 - 1.8 Ga) and great amount of magmatic activity
(1.89 - 1.8 Ga) (Lahtinen et al., 2011). There are more mineral deposits associated with the
Svecofennian orogen than the Lapland-Kola orogen.
The composite Svecofennian orogen is a good environment for the formation of orogenic gold.,
such as the world class Kittilä gold mine. Some VMS mineralisations are also associated with the
Svecofennian orogen in the Pyhäsalmi-Vihanti area (Lahtinen et al., 2011). There is also potential
for Li-Nb-Ta in pegmatitic granite.
The final assembly of Columbia happened at 1.63 Ga. The last major event in the Finnish part of
the Fennoscandian Sshield is the emplacement of rapakivi granite massifs. They are located in
the south of the country and are associated to anorogenic magmatism. There are only a few
occurrences of skarn, Fe-Ti-V and Ni-Cu in mafic intrusion associated with this lithological unit.
However the rapakivi granite itself is economically useful, as it is used as dimensional stone in
the construction industry.
In conclusion, many ore deposit in Finland can be associated to specific geodynamic settings, but
others seem unrelated to any geodynamic environment. Briefly, there are three main stages
8
utilized to classify the mineral deposits of the Fenoscandian shield: early assembly, final
assembly and break-up. They roughfly correspond to the stages of a supercontinent cycle.
Acknowledgements
We are extremely grateful to Pasi Eilu, who kindly came into the office on a Saturday to present
the geological history of Finland and its association to mineral deposits.
References
Raimo Lahtinen R.,. Garde A.A., and Melezhik V. A. (2008) Paleoproterozoic evolution of
Fennoscandia and Greenland. Episodes, Vol.31, No.1, pp. 1-9
Lahtinen, R., Hölttä P., Asko Kontinen A., Niiranen T., Nironen M., Saalmann K. and –Ward P.S.
(2011) Tectonic and metellogenic evolution of the Fennoscandian shield : Key question with
emphasis on finland. Geological Survey of Finland, Special Paper 49, 23–33
9
May 1st – Rapakivis granites
There are four major intrusions situated in southern Finland: Wiborg (1.65 - 1.61 Ga) which we
visited, Laitila (1.57 - 1.54 Ga), Veimna (1.57 Ga) and Aland (1.58 - 1.57 Ga).
Figure 4: Main rapakivi granite batholites of Finland (Karell et al., 2014)
STOP 1: Rapakivi granite outcrop
First, we departed from Helsinki after a traditional Finnish picnic which marked the end of
“Vappu”, a Finnish holiday. We rented cars and got on our way to the selected quarry. We
stumbled upon a beautiful outcrop of rapakivi granite alongside of the road and we decided to
stop there instead of going further.
Figure 5: Well-developed rapakivi texture.
10
STOP 2: White granite quarry
Later on, we went to see a white granite quarry. This white granite is fine-grained to mediumgrained and homogenous. We observed pockets made of pegmatitic microcline. Biotite is the
only mafic mineral observed on the outcrop.
Figure 6: White granite quarry at dawn (left); Pegmatitic pockets with microcline and quartz (right).
References
Karell, F., Ehlers, C., & Airo, M. L. (2014). Emplacement and magnetic fabrics of rapakivi granite
intrusions within Wiborg and Åland rapakivi granite batholiths in Finland. Tectonophysics, 614,
31-43.
11
May 2nd – Rapakivis granites and spectrolite gems quarry
STOP 1: Rapakivi quarry
We visited a rapakivi granite quarry near the city of Ylämaa (Figure 7). The rocks mined there
were later transformed into architectural stones, countertops and others.
Figure 7: A granite quarry pit, flooded by water. The rest of the quarry is still exploited.
STOP 2: Ylämaa Massive Granite Oy
We went to Ylämaa Massive Granite Oy factory that cuts the granite from the quarry. Director
Jussi Eskelinen guided us trough their installations. We were able to see all the steps in the
granite transformation process, from a massive bloc to a polished granite piece.
Figure 8: One of the saw which cut the first piece of granite from the massive boulders.
12
STOP 3: Spectrolite quarry
In the afternoon, we went to Ylämaa Jalokivikylä, a spectrolite gem centre. Spectrolite is a
plagioclase feldspar, sharing the same composition as labradorite, with approximately 55%
anorthite. Though spectrolite and labradorite share the same chemical formula, several things
distinguishes the two, according to our guide Mr. Esko Hamalainen: firstly, spectrolite is darker
and more opaque than labradorite, which gives its iridescence a fuller spectrum of colors, and
secondly, spectrolite is quite hard and of gemstone quality.
Mr. Esko Hamalainen brought us to the spectrolite quarry. This quarry is mined very carefully in
order not to damage the large spectrolite crystals. Explosives are set in a 1m by 1m pattern, and
the resulting blocs are excavated by hand. Two to three kilograms of spectrolite crystals can be
excavated in 1 metric cube of rock in this manner. The selling price of each spectrolite crystals is
proportional to the size of the crystal, the brilliance of its colours and whether there are
imperfections in the crystal.
Figure 9: Hand sample with a large spectrolite phenocrystal (right). Our group searching for spectrolite in the
quarry (left).
