Gold deposits in northern Finland - Arkisto.gsf.fi

12th Biennial SGA Meeting 

12–15 August 2013, Uppsala, Sweden 

Mineral deposit research 

for a high-tech world 

Excursion Guidebook FIN1 

Gold deposits in northern Finland

Geological Survey of Sweden 

Box 670 

SE-751 28 Uppsala 

Sweden 

Phone: +46 18 17 90 00 

E-mail: kundservice@sgu.se 

www.sgu.se 

Cover photograph: Pahtavaara mine in 2012. 

Photo: Courtesy of Lappland Goldminers. 

© Sveriges geologiska undersökning, 2013 

Layout: Jeanette Bergman Weihed, SGU

Excursion Guidebook FIN1 

Gold deposits in northern Finland 

Pasi Eilu and Tero Niiranen, Geological Survey of Finland (GTK) 

Excursion held 16–18 August 2013

Dear field trip participant 

You are holding in your hand a guidebook for 

one of several field trips offered in conjunction 

with the 12th SGA biennial meeting held in 

Uppsala, Sweden 12–15 August 2013. As president 

of The Society for Geology Applied to Mineral 

Deposits (SGA) I welcome you to the field 

trip and hope that it will be rewarding with interesting 

geology and stimulating discussions. 

The field trips organised in conjunction with 

the SGA biennial meetings have, so far, been a 

success and are regarded as an important part of 

the science SGA offers to its members and other 

interested geoscientists. 

As a scientific society, we are proud to be able 

to offer the field trips this time in northern Europe 

in the Fennoscandian Shield and Greenland. 

The trips offered deal with ore deposits in 

Precambrian shield areas and thus reflect the 

metallogeny of the Precambrian. In the Fennoscandian 

shield, the main economic deposits are 

hosted in Palaeoproterozoic rocks, not in Archaean. 

This will be further explained during 

the individual trips. 

The field trips organised will visit many different 

deposit types, e.g. mafic-ultramafic hosted 

Ni-Cu-PGE, IOCG, orogenic gold and VMS, 

in the main metallogenetic belts. 

SGA would like to acknowledge the hard work 

done by the local organising committee in general 

and especially the Geological Survey of Sweden 

which is the main organiser of the 12th Biennial 

meeting and which has compiled all the field trip 

guidebooks. Dr Magnus Ripa and the technical 

editors from the Geological Survey of Sweden 

are especially acknowledged as responsible for 

the field trip programme. Their colleagues from 

the Geological Survey of Denmark, Prof. Jochen 

Kolb, the Geological Survey of Finland, Prof. 

Raimo Lahtinen, and the Geological Survey of 

Norway, Dr Rognvald Boyd, are all thanked for 

working hard to realise the field trip programme. 

I would also like to express SGA’s sincere 

gratitude to all the individual field trip leaders 

and contributors: Tobias Bauer (Luleå University 

of Technology), Holger Paulick (Boliden 

AB), Benno Kathol (Geological Survey of Sweden), 

Iain Pitcairn (Stockholm University), Erik 

Jonsson (Geological Survey of Sweden), Rodney 

Allen (Boliden AB), Nils Jansson (Boliden AB), 

Magnus Ripa (Geological Survey of Sweden), 

Michael Stephens (Geological Survey of Sweden), 

Christina Wanhainen (Luleå University 

of Technology), Olof Martinsson (Luleå University 

of Technology), Ingmar Lundström (formerly 

Geological Survey of Sweden), Per Nysten 

(Geological Survey of Sweden), Karin Högdahl 

(Uppsala University), Sten Anders Smeds (formerly 

Geological Survey of Sweden), Eero Hanski 

(Oulu University), Wolfgang Maier (Oulu 

University), Yury Voytekhovsky (Kola Science 

Centre), Pasi Eilu (Geological Survey of Finland), 

Tero Niiranen (Geological Survey of 

Finland), Asko Kontinen (Geological Survey 

of Finland), Jukka Kousa (Geological Survey 

of Finland), Peter Sorjonen-Ward (Geological 

Survey of Finland), Hannu Makkonen (Geological 

Survey of Finland), Terje Bjerkgård 

(Geological Survey of Norway), Sven Dahlgren 

(Buskerud, Telemark and Vestfold counties), 

Henrik Schiellerup (Geological Survey of 

Norway), Are Korneliussen (Geological Survey 

of Norway), Pål Thjøemøe (Magma Geo park), 

Jan Sverre Sandstad (Geological Survey of Norway) 

and Espen Torgersen (Geological Survey 

of Norway). 

With these words, I welcome you to northern 

Europe and the fantastic geology both in the 

Fennoscandian Shield and on Greenland. Enjoy! 

Pär Weihed 

President SGA 

Excursion Guidebook FIN1 3

Contents 

Programme ............................................................................................................................................................................. 6 

Contact details of your guides .................................................................................................................................. 6 

Introduction ........................................................................................................................................................................... 8 

Geological and tectonic evolution of the northern part of the Fennoscandian shield ...... 8 

Palaeoproterozoic 2.45–1.88 Ga supracrustal sequences ..................................................................................... 12 

Palaeoproterozoic intrusive magmatism ..................................................................................................................... 18 

Early rifting and layered intrusions ....................................................................................................................... 18 

Mafic dykes ....................................................................................................................................................................... 18 

Granitoids .......................................................................................................................................................................... 18 

Palaeoproterozoic deformation and metamorphism ............................................................................................. 20 

Epigenetic gold deposits in northern Finland ................................................................................................. 21 

Pahtavaara gold mine ........................................................................................................................................................... 24 

Geology and hydrothermal alteration .................................................................................................................. 24 

Mining ................................................................................................................................................................................ 27 

Saattopora gold mine ............................................................................................................................................................ 28 

Kittilä gold mine (Suurikuusikko deposit) ................................................................................................................ 31 

Exploration history ........................................................................................................................................................ 31 

Geology ............................................................................................................................................................................... 33 

Acknowledgements ....................................................................................................................................................... 42 

Rompas-Rajapalot gold-uranium project, Peräpohja Schist Belt .................................................................... 42 

Regional geology ............................................................................................................................................................ 44 

Rompas area geology .................................................................................................................................................... 44 

Mineralisation ................................................................................................................................................................. 46 

Mawson exploration team .......................................................................................................................................... 49 

References ............................................................................................................................................................................... 49 


Programme 

Day 1. Friday 16 August 

8.30 Leave GTK North Finland Office. 

9.00 Leave from hotel Pohjanhovi (downtown 

Rovaniemi). 

9.30 Leave from Rovaniemi airport. 

Stop 1. Lunch at Sodankylä town. About 130 km 

drive (2 h) north from Rovaniemi. 

Stop 2. Pahtavaara gold mine (Lappland Goldminers) 

at Sodankylä. About 35 km drive northwest 

from Sodankylä town. We will visit the 

active Pahtavaara gold mine. Possibility to see 

the ore and the hosting sequence, as well as the 

processing plant. 

Stop 3. Levi, Kittilä. 80 km west from Pahtavaara, 

but 135 km along road. Accommodation 

at Hotel K5, dinner in the evening at the hotel. 

Day 2. Saturday 17 August 

8.00 Leave hotel. We will return to the same 

hotel in the evening. 

Stop 1. Saattopora gold-copper mine (closed 

mine). About 45 km drive (45 min) to the westnorth-west 

from Kittilä town. Visit open pit 

and waste rock piles, see the ore and the hosting 

sequence. 

Stop 2. Lunch at Kittilä town. 

Stop 3. Kittilä Mine. Agnico Eagle geologists’ 

presentation on the geology and mining operations. 

The exact localities to be visited depend on 

the accessibility to different parts of the mine. 

Possibly visit to the core yard near Kittilä town 

after the mine visit. 

Stop 4. Levi, Kittilä. About 40 km drive from 

Kittilä mine. Accommodation at Hotel K5, dinner 

in the evening at the hotel. 

Day 3. Sunday 18 August 

9.00 Checkout and leave hotel. Drive 210 km 

(3 h) south to the Rompas area. 

Stop 1. Rompas Au-U prospect. Mawson Resources 

geologists’ presentation on the project. 

Visit to exploration trenches, outcrops with visible 

gold, see the project terrain and geophysical 

and geochemical exploration data. Field lunch. 

16.00 About 40 km, c. 45 min. drive to Rovaniemi 

to the east. The bus will stop at the hotels 

downtown and at the Rovaniemi airport. 

Contact details of your guides 

Pasi Eilu: +358 40 8649 165, 

E-mail: pasi.eilu@gtk.fi 

Tero Niiranen: +358 50 3487 621, 

E-mail: tero.niiranen@gtk.fi 

6 Pasi Eilu & Tero Niiranen (ed.)

Saattopora 

Levi 

Suurikuusikko 

(Kittilä mine) 

68°0'0"N 

65°0'0"N 

Rovaniemi 

KITTILÄ 

Pahtavaara 

SWEDEN 

FINLAND 

KOLARI 

SODANKYLÄ 

60°0'0"N 

Uppsala 

Stockholm 

20°0'0"E 

25°0'0"E 

Helsinki 

30°0'0"E 

PELLO 

67°0'0"N 

Field trip location 

Day 1 route 

Day 2 route 

Day 3 route 

0 25 50 km 

24°0'0"E 

Rompas 

ROVANIEMI 

26°0'0"E 

Arctic circle 


Introduction 

Pasi Eilu & Tero Niiranen, Geological Survey of Finland 

The Fennoscandian shield forms the northwestern 

part of the East European craton, and 

comprises most of Finland, Sweden, Karelia, 

the Kola Peninsula and, with the Caledonides, 

most of Norway (Fig. 1). The oldest rocks have 

been dated at 3.6 Ga (Huhma et al. 2004), but 

most of the shield comprises Neoarchaean to 

Palaeoproterozoic rocks (Lahtinen et al. 2008). 

Meso- to Neoproterozoic crust dominates in the 

south-western part of the shield, and the Caledonides 

form a major part of the west of the region. 

Economic mineral deposits occur in rocks of 

nearly all ages, with major peaks of formation 

during the Palaeoproterozoic and Caledonian 

orogenies. 

Northern Finland comprises rocks of c. 3.1 

to 1.8 Ga. Metallogenic belts cover large parts 

of the area (Fig. 2). Despite extensive Neoarchaean 

rocks in the area, no economic mineralisation 

predating 2.45 Ga has so far been 

discovered. The detected Archaean BIF, epigenetic 

Au and komatiitic Ni occurrences are 

rather small (FODD 2013). Major mineralisation 

stages in northern Finland relate to 2.45 Ga 

layered intrusions (PGE ± Ni-Cu, Cr, V-Ti-Fe), 

2.1–1.9 Ga (?) supracrustal sequences (komatiitic 

Ni, stratabound Cu-Zn, BIF, possible Au), 

c. 2.06 Ga mafic to ultramafic intrusions (Ni- 

Cu ± PGE), and the 1.94–1.79 Ga Lapland– 

Kola and Svecofennian orogenies (Au ± Cu ± 

Co, IOCG). 

Presently, mining takes place in the 2.45 Ga 

and 2.06 Ga intrusions (Cr and Ni-Cu-PGE, 

respectively) and the Palaeoproterozoic supracrustal 

rocks mineralised during the Lapland– 

Kola to Svecofennian orogenies (Au). This field 

trip targets on the latter: orogenic gold and of 

possibly other types of epigenetic gold deposits 

(Suurikuusikko, Saattopora, Rompas), but we 

will also see a gold deposit that may be of syngenetic 

type (Pahtavaara). Despite mining, a lot of 

genetic uncertainties still relate to these deposits, 

matters that we expect to be widely discussed 

during this field trip. 

Geological and tectonic evolution of the northern part 

of the Fennoscandian shield 

Pasi Eilu, Tero Niiranen & Laura Lauri, Geological Survey of Finland 

The bedrock of northern Finland comprises 

Mesoarchaean to Palaeoproterozoic rocks. Their 

geological evolution can only be described in 

the context of the entire Fennoscandian shield. 

Below, we describe this evolution in three parts, 

the Archaean, the Proterozoic predating the 

Svecofennian orogeny and the Svecofennian. 

This description is essentially based on Lahtinen 

(2012) unless otherwise is indicated. 

The Archaean crust, either exposed or concealed 

under Palaeoproterozoic cover rocks 

and granitoids, occurs in the east and north of 

Fenno scandia. Four major Archaean provinces 

have been outlined (Fig. 1, modified after Hölttä 

et al. 2008). The western and eastern parts of the 

Karelian province comprise Mesoarchaean, 2.8– 

3.0 Ga rocks, but rocks older than 3.0 Ga occur 

locally. The central part of the Karelian province 

is mainly Neoarchaean, having plutonic and volcanic 

rocks that are 2.75–2.70 Ga in age. The 

volcanic belts formed in various geo dynamic settings, 

including oceanic plateau, island arc, back 

arc, intra-arc and intra-continental rift. Neoarchaean 

accretion at c. 2.83–2.75 Ga and sub 


Timanide orogen 

500 km 

Murmansk 

Lapland-Kola 

Kola province 

Ki 

K 

Belomorian province 

Norrbotten 

province 

Karelian province 

SA 

J 

SB 

WGC 

NORWAY 

Svecofennian 

province 

CS 

CFGC 

FINLAND 

O 

RUSSIA 

SWEDEN 

SS 

Ladoga 

T 

DENMARK 

Oslo 

OR 

G 

Småland 

BA 

Stockholm 

BALTIC SEA 


ESTONIA 

LATVIA 

St. Petersburg 

East European Craton 

Atlantic 

Baltic Sea 

Archaean 

FENNOSCANDIAN 

SHIELD 

Palaeoproterozoic 

Fennoscandia 

VOLGO-URALIA 

R.F. 

