Korpilampi - Gold Database

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Name	Korpilampi	DATA UPDATED	24.5.2007
Alternative names	Korpi
Deposit summary	KORPILAMPI is an Archaean orogenic gold deposit with no resource estimate available. It is hosted by intermediate volcanogenic metasedimentary rock, and comprises a set of gently-dipping lenses located at contact with pegmatite dikes in a small ductile shear zone in the Pampalo shear zone system. Native gold disseminated in the host rock, intergrown with bismuth, galena and bismuthinite, locally as inclusions in garnet.
LOCATION
Geological domain	Archaean	Belt	Ilomantsi
Site photo		Regional map
Map sheet	433308
Northing (kkj)	6991800	Easting (kkj)	4562050
Latitude	63.02426N	Longitude	31.22240E
Municipality	Ilomantsi
Nearest town, roads	40 km NE from Ilomantsi, 100 km NE from Joensuu. A sealed road across the area.
MINING
Exploration licence no	5402/1–2, 5356/1–4, 5498/2, 5840/3, 7389/1	Mining concession no
Present holder	Endomines Oy (1994–)
Previous holders	Geological Survey of Finland (GTK) (–1994)
Mine photo 1		Mine photo 2
Mine photo 3		Mine photo 4
Status of development	Prospect
When mined
Resources	none reported
Deposit size (Mt)		Reference (size)
Total in-situ gold (kg)		Reference (in-situ Au)
Total gold production (kg)		Reference (gold prod)
Production of other metals
Extent of mineralisation
Lodes	Gently dipping lodes: dissemination at contact with pegmatite dikes in a ductile shear zone [2,4].
Best sections	2.4 m @ 1.1 ppm, 1 m @ 1.7 ppm, 1 m @ 1.4 ppm Au [1,2,11].
EXPLORATION
Discovery year	1988
Discovery	By GTK: the first indication was the discovery of an auriferous, sulphidised and tourmalinised outcrop in a road cut, the occurrence was found by drilling into an area defined as teh locally most significant Au anomaly in till [2,10].
Exploration history	GTK (1987–1995) [1,2,3,5,9,10,11]: Detailed geochemical till sampling: sampling grid 250x250 m over the greenstone belt covering 400 km2. Follow-up as till-bedrock interface geochemistry, samples collected across the Au anomaly along traverses 100 m apart with sampling distance 10-30 m. Low-altitude air- and ground-magnetic, slingram and IP survey. Bedrock mapping based on outcrops, geophysics, trenching and diamond drilling. Special studies on Quaternary geology, ore mineralogy [8] and geochemistry, and petrogenesis. SIP investigations. Endomines Oy (1996–) [4,12]: RC and diamond drilling.
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	[2]: No response on magnetic, slingram or IP methods. Magnetic and electric methods do show the structural features of the area, including those which control gold mineralisation.
Drilling	GTK (1987–1993) [1,2,10,11]: 12 diamond-drill holes, total 1056 m. Endomines (2004) [12]: One diamond-drill hole.
Elements analysed	Ag, Al, As, Au, B, Ba, Bi, Ca, Cd, Co, CO2, Cr, Cu, Fe, K, LOI, Mg, Mo, Na, Nb, P, Pb, Rb, REE, S, Sb, Sc, Se, Si, Sr, Te, Ti, Th, U, V, W, Y, Zn, Zr [2,3].
Primary dispersion	[2,3]: Au and Te show good correlation; Ag and Bi show moderate correlation with Au. No consistent chemical zoning found yet.
Secondary dispersion	[2]: Regional Au, As and B till anomaly, local Au, Te and Bi anomaly. Au content within the till anomaly is from tens of ppb to >1 ppm. Best combination for defining exploration targets: Au + Te + Bi- better than Au alone.
Primary anomaly fig 1		Secondary anomaly fig 1
Primary anomaly fig 1		Secondary anomaly fig 1
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
Exploration geologist in charge	Endomines Oy: Jaakko Liikanen; GTK: Martti Damsten.
ORE
Siting of gold	Dissemination in the host rock at contact with pegmatite dikes, native gold intergrown with bismuth, galena and bismuthinite, locally as inclusions in garnet [8].
Fineness
Major opaques	Pyrrhotite, pyrite [8]
Minor opaques	Native gold, bismuth, bismuthinite, arsenopyrite, chalcopyrite, galena, pentlandite, arsenopyrite, rutile [8].
Gangue	Quartz, tourmaline, albite, K feldspar, biotite, muscovite, garnet, calcite?, chlorite, scheelite, titanite [8].
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 + Te, Bi, Se, B, K, Rb, S, CO2 [2,3].
Ore fluid
Stable isotopes
Pb isotope data
GEOLOGY
Geological setting	The mineralisation is in the central part of the 2754–2726 Ma Hattu Schist Belt [13]. The hosting komatiitic and intermediate metavolcanic rocks are intruded by pegmatite dikes, all lithological units show complicated folding and contain sulphide dissemination [2].
Major host rocks	Intermediate schist (tuffite) [2,4,10].
Minor host rocks	Komatiitic and basaltic metavolcanic rocks, granite pegmatite, tonalite [2,10].
Intrusives	Pegmatites, predate gold mineralisation? [2].
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	[2]: Progressive regional metamorphism on ca. 2750–2700 Ma, apparently peaked soon after gold mineralisation, at a temperature of about 550±50°C. Thermal peak was synchronous or outlasted deformation. A relatively strong, but unevenly distributed Palaeoproterozoic overprint [7].