STOP 4 : Interpretation center
We stopped by the spectrolite interpretation center and shop, where we were able to learn
about the history of spectrolite. As one of the only Finnish gemstone meeting the three basic
requirements for beauty, hardness and rareness, spectrolite is a pride of the Finnish people. It
was discovered during World War II, when the Finns built anti-tank obstacles. The shiny surfaces
of the spectrolite stones were very visible, and after the war, quarries in these areas were
started. The first cutting and polishing of this stone would not commence until 1973 however.
The tools which were and still are used today for the cutting and polishing process were
presented to us at the gemstone shop. Today, there are 10 spectrolite quarries across Finland,
and the gemstones produced are exported worldwide.
Acknowledgements
This stop was suggested to us by our fellow geology students from the University of Helsinki. We
thank them for this great idea. We also thank Mr. Jussi Eskelinen, director of Ylamaa Massive
Granite Oy for his time in guiding the visit in his factory, as well as Mr. Esko Hamalainen, owner
of Spectrolite Finland and Stonework Ltd,for his time in bringing us to the spectrolite quarry and
explaining the history of spectrolite in Finland.
13
May 3rd – Luumaki beryl pegmatite quarry
Geology review
Inthe Luumaki area, there is a 20m x 10m wide pegmatitic dyke that intrudes into the Wiborg
rapakivi granite batholith. This dyke bears beryl gemstones. There is now a pit about 5m deep
(Figure 10) that has been mined intermittently in the summer months by a Finnish company,
Suomen Jalokivikaivos. This is the only beryl quarry in Finland.
Two types of beryl can be found in the dyke: the first one is opaque because it has been affected
by a ferruginous alteration.
The second is gem quality, transparent and can be found only in coarser grained pockets. The
gems are associated with common beryl or embedded in the microcrystalline reddish quartz.
They are typically cigar shaped with yellow and pale green coloration. They generally range from
a few grams to several tens of grams.
We were guided by the owner of Suomen Jalokivikaivos, Mr. Timo Ronka. He kindly offered
pieces of beryl since no one was able to find and collect any gems from the quarry.
Figure 10: Overview of the beryl quarry.
14
Figure 11: Coarse grained pockets that bears gem qualiy beryl (now exploited).
Figure 12: Polished gemstones that were found in the Luumaki beryl pegmatite.
15
May 4th – Diamond tests pits (kimberlites)
Unfortunately, the Lahtojoki kimberlite test pits were inactive when we were there, particularly
because the company A&G Mining Oy was transferring their diamond mining permit to the
company Karelian Diamond Resources. Furthermore, this kimberlite is still at advanced
exploration stage, even if the resources and the potential to become an open pit mine were
demonstrated. These exploration data were acquired by drilling and bulk sampling, and
geophysical anomalies were detected over and adjacent to the area. The new inquisitors have
planned to remodel the diamondiferous pipe and target locations for more drilling and bulk
sampling. (Karelian Diamond Resources - website, 2016).
We visited the Lahtojoki kimberlite pipe by ourselves. The site is well accessible by car and then
by walk in forest trails for around 1 km (Figure 13). The 200 x 100 m pipe exact location was
revealed by test pits which are now filled with water. We have walked on the ramp of the
flooded pit looking for interesting samples but there was only till overburden in the whole area
(Figure 14). Thought we took the time to discuss several interesting aspects of kimberlite and
diamonds genesis, we have not been able to observe the different facies of the diatreme.
Figure 13. Satellite view of the Lahtojoki kimberlite area showing the pipe and the dump.
16
Figure 14. The flooded Lahtojoki pit showing the ramp and the till overburden.
17
May 5th – Public holiday in Kupio
May 5th is 'Ascension Day' in Finland, a national holiday. We used our free time in
Kuopio city center to see the Puijo ski jump, located on a 150 m high hill.
Figure 15: Puijo ski jumping hill
We also went hiking on a local 230-hectare trail reserve which is part of the Natura 2000
network of the European Union.
18
May 6th – Silinjärvi apatite mine
Geology review
The Siilijävi mine began with the exploitation of a carbonatite type intrusion. The mineral of
interest here is apatite which constitutes 10% of the ore. As such, the grade in phosphorus in
the excavated rock is close to 1.5%. Apatite is not the only valuable mineral, as phlogopite,
calcite/dolomite are also used in the production. They constitute 65% and 19% of the ore
respectively. The remaining content in the ore is mainly amphiboles. The ore body has a subvertical shape and is stretched in the N-S direction. The ore deposit has been drilled to a depth
of 800 meters and remains open. The current exploitation plan extends until 2035, however, as
the deposits remains open at depth, it is likely the mine will continue beyond this date. The
carbonatite is surrounded by a reaction aureole of fennite which is caused by metasomatism of
the hosting Archean gneiss. U-Pb analysis on zircon gave an age of 2610 ±3 Ma (O'Brien et al.,
2015), making the Siilinjärvi carbonatite one of the oldest on Earth.
The site is owned by Yara, a Norwegian company specializing in the production of fertilizer. They
produce 10.9 Mt of ore annually, which is the second highest tonnage of rock mined in Finland.
The installations include two open pits and a chemical complex for the production of fertilizer,
phosphate, nitric acid and sulfuric acid. The production is directly shipped by boat. The mine
benefits from some strategic advantage, as it is the only producer of phosphate in Western
Europe. It is also a type of apatite deposit where the content of uranium is very low. This
characteristic is very interesting for the production of fertilizers. These advantages allow the
Sillinjärji carbonatite to be the lowest phosphorus grade actually mined in the world.