LITHUANIA 

Ukrainian 

Shield 

SARMATIA 

Caledonian orogenic belt (510–400 Ma) 

Archaean and cover rocks in Lower Allochthon 

Phanerozoic to Neoproterozoic rocks 

Alkalic plutonic rocks 

Sedimentary rocks 

Mesoproterozoic rocks 

Rapakivi granite association (1650–1470 Ma) 

Sedimentary rocks (1500–1270 Ma) 

Projected Archaean–Proterozoic boundary 

Province and sub-province boundaries 

Sveconorwegian orogenic belt (1100–920 Ma) 

Sedimentary and volcanic rocks (2500–1960 Ma) 

Palaeoproterozoic rocks 

Mafic plutonic rocks (2500–1960 Ma) 

Sedimentary and volcanic rocks (1950–1800 Ma) 

Plutonic rocks (1960–1840 Ma) 

Plutonic rocks (1850–1660 Ma) 

Archaean rocks 

Plutonic rocks and gneisses (3500–2500 Ma) 

Volcanic and sedimentary rocks (3200–2700 Ma) 

Rocks >3000 Ma 

Figure 1. Fennoscandia and its location within the East European Craton (Lahtinen 2012). Simplified geological map 

based on Koistinen et al. (2001) and inset map based on Gorbatschev and Bogdanova (1993). Subareas: CS – Central 

Svecofennia, SS – Southern Svecofennia. Areas and localities: BA – Bergslagen area, G – Gothian terranes, J – Jormua, 

K – Kittilä, Ki – Kiruna, O – Outokumpu, OR – Oslo rift, SA – Skellefte Area, SB – Savo Belt, T – Telemarkian terranes, 

WGC – Western Gneiss Complex. 


25°E 

30°E 

Bjørnevatn 

Fe 

NORWAY 

Bidjovagge 

Au-Cu 

Pechenga 

Ni 

69°N 

RUSSIA 

Saattopora 

Au-Cu 

Suurikuusikko 

Au 

Koitelainen 

Cr-V 

Sokli P(Nb) 

Hannukainen 

Fe 

Kittilä 

Pahtavaara 

Au 

Kevitsa 

Ni-Cu-PGE 

Sakatti Ni-Cu 

Tapuli Fe 

Sodankylä 

Akanvaara 

Cr-V 

SWEDEN 

FINLAND 

Rovaniemi 

Konttijärvi 

PGE 

Siika-Kämä 

PGE 

Juomasuo 

Au-Co 

66°N 

Ahmavaara 

PGE 

0 50 km 

Kemi Cr 

Mustavaara 

V 

Figure 2. Metallogenic belts and major metallic mineral deposits of northern Finland and surroundings 

(Eilu et al. 2009, FODD 2013). Legend on the facing page. 


Metallogenic Areas and Mineral Deposits 

Base metals: Co, Cu, Pb, Zn 

Base metals: Ni 

Ferrous metals: Cr, Fe, Mn, Ti, V 

Precious metals: Ag, Au 

PGE: Pd, Pt, Rh 

Special metals: Be, Li, Mo, Nb, REE, Sc, Sn, Ta, W, Zr 

Energy metals: U, Th 

Deposit size 

Small, Showing 

Potentially large, Medium 

Very large, Large 

Neoproterozoic (and possibly Mesoproterozoic) and Phanerozoic rocks 

outside the Caledonian orogenic belt 

Vendian to Cambrian and Devonian alkaline igneous rocks 

Upper Riphean (and possibly older) Vendian and Phanerozoic sedimentary rocks 

Caledonian orogenic belt 

Neoproterozoic and Palaeozoic (Cambrian to Devonian) rocks 

along the shortened Baltoscandian continental margin 

Proterozoic rocks (c. 2.30–0.90 Ga) along the shortened Baltoscandian continental margin 

Palaeoproterozoic rocks (2.50–1.75 Ga) 

Volcanic rocks (c. 1.96–1.75 Ga) 

Supracrustal rocks, predominantly sedimentary rocks (1.96–1.75 Ga) 

Intrusive rocks, predominantly granitoids (1.96–1.75 Ga) 

Supracrustal rocks, predominantly mafic to ultramafic volcanic rocks 

and sedimentary rocks (2.50–1.96 Ga) 

Intrusive rocks, predominantly mafic and ultramafic (2.50–1.96 Ga) 


Intrusive rocks, orthogneiss, migmatitic gneiss (c. 3.20–2.50 Ga and possibly older) 

Supracrustal rocks (c. 3.20–2.75 Ga and possibly older) 

sequent collisional stacking at 2.73–2.68 Ga is 

the proposed model for the amalgamation of the 

Karelia Province (Hölttä et al. 2012). 

The Belomorian province (Fig. 1) is dominated 

by 2.9–2.7 Ga granitoids and includes volcanic 

rocks formed at 2.88–2.82 Ga, 2.8–2.78 Ga 

and 2.75–2.66 Ga. The Neoarchaean ophiolitelike 

rocks and 2.7 Ga eclogites in the Belomorian 

province are possible examples of Phanerozoic-style 

subduction and collision (Hölttä et al. 

2008). The Kola province (combined Kola and 

Murmansk provinces of Hölttä et al. 2008) is a 

mosaic of Mesoarchaean and Neoarchaean units, 

together with some Palaeoproterozoic components. 

The Archaean part of the Norrbotten province 

is mainly concealed under cover rocks, and 

very limited data are available (Mellqvist et al. 

1999, Bergman et al. 2001). 

Rifting of the Archaean continent or continents 

began in north-eastern Fennoscandia 

and became widespread after the emplacement 

of 2.50–2.44 Ga, plume-related, layered gabbro-norite 

intrusions and dyke swarms (Iljina 

& Hanski 2005). Erosion and deep weathering 

after 2.44 Ga was followed by glaciation, and 

later deep chemical weathering again covered 

large areas in the Karelian province at c. 2.35 Ga 

(Laajoki 2005, Melezhik 2006). Rifting events 

at 2.4–2.1 Ga are associated with mostly tholeiitic 

mafic dykes and sills, sporadic volcanism 

and typically fluvial to shallow-water sedimentary 

rocks (Laajoki 2005, Vuollo & Huhma 

2005). Local shallow marine environments were 

marked by deposition of carbonates, and possibly 

evaporites, at 2.2–2.1 Ga, showing a large 

positive δ 13 C isotope anomaly during the Lomagundi–Jatuli 

Event (Karhu 2005, Melezhik 

et al. 2007, Kyläkoski et al. 2012a). Along the 

present western edge of the Karelian province, 

2.05 Ga bimodal felsic-mafic volcanic rocks of 

alkaline affinity are intercalated with deep-water 

turbiditic sedimentary rocks. 


No clear examples of subduction-related 

magmatism between 2.70 and 2.05 Ga have 

been found in Fennoscandia. The 2.02 Ga, felsic 

sub-volcanic and possibly volcanic rocks in 

Finnish Lapland (Kittilä in Fig. 1) occur in association 

with oceanic island arc-type rocks and 

are the oldest candidates for Palaeoproterozoic 

subduction-related rocks (Hanski & Huhma 

2005). Associated continental within-plate volcanic 

rocks are possibly related to the continued 

break-up of the craton. Bimodal alkaline– 

tholeiitic magmatism in central Lapland (Hanski 

et al. 2005) and rift-related magmatism in 

Kola (Pechenga) show that rift magmatism continued 

until 1.98 Ga. The Jormua–Outokumpu 

ophiolites (Fig. 1), tectonically intercalated with 

deep-water turbidites, are unique examples of 

Archaean subcontinental lithospheric mantle 

with a thin veneer of oceanic crust formed at 

1.95 Ga along the western edge of the present 

Karelian province (Peltonen 2005). 

The main Palaeoproterozoic orogenic evolution 

of Fennoscandia can be divided into the 

Lapland–Kola orogen (1.94–1.86 Ga, Daly 

et al. 2006) and the composite Svecofennian 

orogen (1.92–1.79 Ga, Lahtinen et al. 2005, 

2008). The latter is divided into the Lapland– 

Savo, Fennian, Svecobaltic and Nordic orogens. 

Whereas the Lapland–Kola orogen shows only 

limited formation of new crust, the composite 

Sveco fennian orogen produced a large volume 

of Palaeoproterozoic crust in the Svecofennian 

province. It should be noted that igneous rocks 

of 1.9–1.8 Ga age in northern Finland show 

a large contribution of older LREE-enriched 

litho sphere (Huhma et al. 2011) verifying the 

occurrence of Archaean crust below the Palaeoproterozoic 

cover in the Karelian province. 

Palaeoproterozoic 2.45–1.88 Ga 

supracrustal sequences 

Palaeoproterozoic supracrustal sequences overlie 

much of the northern part of the Fennoscandia. 

In Finland, the main sequences are the Central 

Lapland Greenstone Belt, Peräpohja and Kuusamo 

schist belts and the Lapland granulite belt 

(Figs. 1, 3–6). Figure 4 summarises the stratigraphy 

of the Central Lapland Greenstone Belt 

(CLGB), which is the dominant supracrustal sequence 

of the region. This stratigraphy has been 

applied also to the Peräpohja and Kuusamo belts 

with variable success. Figures 5 and 6 show the 

major stratigraphic units for the Peräpohja belt. 

The lowermost units of the greenstones, the 

Vuojärvi and Salla groups, lie unconformably 

on the Archaean TTG rocks. The rocks of the 

Salla Group are clearly of early Palaeoproterozoic 

age. However, the age of the Vuojärvi Group is 

uncertain and can even be of the latest Neoarchaean. 

The Vuojärvi and Salla groups are followed 

by sedimentary and volcanic units which 

precede the c. 2.2 Ga igneous event and comprise 

the Kuusamo and Sodankylä Groups in 

the CLGB and in the Kuusamo schist belt. The 

Sodan kylä Group also hosts many, but not all, 

of the known Palaeoproterozoic syngenetic sulphide 

occurrences in the CLGB. 

The mafic to ultra mafic volcanic and shallow 

marine sedimentary units of the Savukoski 

Group were deposited during 2.2–2.01 Ga in 

the CLGB, and similar units were also formed 

in the Kuusamo and Peräpohja belts (Lehtonen 

et al. 1998, Rastas et al. 2001). In the latter belt, 

rocks aged from the Petäjäskoski Formation to 

Väystäjä Formation (Fig. 5) seem to be contemporaneous 

with the Savukoski Group (Kyläkoski 

et al. 2012a). Age data from the Palaeoproterozoic 

greenstones (e.g. Perttunen & Vaasjoki 

2001, Rastas et al. 2001, Väänänen & Lehtonen 

2001, Kyläkoski et al. 2012a) suggest a major 

magmatic and rifting event at c. 2.1 Ga with the 

final break up taking place at 2.06 Ga. Extensive 

occurrences of 2.13 and 2.05 Ga dolerites 

also support these dates. Thick piles of mantlederived 

volcanic rocks, including komatiitic and 

picritic high-temperature melts, are restricted to 

the Kittilä–Karasjok–Kauto keino–Kiruna area 

and are suggested to represent plume-generated 

volcanism (Martinsson 1997). The rifting of the 

Archaean craton along a north-west-trending 


24°0'0"E 

26°0'0"E 

68°0'0"N 

Suurikuusikko 

STZ 

Saattopora 

Sirkka 

STZ 

KITTILÄ 

Hannukainen 

VTZ 

Kutuvuoma 

Pahtavuoma 

Rautuvaara 

STZ 

VTZ 

VTZ 

SODANKYLÄ 

0 10 20 km 

Palaeoproterozoic Groups 

Kumpu Group 

Quartzite, siltstone, conglomerate, 

intermediate to felsic volcanic rocks 

Kittilä Group 

Tholeiitic volcanic rocks, graphite- and sulphide-bearing tuffite, 

BIF, phyllite, mica schist, graywacke 

Savukoski Group 

Tholeiitic and komatiitic volcanic rocks, phyllite, graphite and 

sulphide-bearing schist, tuffite, dolomite 

Sodankylä Group 

Quartzite, mica schist, mica gneiss, mafic volcanic rock 

Kuusamo Group 

Tholeiitic and komatiitic volcanic rocks 

Salla Group 

Intermediate to felsic volcanic rocks 

Vuojärvi Group 

Quartzite, mica gneiss, possibly volcanic in origin 

Palaeoproterozoic complexes 

Lapland granulite complex 

Vuotso complex 

Hetta complex 

Central Lapland granitoid complex 

Archaean complexes 

Pomokaira and Muonio complexes 

Palaeoproterozoic supracrustal suites 

Nuttio suite 

Olostunturi suite 

Diverse lithodemes 

Palaeoproterozoic hypabyssal suites 

Haaskalehto gabbro-wehrlite suite 

Palaeoproterozoic intrusive suites 

Nattanen granite suite 

Haaparanta suite 

Nilipää granite suite 

Eastern Lapland layered intrusion suite 

Keivitsa layered intrusion suite 

Major structures 

Shear or fault zone 

Thrust zone 

Gold deposits 

Active or past-producing mine 

Prospect 

Figure 3. Geology of the Central Lapland greenstone belt, with the CLGB gold occurrences listed in Tables 1 

and 2. Compiled by Tero Niiranen, geology based on the GTK digital bedrock database. STZ – Sirkka Thrust Zone, 

VTZ – Venejoki Thrust Zone. 


Central Lapland Greenstone Belt stratigraphy and igneous ages 

>1.88 Ga terrestrial sediments, 

intermediate to felsic volcanic 

rocks 

1.80 

Kumpu Gp 

~2.0 Ga tholeiitic volcanic rocks, 

shallow to deep marine sediments 

Kittilä Gp 

>2.05 Ga komatiitic to mafic volcanic 

rocks, shallow marine sediments 

1.91 

Savukoski Gp 

1.89– 

1.86 

>2.2 Ga terrestrial to shallow marine 

sediments, mafic to intermediate 

volcanic rocks 

Sodankylä Gp 

2.05 

Tholeiitic and komatiitic 


2.44 Ga felsic to intermediate 


Undefined quartzite, mica gneiss 

and felsic to intermediate volcanic 

rocks, possibly Archean in age 

Felsic intrusions 

2.1 

Kuusamo Gp 

Salla Gp 

Vuojärvi Gp 

2.2– 

2.14 

Mafic to felsic intrusions 

Mafic layered intrusions, 

mafic sills and dykes 

Archean Basin 

Tectonic contact with 

ophiolite fragments 

2.44 

2.1 Igneous age in Ga 

Figure 4. Stratigraphy of the Central Lapland greenstone belt. Ages given as Ga. ‘Archaean Basin’ means the 

Archaean TTG rocks on which part of the Palaeoproterozoic sequence unconformably lies. Compiled by Tero 

Niiranen (GTK), after Hanski et al. (2001) and the 2013 version of the GTK digital bedrock database. 

