Kuittila - Gold Database

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Name	Kuittila	DATA UPDATED	12.9.2008
Alternative names
Deposit summary	KUITTILA, in the Ilomantsi greenstone belt, has an in situ resource estimate of 700 kg gold (no JORC-compliant resource calculation is available). It is an Archaean orogenic gold deposit of one subvertical lode comprising a set of laminated quartz±tourmaline±carbonate veins and sulphides and gold dissemination in a tonalite, close to the NE-trending Kelokorpi shear zone. The auriferous veins postdate sets of molybdenite-bearing and barren quartz veins. Chiefly native gold as inclusions and intergrowths with pyrite in association with tellurides.
LOCATION
Geological domain	Archaean	Belt	Ilomantsi
Site photo		Regional map
Map sheet	4244 08
Northing (kkj)	6963800	Easting (kkj)	4561400
Latitude	62.77321N	Longitude	31.19926E
Municipality	Ilomantsi
Nearest town, roads	25 km NE from Ilomantsi, 90 km NE from Joensuu. A sealed road 5 km from the area, a gravel road 200 m from the area.
MINING
Exploration licence no	3808, 3956, 7558/3	Mining concession no
Present holder	Endomines (2006–)
Previous holders	Geological Survey of Finland (GTK) (1984–), Polar Mining (2003–2006)
Mine photo 1		Mine photo 2
Mine photo 3		Mine photo 4
Status of development	Prospect
When mined
Resources	0.14 Mt 4 ppm Au or 0.275 Mt 2.58 ppm [1,3,4,5].
Deposit size (Mt)	0.14	Reference (size)	[1,3,4,5]
Total in-situ gold (kg)	709	Reference (in-situ Au)	[1,3,4,5]
Total gold production (kg)		Reference (gold prod)
Production of other metals
Extent of mineralisation
Lodes	The NW-SE trending, subvertical lode is formed by dissemination and a set of quartz veins within a shear zone in tonalite [5].
Best sections	1 m @ 19.4 ppm Au, 1 m @ 8.1 ppm Au, 2 m @ 10.4 ppm Au, 4 m @ 4.5 ppm Au, 5 m @ 4 ppm, 7 m @ 2.1 ppm Au, 9 m @ 1.4 ppm Au [9,12,14,15]. 5.2 m @ 4.8 ppm Au, 0.5 m @ 21.2 ppm Au, 1.6 m @ 5.8 ppm Au [17].
EXPLORATION
Discovery year	1984
Discovery	By GTK during a follow-up survey to determine source for scheelite grains and W and Mo anomalies in till [1,5].
Exploration history	GTK (1984–1994) [1,2,3,4,5,7,9,11,12,13,14,15]: 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 local W and Mo anomalies with sampling grid 50x50 m. Low-altitude air- and ground-magnetic, slingram and IP survey. Bedrock mapping is based on outcrops, geophysics, trenching, diamond and percussion drilling. Special studies on Quaternary geology, silicate and opaque mineral mineralogy [11] and geochemistry [2,11], and petrogenesis.
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	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 [1,5].
Drilling	GTK (1985–1987) [1,2,5,15]: 20 diamond-drill holes, total 2727 m.
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 [1,5,6].
Primary dispersion	[5]: Au and Te show a good mutual correlation; Ag and Bi show moderate correlation with Au. No consistent chemical zoning found yet. Lithogeochemical anomalies: Mo, W, CO2, Cu, S, Rb, K, Si and LOI enrichment and Na and Sr depletion define anomalies for hundreds metres around the Au mineralisation.
Secondary dispersion	[5]: Regional Au, As and B till anomaly, local Au, Te and Bi anomaly in till. 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. A 0.5–1 km wide Au anomaly in till along the western-southwestern contact of the Kuittila tonalite.
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
Exploration geologist in charge	GTK: Martti Damsten. Endomines: Jaakko Liikanen
ORE
Siting of gold	Chiefly as native as inclusions and intergrowths with pyrite in association with tellurides, but also associated with galena, pyrrhotite, quartz, muscovite and biotite [1,2,9,11]. A minor volume of gold in electrum and tellurides [2].
Fineness	75–95% Au, 5–25% Ag; avg 92% Au, 6% Ag [2,11].
Major opaques	Pyrrhotite, pyrite [1,2,9,11].
Minor opaques	Native gold, electrum, native silver, hessite, petzite, altaite, frohbergite, tellurobismuthinite, native tellurium, chalcopyrite, sphalerite, galena, pentlandite, arsenopyrite, cubanite, molybdenite, mackinawite, ilmenite, rutile [1,2,9,11].
Gangue	Quartz, albite, K feldspar, biotite, muscovite, garnet, calcite, chlorite, scheelite, titanite, tourmaline [1,2,11].