STOP 1 : Open pit
Figure 16: Glimmerite-carbonatite injected by Proterozoic mafic dykes.
In the open pit, we had a very nice view of the carbonatite intrusion (Figure 14). We can see the
large scale magmatic layered structure of the carbonatite and also the late mafic dyke cross-
19
cutting the carbonatite. The contact within the dykes and the carbonatite is frequently sheared,
causing some stability problems such as wedge failure.
At the same location, we had access to many samples of carbonatite produced by a previous
blast. We observed glimmerite, a rock composed of phlogopite, amphibole and apatite. It has a
brownish colour as phlogopite is the main mineral. It is possible to find large centimetric to
decimetric crystals of phlogopite, as the abundance of volatile in this kind of magma generates
pegmatitic grains. The white, layered material is composed of calcite, dolomite and apatite.
Figure 17: Left; and right; Well preserved magmatic texture of carbonates and apatite (white) flowing through
phlogopite rich clusters (brown).
The observation of ore boulders and the pit face reveals that the deposit's heterogeneity. Our
guide discussed the importance of the mine geologist's role in assuring a constant feed to the
plant for an optimized recuperation process. To accomplish this, they have access to drilling core
in order to control six parameters: % CO2, % P2O5, % amphiboles (maximum 10%), the shear
class and the grindability. The amphiboles proportion is the main issue as they are very common
in the ore and they reduce the recuperation rate during flotation.
STOP 2 : Overview from the top of the pit
Finally, we headed at a lookout for a scenic view of the mine.
Figure 18: Group photo at Siilinjärvi apatite mine.
20
Pilow basalt outcrop
During dinner, we discussed with our guide, Aleksi Salo, about other interesting geological
features in the region. He suggested we visit a well preserved sequence of pillow basalt. The
outcrop was about 200m2 and located on the roadside. On the horizontal surface, it was
possible to see pillow structures indicating that the sequence has been tilted to a sub-vertical
position. Fortunately, deformation did not alter the pillow structure, so it was possible to look
for way up criterions. We observed that the shape of the pillow indicated a way up direction
toward south as the bottom of the pillow formed sharp shapes on the lower pillows. We also
noticed concentric cracking on the edge of the pillow. Those are interpreted as primary cracking
due to rapid cooling during submarine volcanism, causing an important temperature gradient
between the edge and the center of the pillow.
Figure 19: Left; way up indicator, notice the sharp edge toward the bottom and the convex shape toward the top
indicating a way up toward the South (top of the picture). Right; concentric cracks on the edge of a pillow.
Acknowledgements
We are grateful towards our guides Seppo Gehör and Aleksi Salo from Siilinjärvi Mining.
References
O'Brien, H., Heilimo, E., & Heino, P. (2015) Chapter 4.3 The Archean Silinjarvi carbonatite
complex. In:Maier, W., O'Brien, H., Lahtinen, R. (Eds.) Mineral deposits of Finland, Elsevier,
Amsterdam, 327-343.
21
May 8th – Rokua geopark
Geology review
Although Finland boasts one of the highest percentage of rock outcrops in the world, it
accounts only for approximately 4% of the country's surface (Eilu, personal
communication). Thus, an understanding of glacial deposits and glacial flow is necessary
for any useful exploration strategy. As Finland was situated close to the glaciation center
of the Scandinavian ice sheet, the different ice-advances and retreats eroded and
deformed most of previously deposited interglacial and glacial sediments so that only
the sediments from the last cold stage, the Weichselian, rest on the Precambrian
bedrock (Lunkka et al., 2001).
The last glacial period and its associated glaciation is known in Northern Europe and
northern Central Europe as the Weichselian glaciation (Lunkka et al., 2001). This is
equivalent to the Wisconsin glaciation in North America. The Scandinavian Ice Sheet
(SIS) was one of the largest ice sheets in Eurasia during the Weichselian glaciation,
attaining its maximum extent in the east during the Late Weichselian between 18 000–
15 000 years ago. At this point, it covered the whole of Fennoscandia, northwestern
Russia and northern Continental Europe (Putkinen, 2011) before beginning its retreat.
Finland was completely deglaciated by ca. 10 ka ago (Luunka et al., 2001). This last cycle
of glaciation and deglaciation left its mark in Finland’s topography in the form of glacial
deposits such as moraines, erratic boulders and eskers. These clues into Finland's
glaciation history can be observed at Rokua National Park, which was affected by the ice
sheet's retreat as well as the uplift which followed (Rokua Geopark, 2016).
The Rokua national park is a UNESCO Geopark located in Northern Finland. The Rokua
Geopark's geosites outline the gradual development of the terrain from below an ice
mass of several kilometers thick to the deep bottom of the ancient Baltic Sea and
further via an island and shore stage to become the present inland area. During the
deglaciation, the ice sheet was divided into several lobes, which flowed in different
direction. As seen in Figure 18, Rokua National Park was mainly affected by the North
Karelian lobe, which flowed in a south-eastern direction.
22
Figure 20: Ice lobes in Finland during the deglaciation stage
Travel Logistics
Everymans right in Finland allows for camping within the park, but only at designated
areas. In the Rokua summer trail map (Figure 19), areas that are shaded ‘Conservation
area’ or ‘Protected area’ are restricted and camping is not allowed.
The following directions for access to Rokua Geopark by car is taken from the official
website for the park :
Access to Rokua Geopark by car is very easy. From Oulu, head southeast toward
Rajaani, for 86 km and follow signs for ‘ROKUA’. If going to Rokua National Park
by car, several parking options are available. In this instance, our group parked at
the Rokua Health and Spa.