Haparanda Suite 

CLGC 

Pöyliövaara 

Korkiavaara 

Väystäjä 

PAAKKOLA 

GROUP 

Martimo 

Rantamaa/Poikkimaa 

Tikanmaa 

Kvartsimaa 

Jouttiaapa 

2.1, 2.05 Ga? 

Petäjäskoski 

KIVALO 

GROUP 

Mafic sills 

2.1 Ga 

Palokivalo 

Runkaus 

2.2 Ga 

Sompujärvi 

Pudasjärvi Basement Complex 

2.4 Ga Layered intrusions 

Figure 5. Stratigraphy of the 

Peräpohja schist belt (Kyläkoski 

et al. 2012a), largely based on 

Perttunen & Hanski (2003). 


24°0'0"E 

25°0'0"E 

26°0'0"E 

N Rompas 

Palokas 

C Rompas 

Joki 

S Rompas 

Hirvimaa 

Rumajärvi 

66°20'0"N 

Vinsa 

Petäjävaara 

Sivakkajoki 

Kivimaa 

Vähäjoki 

66°0'0"N 

Laurila 

0 10 20 km 

Paakkola Group 

Pöyliövaara–Martimo fm 

Heraselkä fm 

Mäntyvaara fm 

Väystäjä fm 

Korkiavaara fm 

Kivalo Group 

Rantamaa–Poikkimaa fm 

Tikanmaa–Hirsimaa fm 

Kvartsimaa fm 

Jouttiaapa fm 

Palokivalo–Ounasvaara fm 

Runkaus fm 

Sompujärvi fm 

2.2–2.05 Ga mafic dykes and sills 

1.91–1.89 Ga Haaparanta suite intrusions 

2.44 Ga layered intrusions 

Central Lapland granitoid complex, Mellanjoki suite 

Central Lapland granitoid complex 

Neoarchean schist and greenstone belts 

Pudasjärvi basement complex 

Au deposit 

Figure 6. Geology of the Peräpohja schist belt (Kyläkoski et al. 2012a). Geology based on the GTK digital 

bedrock database. 


Table 1. Gold and gold-base metal deposits in the Central Lapland greenstone belt and Peräpohja schist belt with 

a resource estimate. The data are from the FINGOLD database (Eilu & Pankka 2009) and FODD (2013). Mining by 

the end of 2012, mined tonnages and grades as reported by the mining companies. Size indicates global resource + 

mined in millions of tonnes of ore. 

Deposit 

Size 

(Mt) 

Mined 

(Mt) 

Au 

(g/t) 

Co 

(%) 

Cu 

(%) 

Ni 

(%) 

Host rocks 1 

Siting of gold 

Central Lapland greenstone belt 

Orogenic gold deposit 

Hirvilavanmaa 0.11 2.9 Komatiite Free native with pyrite and 

tellurides 

Kaaresselkä 0.3 5 0.03 0.2 Mafic tuffite Free native assoc. with gangue 

and sulphides 

Kettukuusikko 0.44 1.8 nr Komatiite Free native assoc.with pyrite 

and vein quartz 

Kuotko 1.823 2.89 Mafic volcanic 

rocks 

Kutuvuoma 0.068 0.02 6.7 Komatiite, 

phyllite 

Free native assoc. with 

arsenopyrite and pyrite 

Free native assoc. with 

arsenopyrite and pyrite 

Loukinen 2 0.114 0.5 nr 0.45 Komatiite Free native + inclusions in 

sulphides 

Saattopora Au 3 2.163 2.163 2.9 0.25 Albitised 

phyllite 

Sirkka (Sirkka kaivos) 0.25 0.8 0.1 0.38 0.32 Albitised 

phyllite 

Free native assoc. with gangue 

and sulphides 

Free native assoc. with gangue 

and sulpharsenides 

Soretialehto 0.013 3.5 Komatiite Free native assoc. with quartz 

and pyrite 

Kittilä Mine 

(Suurikuusikko) 

64.09 4.14 4.15 Mafic volcanic 

rocks, phyllite 

Refractory in arsenopyrite and 

pyrite 

Syngenetic Cu overprinted by orogenic gold or orogenic gold with an anomalous metal association 

Riikonkoski 9.45 nr 0.45 Intermediate 

tuffite 

Saattopora Cu 11.6 0.25 0.01 0.62 0.1 Intermediate 

tuffite 

Assoc. with arsenopyrite ± 

chalcopyrite 

Associated with chalcopyrite? 

Orogenic or syngenetic 

Pahtavaara Au 7.74 4.98 2.65 Komatiite Free native assoc. with gangue 

Peräpohja schist belt 

Kivimaa 0.023 0.018 5.3 1.87 Dolerite Assoc. with arsenopyrite ± 

free gold. 

Vähäjoki 4 10.5 0.2 0.03 0.17 Mafic tuffite, 

marl 

Assoc. with pyrite, cobaltite 

and arsenopyrite 

nr Not reported in resource estimate, but analysed drill intercepts indicate that the deposit contains, at least in 

parts, several g/t gold (if Cu reported) or 0.1−2% copper (if Au reported). 

1 All host rocks are metamorphosed; hence, the prefix meta is implied but omitted. ‘Intermed tuffite’ and ‘phyllite’ 

define a sequence varying from volcanic to clastic-dominated types of fine-grained, schistose rock. 

2 Four or five ore bodies known, some probably with higher gold and lower base metal grades, but only one with 

a reported resource estimate. 

3 Only the mined tonnage has been reported; there probably are resources at depth, but their volume is unknown. 

4 Also contains 39.4% Fe. 


Table 2. Selected, potentially significant gold (± base metal) occurrences without a resource estimate in the Central 

Lapland greenstone belt (CLGB) and Peräpohja schist belt (PSB). 

Name Best section Host rocks Siting of gold Reference 

CLGB 

Aakenusvaara 

Harrilommol 

Kellolaki 

20 m at 6.0 g/t Au, 0.1% Cu; 

6.4 m at 7.3 g/t Au, 0.05% Cu 

3 m at 5.0 g/t Au; 

12 m at 0.51 g/t Au, 0.16% Cu 

5 m at 10.00 g/t Au; 

5 m at 7.46 g/t Au 

Albitised phyllite Similar to Saattopora? Lahtinen et al., 

unpublished report 

2005) 

Albitised phyllite Similar to Saattopora Korvuo (1997) 

(Table 1)? 

Mafic volc. rocks Native gold assoc. Talikka & Eilu (2011) 

with pyrite? 

Kerolaki 1 m at 12.6 g/t Au Chert Native gold inclusions 

in arsenopyrite; also 

free gold? 

Kiimakuusikko 

Kiimalaki 

Muusanlammit 

Naakenavaara 

Palolaki 

3.45 m at 3.94 g/t Au; 

grab samples up to: 3.82 g/t 

Au, 954 g/t Ag, 0.36% Cu, 

8.09% Pb, 0.42% Zn, 1.97% Sb 

10.6 m at 4.86 g/t Au; 

11.7 m at 4.5 g/t Au 

4.8 m at 1.0% Cu; 

several 1.5 m sections at 

2–7 g/t Au and 5–14 g/t Ag. 

1 m at 1–10 g/t Au; 

15 m at 0.3% Cu 

1 m at 1.6 g/t Au; 

1 m at 1.1 g/t Au, 1.3 g/t Pd, 

0.37 g/t Pt 

Albitised qtzfsp-porphyry 

Albitised qtzfsp-porphyry 

Phyllite, 

intermed. tuffite 

Native gold assoc. 

with pyrite? 

Native gold assoc. 

with pyrite? 

Hulkki et al. (2010) 

Talikka & Eilu (2011) 

Talikka & Eilu (2011) 

Not reported Reino 1976, 

unpublished report, 

Outokumpu Mining 

Oy 

Albitised phylite Free native assoc. 

with gangue and 

sulphides 

Keinänen (2002) 

Intermed. tuffite Not reported Hulkki (2002), Hulkki 

et al. (2010) 

Pikku-Mustavaara 5 m at 2.8 g/t Au, 0.3% Cu Albitised phylite Free native assoc. 

with sulphides 

Ruosselkä 

Sukseton 

Tuongankuusikko 

7 m at 13.7 g/t Au; 

6 m at 4.8 g/t Au 

4.6 m at 2.8 g/t Au; 6.48 m at 

0.35 g/t Au, 0.61% Cu 

28 m at 0.41 g/t Au, 1.36% Cu, 

0.14% Ni; 

1 m at 1–4 g/t Au 

Phyllite, Mafic 

volc. rocks 

Intermed. tuffite 

Free native assoc. 


sulphides 



arsenopyrite 

Keinänen (1990) 

Pulkkinen et al. 

(2005) 

Korkalo (2006) 

Phyllite Not reported Korkalo (2006) 

PSB 

South Rompas 6 m at 617 g/t Au Mafic volc. rocks, 

Calc-silicate 

rocks 

North Rompas 1.40 m at 2529 g/t Au, 5.1% 

U 3 O 8 (channel sampling) 

Mafic volc. rocks, 

Calc-silicate 

rocks 


with uraninite 


with uraninite 

www. 

mawsonresources. 

com 

www. 

mawsonresources. 

com 


line from Ladoga to Lofoten was accompanied 

by the formation of north-west- and north-easttrending 

rift basins (Saverikko 1990) and injection 

of 2.1 Ga dyke swarms parallel to these 

(Vuollo 1994). 

Rifting culminated in mafic and ultramafic 

volcanism and the formation of oceanic crust 

at c. 1.97 Ga. This is indicated by the extensive 

komatiitic and basaltic lavas of the Kittilä 

Group of the CLGB (Figs. 3 and 4). The 1.97 Ga 

stage also included deposition of shallow to deep 

marine sediments, the latter indicating the most 

extensive rifting within Fennoscandia. Fragments 

of oceanic crust were subsequently emplaced 

back onto the Karelian craton in Finland, 

as indicated by the Nuttio ophiolites in central 

Finnish Lapland and the Jormua and Outokumpu 

ophiolites farther south (Kontinen 1987, Sorjonen-Ward 

et al. 1997, Lehtonen et al. 1998). 

In northern Finland, pelitic rocks in the Lapland 

Granulite Belt were deposited after 1.94 Ga 

(Tuisku & Huhma 2006). In central Lapland, 

the Kittilä Group greenstones are overlain by 

intermediate to felsic volcanic and terrestial 

sedimentary rocks. Regionally, they exhibit 

considerable variation in lithological composition 

due to partly rapid changes from volcanic 

to sedimentary dominated facies. Within the 

CLGB, these rocks are mainly represented by 

the Kumpu Group (Lehtonen et al. 1998) and 

by the Paakkola Group in the Peräpohja area 

(Perttunen & Vaasjoki 2001). The molasse-like 

conglomerates and quartzites comprising the 

Kumpu Group were deposited in deltaic and 

fluvial fan environments after 1913 Ma and before 

c. 1880 Ma (Rastas et al. 2001). 

Palaeoproterozoic intrusive 

magmatism 

Early rifting and layered intrusions 

The 2.50–2.44 Ga rifting event, possibly related 

to a major mantle plume, is indicated by 

the intrusion of numerous layered mafic igneous 

complexes and associated silicic intrusions 

in northern Fennoscandia (Alapieti et al. 1990, 

Lauri et al. 2012a). Most of the intrusions are 

located along the margin of the Archaean domains, 

either at the boundary against the Proterozoic 

supracrustal sequence, totally enclosed 

by the Archaean granitoids, or enclosed by a 

Protero zoic supracrustal sequence. Most of the 

intrusions define the west-trending Tornio– 

Näränkävaara belt of layered intrusions (Iljina 

& Hanski 2005). The rest of the intrusions are in 

north-western Russia, central Finnish Lapland 

and north-western Finland. 

Mafic dykes 

Mafic dykes are locally abundant in northern 

Finland, and show a variable strike, degree of 

alteration and metamorphic recrystallisation 

which, with age dating, indicate multiple igneous 

episodes. Albite diabase (a term commonly 

used in Finland and Sweden for any albitised 

dolerite) is a characteristic type of intrusion that 

forms up to 200 m thick sills. They commonly 

have a coarse-grained central part dominated 

by albitic plagioclase and constitute laterally 

extensive, highly magnetic units. In northern 

Finland, albite diabases, both sills and dykes, 

form age groups of 2.2, 2.13, 2.05 and 2.0 Ga 

(Vuollo 1994, Lehtonen et al. 1998, Perttunen & 

Vaasjoki 2001, Rastas et al. 2001, Figs. 4 and 5). 

These ages also reflect extrusive magmatism in 

the region. The dykes vary in width from less 

than 1 m to one kilometre. Nearly all show internal 

differentiation and igneous textures but 

consist of metamorphic and altered mineral assemblages 

(carbonate, sericite, epidote, biotite 

and scapolite). In areas with greenschist facies 

regional metamorphism they are commonly surrounded 

by albitised and carbonated country 

rocks (Eilu 1994). 

Granitoids 

A major part of the bedrock in northern Finland 

is composed of various types of granitoid rocks. 

A conspicuous feature in the bedrock map is the 

Central Lapland Granitoid Complex (CLGC), 

which lies south of the Central Lapland Green 


stone Belt (CLGB). The CLGC is geologically 

not as well known as the surrounding supracrustal 

belts, but recent data suggest that the complex 

hosts several granitoid suites that range in age 

from >2.1 Ga to 1.76 Ga (Lauri et al. 2012b). 

The classification of granitoid suites used in 

Sweden (see Bergman et al. 2007) thus seems 

to be only partly applicable to the CLGC. Isotope 

geochemical data (Huhma 1986, Ahtonen 

et al. 2007) suggest that the CLGC has a strong 

Archaean source component. However, no Archaean 

rocks have so far been found within the 

complex. The oldest, >2.1 Ga granitoids are situated 

at the north-eastern margin of the complex, 

adjacent to the CLGB, forming a 150 km long 

line of intrusions with approximately similar 

ages (Lauri et al. 2012b). The central parts of the 

CLGC contain deformed granitoids with ages 

of 1.85 Ga (Ahtonen et al. 2007). Even older, 

c. 1.99 Ga, heavily deformed porphyritic granites 

are found within the supracrustal Peräpohja 

belt in the south (J.P. Ranta, unpublished). In 

the Lapland Granulite Belt, arc-related rocks of 

the norite-enderbite series intruded the supracrustal 

sequence at 1920–1905 Ma (Tuisku & 

Huhma 2006). 