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	Bulk ore 4 ppm Au [11]. Diamond-drill core [5]: 3.5 ppm Au, 4.7 ppm Ag, 3.0 ppm As, 163 ppm B, 1020 ppm Ba, 1.2 ppm Bi, 17 ppm Co, 14 ppm Cu, 6.0 ppb Hg, 75 ppm Mo, 49 ppm Ni, 21 ppm Pb, 114 ppm Rb, 630 ppm S, 0.2 ppm Sb, 0.10 ppm Se, 485 ppm Sr, 2.1 ppm Te, 6.4 ppm Th, 2.9 ppm U, 90 ppm V, 23 ppm W, 55 ppm Zn; 68.9% SiO2, 0.38% TiO2, 13.3% Al2O3, 3.70% Fe2O3, 2.41% MgO, 2.69% CaO, 3.12% Na2O, 3.27% K2O, 0.13% P2O5, 1.16% LOI
Enriched elements	Au + Bi, Te, Ag, Mo, Pb, As, W, B, K, Rb, S, CO2 [5,6,9].
Ore fluid	Fluid inclusions: max T = 237–251°C, salinity 7 wt.% NaCl eq. [5].
Stable isotopes	[5]: δ18O (SMOW): +4.66 - +10.68 per mill (calcite), +4.3 - +9.3 per mill (quartz), +1.0 - +3.9 per mill (biotite), +9.3 per mill (calcite), +9.2 per mill (albite); => T = 500°C; δD (SMOW): -60 - -47 per mill (biotite); δ13C (PDB): -9.71 - 7.17 per mill (calcite).
Pb isotope data	Pb-Pb age for galena: 2700±75 Ma [5].
GEOLOGY
Geological setting	The mineralisation is in the central part of the 2754–2726 Ma [16] Hattu Schist Belt, in the sheared, quartz-sericite altered Kuittila Tonalite, near tonalite-mica schist contact, in the SW part of the intrusion [1,5,9].
Major host rocks	Tonalite [1,2,5,6,11,14].
Minor host rocks
Intrusives	[5]: The 2745±10 Ma [16] tonalite hosting the deposit predates all mineralisation. The tonalite is cross cut by a mafic dike which also predates both W-Mo- and Au-bearing quartz veins.
Regional geol map 1		Outcrop photo 1
Regional geol map 2		Outcrop photo 2
Local geology map 2
METAMORPHISM
Metamorphic history	[5]: Progressive regional metamorphism on ca. 2750–2700 Ma, apparently peaked soon after gold mineralisation, at a temperature of about 550±50°C (according to biotite-garnet thermometry within the schist belt). Thermal peak was synchronous or outlasted deformation. A relatively strong, but unevenly distributed Palaeoproterozoic overprint [10].
Metamorphic grade	Greenschist-amphibolite facies transition [5].
Metamorphic mineral assemblage	Tonalite: plagioclase-quartz-biotite-muscovite(-K feldspar-tourmaline-garnet-apatite-zircon) [2,9,11].
Metamorph photo 1		Metamorph photo 2
STRUCTURE
Structural style	Ductile-dominated.
Closest major shear	Kelokorpi Shear Zone 1.3 km to the east of the deposit [5].
Controlling structure	A shear zone along contact between the tonalite intrusion and its wallrocks(?), sinistral sense of shear in the area of the deposit [5].
Deformation history	Rapid and extensive crustal generation and progressive deformation between 2.76–2.73 Ma, in a transpressional regime [16].
Ore fabric
Veins	[9,11]: Two pre-gold, scheelite(-powellite)- and molybdenite-bearing quartz vein sets: two sets or a set of conjugate veins. These are followed by barren quartz veins. The latest set of quartz-tourmaline±calcite veins is gold-bearing, commonly laminated and may also show other features of repeated opening and sealing. The vein thickness varies from 0.5 cm to 40 cm [9].
Structure photo 1		Vein photo 1
Structure photo 2		Vein photo 2
Structure photo 3		Vein photo 3
ALTERATION
General alteration	Pervasive alteration and ductile deformation are only related to the auriferous veins. Formation of the assemblage quartz-albite-muscovite-biotite-tourmaline-rutile-calcite-K feldspar-epidote ± Ba-bearing microcline: hydration, carbonation and K alteration. [2,5,11]
Proximal alteration	Characterised by the assemblage quartz-muscovite-biotite-tourmaline-rutile-calcite [2,6,7,11].
Intermediate alteration
Distal alteration	Albite-quartz-biotite-muscovite ± K feldspar, apatite, calcite [9].