23
Our visit of the Rokua national park
Figure 21: Rokua summer trails with our itinerary highlighted in yellow.
STOP 1 : Aeolian deposits
Aeolian deposits usually take the shape of sand dunes. They are created by the action of
the wind, which picks up particles and transports them. In this case, the particles came
from the Rokua Esker Formation, which was deposited in deep water during the last
glacial melt. As the ice retreated, the continent rose through the process of post-glacial
rebound, as the loss of the ice sheet's mass on the continent gave rise to an isostatic
adjustment. The esker deposits were especially prone to transport by wind, as they
were sand particles. Similar to present day sediment transport dynamics, these deposits
were shaped into dunes, parallel to the shoreline. With the wind blowing inland, these
dunes migrated inland in a parabolic U-shape, which helps modern geologists determine
the direction of the wind by viewing these fossilized dunes.
During our field trip to Rokua National Park, we were able to witness the ancient
fossilized dunes, located in Figure 20. These were covered in vegetation, but had
retained their parabolic U-shape. We were able to determine that the winds were
blowing in an approximate southeastern direction.
24
Figure 22: A 3D model of the Rokua Geopark. The highlighted area indicates the approximate location of the
fossilized dunes.
STOP 2 : Erratic boulders
In the second stop, erratic boulders could be viewed on a hillside. Due to the boulders’
rock type, it is possible to determine that they do not come from the underlying
bedrock. The boulders are formed of coarse-grained granite with quartz and reddish
feldspar, likely originating from the Kajaani granite suite to the northwest of Rokua
national park. This intrusive suite crystallized about 1.8 Ga years ago, but were only
revealed 10 ka years ago, with the passage of the glacier and the erosion of the surface
deposits by waves and wind after the glacier’s retreat. The bedrock in the Rokua
national park, however, is mostly composed of miscaschist from siliciclastic sedimentary
rocks and metagraywackes. Thus, it is possible to conclude that these boulders have
been transported by the glacier, which moved in a southeastern direction.
These erratic boulders in Rokua park illustrate an important concept for exploration.
Erratic boulders are often sampled, especially where the bedrock is inaccessible, in
order to pinpoint areas of interest for further exploration methods, such as drilling or
prospection.
25
STOP 3: Combining geology and biology
Figure 23: The lush vegetation surrounding the mire
In the third stop, it was possible to view how geology can affect biology. Most of the
underlying soil in Rokua is very sandy, leading to fast drainage and dry conditions for
plants. These deposits are from the Rokua Esker Formation, from the melting of the
glacier during the deglaciation period. However, in certain areas, fine grained sediments
were deposited in deep water conditions and reworked by waves before being covered
beneath the sandy surface. This silty material has different water retention capabilities
to the sandy material deposited by the esker, which allows for the growth of lusher
vegetation (Figure 21).
STOP 4: Rokua mires and kettles
Kettles are formed during the glacier’s retreat. Ice blocks may break off and get buried
by the sand deposits brought on by glacial rivers. When the ice block melts, depressions
are left behind; these are called kettles. Nowadays, the kettles are visible in the
landscape as lakes and mires. In Rokua, however, the deepest kettle hole Syvyydenkaivo
(Deep Well) is 300m long, which is so large, it can barely be seen in the landscape as in
Figure 22! This kettle hole is 50m deep and, due to the stagnant water that accumulates
in it, contains an impressive 8m of peat in its depths. Aside from Syvyydenkaivo, the
area of Rokua contains many other kettles, especially at the western end of the Rokua
Esker Formation.
26
Figure 24: View of the Syvyydenkaivo kettle hole. The slopes are sand, and at the center of the kettle (barely visible
in the center of the photo) is submerged in the mire
STOP 5 : Glacial bays and inlets
In the fifth stop, we are situated between Saarinen and Salminen, two large lakes that
are also kettles. They are two of the deepest such lakes in Rokua. During the glacier’s
retreat, melting glacial water passed through a subglacial tunnel, depositing sediments
that would later become the Rokua Esker Formation, but also carving out ice blocks that
would later form these two lakes.
References
Punkari, M. (1980). The ice lobes of the Scandinavian ice sheet during the deglaciation in
Finland. Boreas, 9(4), 307-310. doi: 10.1111/j.1502-3885.1980.tb00710.x
SVENDSEN, J. I., ASTAKHOV, V. I., BOLSHIYANOV, D. YU., DEMIDOV, I., DOWDESWELL, J.
A., GATAULLIN, V., HJORT, C., HUBBERTEN, H. W., LARSEN, E., MANGERUD, J., MELLES,
M., MÖLLER, P., SAARNISTO, M. and SIEGERT, M. J. (1999), Maximum extent of the
Eurasian ice sheets in the Barents and Kara Sea region during the Weichselian. Boreas,
28: 234–242. doi:10.1111/j.1502-3885.1999.tb00217.x
Lunkka, J. P., Johansson, P., Saarnisto, M., & Sallasmaa, O. (2004). Glaciation of Finland.
In J. Ehlers & P. L. Gibbard (Eds.), Developments in Quaternary Sciences (Vol. Volume 2,
Part 1, pp. 93-100): Elsevier.
Rokua Geopark. Rokua Geopark - Geology. URL :
http://www.rokuageopark.fi/en_rokua_geopark_3_1 Consulted on August 30th, 2016.