A major suite of c. 1.88–1.86 Ga calc-alkaline 

granitoids is known in both Sweden and 

western Finnish Lapland. The name Haparanda 

Suite was originally assigned to intrusions in 

south-eastern Norrbotten, Sweden (Ödman et 

al. 1949). Later, it was extended to comprise petrographically 

similar rocks in northern Norrbotten 

and Finland (Ödman 1957, Hiltunen 1982). 

These intrusions are medium- to coarse-grained, 

even-grained, moderately to intensely deformed 

grey tonalites and granodiorites, which are associated 

with gabbros, diorites and rare true granites 

(Ödman 1957). Compositional variations 

are not prominent in individual intrusions, and 

the variation from intermediate to felsic types 

can mainly be seen between separate intrusive 

bodies. The geochemical signature of the 

Haparanda suite is typical for ‘volcanic arc granitoids’ 

with low Rb, Y and Nb contents (Mellqvist 

et al. 2003). They define a calc alkaline trend 

and are metaluminous to slightly peraluminous. 

An age range of 1.89–1.86 Ga has been defined 

for the suite in the western parts of northern Finland 

(Huhma 1986, Perttunen & Vaasjoki 2001, 

Rastas et al. 2001, Väänänen & Lehtonen 2001, 

Figs. 4 and 5). The compositional range and the 

chemical characteristics of the Haparanda Suite 

are very similar to that of the arc-related volcanic 

rocks in northern Sweden. Thus, the Haparanda 

Suite intrusions are regarded as comagmatic 

with extrusive phases of the early Svecofennian 

arc magmatism. This is supported by their calcalkaline 

character (Bergman et al. 2001) and also 

by the contemporaneity with subduction in the 

shield (Lahtinen et al. 2005). 

The north-western and south-eastern corners 

of the CLGC host crustally derived, leucocratic 

microcline granites with ages of 1.81 Ga 

(Väänänen & Lehtonen 2001, Ahtonen et al. 

2007, Lauri et al. 2012b). These are abundant 

especially in the south-eastern part of the complex, 

where they seem to be limited to the extent 

of the Archaean Pudasjärvi complex underneath 

the Palaeoproterozoic cover. In the central part 

of the CLGC a suite of mantle-derived, appinitic 

rocks, ranging in composition from quartz 

diorites to syenites, has an age of c. 1796 Ma 

(Väänänen 2004, Ahtonen et al. 2007). The main 

phase of the CLGC seems to be constrained between 

1.79–1.76 Ga (Ahtonen et al. 2007, Lauri 

et al. 2012b). Abundant granites intruded the 

older rock types at this stage. The granites vary 

from deformed, migmatitic varieties to crosscutting, 

undeformed types. The southern margin 

of the CLGC seems to be mainly composed 

of 1.77 Ga, pink, even-grained granite that has 

an exceptionally high Th/U ratio (J.P. Ranta, 

unpublished). Despite the similar age these granites 

are different from the Nattanen-type granites 

in the northern part of the CLGB that occur 

as postcollisional, discordant stocks (Heilimo et 

al. 2009). It seems that the tectonic regime was 

still mainly compressional in the southern part 

of the CLGC whereas the post-tectonic stage was 


already reached in the northern part. The last 

phase of granitic magmatism comprises tourmaline- 

and beryl-bearing pegmatites that occur 

as dykes and small intrusions at the southern 

parts of the CLGC. The age of the pegmatites is 

uncertain. However, they sharply cross-cut the 

1.77 Ga, Th-rich granites and are thus younger 

(J.P. Ranta, unpublished). 

Palaeoproterozoic deformation 

and metamorphism 

The Palaeoproterozoic rocks in the northern part 

of the Fennoscandian Shield have undergone 

several phases of deformation and metamorphism. 

Metamorphic grades vary from lowergreenschist 

in the CLGB to granulite facies in 

the Lapland Granulite Belt. 

A sequence of ductile deformation events in 

the CLGB is reported in Hölttä et al. (2007) 

and Patison (2007) and references therein. The 

main deformation features relate to thrusting 

events at the margins of the CLGB. North- to 

north-east-directed thrusting in the southern 

margin was driven by the Svecofennian orogenic 

events and south-west-directed thrusting 

of the Lapland Granulite Belt in the north by 

collision of the Kola and Karelian cratons. It is 

currently unclear if these events were contemporaneous 

or successive. Clear overprinting deformation 

features of these thrusting events are 

lacking, therefore they are generally referred to 

as the D1–2 stage (e.g. Patison 2007). The earliest 

detected foliation (S1) is bedding-parallel 

and can locally be seen in F2 fold hinges and as 

inclusion trails in andalusite, garnet and staurolite 

porphyroblasts. The main deformation features 

consist of flat-lying to gently-dipping S2 

foliation and recumbent or reclined F3 folding. 

The D1–2 structures are overprinted by sets of 

D3 structures consisting of F3 folding and late 

shear zones. The orientation of F3 folds is highly 

variable with east and north striking axial 

traces dominating. The dips vary from horizontal 

through moderately dipping to vertical. The 

ductile deformation features are overprinted by 

brittle faulting related to the latest deformation 

stage D4. 

The north- to north-east-directed thrusting 

during the D1–2 stage resulted in the development 

of two major thrust zones: the Sirkka 

and Venejoki thrust zones (Fig. 3). The Sirkka 

thrust zone is a rheological boundary between 

the Savu koski Group volcano-sedimentary sequence 

in the south and the Kittilä Group in 

the north, and it hosts numerous gold deposits 

and occurrences. It consists of a series of closelyspaced, 

south-dipping thrusts, vertical to subvertical 

shear zone segments and, based on seismic 

data, it dips at about 40 degrees to the south 

reaching a depth of at least 9 km (Patison et al. 

2006). The D3 stage resulted in the development 

of a set of north to north-east striking strike-slip 

shear zones which intersect and, in some places, 

displace the early thrust zones. A number of 

gold occurrences are spatially correlated to these 

structures and the largest known gold deposit, 

Suurikuusikko, is hosted by one of such structures. 

There are also clear indications of reactivation 

of the early thrust structures during D3. 

Abrupt changes in metamorphic grade are associated 

with D3 shear zones suggesting that they 

were active after the peak of the metamorphism. 

Direct age data on the deformation and 

metamorphism is limited. The south-west directed 

thrusting of the Lapland Granulite belt 

took place in 1.91–1.88 Ga (Tuisku & Huhma 

2006) and can be considered as the maximum 

age for the D1–2 stage. The Haparanda suite 

magmatism during 1.89–1.86 Ga is considered 

to be contemporaneous with D1–2 suggesting 

that the minimum age for the D1–2 is around 

1.86 Ga. A minimum age for the D3 deformation 

is given by post-collisional 1.77 Ga Nattanen-type 

granites. This is also the maximum age 

for D4. The maximum age of D3 is unknown, 

but is very likely around 1.86 Ga. The regional 

metamorphic peak was reached during the 

D1–2 stage. 

The metamorphic grade is mainly of low to 

intermediate-pressure type, from lower green 


schist to upper amphibolite facies. Granulite 

facies rocks are only of minor importance, except 

in northernmost Finland and the Kola Peninsula 

within the arcuate Lapland Granulite Belt 

(Fig. 1). In central Finnish Lapland, the following 

metamorphic zones have been mapped 

(Hölttä et al. 2007): 

I) Granulite facies migmatitic amphibolites 

south of the Lapland Granulite Belt. 

II) High pressure mid-amphibolite facies 

rocks south of zone I, characterised by garnet-kyanite-biotite-muscovite 

assemblages 

with local migmatisation in metapelites, 

and garnet-hornblende-plagioclase assemblages 

in mafic rocks. 

III) Low-pressure mid-amphibolite facies rocks 

south of zone II, with garnet-andalusitestaurolite-chlorite-muscovite 

assemblages 

with retrograde chloritoid and kyanite in 

metapelites, and hornblende-plagioclasequartz 

± garnet in metabasites. 

IV) Greenschist facies rocks of the CLGB, with 

fine-grained white mica-chlorite-biotitealbite-quartz 

in metapelites, and actinolite-albite-chlorite-epidote-carbonate 

in 

metabasites. 

V) Prograde metamorphism south of zone IV 

from lower-amphibolite (andalusite-kyanite-staurolite-muscovite-chlorite 

± chloritoid 

schists), to mid-amphibolite facies 

kyanite-andalusite-staurolite-biotite-muscovite 

gneisses, and upper amphibolite facies 

garnet-sillimanite-biotite gneisses. 

VI) Amphibolite facies pluton-derived metamorphism 

related to heat flow from central 

and western Lapland granitoids. 

The present structural geometry shows an inverted 

gradient where pressure and temperature 

increase upwards in the present tectonostratigraphy 

from greenschist facies in zone IV 

through garnet-andalusite-staurolite grade in 

zone III and garnet-kyanite grade amphibolite 

facies in zone II to granulite facies in zone I. The 

inverted gradient could be explained by crustal 

thickening caused by overthrusting of the hot 

granulite complex onto the lower grade rocks. 

Metamorphism in the Lapland Granulite Belt 

occurred at 1.91–1.88 Ga (Tuisku & Huhma 

2006), but the present metamorphic structure 

in central Finnish Lapland may record later, 

postmetamorphic thrusting and folding events 

(Hölttä et al. 2007). 

Epigenetic gold deposits in northern Finland 

Pasi Eilu & Tero Niiranen, Geological Survey of Finland 

Epigenetic gold deposits in northern Finland 

have an extensive variation in the style of mineralisation, 

alteration, metal association and 

host rock. Most deposits and occurrences so far 

discovered are in the Palaeoproterozoic Central 

Lapland Greenstone Belt and the Kuusamo 

and Peräpohja schist belts, whereas only a few 

are known from the Neoarchaean greenstones 

(Fig. 7). Due to their variable and overlapping 

features (Tables 1 and 2), several genetic types 

have been proposed for these occurrences (e.g. 

Eilu & Pankka 2009, Eilu et al. 2012a, b, Kyläkoski 

et al. 2012b). Here, we only discuss deposit 

types detected in the area covered by the present 

field excursion. 

Many parameters in the north Finland gold 

occurrences are similar especially to IOCG and 

orogenic gold styles of mineralisation. Features 

suggesting orogenic gold mineralisation (sensu 

Groves 1993) include: 1) proximal to distal carbonatisation 

and proximal sericitisation or biotitisation, 

2) PT conditions at 300–500 °C and 

1–3 kbar, 3) pyrite, pyrrhotite and arsenopyrite 

as the main sulphides, 4) consistent enrichment 


25°E 30°E 

66°N 67°N 68°N 

Kittilä 

Rovaniemi 

Sodankylä 

Kuusamo 

0 25 50 km 

Devonian alkaline igneous rocks 

Palaeoproterozoic rocks (2.50-1.75 Ga) 

Volcanic rocks (c. 1.96-1.75 Ga) 

Supracrustal rocks, predominantly 

sedimentary rocks (1.96-1.75 Ga) 

Intrusive rocks, predominantly 

granitoids (1.96-1.75 Ga) 

Supracrustal rocks, predominantly mafic to ultramafic 

volcanic rocks and sedimentary rocks (2.50-1.96 Ga) 

Intrusive rocks, predominantly mafic 

and ultramafic (2.50-1.96 Ga) 


Intrusive rocks, orthogneiss, migmatitic 

gneiss (c. 3.20-2.50 Ga and possibly older) 

Supracrustal rocks (c. 3.20-2.75 Ga 

and possibly older) 

Au deposits 

Figure 7. Gold deposits and occurrences shown by drilling in northern Finland (Eilu & Pankka 2009, Hulkki et 

al. 2010, Talikka & Eilu 2011, www.mawsonresources.com). In the immediate vicinity of Rompas, only the S and 

N Rompas and Rajapalot occurrences have been drilled. Geology based on Geological Survey of Finland in-house 

bedrock data base. 


of Ag, Au, As, CO 2 , K, Rb, S, Sb and Te, 5) Au/ 

Ag ratios above 1, 6) low-salinity aqueous fluids, 

7) any primary rock type within the greenstone 

belts may act as host rock and 8) most occurrences 

are in greenschist facies rocks (Eilu et al. 

2007, Hulkki & Keinänen 2007, Patison 2007). 

In several cases, the host rocks have also been 

albitised and carbonatised before gold mineralisation 

(Hulkki & Keinänen 2007, Patison 

2007). This pre-mineralisation alteration has 

prepared the ground for mineralisation as described 

below. 

Similarities to IOCG mineralisation, as the 

deposit category was originally defined by Hitzman 

et al. (1992), occur in a number of gold 

occurrences. These features include: 1) highsalinity 

aqueous-carbonic fluids, 2) multi-stage 

alteration, 3) deposits are enriched in Cu, Co, 

Ag and/or U in addition to Au, and Au is typically 

a subordinate commodity with respect to 

Cu and 4) there are abundant iron oxides in the 

ore. Especially the Kolari magne tite-dominated 

deposits contain many of these features (Niiranen 

et al. 2007). Also many of the gold deposits 

in the Kuusamo, Peräpohja and central 

Lapland belts have some of these features (but 

do not contain iron oxides). However, at least 

the CLGB Au-Cu ± Ni deposits fulfil practically 

all the diagnostic features of the orogenic 

gold category, except the high base metal content 

and indications of medium-salinity fluids. 

These exceptional features have been explained 

by attributing such deposits to the subcategory 

of ‘anomalous metal association’ as defined by 

Goldfarb et al. (2001) for similar deposits at, 

for example, Sabie–Pilgrim’s Rest in South Africa 

and Tennant Creek, Pine Creek and Telfer 

in Australia. 

About 60 epigenetic gold occurrences shown 

by drilling are presently known from the Central 

Lapland Greenstone Belt, and 13 occurrences 

from the Peräpohja schist belt (Fig. 7). Of these, 

the Suurikuusikko deposit (Kittilä Mine, Table 

1) is, by far, the largest deposit, and it is a 

classic example of a gold-only orogenic deposit 

hosted by a north-striking shear zone in lower 

greenschist facies greenstones (Patison 2011). 

