Name
Pahkalampi
Alternative names
Tormua 6
DATA UPDATED 9.2.2006
LOCATION
Geological domain
Archaean
Site photo
Belt
Suomussalmi
Regional map
Map sheet
451309
Northing (kkj)
241300
Easting (kkj)
4479300
Latitude
65.26694256N
Longitude
29.55330056E
Municipality
Suomussalmi
Nearest town,
roads
52 km NE from Suomussalmi. 6 km from a sealed road, 1.5 km from a
gravel road.
MINING
Exploration
licence no
5232/1, 7980/6
Present holder
Nordic Mines AB (2005–)
Previous holders
Geological Survey of Finland (GTK), Endomines Oy (–2005)
Mining concession
no
Mine photo 1
Mine photo 2
Mine photo 3
Mine photo 4
Status of
development
Prospect
When mined
Resources
0.05 Mt @ 5.5 ppm Au (lode Pahkalampi I) [3,4]. Indicated 0.05 Mt @
5.6 ppm + inferred 0.2 Mt @ 3 ppm Au (cutoff 2 ppm) [9].
Deposit size (Mt)
0.25
Reference (size)
[9]
Total in-situ gold
(kg)
880
Reference (in-situ
Au)
[9]
Total gold
production (kg)
Reference (gold
prod)
Production of
other metals
Extent of
mineralisation
Lodes
Possibly, several lodes – the resource estimate only includes one lode
[3,4]. A set of pipes or thin flat lodes plunging 52–60° to the NNE [9].
Best sections
EXPLORATION
Discovery year
1996
Discovery
By GTK: a tiny mineralised outcrop found during exploration for base
metals at Moukkori. This led to extensive ground geophysical and till
geochemical surveys in the region. The Pahkalampi deposit was detected
by driling into a till geochemical anomaly [4]. First indication for gold in
the region were the auriferous glacial erratics found by an amateur
prospector in 1989 [11].
Exploration
history
GTK (1990–97) [1,2,3,4,8]: Bedrock mapping, ground magnetic,
slingram, VLF-R, total intensity and IP survey, till geochemical survey,
trenching, diamond and RC drilling; ore mineralogy investigations [1].
Section figure 1
Plan figure 1
Section figure 2
Plan figure 2
Section figure 3
Plan figure 3
Trench fig 1
Trench fig 4
Trench fig 2
Trench fig 5
Trench fig 3
Trench fig 6
Explor site photo 1
Explor site photo
2
Geophysical
response
Drilling
Elements analysed
Primary
GTK: 34 diamond-drill holes, total 3804 m, and 8 RC holes, total 446 m
[4].
dispersion
Secondary
dispersion
Primary anomaly
fig 1
Secondary
anomaly fig 1
Primary anomaly
fig 2
Secondary
anomaly fig 2
Primary anomaly
fig 3
Secondary
anomaly fig 3
Primary anomaly
fig 4
Secondary
anomaly fig 4
Primary anomaly
fig 5
Secondary
anomaly fig 5
Economic
evaluations
Resource estimates for Endomines by GTK in 2001 [9].
Exploration
geologist in charge
GTK: Erkki Luukkonen.
ORE
Siting of gold
Native gold is intergrown with tellurides; Au also in gold tellurides; gold
and tellurides are commonly as inlusions in pyrite, pyrrhotite, quartz,
albite and K feldspar [1]. In addition, there are free gold grains with
silicates [1,5]. Grain size of gold is <15 m, generally <5 m –
significantly coarser gold may occur in quartz veins [1].
Fineness
53–92% Au, 0–46% Ag [1].
Major opaques
Pyrrhotite [1].
Minor opaques
Pyrite, ilmenite, rutile, cobaltite, chalcopyrite, sphalerite, volynskite,
hessite, petzite, frohbergite, calaverite, tellurobismuth, bismuth,
loellingite, galena, gold, electrum [1].
Gangue
Quartz, plagioclase, K feldspar, biotite, scheelite, tourmaline, rutile,
titanite [1,4].
Ore miner. photo 1
Ore miner. photo
5
Ore miner. photo 2
Ore miner. photo
6
Ore miner. photo 3
Ore outcrop photo
1
Ore miner. photo 4
Ore outcrop photo
2
Ore composition
Enriched elements
Au, Ag, As, B, Bi, S, Te, W [1,4].
Ore fluid
Stable isotopes
Pb isotope data
GEOLOGY
Geological setting
The deposit is in the Tormua Schist Belt which forms the NE part of the
late Archaean Suomussalmi Greenstone Belt and is in the rocks of the 3.0–
2.8 Ga Luoma Group of the greenstone belt [4,6,8].
Major host rocks
Amphibolite [1,4].
Minor host rocks
Uralite-porphyrite, intermediate schist, tourmaline-bearing granitoid [4].
Intrusives
TTG granitoids, from 2739±8 Ma to 2697±10 Ma of age, are abundant
within and near the greenstone belt [4]. Ca. 2700 Ma granitoids (syn–D3)
have intruded into the supracrustal sequence [11].
Regional geol map
1
Outcrop photo 1
Regional geol map
2
Outcrop photo 2
Local geology map
1
Outcrop photo 3
Local geology map
2
METAMORPHISM
Metamorphic
history
Metamorphic
grade
Amphibolite facies, at about 5 kbar and 600°C [4].
Metamorphic
mineral
assemblage
Metamorph photo
1
Metamorph photo
2
STRUCTURE
Structural style
Brittle-ductile [4].