27
May 9th – Otanmäki Fe-Ti-V mine
Geology review
The Otanmäki area is defined by several vanadium-rich magnetite-ilmenite ore lenses in a
Palaeoproterozoic belt of orthoamphibolite- gabbro-anorthosite intrusives and alkaline
granitoids along the boundary between the Archaean Pudasjärvi and Iisalmi blocks, immediately
to the west of the Palaeoproterozoic Kainuu schist belt. Lithological units in Otanmäki region
have been classified as follows : (a) Archean (pre-Svecokarelian) basement consisting of tonalite
migmatite or gneiss, (b) supracrustal schists and metavolcanics, (c) Otanmäki association which
consists of several separate gabbro-anorthosite intrusives that hosts Fe-Ti-V oxides ore, (d)
metasomatized alkali gneiss and (e) microcline granite (Schlöglova et al., 2014).
A major rifting event and continental breakup of prolonged Archean crust (presumed
supercontinent) took place in northern Fennoscandia at 2.1 – 2.04 Ga. The event was fertile for
Cr, PGE, Ni, Cu, Ti and V ore formation (Lahtinen et al. 2005). Therefore, Otanmäki is considered
as an orthomagmatic deposit (Hokka & Jylänki, 2014).
The ore minerals at Otanmäki are vanadium-bearing magnetite and ilmenite with chlorite,
hornblende and plagioclase waste minerals. Sulphides (pyrite, pyrrhotite and chalcopyrite) are
also found in small amounts (1-5%) and have been mined along with the Fe-Ti-V ore (Hokka &
Jylänki, 2014). Banded structures are found in Otanmäki ore, with the bands flowing around
fragments with turbulent features. Also, the plagioclase crystals have a weak flow lamination
texture.
The ore zone contains abundant variable size anorthositic and gabbroic bodies and fragments
which impart an brecciated appearance. Due to the regional metamorphism and complex
deformation, it is difficult to determine whether the ore bodies were originally emplaced in a
horizontal position and tilted after deformation. In that case, the banding structures would
represent primary layer features. Another possibility is flow differentiation, where intrusion
would have been placed and crystallized almost in its original position (Hokka & Jylänki, 2014
and references therein).
28
STOP 1 : Geology and history of Otanmäki
We began our day as our hosts gave us a talk about the history of mining in Otanmäki town, the
planned re-opening of the mine, the regional geology of Otanmäki and the characteristics of this
Fe-Ti-V deposit. We then headed to the old Otanmäki mine Site.
Figure 25: Our hosts, Jouko Jylänki (owner of Otanmäki Mine Oy) and J. Hokka (senior scientist at GTK).
STOP 2 : Main shaft
We climbed all the way up the main shaft of the ancient Otanmäki mine and admired the view
of the old mine site from up above.
Figure 26: Left; the main shaft of Otanmäki mine. Right; view from the bottom to the top of the shaft.
Figure 27: Left; machinery located at the very top of the shaft. Right; ancient tailing pond and part of the historic
mine site.
29
STOP 3 : Trench
In the Metsämalmi area, there is a 250 x 200 meter outcrop that gives a great opportunity to see
ore textures. It was supposed to be an open-pit mine in the 1980’s and so the overburden was
completely removed (Hokka & Jylänki, 2014). We observed the main ore types and several
microstructures and discussed Fe-Ti-V ore metallogeny with respect to the Otanmäki mining
complex.
Figure 28: Textures from the Metsämalmi outcrop area. Top left; Rusty centimeter thick ilmenite-magnetite
discontinuous bands. Top right; Alternating centimeter thick leuco- to melanocratic beds with a meter sized bed of
massive iron oxide ore. Bottom left; Typical aspect of the deformed heterogenous mafic host. Bottom right;
Banding of both host rock and iron oxide ore.
30
STOP 4 : Sattelite deposit
This pit was once a tunnel of the satellite deposit Suomalvi (Figure 27). It was blasted due to the
risks of it caving in. However, the surfaces of the excavation allowed us to have a look at the
ore's geometry.
Figure 29: Fe-Ti ore visible from the other side of the pit. It is subvertical and few meters thick
STOP 5 : Visit underground
We also had the chance to go underground. We took passage in an evacuation shelter tunnel
(Figure 28).
Figure 30: Stairs going down into the evacuation shelter tunnel.
31
STOP 6: Vuorokas Quarry
We also visited the Vuorokas quarry, located about 3 km eastward from Otanmäki main shaft.
This quarry was once a satellite deposit of Otanmäki exploited for Fe-Ti-V ore. Now, it serves as
a source of gravel for roads.
Figure 31: A backhoe feeding a crusher and a loader taking the gravel to a 10-wheeled truck.
STOP 7: Short Geological Trail
At this point, our tour of Otanmäki was over. Since our host Jouku and our group both needed
to drive to Oulu, we followed him to an extra stop unrelated to Otanmäki or Fe-Ti-V
metallogeny.
About 70 km before arriving to Oulu from Otanmäki (road E75), we stopped along the road in a
truck stop to visit a short geological trail designed by Finland’s GTK. It comprises 55 boulders
that each record of ancient environment and events that have shaped Finland. It is quite short
and easy to walk since each step along the path takes you through about 25 My of Earth history.
Figure 32: Geological trail along the road to Oulu. (Left) Marie-Pier and Loraine having a look at a lapilli tuff
boulder, and (right) Impressive slab of orbicular granite.