Nearly all occurrences in central Lapland 

probably belong to the orogenic category in 

the sense the deposit class is defined by Groves 

(1993) and Goldfarb et al. (2001). For example, 

more than 30 deposits and occurrences shown 

by drilling occur within the Sirkka Thrust Zone 

and subsidiary faults branching from this crustal-scale, 

more than 100 km long structural 

break within the Central Lapland Greenstone 

Belt in Finland (Eilu et al. 2007, 2012b). Locally, 

the two most significant controls of mineralisation 

are structure and rock type; some of the 

ore bodies are hosted by local dilatational sites 

and by the locally most competent lithological 

units, some are at locations with soft and hard 

rock units in contact. For many lodes, part of the 

local control is the intersection of two faults or 

a fault along the boundary between lithological 

units with contrasting competence (Sorjonen- 

Ward et al. 2003, Holma & Keinänen 2007, 

Patison 2007, Saalmann & Niiranen 2010). In 

addition to structure and the primarily competent 

lithological units, a further significant factor 

in locally controlling gold mineralisation is 

the ground preparation by pre-gold alteration: 

pervasive albitisation (± carbonatisation) of tuffite 

and phyllite units and carbonatisation of 

komatiitic units changed these originally soft 

rocks into hard and competent units. During 

the later orogenic stages, these were the locally 

most competent units, and thus provided the 

best sites for local dilation, veining and mineralisation 

(e.g. Grönholm 1999, Saalmann & 

Niiranen 2010). Fluid compositions (Billström 

et al. 2010, Niiranen et al. 2012) suggest variable, 

mixed origins for volatiles and metals with 

no obvious indications of local sources. These 

features are present in both the gold-only and the 

anomalous metal association (typically Au-Cu) 

subtypes. Obvious IOCG-type deposits have 

been detected only at Kolari, in westernmost 

Finnish Lapland in the western margin of the 

Central Lapland Greenstone Belt (Niiranen et 


al. 2007). The IOCG deposits are covered by 

another field excursion of the SGA 2013 congress 

(SWE5) and are not discussed further here. 

Very limited geochronological data are available 

from the deposits. Close to syn-peak metamorphic 

timing has been suggested for most of 

the occurrences in Finland (Mänttäri 1995, Eilu 

et al. 2007). However, based on the structural 

relationships a post-peak metamorphic age for 

most of the deposits in CLGB area is also suggested 

(Patison 2007, Saalmann & Niiranen 

2010, Niiranen et al. 2012). 

One of the possible exceptions to the orogenic 

type of gold mineralisation within the 

Central Lapland Greenstone Belt is represented 

by the Pahtavaara gold deposit. Pahtavaara 

has an anomalous barite-gold association and a 

very high fineness (>99.5% Au) of the gold. Furthermore, 

the geometry of high-grade quartzbarite 

lenses and amphibole rock bodies relative 

to biotite-rich alteration zones is anomalous to 

an orogenic or an IOCG deposit. Pahtavaara 

is described further and discussed in a separate 

section below. A few gold and base metal occurrences, 

such as Riikonkoski, Saattopora Cu 

and Kiimakuusikko (Tables 1 and 2), suggest 

an orogenic gold overprint to syngenetic basemetal 

occurrence. In most cases, however, there 

are no obvious indications of premetamorphic 

mineralisation for gold and base metal occurrences 

within Central Lapland. 

Pahtavaara gold mine 

Nicole Patison, Geological Survey of Western 

Australia 

Pasi Eilu & Tero Niiranen, Geological Survey of 

Finland 

Juhani Ojala, Store Norske Gull AS, Finland 

Pahtavaara is an active gold mine with a total 

in situ size estimate of about 20 tonnes of gold 

(production and resource at the end of 2012, 

Finnish Mining Registry statistics). Initial production 

took place 1996–2000 and the mine was 

reopened in 2003 (Eilu & Pankka 2009). The 

present measured and indicated resources are 

1.274 million tonnes at 2.07 g/t Au and inferred 

resources are 1.482 million tonnes at 1.77 g/t 

Au (www. lapplandgoldminers.com). In total, 

11 400 kg gold from 4.98 million tonnes of ore 

has been produced from the mine (Finnish Mining 

Registry cumulative data). 

The deposit is hosted by an altered komatiitic 

sequence at the eastern part of the Central 

Lapland Greenstone Belt (Figs. 3, 7 and 8). It 

comprises a swarm of subparallel lodes and nearly 

all gold is free native. Lodes are apparently 

folded and they plunge steeply to the west or 

west-south-west. The deposit has many of the 

alteration characteristics of amphibolite-facies 

orogenic gold deposits and an obvious structural 

control, but has an anomalous barite-gold association 

and a very high fineness (>99.5% Au) of 

gold (Kojonen & Johanson 1988, Korkiakoski 

1992). The geom etry of high-grade quartz-barite 

lenses and amphibole rock bodies relative to 

biotite-rich alteration zones is also anomalous, 

as is the δ 13 C of alteration carbonate minerals. 

Pahtavaara is best interpreted as a metamorphosed 

seafloor alteration system with ore lenses 

as either carbonate and barite-bearing cherts 

or quartz-carbonate-barite veins (David Groves, 

pers. comm. 2006). The gold may have been 

introduced later, but its grain size, textural position 

(nearly all is free, native and occurs with 

silicates instead of sulphides) and high fineness 

point to a pre-peak metamorphic timing which 

is highly anomalous for orogenic gold. In addition, 

the interpreted ore zone geom etry is also 

compatible with folding of the syn genetic alteration 

zone and remobilisation of gold and 

the formation of late veins in F2 fold fractures 

(secondary veins on the geology map in Fig. 9) 

or remobilisation and vein formation in a shear 

zone (Fig. 10). 

Geology and hydrothermal alteration 

The following description is extracted from 

Korkiakoski (1992) unless otherwise is indicated. 

The Pahtavaara gold mine is hosted by the 

predominantly pyroclastic Sattasvaara komatiite 


3472000 3476000 3480000 3484000 

7500000 7504000 7508000 

Pahtavaara mining concession 

Public road 

Fault or shear zone 

Savukoski group, Matarakoski formation 

Savukoski group, Sattasvaara formation 

Sodankylä group, Postojoki formation 

Kuusamo group, Möykkelmä formation 

0 2.5 5 km 

Figure 8. Geology around the Pahtavaara gold mine, 

based on the current GTK digital bedrock database. 

complex within the Sattasvaara Formation of the 

Central Lapland Greenstone Belt. There is no reliable 

radiometric age data on the volcanic rocks 

of the Sattasvaara Formation in Finland, but 

one of its branches continues far into northern 

Norway where Krill et al. (1985) have reported 

a Sm-Nd age of 2085±85 Ma from the komatiites. 

The present mineral compositions of the 

least-altered komatiites are serpentine-chloritetremolite-anto 

phyllite and tremolite-antophyllite 

resulting from regional upper-greenschist facies 

metamorphism (Hulkki 1990, Korkiakoski 

1992). The intensely altered rocks consist of 

two heterogeneous and intercalated lithological 

types: (1) biotite schists with talc-carbonate ± pyrite 

± magnetite veins and (2) coarse-grained and 

non-schistose amphibole rocks with associated 

quartz ± barite veins and pods. The ore and the 

intensely altered rocks occur within a discontinuous, 

about 8 km long, generally east-trending 

“skarn” zone characterised by the mineral assemblage 

chlorite-calcite-talc-tremolite ± albite 

(Hulkki 1990, K. Niiranen, pers. comm. 1998). 

The least altered amphibole-chlorite schists 

correspond compositionally to Geluk-type (Korkiakoski 

1992) basaltic komatiites. The original 

komatiitic nature of the altered rocks is indicated 

by (1) the similarity in homogeneous immobile 

element ratios (Al/Ti) compared to those of a less 

altered type, (2) mineralogical and geochemi 


cal gradations between the types and (3) similar 

REE patterns to those of the Sattasvaara komatiites. 

Mass balance calculations have shown that 

biotite schists have been enriched in CO 2 , K, Fe, 

Au, Ba, S, W, Te, Sr and Mn, and depleted in 

Mg, Ca, Co, Si and Zn, accompanied by a 10– 

100 m 

Main ore zone 

Secondary ore 

(quartz and quartz-baryte veins) 

Proximal alteration zone 

(intense biotite ± talc alteration) 

Distal alteration (talc-chlorite 

altered komatiite) 

Outline of A-pit 

Figure 9. Geological map of the Pahtavaara Mine open pit (compiled by N. Patison in 2000). North up. 

F2-related gold lodes 

Dykes at Länsi 

Rigid (competent) rock 

Schistosity 

Gold mineralization 

The Green Fault 

Figure 10. Fold model for the Pahtavaara gold 

deposit. View to the NW. Image courtesy 

Warren Pratt (Geologcal Mapping Ltd) and 

Lappland Goldminers AB. 


30% decrease in net volume. Amphibole rocks 

record a marked increase in volume, with gains 

in Ca, Si, Au, Na, Ba, Te, S, W, Sr and P, and 

losses in CO 2 , Co, Mg, Fe and Zn. 

The two major altered rock types reflect 

two stages of hydrothermal alteration (Fig. 9) 

which, on the basis of textural and geochemical 

evidence, include: (1) earlier biotitisation 

(K alteration) and (2) later amphibole overgrowth 

(Ca-Si alteration). The former has 

been interpreted to have taken place during or 

immediately after the peak of regional metamorphism, 

and during ductile deformation. Its 

distribution was controlled by a combination of 

high permeability in the originally pyroclastic 

komatiites, and north-east-trending deformation 

zones. Later amphibole growth was related 

to the north-north-east-trending shearing resulting 

in the formation of zones of dilation 

into which hydrothermal fluids were focused 

under conditions straddling the brittle-ductile 

transition. Note that this interpretation of timing 

of alteration by Korkiakoski (1992) is in 

contrast to the later suggestions of premetamorphic 

alteration described above. 

Mining 

The gold ore at Pahtavaara forms narrow lodes 

generally 5–10 m wide, that strike almost east– 

west and, in the upper parts at least, dip westwards 

at about 70–80° (Figs. 11 and 12). Presently, 

the ore is mined by sub-level caving. The 

only economically recoverable metal is gold. 

Sulphides are relatively rare, with pyrite being 

the most abundant, comprising about 1% of the 

ore. Magnetite can constitute up to 5–10% of 

the ore grade material, particularly in the biotite 

schists. Gold is free milling and occurs as discrete 

grains that are highly variable in size between 

silicate grains and along fracture surfaces. 

Some 50–60% of gold grains are less than 50 μm 

in diameter. In addition to pyrite and gold, trace 

amounts of chalcopyrite, rutile, chromite, hematite, 

pentlandite, pyrrhotite, violarite, miller 

Z 

Y 

X 

Resource classification 

Measured resources 

Indicated resources 

Inferred resources 

Figure 11. Open pits (grey) and resource blocks, as of 1 January 2013, in the Pahtavaara gold mine. View to the NW. 

Image courtesy Lappland Goldminers AB. 


Lansi 

Karolina 

Z 

Mobydick 

Y 

X 

Whaleback 

Figure 12. Resource blocks 

beyond the past and present 

mining, as of October 

2012, in the Pahtavaara 

gold mine. View to the NW. 

Image courtesy Lappland 

Goldminers AB. 

ite, cubanite, gold, clausthalite and merenskyite 

have been detected in the ore (Hulkki 1990, 

Korkiakoski 1992, Kojonen & Johanson 1988). 

As the gold occurs as free grains, the ore can 

be concentrated using a gravity and a flotation 

circuit, as described on Lappland Goldminers’ 

web site (www.lapplandgoldminers.se): “The ore 

is first crushed and then ground down into a 

1.5 mm grain size. This finely-ground material 

goes through a cyclone, where heavier material 

continues on to a cone separator. Afterwards the 

material continues through a magnetic separator 

and spiral separators before coming out onto the 

concentrating table. The lighter material continues 

after the cyclone to a flotation circuit. 

The final product is three different concentrates: 

gravitation concentrate, middling concentrate 

and flotation concentrate. Concentration has a 

capacity of 1 500 tons of raw ore/day.” 

Saattopora gold mine 

Tero Niiranen, Geological Survey of Finland 

The Saattopora Au(-Cu) deposit is located in 

the western part of the Central Lapland Greenstone 

Belt next to the crustal-scale Sirkka thrust 

zone (Fig. 3). The deposit was discovered in 

1985 by Outokumpu Oyj and was subsequently 

mined 1988–1995 from two open pits and 

underground workings. The total amount of 

gold produced was 6 279 kg, and 5 177 tonnes 

of copper was recovered as a by-product from 

2.163 million tonnes of ore. Mill feed grades 

were 3.29 g/t Au and 0.28% Cu (Lahtinen et al. 

2005, unpublished report, Outokumpu Mining 

Oy). Saattopora is one of several gold deposits 

discovered along the east–west trending 

Sirkka Thrust Zone. However, it is the only deposit 

which has been under full-scale mining. 

The deposit consist of two, roughly east–west 

trending lodes which are hosted by variably altered 

mica schist, phyllite, komatiite, mafic tuff 

and mafic lava of the >2.2 Ga Savukoski Group 

sequence (Fig. 13). The intrusions in the area 

consist of 2.2–2.0 Ga dolerite and c. 2.0 Ga 

felsic porphyry dykes. The former occurs in the 

ore-hosting sequence. 

The deposit consists of north-striking, subvertical 

to vertical, auriferous quartz-carbonate-sulphide 

veins, vein arrays and hydrothermal 

breccias (Fig. 14). Gold occurs as free and 

native gold in association with the sulphides, 

quartz and carbonates. Pyrite and pyrrhotite 

are the main opaque phases, and chalcopyrite, 

gers dorffite, rutile, pentlandite, tucholite, 

urani nite, bismuthite and niccolite com 


7525300 

A’ 

3391900 

3390500 

A 

200 m 

7524600 

A A’ 

230 m 

30 m 

Mafic tuff, phyllite & mafic lava intercalations 

Phyllite, mica schist intercalations 

Komatiite 

Tholeiitic lava 

Shear zone 

Au lodes (1 g/t cut off) 

Figure 13. Simplified geology of the Saattopora deposit 

with 1 g/t Au envelopes. 

prise the minor opaque phases together with 

the gold. Ferrous dolomite and quartz are the 

main gangue minerals. 

