Kivisuo - Gold Database

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Name	Kivisuo	DATA UPDATED	24.5.2007
Alternative names	Teponsärkkä
Deposit summary	KIVISUO, in the Ilomantsi greenstone belt, is an Archaean orogenic gold occurrence with no resource estimate available. It comprises subvertical lodes formed by dissemination and auriferous tourmaline-quartz veins in intermediate volcanogenic metasedimentary rock, close to the NE-trending Korvilansuo shear zone. Native gold disseminated in the host rock and quartz veins with tellurides, arsenopyrite and pyrrhotite in silicate matrix.
LOCATION
Geological domain	Archaean	Belt	Ilomantsi
Site photo		Regional map
Map sheet	424408
Northing (kkj)	6968000	Easting (kkj)	4560800
Latitude	62.81098N	Longitude	31.18903E
Municipality	Ilomantsi
Nearest town, roads	30 kmm NE from Ilomantsi, 95 km NE from Joensuu. A sealed road 200 m from the area.
MINING
Exploration licence no	7742/5–6	Mining concession no
Present holder	Endomines (2006–)
Previous holders	Geological Survey of Finland (GTK), Polar Mining (2003–2 006)
Mine photo 1		Mine photo 2
Mine photo 3		Mine photo 4
Status of development	Prospect
When mined
Resources
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	N-NE striking, subvertical lodes formed by dissemination and quartz-tourmaline veins [2].
Best sections	4.9 m @ 4.0 ppm, 2 m @ 9.5 ppm Au, 2 m @ 4.4 ppm Au [1,2,6,7,9].
EXPLORATION
Discovery year	1986
Discovery	By GTK: arsenopyrite-bearing outcrop samples assayed 4-8 ppm Au; these samples were from an exploration pit excavated into one of the peak areas of an Au anomaly in till [2].
Exploration history	GTK (1989–1994) [1,2,7,8,9]: 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 [6] and geochemistry, 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 [2].
Drilling	GTK (–1993) [1,2,7,9]: 13 diamond-drill holes, total 1763 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 [2,3].
Primary dispersion	Au and Te show good correlation; Ag and Bi show moderate correlation with Au. No consistent chemical zoning found yet [2,3].
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. 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	Disseminated in host rocks and in quartz-tourmaline veins. Gold occurs intergrown with tellurides, arsenopyrite and pyrrhotite in silicate matrix and, in the mafic metavolcanic rocks, the tellurides and arsenopyrite are associated with sulphides and ilmenite [6].
Fineness	86% Au, 12% Ag (one anal. sample) [6]
Major opaques	Pyrite, pyrrhotite [6].
Minor opaques	Native gold, tsumite, hedleyite, bismuth, arsenopyrite, marcasite, pentlandite, mackinawite, chalcopyrite, sphalerite, molybdenite, rutile, ilmenite [6].
Gangue	Quartz, albite, K feldspar, biotite, muscovite, calcite, siderite, scheelite, titanite, tourmaline [2,3,6].
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, W, Ag, As, B, S, CO2 [2,3].
Ore fluid	Fluid inclusions: max T = 270–350°C, salinity 6-12 wt.% NaCl eq. [2].
Stable isotopes	[2]: δ18O (SMOW): +10.57 – +13.56 per mill (calcite), +8.6 – +11.8 per mill (quartz), +5.8 per mill (biotite), +11.8 per mill (calcite), -2.1 – +4.1 per mill (scheelite), +9.7 – +10.3 per mill (tourmaline), +9.4 per mill (actinolite), +2.9 per mill (epidote); => T = 411–500°C; δD (SMOW): -140 – -114 per mill (tourmaline), -110 per mill (actinolite); δ13C (PDB): -10.92 – 9.25 per mill (calcite).
Pb isotope data
GEOLOGY
Geological setting	The mineralisation is in contact zone between a tonalite and schists, in the central part of the 2754–2726 Ma [11] Hattu Schist Belt. The mica schists of volcano-sedimentary origin are interbedded with mafic metatuffites and intruded by felsic porphyry dikes [2].
Major host rocks	Volcanogenic mica schist [2,6].
Minor host rocks	Mafic metatuffite [2], meta-andesite [7].
Intrusives	Felsic porphyry dikes [2], which are not mineralised [8]. A 2747±6 Ma tonalitic intrusion next to mineralisation [10,11].
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	[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 [5].
Metamorphic grade	Greenschist-amphibolite facies transition [2].
Metamorphic mineral assemblage	Mica schist: plagioclase-quartz-biotite [6].
Metamorph photo 1		Metamorph photo 2
STRUCTURE
Structural style	Dominantly ductile [2].
Closest major shear	Korvilansuo-Muurinsuo Shear Zone system adjacent to the deposit [2].
Controlling structure	Korvilansuo shear zone [2].
Deformation history	Rapid and extensive crustal generation and progressive deformation between 2.76–2.73 Ma, in a transpressional regime [11].
Ore fabric
Veins	Quartz-tourmaline veins [2,6].
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, hornblende, tourmaline, rutile, calcite, titanite [2,6].
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 peakmetamorphism). [4]: 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".
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. 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. 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, and arsenopyrite 330–340°C [6].
Genetic type	Orogenic	References	[6]
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. 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. 5. 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. 6. 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. 7. 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) 8. Hartikainen, A. & Niskanen, M. 2001. maaperägeokemialliset kultatutkimukset Hatun liuskejaksolla Ilomantsissa vv. 1983-1995. Geol. Surv. Finland, Report S/41/4244/1/2001. 22 p. 9. 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) 10. Sorjonen-Ward, P. 2005. Personal communication 26/09/2005. 11. 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.
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