Closest major
shear
A NNE-trending shear zone at the eastern boundary of the greenstone belt,
1 km SE from the deposit [8].
Controlling
structure
A second-order D3 structure [3,4,5].
Deformation
history
At least, four deformation stages during the late Archaean and two
deformation stages during the Palaeoproterozoic time detected in the area;
gold mineralisation is related to the Archaean late D3 stage [3,4,5].
Age of D2 is probably 2820±15 Ma [11]. The D3 started as a plastic stage,
dominantly dextral folding and formation of strong N-trending shear
zones; this is partially overprinted by the NW-trending D4 foliation under
retrograde conditions [11].
Syn-D3 granodiorite suggests an age of ca. 2718 Ma for the D3 stage [11].
Ore fabric
Granoblastic, disseminated [1].
Veins
Abundant quartz veins [1,4].
Structure photo 1
Vein photo 1
Structure photo 2
Vein photo 2
Structure photo 3
Vein photo 3
ALTERATION
General alteration
Sericitisation and epidotisation [4].
Proximal
alteration
Amphibolite: plagioclase-hornblende-quartz-epidote-titanite;
intermediate schist: K feldspar-albite-quartz-biotite-titanite-scheelite [1].
Intermediate
alteration
Distal alteration
Zonation figure
Prox alteration
photo 1
Alteration photo 1
Prox alteration
photo 2
Alteration photo 2
Intermed
alteration photo
Alteration photo 3
Distal alteration
photo 1
Postmineralisation
modifications
Post-mineralisation D4 deformation [8].
TIMING
Late Archaean [5].
GENETIC
MODEL
Orogenic "mesothermal" deposit, formed during D3 deformation at peakmetamorphic 5 kbar and 600°C or under slightly lower temperature [4],
during late-Archaean cratonisation [10].
GENETIC TYPE
Orogenic 'mesothermal' [10].
References
1. Kojonen, K., Pakkanen, L. & Johanson, B. 1996. Kullan esiintyminen Suomussalmen
Pahkalammen kultamalmiaiheessa. Geol. Surv. Finland, Report M42.4/4513/-96/1. 5 p. (in
Finnish)
2. Pietikäinen, K. 1998. Personal communication 14/9/1998.
3. Ministry of Industry and Trade 1998. International tender notice. Tormua gold prospect,
Suomussalmi, Finland. Press release 6/10/1998.
4. Luukkonen, E., Heino, T., Tenhola, M., Niskanen, M. & Hartikainen, A. 1997.
Tutkimustyöselostus Suomussalmen kunnassa valtausalueella Saarilampi 1 (kaivosrekisteri
5351/1), Housuvaara 1–2 (kaivosrekisteri 4876/1–2), Mullikko 1 (kaivosrekisteri 5029/1), Pahka
1 (kaivosrekisteri 5029/2/1) ja Pahkalampi 1 (kaivosrekisteri 5232/1) suoritetuista
kultamalmitutkimuksista vuosina 1990–1997. Geol. Surv. Finland, Report M06/4513/-97/1/10.
21 p. (in Finnish)
5. Luukkonen, E., Pajunen, M. & Poutiainen, M. 1992. Kuhmo–Suomussalmen alueen arkeeisen
kallioperän rakenne-evoluutio ja Au-aiheet. In: E. Ekdahl (ed.) Suomen kallioperän kehitys ja
raaka-ainevarat. Vuorimiesyhdistys, Sarja B, 51, 11–12.
6. Luukkonen, E. 1992. Late Archaean and Early Proterozoic structural evolution in the Kuhmo–
Suomussalmi Terrain, eastern Finland. Annales universitatis Turkuensis. Ser. A. II 78, 1–37.
7. Sorjonen-Ward, P., Nironen, M. & Luukkonen, E. 1997. Greenstone associations in Finland.
In: M. J. de Wit and L. D. Ashwal (eds) Greenstone Belts. Clarendon Press, Oxford. 677–698.
8. Luukkonen, E. (ed.) 1998. Suomussalmen, Kuhmon ja Kostamuksen arkeeiset
vihreäkivivyöhykkeet ja niihihn liittyvä malminmuodostus. Ekskursio-opas. Vuorimiesyhdistys,
Sarja B, No 66, 40 p. (in Finnish)
9. Parkkinen, J. 2001. Quality control of mineral resource estimates: Laivakangas, Hosko,
Kuivisto E, Other, Osikonmäki, Pirilä, Housuvaara, Pahkalampi. Geol. Surv. Finland, Report. 27
p.
10. Papunen, H., Halkoaho, T., Liimatainen, J. & Luukkonen, E. 2001. Metallogeny of the
Archaean Tipasjärvi–Kuhmo–Suomussalmi greenstone belt, Finland. AGSO – Geoscience
Australia, Record 2001/37, 456–458.
11. Luukkonen, E., Halkoaho, T., Hartikainen, A., Heino, T., Niskanen, M., Pietikäinen, K. &
Tenhola, M. 2002. Itä-Suomen arkeeiset alueet –hankkeen (12201 ja 210 5000) toiminta vuosina
1992–2001 Suomussalmen, Hyrynsalmen, Kuhmon, Nurmeksen, Rautavaaran, Valtimon,
Lieksan, Ilomantsin, Kiihtelysvaaran, Enon, Kontiolahden, Tohmajärven ja Tuupovaaran
alueella. Geol. Surv. Finland, Report M19/4513/2002/1. 265 p. (in Finnish, 130 MB)