Metamorphic grade	Greenschist-amphibolite facies transition [2].
Metamorphic mineral assemblage
Metamorph photo 1		Metamorph photo 2
STRUCTURE
Structural style	Brittle-ductile, ductile-dominated [2].
Closest major shear	The Pampalo Shear Zone system adjacent to the deposit [2].
Controlling structure	Pampalo shear system [2].
Deformation history	Rapid and extensive crustal generation and progressive deformation between 2.76–2.73 Ma, in a traspressional regime [13].
Ore fabric
Veins
Structure photo 1		Vein photo 1
Structure photo 2		Vein photo 2
Structure photo 3		Vein photo 3
ALTERATION
General alteration	Formation of quartz, biotite, muscovite, albite, chlorite, K feldspar, epidote, rutile, tourmaline, garnet, titanite [2,3].
Proximal alteration
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	[2]: Probably, an Archaean post-mineralisation metamorphic overprint at about 500±50°C with deformation and porphyroblast overgrowth. This also affected δ18O values of minerals. On ca. 1800 Ma, a Proterozoic regional metamorphic overprint which is shown by K-Ar and Rb-Sr ages of micas.
TIMING	[2]: Either pre-peak metamorphic and formed under greenschist-facies conditions, or syn-peak metamorphic. Minimum age 2708–2693 Ma (U-Pb of titanite and monazite indicating peak metamorphism).
GENETIC MODEL	[2]: Formed in a structurally favourable, the most competent lithological units in the area. Precipitation of gold by desulphidation of fluid and, possibly, by decomposition of Au-bisulphide, -thiosulphide and -telluride complexes of fluid due to cooling and/or changes in pH and fO2. Probably, gold precipitated just below 500°C with sulphides due to reaction between the mineralising fluid and wall-rock (chiefly by sulphidation). The formation of the present low-temperature Te and Bi minerals probably took place as subsolidus reactions with cooling temperature. Note, in any case, that the presence of gold-bismuth-tellurium mineral assemblages indicate crystallisation temperatures for these minerals chiefly in the range 250–350°C [8].
Genetic type	Orogenic	References	[2]
Alternative genetic type 1		References
Alternative genetic type 2		References
References 1. Nurmi, P. A. 1993. Archaean Au in Finland. Engineering and Mining Journal, Nov., 32–34. 2. Nurmi, P. A. & Sorjonen-Ward, P. (eds) 1993. Geological Development, Gold Mineralization and Exploration Methods in the Late Archaean Hattu Schist Belt, Ilomantsi, Eastern Finland. Geol. Surv. Finland, Special Paper 17. 386 p. 3. Rasilainen, K. 1996. Alteration geochemistry of gold occurrences in the late Archean Hattu Schist Belt, Ilomantsi, Eastern Finland. Academic dissertation: synopsis and four research papers. Geol. Surv. Finland. 140 p. 4. Lindborg, T. 1997. Personal communication 2/10/1997. 5. Vanhala, H. 1997. Laboratory and field studies of environmental and exploration applications of the spectral induced-polarization (SIP) method. Geol. Surv. Finland. 104 p. 6. Endomines Oy. 1999. www.endomines.fi on 09/12/99. 7. Korsman, K. (ed.) & Glebovitsky, V. (ed.) 1999. Raahe-Ladoga Zone structure-lithology, metamorphism and metallogeny: a Finnish-Russian cooperation project 1996–1999. Map 2: Metamorphism of the Raahe-Ladoga Zone 1:1000000. Geol. Surv. Finland. 8. Kojonen, K., Johanson, B., O'Brien, H. E. & Pakkanen, L. 1993. Mineralogy of gold occurrences in the late Archaean Hattu schist belt, Ilomantsi, eastern Finland. In: P. Nurmi & P. Sorjonen-Ward (eds) Geological development, gold mineralization and exploration methods in the late Archaean Hattu schist belt, Ilomantsi, eastern Finland. Geol. Surv. Finland, Special Paper 17, 233–271. 9. Hartikainen, A. & Niskanen, M. 2001. maaperägeokemialliset kultatutkimukset Hatun liuskejaksolla Ilomantsissa vv. 1983–1995. Geol. Surv. Finland, Report S/41/4244/1/2001. 22 p. 10. Heino, T., Hartikainen, A., Koistinen, E. & Niskanen, M. 1995. Tutkimustyöselostus Ilomantsin kunnassa valtausalueilla Sivakko 1 (5188/1), Korpilampi 1–2 (5402/1–2), Korpi 1–4 (5356/1–4), Kuivisto 1 (5210/1), Kuivisto 2–3 (5356/5–6), Pihlajavaara 1–2 (5511/2–3) ja Valkeasuo 1–2 (4853/1, 5511/1) suoritetuista kultamalmitutkimuksista vuosina 1992–1995 sekä neljältä vireillä olevalta valtaukselta (Sivakko 2–3 ja Valkeasuo 3–4). English summary: Report on exploration in Ilomantsi in 1992–1995, within claims Sivakko 1 (Mine Register no. 5188/1), Korpilampi 1–2 (5402/1–2 ), Korpi 1–4 (5356/1–4), Kuivisto 1 (5210/1), Kuivisto 2–3 (5356/5–6), Pihlajavaara 1–2 (5511/2–3) and Valkeasuo 1–2 (4853/1, 5511/1). Geol. Surv. Finland, Report M06/4333/-95/1/10. 17 p. 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. Endomines Oy. 2005. www.endomines.fi in 12/12/2005. 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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