32
Acknowledgement
We are in debt to Jouko Jylänki (owner of Otanmäki Mine Oy) and J. Hokka (senior scientist at
GTK) who took us thought the best spots in the whole area and shared their knowledge. We
wish them the best of luck in reopening the mine.
References
Hokka, J., Jylänki, J. (2014). Otanmäki Excursion Guidebook. Otanmäki Mine Oy.
Lehtinen, M., Nurmi, P.A., Rämo, O.T. (eds.) (2005): Precambrian Geology of Finland, 1, Elsevier,
Amsterdam.
Schlöglova, Katerina, Lecumberri-Sanchez, Pilar, Steele-MacInnis, Matthew and Heinrich,
Christoph Andreas. Ore deposits, magmatism and precambrian geology of Finland. field trip
guidebook. ETH-Zürich (2014). http://dx.doi.org/10.3929/ethz-a-010223354
33
May 10th – Rompas gold and uranium prospect
Geology review
The Rompas project is contained in the Peräpohja Schist Belt, a volcanosedimentary sequence of
quartzites, mafic volcanics, carbonates, shales, mica schists, greywackes and intrusive rocks
(Molnar, 2015). The oldest units of the Peräpohja Schist Belt (PSB) are mafic and ultramafic
intrusives dated at 2.44 Ga (Huhma et al., 1990) that were injected in the Pudasjärvi Archean
Complex gneiss. They were followed by the first sedimentary units of the belt, composed of
quartz sandstones and stromatolitic carbonates with probable metaevaporites and glaciogenic
rocks. They are followed by an alternance of mafic flows, dykes and sills dated at 2.2 to 2.13 Ga
(Perttunen, 1991) with more distal facies sedimentary rocks dominated by aluminous and
arkosic traction sediments. The volcanosedimentary sequence of the PSB is comparable to other
Paleoproterozoic schist belts deposited in the rift basins of the Kenorland Supercontinent
(Ojakangas, 1988). The belt has reached the amphibolites metamorphic facies in the north and
upper greenschist in the south. The main deformation and metamorphism event is believed to
be the Svecofennian orogeny, taking place at 1.9-1.8 Ga in this region. This major deformation
event is also contemporary to the emplacement of the Central Lapland Granite Complex, dated
between 1.8 and 1.84 Ga (Nironen, 2005).
Mineralization at Rompas is quite unique and no easy comparisons with existing deposits can be
made yet. The area was discovered using radiometric spectrometer surveying while exploring
for uranium. After finding significant gold mineralization in grab samples, the project turned to
gold oriented exploration. Gold and uranium are however intimately associated. In the
mineralized zones, gold is comprised in small pockets of up to 300 cubic centimeters parallel to
the N-S trending carbonate vein family in greenschist to amphibolite facies basalts. Bonanza
gold grade of many thousands of ppm are frequently found in these pockets, in drillholes as well
as in drill core. Even though veining occurs in the mafic volcanics as well as in metasediments, it
is important to note that mineralization is only found in significant quantities in the metabasalts.
Gold and uranium are often found together with pyrobitumen in small, undeformed calcite
veins cross-cutting deformed and wider calc-silicate veins and host rock. Four main styles of
mineralization are found at Rompas: (1) uraninite, (2) uraninite with pyrobitumen, (3) uraninite
with gold minerals and (4) uraninite with pyrobitumen and gold (Molnar et al., 2015).
STOP 1 : Roadside Geology
The first stop of the day was the actual Rompas showing where most of the Bonanza gold grades
grab and drill core samples were extracted from. The vast majority of the outcrops were still
covered in snow and only few of them had observable calcite pockets, but most of them already
had been sampled. It was although possible to observe the distribution of calc-silicate and
carbonate veins through the metabasalts and metasedimentary rocks. Our guide brought a
portable radiometric spectrometer and we had the chance to test it against the carbonate pods
we saw to see if they contained uraninite.
34
Figure 33: A carbonate pod triggering the radiometric spectrometer on the frequency of uranium.
STOP 2 : The core shack
After visiting one area of outcrops, our guide realized that other areas were most likely
inaccessible because of the snow and we decided to go directly to the core shack where we
would see much more rock than in the field at this time of the year. Gold, uraninite, and
pyrobitumen were often visible and the cross-cutting relation were again visible.
Figure 34: Abundant visible gold associated with uraninite in drill core from the Rompas project.
Acknowledgements
We thank Janne Kinnunen of Mawson Resources for his time and efforts: we were able to learn
a lot from him despite the inaccessibility of most outcrops.