The host rock sequence was subject to polyphase 

deformation and metamorphism during 

the Svecofennian orogenic events at 1.91– 

1.79 Ga. The earliest ductile deformation stages, 

D1–2, relate to thrusting from the south, and 

the last, D3, stage in the western part of the 

CLGB relates to thrusting from west or southwest 

(e.g. Hölttä et al. 2007, Patison 2007). The 

regional metamorphic grade at Saattopora is of 

mid-greenschist facies and the peak conditions 

were reached during the D1–2 stage (Hölttä et 

al. 2007). The Saattopora deposit is structurally 

controlled by second or lower-order shear zones 

relating to the Sirkka thrust which was initially 

formed during the north-directed thrusting 

of the D1–2 stage and subsequently reactivated 

during the D3 as a strike-slip shear (Patison 

2007, Saalmann & Niiranen 2010). The auriferous 

veins cut across all the ductile deformation 

features. Excluding late, small-scale brittle 


A 

10 cm 

B 

C 

Figure 14. A. Typical Au-bearing quartz-carbonate-sulphide veins at Saattopora. Completely brittle sub-vertical to 

vertical north–south striking veins cross cut albitised phyllite. The A pit. B. Different alteration stages at Saattopora. 

Intense albitisation in phyllite, overprinted by early carbonate alteration (brown material) which is cross cut by 

Au-bearing veins. Note that albitised phyllite is folded in ductile manner, the early carbonatisation is either folded 

or follows the pre-existing folded foliation. The mineralised veins cut across all the early ductile deformation and 

early alteration in a completely brittle manner. The small-scale folding visible in photo relate to D3 stage. C. Polymict 

hydrothermal breccia in the B pit. Quartz, carbonates, sulphides and gold brecciate the host rocks consisting 

of albitised phyllite, mica schist and mafic volcanic rocks. 

faulting, the veins themselves are undeformed 

(Fig. 14). 

Multi-stage alteration has been detected at 

Saattopora. The earliest alteration is regionalscale 

albitisation which has been folded during 

the D3 and possibly already during the D1–2 

stages (Patison 2007, Saalmann & Niiranen 

2010, Niiranen et al. 2012). The albitised rocks 

are overprinted by carbonatisation which is either 

folded in the D3 stage or follows the F1–2 

foliation folded during the D3 (Fig. 14B). The 

mineralised veins cut across these early alteration 

features as well as all ductile deformation features 

in the area. Other alteration styles reported 

from the Saattopora area are chlorite and talcchlorite 

alteration detected in mafic and ultramafic 

rocks. These may, however, be regional 

features related to the development of thrust and 

shear zones, as they also have been reported from 

well outside the mineralised parts of the Sirkka 

thrust zone (e.g. Saalmann & Niiranen 2010). 

Sericite alteration has also been reported from 

the felsic host rocks. It is, however, unclear how 

it is related to the mineralisation. 

Fluid inclusion data from the mineralised 

quartz-carbonate veins indicate that the mineralising 

fluid was moderately saline (about 9% 

NaCl eq.) aqueous-carbonic fluid and the min 


eralisation took place at 300–350 °C (Niiranen 

et al. 2012). Fluid inclusion data also suggest 

that the mineralisation was most likely due to 

phase separation between the aqueous and carbonic 

phases of the gold-carrying fluid, a feature 

which is further supported by the presence of 

hydrothermal breccias (Fig. 14B). 

The oxygen and carbon isotope values of the Fe 

dolomite in the auriferous veins yield δ 18 O SMOW 

values of 12.19–12.44‰ and δ 13 C PDB values of 

–6.87 to –7.68‰ (Hölttä & Karhu 2001). Using 

fractionation factors of Golyshev et al. (1981) for 

dolomite-H 2 O and a temperature of 300–350 °C 

outlined by the fluid inclusion work, the oxygen 

isotope composition of the mineralising fluid 

range was δ 18 O SMOW = 6.78–8.56‰. 

The age of the mineralisation event in Saattopora 

is somewhat unclear. Mänttäri (1995) suggested 

that the 1907–1885 Ma Pb-Pb age for the 

sulphides in the mineralised veins represent the 

age of the mineralisation. Based on the structural 

relationship between the mineralised veins 

and the regional deformation features, Patison 

(2007) and Niiranen et al. (2012) suggested that 

the mineralisation took place in a late stage of 

the regional D3 deformation or post-dates it. If 

this is true, the 1781±18 Ma U-Pb age for monazite 

and tucholite (Mänttäri 1995) is most likely 

close to the mineralisation age. 

Kittilä gold mine 

(Suurikuusikko deposit) 

Nicole Patison, Geological Survey of Western 

Australia, 

Juhani Ojala, Store Norske Gull AS, Finland 

Pasi Eilu & Tero Niiranen, Geological Survey of 


The orogenic Suurikuusikko gold deposit is 

situated within the Palaeoproterozoic Central 

Lapland Greenstone Belt, approximately 35 km 

north-east of the town of Kittilä in Finnish Lapland 

(Figs. 3, 7 and 15). The host rocks, timing 

of ore formation relative to regional deformation, 

metamorphic grade, alteration assemblages 

present and structurally controlled nature of the 

deposit make it analogous to better known deposits 

in greenstone belts throughout the world 

(e.g. Yilgarn of Australia and Superior Province 

of Canada). At Suurikuusikko, the gold is refractory 

and occurs within arsenopyrite (>70%) 

and arsenian pyrite as lattice-bound gold or submicroscopic 

inclusions. 

A mining operation at Suurikuusikko, the 

Kittilä Mine, started in 2008, then targeting 

a gold resource of 16 million tonnes (2.6 million 

ounces) averaging 5.1 g/t gold (www.agnicoeagle.com). 

Until the end of 2012, 4.1 million 

tonnes of ore was mined and more than 

16 tonnes of gold produced. The present proven 

and probable reserves total approximately 4.8 

million ounces gold from 33 million tonnes 

grading 4.5 g/t Au (Agnico Eagle 2013). Ore 

intersections have very even grade distribution 

due to the ‘disseminated sulphide-like’ nature of 

the ore. Table 3 shows examples of typical ore 

intercepts in drill core. The deposit still is open 

along strike at both ends and at depth. Presently, 

one of the deepest ore-grade intersections (8.5 m 

true width at 4.2 g/t Au) is about 1 370 m below 

the surface (www.agnicoeagle.com). 

Exploration history 

Visible gold was discovered south-south-west of 

Suurikuusikko in a road cut by the Geological 

Survey of Finland (GTK) in 1986 (Härkönen 

& Keinänen 1989, Valkama 2006). Subsequent 

ground-geophysical surveys and geochemical 

survey on till and the bedrock surface lead to 

the identification of the Kiistala Shear Zone 

(KiSZ or ‘Suurikuusikko Trend’), the deposit’s 

host structure. Suurikuusikko was discovered in 

1986 during diamond drilling by GTK. A total 

of 77 diamond drill holes (9 320 m) were completed 

by GTK, outlining a resource of 1.5 million 

tonnes with an average grade of 5.9 g/t Au 

(285 000 ounces of gold) by 1997 (Parkkinen 

1997). In April 1998, the deposit was acquired 

by Riddarhyttan Resources AB and the company’s 

exploration activities increased the resource 

to over 2 million ounces of gold (Bartlett, pers. 


255 000 mE 256 000 mE 257 000 mE 

7 550 000 N 7 560 000 N 

Lake 

Sarkojärvi 

Kuotko 

Riv. Kapsajoki 

7 540 000 N 

Lake 

Hanhimaa 

Lake 

Munajärvi 

79 

Rimpi 

North Roura 

Central Roura 

Suuri 

Etela 

Ketola 

Riv. Rourajoki 

7 530 000 N 

To Sirka 

(Levi) 

7 520 000 N 

Riv. Ser ujoki 

To Kittilä 

Lake 

Rastijärvi 

Lake 

Vesmajärvi 

Kittila 

Rovaniemi 

Granitoid 

Sedimentary rock 

Volcanic rocks 

Iron-bearing tholeiite 

Magnesium-bearing tholeiite 

Other volcanic rock 

Kittila Mine Licence 

Agnico-Eagle Kittila Property 

Open Pit Outline 

5 km 

Finnish Coordinate System 

KKJ Zone 3 


Figure 15. Geology and infrastructure in the vicinity of the Kittilä Mine, as of January 2012 (image available from 

www.agnicoeagle.com). 


comm. 2002). Ore-grade rock was found over a 

five-kilometre strike length of the KiSZ in similar 

structural and stratigraphic positions. Feasibility 

studies began in the winter of 2000. In 

2004, Agnico Eagle Mines Limited acquired a 

14% ownership interest in Riddarhyttan, and 

in 2005 acquired the remaining Riddarhyttan 

shares. In June 2006, a decision was made 

to begin mine development. The Kittilä Mine 

started commercial production in May 2009 

(Figs. 16–18). 

Geology 

Suurikuusikko occurs within greenschist-facies 

metavolcanic rocks of the c. 2.0 Ga Kittilä 

Group (Fig. 15). Geochemical heterogeneity 

among the Kittilä Group rocks has been interpreted 

to indicate that the group is a composite 

of arc terranes and oceanic plateau amalgamated 

during oceanic convergence (Hanski & Huhma 

2005). Significant variations in metamorphic 

grade within the group also suggest that a 

number of distinct lithological elements could 

be present within the area currently mapped as 

the Kittilä Group, and seismic surveys across 

central Lapland indicate a number of distinct 

crustal blocks (Patison et al. 2006). The maximum 

current thickness of the Kittilä Group is 

between six and seven kilometres (Luosto et al. 

1989) in the Kittilä Mine area. 

The ore is mostly hosted by a transitional 

formation between two thick (several hundred 

metres) mafic lava sequences (Figs. 19–22). The 

north- to north-north-east-trending host structure 

(KiSZ) for the deposit coincides with this 

contact between the western and eastern lava 

packages. In the area of the ‘Main’ ore zone, 

host rocks change from mafic pillow and massive 

lavas west of the mineralised zones to mafic 

transitional to intermediate lavas (andesite flows 

of Powell, pers. comm. 2001) and minor pyroclastic 

material within the mineralised zones. 

Graphitic sedimentary intercalations containing 

chert, argillitic material and BIF occur within 

the mafic volcanic sequence at the eastern margin 

of the mineralised zones, followed farther 

east by mafic lava packages and ultramafic volcanic 

rocks. The extent of intermediate and felsic 

rock compositions in the deposit is still under 

investigation. The variation in appearance (and 

hence the logging and mapping terminology for 

rock compositions used here) may also result 

Table 3. Kittilä Mine. Examples of gold intercepts from drill core. 

Zone Drill hole number Mineralised section length (m) Averaged grade of section (g/t Au) 

Ketola 02114 6.40 4.20 

Ketola 02107 7.00 11.10 

Ketola 02107 3.20 7.10 

Ketola 02104 10.70 4.00 

Etelä R407 7.00 7.50 

Etelä 01802 5.60 8.60 

Etelä 02039 8.10 9.50 

Main R473 14.00 10.40 


Main 00717 14.30 10.60 








Figure 16. Wallrock transport from the open pit Kittilä Mine. Photo courtesy Agnico Eagle Mines. 

Figure 17. From the bottom of the open pit at the Kittilä Mine. Photo courtesy Agnico Eagle Mines. 


Figure 18. Loading ore. Underground operations at the Kittilä Mine. Photo courtesy of Agnico Eagle Mines. 

7534600N 

7535000N 7535400N 7535800N 7536200N 7536600N 

2558200E 

2558600E 

2559000E 

2558200E 

2558600E 

2559000E 

Figure 19. Total magnetic field (left) and electromagnetic (slingram out-of-phase, right) images for the southern 

part of the Suurikuusikko area, in 200 m grid. The blue colour represents magnetic lows and conductivity highs in 

figures on left and right, respectively. Names refer to individual ore zones. Coordinates according to the Finnish 

national KKJ grid. Image by Riddarhyttan Resources AB. 


2 558 450 mE 

2 558 500 mE 2 558 550 mE 

7 535 550 mN 

Overburden 

Mafic volcanic rock 

Mafic pyroclastic rock 

Black chert/silicified sediments 

Volcanoclastic and sedimentary rock 

Mafic dyke 

Graphitic fault zone 

Main shear 

Minor shear 

7 535 400 mN 

7 535 450 mN 

7 535 500 mN 

0 

5 

10 

20 

metres 

Figure 20. Geological map of the recently stripped Etelä Pit area at the Kittilä Mine. This area is expected to be visited 

during the field trip. Grid 50 m. Coordinates according to Finnish national KKJ grid. Image courtesy of Agnico 

Eagle Mines. 


from progressive alteration of mafic rocks. Most 

ore is hosted by mafic rocks and rocks mapped 

as intermediate or felsic volcanic rocks. Metasedimentary 

units including BIF typically have 

low to no gold grade, and the ultramafic rocks 

are unmineralised. 

Orogenic events relating to CLGB development 

generated several phases of deformation. 

The earliest deformation phases preserved 

(D1– D2) involved roughly synchronous northto 

north-north-east- and south- to south-westdirected 

thrusting at the southern and northeastern 

margins of the CLGB (Ward et al. 1989). 

North-west-, north-, and north-east-trending 

D3 strike-slip shear zones, including the KiSZ 

hosting the Suurikuusikko deposit, cut early 

folding and thrusting, but may also reflect reactivation 

of older structures. Post-D3 events are 

limited to brittle, low-displacement faults. 

Representative structural data for the deposit 

are shown in Figure 23. The Kiistala Shear Zone 

(Suurikuusikko Trend) has a strike length of at 

W 

E 

Schematic vertical section 

of pre-deformation stratigraphy 

50 m 

Ultramafic volcanic rocks 

Mafic lava (massive and pyroclastic) 

Mafic lava (pillow) 

Mafic pyroclastic rock 

Mafic intrusion 

Mafic–intermediate (transitional 

composition) lavas and pyroclastic rocks 

Felsic volcanic rock 

Volcano-sedimentary (reworked) rock 

BIF 

Chert 

Argillite 

Lapilli 

Stratigraphic facing 

Hole trace 

Figure 21. Simplified vertical section 

across the Suurikuusikko 

deposit (Kittilä Mine), by Nicole 

Patison (2004), originally published 

in Eilu & Weihed (2005). 


Figure 22. Dark graphitic shear 

zone hosting the ore on right, pale 

grey mafic volcanic rock on left. 

Main open pit at the Kittilä Mine. 