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	[5]: Probably, an Archaean post-mineralisation metamorphic overprint at about 500±50°C with deformation and porphyroblast overgrowth. This also affected D18O 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	[5]: The U-Pb zircon age of the tonalite is 2745±10 Ma [16]. Rb-Sr age of the tonalite, 2789±290 Ma, is poorly constrained. The mineralisation is 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). Pb-Pb age for galena: 2700±75 Ma. [8]: Re-Os gives 2780±8 Ma for molybdenite (pre-gold stuff), but pyrite gives 2607±47 Ma, "which is in accordance with the titanite and monazite ages for gold mineralisation". A re-evaluation of the molybdenite Re-Os age is very close to the syn-magmatic 2754 Ma [16].
GENETIC MODEL	[5]: 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. The combination of arsenopyrite and oxygen isotope thermometry, sphalerite geobarometry, with the dominance of pyrrhotite and calcite instated of pyrite and dolomite, respectively, suggests uppermost-greenschist facies or conditions transitional between greenschist and amphibolite facies for mineralisation: T = 450–500°C, p = 2–3 kbar. The proximal alteration assemblage given in [9] also supports these PT-conditions for gold mineralisation. 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 [2,11].
Genetic type	Orogenic	References	[5]
Alternative genetic type 1		References
Alternative genetic type 2		References
References 1. Damsten, M. 1990. Tutkimustyöselostus Ilomantsin kunnassa valtausalueilla Kuittila 1–3, kaiv. rek. no. 3808 ja 3956, suoritetuista tutkimuksista. Geol. Surv. Finland, Report M06/4244/-90/1/10. 8 p. (in Finnish, 705 KB) 2. Kojonen, K. & Johanson, B. 1989. Ilomantsin Kuittilan Au-malmiaiheen mineralogiaa ja petrografiaa. Geol. Surv. Finland, Report M19/4244/-89/1/42. 17 p. (in Finnish, 2.8 MB) 3. Nurmi, P. A., Lestinen, P. & Niskavaara, H. 1991. Geochemical characteristics of mesothermal gold deposits in the Fennoscandian Shield, and a comparison with selected Canadian and Australian deposits. Geol. Surv. Finland, Bulletin 351. 101 p. 4. Nurmi, P. A. 1993. Archaean Au in Finland. Engineering and Mining Journal, Nov., 32–34. 5. 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. 6. 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. 7. Salminen, R. 1986. Au, W, Mo sekä eräät muut metallit maaperässä ja kallioperässä Kuittilassa Ilomantsissa. Geol. Surv. Finland, Report S/41/4244/1/1986. 8 p. (in Finnish, 150 KB) 8. Stein, H., Morgan, J. W., Markey, R. J. & Hannah, J. L. 1998. An introduction to Re-Os. What's in it for the mineral industry? SEG Newsletter 32, 1–15. 9. Ojanen, H. 1993. Ilomantsin Kuittilan ja Muurinsuon Au- ja Mo-W-mineralisaatioiden petrografia ja malmimineralogia. Unpublished MSc thesis. Dept of Geology, Univ. of Oulu. 108 p. (in Finnish) 10. 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. 11. 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. 12. Damsten, M. & Nurmi, P. 1994. Alustava raportti kultamalmitutkimuksista ns. Kuittilan vyöhykkeellä Ilomantsin kunnassa. Geol. Surv. Finland, Report M 19/4244/94/1/10. 14 p. (in Finnish, 1.9 MB) 13. Hartikainen, A. & Niskanen, M. 2001. maaperägeokemialliset kultatutkimukset Hatun liuskejaksolla Ilomantsissa vv. 1983–1995. Geol. Surv. Finland, Report S/41/4244/1/2001. 22 p. 14. Damsten, M., Hartikainen, A., Koistinen, E. & Nurmi, P.A. 1994. Tutkimustyöselostus Ilomantsin kunnassa valtausalueilla Muurinsuo (kaivosrekisterinro 4273/1), Korvilansuo 1 (4165/1), Kelokorpi 1 (4165/2), Palosuo (5027/1), Muurinsuo 2 (5359/1), Muurinsuo 3 (5359/2) sekä valtausvarausalueilla Elinsuo (156/93), Kiimasuo (156/93) ja Viinivaara (25/94) suoritetuista kultamalmitutkimuksista vuosina 1984–1993. English summary: Report on exploration in Ilomantsi during 1984–1993 in claims Muurinsuo (Mine Reg. No. 4273/1), Korvilansuo 1 (4165/1), Kelokorpi 1 (4165/2), Palosuo (5027/1), Muurinsuo 2 (5359/1), Muurinsuo 3 (5359/2) and claim reservation areas Elinsuo (156/93), Kiimasuo (156/93) and Viinivaara (25/94). Geol. Surv. Finland, Report M06/4244/-94/1/10. 14 p. (790 KB) 15. 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) 16. 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, 19-99. 17. Endomines 2008. Press release 16 June 2008.
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