References
Huhma H, Cliff R, Perttunen V, Sakko M (1990) Sm-Nd and Pb isotopic study of mafic rocks
associated with early Proterozoic continental rifting: the Peräpojha schist belt in northern
Finland. Contrib Mineral Petrol 104:367–379
35
Molnar F et al. (2015) Association of gold with uraninite and pyrobitumen in the metavolcanic
rock hosted hydrothermal Au-U mineralisation at Rompas, Peräpohja Schist Belt, northern
Finland, Miner Deposita, 51: 681–702
Ojakangas RW(1988) Glaciation: and uncommon mega-event as a key to intracontinental and
intercontinental correlation of Early Proterozoic basin fill, North American and Baltic cratons. In:
Kleinspeh KL, Paola C (eds) New perspectives in basin analysis. Springer, Berlin, pp 431–444
Perttunen V (1991) Kemin, Karungin, Simon ja Runkauksen karttaalueiden kallioperä. PreQuaternary rocks of the Kemi, Karunki, Simo and Runkaus map-sheet areas. Geological map of
Finland, 1: 100 000. Explanation to the maps of Pre-Quaternary rocks, sheets 2541 Kemi, 2542 +
2524 Karunki, 2543 Simo and 2544 Runkaus. Geological Survey of Finland, pp 1–80
Lahtinen R, Korja A, Nironen M (2005) Paleoproterozoic tectonic evolution. In: Lehtinen M,
Nurmi PA, Rämö OT (eds.) Precambrian geology of Finland, key to the evolution of the
Fennoscandian Shield. Elsevier, Berlin, Developments of Precambrian Geology, 14: 481–533
36
May 11th – Day off at Skibotn Fjord
Since no visit were scheduled on thisday, we decided to do a quickout and back in Norway. We
headed up north from Kittilä to Skibotn Fjord, a small town located on the 69th parallel.
Figure 35: Marie-Christine Lauzon picturing the Skibotn Fjord at low tide. Warm clothes are required even at this
time of the year!
We encountered many reeindeers along the road and stopped at some interesting rock cuts.
Figure 36: Left; One of many reindeers living along the road to Skibotn Fjord. Right; a gneissic rock formation seen
from the roadside.
37
May 12th – Kittilä gold mine
Geology review
The Suurikuusikko deposit associated with the Kittilä Gold Mine is located in the central Finnish
Lapland and holds approximately 8 millions ounces of Au. The mineralization is hosted in
tholeiitic mafic rocks comprised in the 2 Ga Kittilä group of the Central Lapland Greenstone Belt
(CLGB).
Figure 37: Regional geology of the Suurikuusikko deposit (Wyche, 2015).
The CLGB is part of the Karelian Craton, a piece of the Fennoscandian Shield. It is divided into
seven groups, including the Kittilä group, composed of four formations. These four formation
include tholeiitic volcanic rocks, oxide and carbonate facies banded iron formation and
sedimentary schists. Gold is contained in pyrite and arsenopyrite and associated with strong
pre-mineralization albite and syn-mineralization carbonate-sericite alteration in the central part
of the Kittliä group rocks. Ore lenses are aligned in the steeply east-dipping NS Kiistala shear
zone. Gold is associated with the second of the four stages of pyrite and arsenopyrite
mineralization. Arsenopyrite associated with gold was dated at 1916 ± 19 Ma with the Re-Os
38
dating method, suggesting that mineralization took place 100 Ma after the deposition of the
Kittilä group rocks.
STOP 1 : The tailing ponds
Our visit of the Kittilä mine started with the tail ponds. We were explained the processes of used
waters and the management of the tailings.
Figure 38: The Kittilä mine tailing ponds
STOP 2 : The core shack
We then visited the core shack to see the lithologies and mineralization that compose the heart
of the deposit. Some visible gold in deformed carbonate-sericite alteration zones and veins in
mafic volcanic rocks was observed.
Figure 39: Hand sample of typical pyrite stringers in the Kittilä Gold Mine.
STOP 3 : The pit
Our last stop of the day was the now closed open-pit. It was possible to observe the larger
structures controlling the mineralization. The vertical shear zone is now exploited with
underground methods.
39
Figure 40: The now closed Kittilä mine pit
Acknowledgements
We thank Jyrki Korteniemi and Jukka Välimaa for their time and effort in getting us to the Kittilä
mine. We also want to thank Tuomas Väliheikki and many other Agnico-Eagle employees for the
interesting discussions we had about their mine.
References
Wyche, N.L. (2015) The Suurikuusikko Gold Deposit (Kittilä Mine), Northern Finland. Mineral
Deposits of Finland, pp.411-433
40
May 13th – Kevitsa Ni-Cu mine
Geology Overview
The Kevitsa deposit is situated in a mafic-ultramafic layered intrusion in northern Finland. It is
one of the youngest intrusions of the Central Lapland Greenstone Belt (CLGB) (Kalla, personal
communication), dated at 2.05 Ga. This intrusion is hosted in a Paleoproterozoic volcanosedimentary sequence, both of which were later metamorphosed to greenschist facies (Yang et
al., 2013). Komatiitic lava flows and tuffs overlay a thick sequence of black and mica schists with
graphite and sulphides; the presence of both is thought to contribute to the enrichment in
nickel (Malehmir, 2014; Yang et al., 2013).
Figure 41 - A) Localisation of the Kevistsa mafic-ultramafic intrusion, in northern Finland. B) Geology map of the
Kevistsa mafic-ultramafique intrusion hosted in the Central Lapland greenbelt rocks. C) Cross section A-A’ shown in
B) based on drilling information (Yang et al., 2013).
Our visit of Kevitsa mine
Our visit began with short presentations. The first was a presentation on the safety in the mine.
The second described the geology of the mine, as well as key aspects of the mine’s operations.
The following is a short summary of our host’s presentation.