View to the north. Photo courtesy 

Agnico Eagle Mines. 

A 

N 

B 

N 

C 

N 

N=8 

N=78 

N 

D 

N=52 N=14 

Figure 23. These stereoplots 

show the orientations of deformation 

features observed 

for Suurikuusikko (ordered 

from oldest to youngest). 

A. Bedding (dots), the trend of 

the typical regional foliation 

(lines) formed prior to movements 

of the KiSZ related to 

mineralisation, and fold axes 

measured in the deposit area 

(stars). B. C. Orientation of 

the ‘graphitic’ shear zones associated 

with the KFZ and ore 

zones. D. Common orientation 

of post-mineralisation faults. 

Lower hemisphere projections 

on equal area nets. Plots after 

Patison (2001) and Patison et 

al. (2006). 


least 25 km (Fig. 15). The dip of this shear zone 

in the Suurikuusikko area is steeply east to subvertical 

(Figs. 23B and 23C). Known mineralisation 

occurs within north-trending and less 

frequently north-east-trending shear zone segments 

(e.g. Ketola ore bodies, Fig. 19) . The KiSZ 

is a complex structure, recording several phases 

of movement. Most deformation has occurred 

by flattening accompanied by some strike-slip 

movement. Aeromagnetic images of the KiSZ 

indicate early sinistral strike-slip movement 

along the zone. Immediately above the widest 

mineralised zones, late dextral strike-slip movements 

are recorded on shear planes bounding 

mineralised zones. It is not yet clear if the timing 

of mineralisation coincides with a combination 

of early and late shearing or only to the later 

dextral shearing event which now delineates the 

limits of gold mineralisation in most ore zones. 

An apparent correlation exists between points of 

more intense shearing within the KiSZ and the 

amount of gold present in host rocks. 

The envelopes of ore bodies strike north and 

have a moderate northerly plunge (Fig. 24). The 

control on the northerly plunge is not completely 

resolved: factors to be explored include the role 

of intersections between multiple shear planes, 

and of intersections of depositional surfaces and 

shear planes. The orientation of regional fold 

axes (similar to axes in Fig. 23A) may also have 

a role in determining favourable sites for mineralisation 

during shearing. Sulphides and host 

rocks show some evidence for deformation relating 

to post-mineralisation movements on host 

shear planes. Post-mineralisation brittle faults 

cross-cut mineralised zones but are not known 

to cause significant displacement of ore lenses. 

Much of the geometry of shear structures, formation 

of many shear zones and their complex 

kinematic history could be explained by flattening 

of a layered stratigraphy. During the same 

deformation, several types of layer-normal compression 

structures can form in layered systems. 

According to Cosgrove (2007, Fig. 11), the first 

structures to form are boudins which fail by the 

formation of extensional fractures, and with progressive 

deformation the deflection of the layered 

matrix into the neck region between separating 

boudins generate a series of interlocking pinch 

and swell structures (Figs. 25 and 26). 

(m) 

0 

S 

Ketola Etela Suuri Roura Rimpi 

N 

–250 

–500 

OPEN 

–750 

OPEN 

Rimpi Trend 

–1000 

–1250 

–1500 

OPEN 

OPEN 

Suuri Trend 

Roura Trend 

OPEN 

OPE 

N 

7535000 N 7536000 N 7537000 N 7538000 N 7539000 N 

2012 Mineral Reserve 

2012 Mineral Resource 

Mined out areas 

Underground mine workings 

Planned Rimpi production ramp 

2013 Drilling target areas 

Open pit outline 

1000 m 


KKJ Zone 3 

Figure 24. Kittilä Mine long section as of December 

2012. View towards west. Image available at www. 

agnicoeagle.com. 


A 

B 

Figure 25. A. Colour photo from Etelä pit at Kittilä Mine, August 27th 2011. B. Structural interpretation of the same 

area. Photograph shows chert boudins, and both sinistral and dextral shear zones. Marker pen for scale. North to 

right. Photo and interpretation Juhani Ojala. 

Figure 26. An underground 3D image across ore. Distance between inner green markings is 5.5 metres. Image courtesy 

Agnico Eagle Mines. 

Alteration in and around the deposit appears 

typical for deposits of this type. Visually, intense 

carbonate and albite alteration are associated with 

gold-rich arsenopyrite and pyrite. Albite occurs 

as a matrix overprint that typically extends from 

a few tens of metres to up to 100 m into barren 

rock, and as brecciating micro veinlets. Barren 

carbonate alteration includes distal calcite veins, 

and dolomite-ankerite veins and infilling tectonic 

or hydrothermal breccia within proximal alteration 

zones and ore lodes, respectively. Table 4 

presents a summary of progressive alteration of 

mafic pillow lavas; missing in this table is amorphous 

carbon. The abundance of this ‘graphitic’ 

carbon correlates with the intense shearing that 

bounds most mineralised zones. The presence of 

such carbon suggests extremely reducing fluid 

conditions during shearing and possibly mineralisation. 

Gold-bearing sulphides commonly nucleated 

on shear planes, stylolitic cleavage, and 

on fractures bearing amorphous carbon (Fig. 27). 

Carbon isotope data indicate that this material is 

sourced from carbon-rich sediments within the 

host sequence (Patison, unpublished data). Ar 


Table 4. Alteration minerals present in progressively altered mafic pillow lava. The data used are modal weight percentages 

of mineral phases calculated using Mineral Liberation Analysis data collected at GTK. The thickness of line 

is proportional to the relative volume of each mineral present in the sample. A mafic pillow lava sequence was used 

for this example to ensure a constant rock type, although pillow lavas do not host significant volumes of ore. The 

‘felsic’ mineralised sample is included for comparison and may, in fact, be the most altered end-member of a mafic 

rock alteration sequence. 

Alteration Zone Distal Intermediate Proximal / Ore Ore Ore 

Rock type Mafic pillow lava Mafic pillow lava Mafic pillow lava Mafic pillow lava ‘Felsic’ 

Sample F5-001 F5-007 00404 189.90 F5-003 F5-002 

Silicates 

Actinolite 

▬▬▬ 

Epidote 

▬▬▬▬▬ 

Titanite ---------------- --------------- ------------- 

Chlorite ▬▬ ▬▬▬ ---------------- ▬▬▬ 

Muscovite ------------------ ------------- ------------ 

Albite ▬▬▬ ▬▬ ▬▬ ▬ 

Microcline --------------- ---------------- ------------ 

Plagioclase 

Clinopyroxene 

(matrix) 

▬▬▬ 

========= 

Quartz ------------------ −−−−−−−−− ---------------- ------------- ------------ 

Carbonates 

Calcite ======== −−−−−−−−− ▬▬▬▬ 

Dolomite ▬▬▬ - - - - - - - - ▬▬▬▬ 

Phosphates 

Apatite - - - - - - - - - - - - - - - - - - - 

Oxides 

Rutile --------------- ------------------ ------------- ------------ 

Sulphides 

Arsenopyrite ========== ======== ======= 

Pyrite −−−−−−−−−− −−−−−−−− ======= 

Pyrrhotite ------------------ ------------- ------------ 

Gold grade (g/t) 0 0 5.16 3.3 8.71 

gillite-rich units intercalated with volcaniclastic 

material have high primary carbon contents, and 

may have been chemically important for localising 

gold-rich phases given the association between 

amorphous carbon and mineralisation. Other alteration 

and ore mineral phases include rutile and 

less abundant sericite, tetrahedrite, chalcopyrite, 

gersdorffite, chalcocite, sphalerite, bornite, chromite, 

galena, talnakhite and Fe-hydroxides (the 

latter produced by weathering) in varying abundances 

(Chernet et al. 2000). 

The gold-rich sulphides appear to have a late 

timing within the paragenetic sequence. The 

majority (71%) of gold occurs within arsenopyrite, 

and visible arsenopyrite is a reliable indication 

of the presence of gold within samples. 

The remaining gold occurs in arsenian pyrite 

(22% of the gold) and infrequently as free gold 

(Kojonen & Johanson 1999). Sub-microscopic 

gold is found as inclusions or solid-solution lattice 

substitutions within arsenopyrite and pyrite 

(Chernet et al. 2000). Gold as inclusions is common 

in pyrite but rare in arsenopyrite (typical 

grain size from

A 

B 

C 

Figure 27. Two back-scattered electron microprobe 

images and one reflected light image of ore samples 

in mafic host rocks. A. Nucleation (or recrystallisation) 

of arsenopyrite in graphitic (black phase) milled zones 

relating to shearing. B. A fractured competent rock 

fragment with arsenopyrite associated with fracture 

infill. A penetrative shear boundary is seen at the edge 

of this mineralised fragment (center of photograph). 

C. The host with abundant fine-grained auriferous 

arsenopyrite-pyrite dissemination and a late, crosscutting 

quartz-carbonate vein. Field of view in A and B 

is 1.5 mm, but 4 cm in C. 

alloys with Ag and Hg (Chernet et al. 2000). 

Rare stibnite veins and amorphous grains contain 

extremely high gold grades and overprint 

the main ore-bearing sulphides. 

Acknowledgements 

Agnico Eagle is gratefully acknowledged for the 

permission to publish the data and all the images. 

The information in this summary reflects 

the opinions of the authors only, unless otherwise 

referenced. The majority of information is 

based on data collected prior to 2005 (during 

the exploration phase of the deposit preceding 

mine development). 

Rompas-Rajapalot gold-uranium 

project, Peräpohja Schist Belt 

Mawson Exploration Team and co-workers 

The Rompas-Rajapalot gold-uranium project is 

located in the Ylitornio municipality of northern 

Finland at 66.45 °N and 24.75 °E, approximately 

50 km west of the Rovaniemi town. The 

initial discovery area, Rompas, was discovered 

by AREVA Resources Finland Oy in September 

2008 as part of regional uranium exploration. 

Limited exploration was undertaken until 

Mawson Resources purchased the exploration 

assets of Areva in 2010. Mawson subsequently 

defined more than 300 bonanza grade gold 

occurrences of vein style mineralisation over a 

6 km strike length. Diamond drilling in 2012 

and early 2013 produced numerous Au-U intersections, 

of which 6 metres at 617 g/t Au remains 

the highlight. Rajapalot is a new grassroots discovery 

made by Mawson, 8 km east of Rompas, 

where a total of 52 outcrop grab samples to date 

average 152.8 g/t gold and range from 0.001 g/t 

to 2 817 g/t gold. 

Mawson holds 833 claims and claim applications 

for 75 340 hectares at the Rompas Project. 

A total of 110 exploration claims that cover a 

surface area of 10 580 hectares and form the core 

claims at Rompas came into legal force on Oc 


tober 15, 2012 (Fig. 28). The presence of European 

Union-defined biodiversity areas (Natura 

2000) means that there is limited drilling access 

in certain parts of the project area. Further applications 

have been made to the relevant Finnish 

granting authorities to allow diamond-drill 

testing of targets within these areas. Approximately 

80% of Mawson’s best gold targets lie 

within Natura 2000 areas. 

We would like to acknowledge the assistance 

of numerous people in this project, including 

present and former staff and consultants 

of Mawson Resources, students and researchers 

from various universities throughout Finland 

and Europe and the GTK in Finland. In addition, 

numerous discussions with visitors to the 

site have aided in reaching the current level of 

understanding of the project. 

To ensure personal safety, please note that 

samples may not be collected without permission 

of Mawson staff as they may contain significant 

uraninite. 

3 370 000 mE 3 380 000 mE 3 390 000 mE 3 400 000 mE 3 410 000 mE 3 420 000 mE 3 430 000 mE 

North Rompas 

7 380 000 mN 

Onkirova 

Central Rompas 

South Rompas 

7 370 000 mN 

Rajapalot area 

Rumavuoma 

7 350 000 mN 

7 360 000 mN 

Mustamaa 

Valtaus hakemus (Mawson Claim Applications) 

Valtaus (Mawson Granted Claims) 

Valtaus (Others Granted Claims) 

10 km 


KKJ Zone 3 

ROMPAS 

Barents 

Sea 

Kola 

Pen. 


Figure 28. Location of Rompas-Rajapalot project and 

Mawson granted claims and claim applications (as at 

April 2013). 

North 

Sea 

Baltic 

Sea 


Regional geology 

The Rompas project lies within the Peräpohja 

Schist Belt (PSB, Figs. 5 and 6), a Palaeoproterozoic 

supracrustal sequence of quartzites, mafic 

volcanic and volcaniclastic rocks, carbonate 

rocks, black shales, mica schists and greywackes 

(Fig. 29). It is generally interpreted as a continental 

rift fill sequence that failed to progress to oceanic 

crust. The metamorphism ranges from mid 

or upper greenschist in the south to amphibolite 

facies with some of the highest grade rocks exposed 

at the Rompas prospect area. The amount 

of strain varies greatly in the PSB. Low strain 

rocks are described well to the south of Rompas 

where vesicles and pillow lavas in mafic rocks 

are preserved. At South Rompas, in contrast, 

the total strain is very high and relic internal 

structure is difficult to identify. Transposition 

of lithologic contacts is observed at both outcrop 

and regional scales (from the interpretation of 

aeromagnetic data). 

Rompas area geology 

The Rompas prospect area (Fig. 29) is dominated 

by a north-trending ridge comprising metabasalt, 

inferred volcaniclastic rocks, carbonate-rich 

rocks and black graphitic metapelites. On the 

ridge crest, these rocks either crop out or are 

covered by thin glacial till (generally less than 

1 m). On either side of the ridge, small lakes, 

peat bogs and thicker till are abundant with isolated 

bedrock outcrops. However, mineralisation 

is known to continue under the deeper till 

cover. The calc-silicate vein-style mineralisation 

at Rompas is nearly all hosted by a metabasalt 

that will be examined on the field trip in various 

locations and in drill core. 

Regional folds, inferred to be related to the 

D2 and D3 deformational events, dominate the 

Rompas area geology. The D1 event is difficult 

to identify, but regional work suggests it is now 

present as transposed isoclinal folds with a high 

temperature foliation parallel or sub-parallel to 

the D2 foliation. The D2 produced upright 

north-striking tight to isoclinal folds at Rompas 

that are in turn folded about upright, open 

to tight east-trending D3 folds. Of significance 

at Rompas is that the D2 foliation is quite variable 

in intensity, and it increases towards South 

Rompas to such an extent that any original basaltic 

rock textures have been destroyed. 

