Pahkalampi - Gold Database

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Name	Pahkalampi	DATA UPDATED	17.1.2008
Alternative names	Tormua 6, Lauttalampi
Deposit summary	PAHKALAMPI, in the Suomussalmi greenstone belt, has an in situ resource estimate of 2100 kg gold. It is an Archaean orogenic gold deposit comprising several subparallel, narrow lodes in mafic metavolcanic rock in a second-order D3 fault zone. The resource estimate only covers one of the lodes. Native gold is intergrown with and as inclusions in tellurides, pyrite, pyrrhotite, quartz, albite and K feldspar. Fine-grained (<5 um) gold in host rock, coarse gold in quartz veins.
LOCATION
Geological domain	Archaean	Belt	Suomussalmi
Site photo		Regional map
Map sheet	451309
Northing (kkj)	7241300	Easting (kkj)	4479300
Latitude	65.26694N	Longitude	29.55330E
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	Mining concession no
Present holder	Nordic Mines AB (2005–)
Previous holders	Geological Survey of Finland (GTK), Endomines Oy (–2 005)
Mine photo 1		Mine photo 2
Mine photo 3		Mine photo 4
Status of development	Prospect
When mined
Resources	0.59 Mt @ 3.5 ppm Au [12]. 0.05 Mt at 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) [5].
Deposit size (Mt)	0.59	Reference (size)	[12]
Total in-situ gold (kg)	2100	Reference (in-situ Au)	[12]
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	16.6 m @ 1.4 ppm, 1 m @ 61.5 ppm, 1 m @ 45.1 ppm, 1 m @ 18.1 ppm, 1 m @ 12 ppm, 1 m @ 7.8 ppm Au [4,9].
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	GTK: 34 diamond-drill holes, total 3804 m, and 8 RC holes, total 446 m [4].
Elements analysed
Primary 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. Outokumpu: Markku Kilpelä.
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 um, generally <5 um – 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] or 2843±18 Ma [13]. 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
Post-mineralisation modifications	Post-mineralisation D4 deformation [8].
TIMING	Late Archaean [5].
GENETIC MODEL	Orogenic "mesothermal" deposit, formed during D3 deformation at peak-metamorphic 5 kbar and 600°C or under slightly lower temperature [4], during late-Archaean cratonisation [10].
GENETIC TYPE	Orogenic	References	[10]
Alternative genetic type 1		References
Alternative genetic type 2		References
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. 677–6 98. 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) 12. Nordic Mines 2007. Press release 17 April 2007. (in Swedish, 98 KB) 13. Sorjonen-Ward, P. & Luukkonen, E.J. 2005. Archean rocks. In: Precambrian Geology of Finland – Key to the Evolution of The Fennoscandian Shield. Elsevier Science B.V., Amsterdam, 19–9 9.
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