The deposit was discovered by the GTK by retracing the movements of boulders in glacial tills,
the 1970s. The property was sold to First Quantum Minerals Ltd in 2008, and mining operations
began in 2010, as Kevitsa is a low grade mine. Now, the mine belongs to a Swedish company,
41
Boliden, the transaction having gone through recently. Approximately 10 000 tons of Ni and 17
000 tons of Cu is produced annually. Though the mine is mainly a Ni-Cu mine, as up to 80% of its
revenues come from these two metals (40% Ni and 40% Cu, respectively), the mine is also an
important provider of platnium group elements. However, geologists at the mine use Ni and Cu
to control the grades, using a NiCu equivalent, and do not consider PGM in the cut-off
calculations. Recovery for Ni is 63% while it is 87% for Cu. The low recovery for nickel is due to
the fact that much of the nickel is trapped within silicate minerals (olivine, for example) in the
ultramafic and mafic host rocks. Samples of the typical mineralisations were also shown during
the presentations (Figure 42).
Figure 42: Left; typical sample of the mineralisation at Kevitsa. Right; local lenses of massive sulphides, as the
results of veins and remobilization.
STOP 1: Open pit observation deck
Our first stop of the day was the open pit observation deck (Figure 43), where our guide
explained the blasting process. Blast movement tracking technology allows the mine to track
exactly the type of rocks that are contained in the loaders. Sensors that can survive the blasts
are placed at lithological contacts and, combined with the GPS in the truck buckets, allow the
mine operators to guide machines in order to pick up as little waste as possible.
Figure 43: View of the open pit from the observation deck
42
As we traveled within the operational area, our guide also explained a few points in regards to
the environmental impact of the mine. As the extraction and treatment process involves the
flottation of pyrrhotite, high sulphide waste can be produced which can create acid mine
drainage (AMD). Thus, waste is classified based on sulphide and nickel content. When sulphide
content exceeds 0.8%, the waste is transferred to a lined tailings pond for encapsulated storage.
The copper and nickel percentage is monitored in this pond’s runoff.
STOP 2: Inside the open pit
Within the open pit, our guide was able to show us the typical rocks that can be encountered in
the mining process. The rocks were mostly mafic and ultramafic rocks, with mineralization
present as pyrrhotite, chalcopyrite and pentlandite. Two types of mineralizations are recognized
at the mine: a “normal” ore, which is rich in copper, nickel and platnium group elements, and a
“Ni-PGE” ore which is particularly enriched in platnium group elements. On average, the
“normal” ore contains 0.3% Cu and 0.2% Ni. Common alterations present in the rocks are
amphiboles, serpentine, talc and various carbonates, associated mainly with faults. When the
rock is unaltered, it is present as pyroxenites.
Our host also spoke about the challenges in rock mecanics for the design of the open pit mine.
As the pit is located in very competent rocks (pyroxenites), most structural problems are related
to the formation of wedge blocks through local discontinuities, especially during spring with the
advent of freeze-thaw cycles. In fact, the original pit design was slightly altered to accomodate
the discontinuities and prevent the formation of wedge blocks.
STOP 3: Core shack visit
After visiting the open pit in very bad weather, we were guided to the core shack where we
could better observe the different geological units and the mineralization of the ore deposit.
Figure 44: Our guide showing us a display with all the different lithologies found on site, in order to help
standardize the core logging between different technicians and geologists.
43
Figure 45: Left; coarse brecciated pyrrhotite. Right; magnetite zone where the pyrrhotite to magnetite reaction can
be observed, along with other interstitial sulphides.
Acknowledgements
We thank Jani Kalla for taking his time in arranging our visit at Kevitsa. We would also like to
thank Robert Lee, the on-site geologist who gave us the presentations and guided us through
the open pit and the core shack.
References
First Quantum Minerals Ltd (2016). Our Business : Kevitsa. Consulted on February 26th, 2016.
URL: http://www.first-quantum.com/Our-Business/operating-mines/Kevitsa/default.aspx
Malehmir A., Koivisto E., Manzi M., Cheraghi S., Durrheim J. R., Bellefleur G., Wijns C., Hein A. A.
K. et King N. (2014). A review of reflection seismic investigations in three major metallogenic
regions: The Kevitsa Ni–Cu–PGE district (Finland), Witwatersrand gold fields (SouthAfrica), and
the Bathurst Mining Camp (Canada). Ore Geology Reviews, vol. 56, pages 423-441. Doi :
10.1016/j.oregeorev.2013.01.003
Yang S.-H., Maier D. W., Hanski J. E., Lappalainen M., Santaguida F. et Määttä S. (2013). Origin of
ultra-nickeliferous olivine in the Kevitsa Ni–Cu–PGE-mineralized intrusion, northern Finland.
Contrib Mineral Petrol, vol. 166, pages 81-95. Doi : 10.1007/s00410-013-0866-5
44
May 14th – Flight back to Quebec
We gave back the rented cars and took the plane from Kittilä and headed for Quebec.
Social events
We were invited by Helsinki students to celebrate their national holiday “Vappu” on arrival. It
was a great way to begin our trip and to get advices about places we would visit.
Enjoying the national holiday “Vappu” in front of the Helsinki Cathedral, with students from
Helsinki University.
Acknowledgments
The field trip would not have been possible without the collaboration of numerous persons.
First, we would like to thank Pasi Eilu who helped us throughout the whole organization. Thank
you for welcoming us and giving us documentation about the global geology of Finland.
We would also like to thank every hosts who guided and welcomed us so warmly.
And finally, a special thanks to Sophie from Helsinki University and Roman Hanes (Université
Laval) who showed us many Finland’s specialities and gave us wise advice.
45
Financial partners
This field trip would not have been possible without support from our
generous sponsors. We are grateful to the followings :
46