Amphibolite facies metamorphism has accompanied 

the development of the S2 foliation 

with biotite and amphibole (largely hornblende) 

defining the fabric. Biotite is an important part 

of the most foliated metabasalts, providing evidence 

of early potassic alteration. 

Within the metabasalts, variably oriented 

large amphibole grains, which are up to 8 mm 

long, grow across the S2 foliation throughout the 

North and South Rompas prospect areas. These 

may belong to the cummingtonite or anthophyllite 

amphibole groups, in addition to ‘more normal’ 

hornblende compositions. Indeed, some 

samples are found to contain hornblende, cummingtonite 

and anthophyllite. 

A comparison of the geochemical composition 

of the Rompas metabasalts with other mafic 

rocks within the PSB by Mustonen (2012) reveals 

a similarity with the Runkaus Formation, 

the oldest basalt within the Peräpohja stratigraphy 

(Figs. 5 and 6). U-Pb dating of secondary 

titanite from the Runkaus Formation has given 

a minimum age of approximately 2.25 Ga (Huhma 

et al. 1990) implying a similar minimum age 

of the Rompas basalts. Near Rompas, zircons 

have been separated from rocks mapped as the 

Martimo Formation, a graphitic schist inferred 

to occur within the Paakkola Group. 

The dilemma at Rompas is that no unconformity 

has yet been recognised in the sequence 

and that the metamorphic age based on uraninite 

textures apparently synchronous with metamorphism 

(see below) is less than the maximum 

age of the Martimo Formation. The Martimo 

Formation appears to have enjoyed the same 

metamorphic history as the metabasalts. At the 

time of writing, this dilemma remains unsolved. 


3 395 000 mE 

3 400 000 mE 

3 405 000 mE 

3 410 000 mE 

7 370 000 mN 7 375 000 mN 

7 380 000 mN 

Rompas 

trend 

Mica Schist 

(magnetic and non-magnetic) 

Amphibolite 

Magnetic metasediment (mixed Pobearing 

BSH, calc-silicate, quartz) 

Mafic meta-volcanic rock 

(intrudes A + B of Rompas) 

Calc-silicate (including 

mapped skarn rocks) 

Quartzite ± calc-silicate + mica schist 

(including altered quartzite) 

Mafic dykes (magnetic and 

non-magnetic) 

F1 folds 

F2 folds 

F3 folds 

Non- to weakly magnetic granitoid 

Pyroxenite to meta-komatite 

Garnet-mica schist 

Strongly magnetic granitoid 

Tremolite-quartz ± mica schist 

Albite Breccia bodies (structurally hosted) 

Felsic meta-volcanic rock 

Magnetic highs 

Granted Claims 

2 km 


KKJ Zone 3 

Figure 29. Regional geology near the Rompas prospect. The Rompas trend is indicated in the red ellipse. Note the 

isoclinal folding of the F1 hinges about the northerly-trending F2 folds. 


the metabasalt, but to date lack any significant 

Au or U intersections. Thus, wallrock interaction 

with the basalt is inferred to be the key control 

on gold and uraninite formation, although the 

actual mechanisms remain the subject of much 

debate at the time of writing (April 2013). 

The gold itself is of high fineness (>95% Au), 

with minor Te, Ag and Cu recorded (CNRS- 

CREGU, University of Nancy, unpublished research). 

Drilling to 100 m depth has not revealed 

any variation in fineness. Petrographic examination 

by a number of workers agree that the gold 

is paragenetically later than the uraninite, commonly 

occupying cracks within uraninite. Sulphide 

minerals are not commonly directly assobasalt 

basalt 

Mineralisation 

Gold and uranium distribution within the initial 

discovery area at Rompas is nuggety. Thin 

and very high-grade drill intercepts are common 

(Figs. 30 and 31), matching the many hundred 

surface trench exposures of bonanza grades 

found over the 6 km trend. A summary of the 

best intersections is presented in Tables 5 and 6. 

What is clear from the drilling and trenching at 

North and South Rompas is the strong host rock 

control on mineralisation – a distinctive metabasalt. 

Uraninite and gold are found within or 

marginal to carbonate-calcsilicate-quartz veins 

in metabasaltic host rocks. Vein densities in the 

adjacent metasedimentary rocks are similar to 

7 373 850 mN 

3 401 250 mE 3 401 300 mE 

basalt 

3 401 350 mE 3 401 400 mE 3 401 450 mE 

basalt 

ROM0025 

ROM0082 

7 373 800 mN 

7 373 750 mN 

basalt 

TR108535 

ROM0012 ROM0070 

ROM0079 

ROM0069 TR104739 

ROM0080 

ROM0028 

TR107580 

ROM0073+ROM0074 

ROM0071+ 

TR107581 

ROM0072 

ROM0014 

ROM0011 ROM0077 

TR107575 

ROM0037 

TR107577 

TR104738 

TR108534 

TR107574 

ROM0075 

ROM0013 

ROM0017 

ROM0009 

ROM0010 

TR104737 

ROM0015 

107578 

TR104730 

TR107582 

ROM0022 

basalt 

TR104731 

ROM0018 

7 373 700 mN 

ROM0020 

basalt 

ROM0036 

ROM0035 

TR107752 

Trench trace 

Quoted assay interval above cut off 

Drill collar and trace 


Rock chip sample 

>100 

10 to 100 

1 to 10 

ciated with the gold and uraninite. Fine-grained 

pyrrhotite is a ubiquitous trace component of the 

metabasalt, resulting in a stronger IP chargeability 

response than in the adjacent rocks. Traces of 

gold together with fine-grained molybdenite has 

also been observed within the ROM0011 intersection 

(pers. comm. Molnàr and others, GTK). 

Uraninite is the predominant uranium-bearing 

mineral, with two varieties observed in petrographic 

work by CREGU/Nancy researchers. 

Paragenetically late gummite is locally present 

in surface samples occurring between uraninite 

grains. Radiogenic galena is also associated with 

the uraninite. 

Due to the recent discovery history at Rajapalot, 

much less information has been collected on 

this deposit. However, the mineralisation differs 

in that is more sulphidic with strong potassic alteration 

and is predominantly of a disseminated, 

replacement style. Four prospect areas have been 

defined within topographic highs in a predominantly 

swampy area. These areas are the Hirvimaa, 

Palokas, Joki and Rumajärvi prospects 

and located in a 2 × 2 km area within the hinge 

of a complex fold structure in quartzitic and 

basaltic rocks which are geochemically distinct 

from the Rompas area. The style of mineralisation 

in the Hirvimaa and Joki areas is similar 

to Rompas and consists of calc-silicate veins in 

albitised quartzites and basalts, with more pyrite 

and magnetite than observed at Rompas. Mineralisation 

at Palokas and Rumajärvi appears 

3 399 350 mE 3 399 400 mE 3 399 450 mE 3 399 500 mE 3 399 550 mE 

TR108569 

7 378 450 mN 

7 378 400 mN 

7 378 350 mN 

ROM0064 

ROM0067 

TR108570 ROM0046 

ROM0056 

ROM0047 

TR108566 

TR108571 

ROM0048 

TR104742 TR104743b 

ROM0045 

ROM0055 

ROM0043 

TR104742C 

TR107451 

TR10744C 

TR104744 

TR10744B 

TR104745 

TR108564 

ROM0040 

ROM0054 

TR108565 

TR104749 

ROM0042 

TR104746 

TR108563 

ROM0041 

TR107446 

TR107438 

TR108572 

ROM0053 

TR107447 

TR107440 

ROM0049 

TR108562 

ROM0044 

ROM0050 

TR108560 

ROM0052 

TR104754 

TR108924 

ROM0051 

TR108559 

Trench trace 


Drill collar and trace 


Rock chip sample 

>100 

10 to 100 

1 to 10 

to be of a new style and consists of highly altered 

quartzites with albite, carbonate, amphibole, 

sericite and biotite with disseminations 

and stockworks of pyrite. Gold mineralisation 

appears to be disseminated, replacement style, 

within the host rock, with no obvious associated 

calc-silicate veining. 

Table 5. South Rompas drilling intersections. 

HoleID Depth from (m) Depth to (m) Interval (m) Au (g/t) U 3 O 8 (g/t) 

ROM0007 36 37 1 1.6 204 

ROM0008 100 101 1 0.547 16.2 

ROM0009 46 47 1 1.725 43.1 

ROM0010 29 30 1 10.75 367 

ROM0010 49 50 1 0.58 5.6 

ROM0011 7 8 1 22.8 1130 

ROM0011 11 12 1 3540 1770 

ROM0011 12 13 1 137 650 

ROM0011 20.1 21 0.9 0.665 25 

ROM0011 87 88 1 9.69 338 

ROM0011 114.5 115.5 1 0.776 24.4 

ROM0012 17.7 18.8 1.1 6.3 409 

ROM0013 36.3 37.6 1.4 0.556 18.2 

ROM0015 14 15 1 2.51 3.7 

ROM0015 44 45 1 114.5 2830 

ROM0017 15 16 1 0.905 19.6 

ROM0017 23 24 1 6.58 95.4 

ROM0018 9 10 1 0.648 27.3 

ROM0022 10 11 1 0.71 2 

ROM0022 22 23 1 0.55 2.1 

ROM0022 145 146 1 1.01 29.3 

ROM0034 98 99 1 2.95 7370 

ROM0037 17 18 1 4.33 38.3 

ROM0037 68 69 1 3.18 1.7 

ROM0070 17.7 18.2 0.5 1.9 104 

ROM0071 16 17.4 1.4 0.86 27 

ROM0071 25.8 27.2 1.4 1.23 2 

ROM0072 18.7 20.1 1.4 0.8 19 

ROM0072 41.8 42.5 0.7 2.29 118 

ROM0073 0.55 1.4 0.85 0.79 33 

ROM0073 4.2 5.6 1.4 1.3 14 

ROM0074 16.45 16.95 0.5 148 4162 

ROM0076 41.35 41.85 0.5 0.39 120 

ROM0077 10.3 10.8 0.5 0.14 672 

ROM0077 31.9 32.4 0.5 0.15 219 

ROM0078 55.4 56.1 0.7 3.07 215 

ROM0079 5.8 7.2 1.4 17.64 270 

ROM0080 32 33.4 1.4 9.19 20 

ROM0081 41.3 42.5 1.2 7.74 267 


Table 6. North Rompas drilling intersections. 

HoleID Depth from (m) Depth to (m) Interval (m) Au (g/t) U 3 0 8 (g/t) 

ROM0042 2.4 3.1 0.7 1 50 

ROM0044 19.7 20.4 0.7 0.1 161 

ROM0044 21.8 22.5 0.7 0.5 3 

ROM0044 23.9 24.6 0.7 0.8 71 

ROM0047 35.4 36.8 1.4 0 395 

ROM0047 44.6 46 1.4 0 181 

ROM0047 51.9 56.1 4.2 0 306 

ROM0048 26 26.7 0.7 1.2 40 

ROM0049 25.9 26.6 0.7 0.3 166 

ROM0050 7.1 7.8 0.7 3.5 67 

ROM0050 19.6 20.3 0.7 0.6 91 

ROM0052 41 41.4 0.4 395 4118 

ROM0052 61.5 62.2 0.7 0 179 

ROM0053 13.7 14.4 0.7 1.1 24 

ROM0053 34.7 35.4 0.7 0.7 15 

ROM0053 78.5 79.6 1.1 9.8 1519 

ROM0057 43.2 43.4 0.2 0 212 

ROM0065 77.8 78.4 0.6 0.11 310 

ROM0067 20.2 20.7 0.5 0.01 136 

ROM0067 52.9 53.6 0.7 0 171 

ROM0068 30.3 31 0.7 2.46 1403 

Mawson exploration team 

The Mawson exploration team presently comprises 

eight geologists directly working on the 

project (Erkki Vanhanen, Nick Cook, Mike 

Hudson, Tuomas Havela, Janne Kinnunen, 

Jukka-Pekka Ranta, Lars Dahlenborg and 

Jan-Anders Perdahl). Former staff on the project, 

consultants and summer students who 

have added significantly to the understanding 

of the Rompas-Rajapalot project include, but 

are not limited to, Terry Lees, Claude Caillat, 

Leigh Rankin, Gerald Purvis, Nicolas Gaillard, 

Pertti Sarala, Eelis Pulkkinen, David McInnes 

and Marcus Tomkinson. In addition, research 

groups based at the GTK (Ferenc Molnàr, Esa 

Pohjalainen, Antonin Richard, Laura Lauri) and 

at Nancy (Michel Cathelineau, Marc Brouand) 

have been instrumental in allowing Mawson to 

develop our understanding of the mineralisation 

at Rompas. 

References 

Agnico Eagle, 2013: Reserves and Resources. 

[www.agnicoeagle.com/en/Operations/Reserves-and-Resources/Pages/default.aspx]. 

Ahtonen, N., Hölttä, P. & Huhma, H., 2007: 

Intracratonic Palaeoproterozoic granitoids 

in northern Finland: prolonged and episodic 

crustal melting events revealed by Nd isotopes 

and U-Pb ages on zircon. Bulletin of the Geological 

Society of Finland 79, 143–174. 

Alapieti, T., Filen, B., Lahtinen, J., Lavrov, M., 

Smolkin, V. & Voitsekhovsky, S., 1990: Early 

Proterozoic layered intrusions in the northeastern 

part of the Fennoscandian Shield. 

Mineralogy and Petrology 42, 1–22. 


Bergman, S., Kübler, L. & Martinsson, O., 

2001: Description of regional geological and 

geophysical maps of northern Norrbotten 

County (east of the Caledonian orogen). Sveriges 

geologiska undersökning, Ba 56, 1–110. 

Bergman, S., Weihed, P., Martinsson, O., Eilu, 

P. & Iljina, M., 2007: Geological and tectonic 

evolution of the northern part of the Fennoscandian 

Shield. Geological Survey of Finland, 

Guide 54, 6–14. 

Billström, K., Eilu, P., Martinsson, O., Niiranen, 

T., Broman, C., Weihed, P., Wanhainen, C. & 

Ojala, J., 2010: IOCG and related mineral deposits 

of the northern Fennoscandian Shield. 

In T. Porter (ed.): Hydrothermal iron oxide-copper-gold 

& related deposits: A global perspective, 

vol. 4. Advances in the understanding of IOCG 

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