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Modified: 12.08.2009

Aittoranta - Gold Database

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Name Aittoranta DATA UPDATED 24.5.2007
Alternative names Iso-Aittojärvi
Deposit summary AITTORANTA, in the Kuhmo greenstone belt, is an Archaean orogenic gold occurrence with no resource estimate available. It is hosted by mafic volcanic rocks, defined by tourmaline-quartz veins and altered host rock, and located in the eastern margin of the main, N-trending shear zone of the greenstone belt.
LOCATION
Geological domain Archaean Belt Kuhmo
Site photo   Regional map kareliamap1_th
Map sheet 441211
Northing (kkj) 7144500 Easting (kkj) 4455200
Latitude 64.39641N Longitude 29.06787E
Municipality Kuhmo
Nearest town, roads 38 km NW from Kuhmo. 2 km from a sealed road, a gravel road to the area.
MINING
Exploration licence no 5032/1 Mining concession no  
Present holder OPEN FOR ACQUISITION
Previous holders Geological Survey of Finland (GTK) (1992–2000)
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 A few hundred metres long and 2–20 m wide zone, open at both ends and in depth [1].
Lodes The mineralised zone may, in fact, comprise a set of narrow, parallel subzones [1].
Best sections  
EXPLORATION
Discovery year 1992
Discovery A mineralised sample from outcrop indicated to GTK by an amateur prospector [1].
Exploration history GTK (1992–1999) [1,8]: bedrock mapping, trenching, magnetic and electromagnetic ground survey, 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  
Drilling GTK: 5 diamond-drill holes [1].
Elements analysed  
Primary dispersion  
Secondary dispersion Au-As anomaly in till [8].
Primary anomaly fig 1 kgb_aeromag_th Secondary anomaly fig 1 kgb_au_as_map_th
Primary anomaly fig 2 palovaara_louhiniemi_aero_electromagn_th Secondary anomaly fig 2 aitto_au_till_th
Primary anomaly fig 3 palovaara_louhiniemi_aeromagn_th 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: Erkki Luukkonen.
ORE
Siting of gold  
Fineness  
Major opaques Arsenopyrite [1].
Minor opaques  
Gangue Quartz, tourmaline [1].
Ore miner. photo 1   Ore miner. photo 5  
Ore miner. photo 2   Ore miner. photo 6  
Ore miner. photo 3   Ore outcrop photo 1 aittoranta1_thumb
Ore miner. photo 4   Ore outcrop photo 2 aittoranta2_thumb
Ore composition  
Enriched elements Au, As, B, S [1].
Ore fluid  
Stable isotopes  
Pb isotope data  
GEOLOGY
Geological setting Located in the northern part of the Late-Archaean Kuhmo Greenstone Belt [3].
Major host rocks Mafic metavolcanic rock [1].
Minor host rocks Felsic schist, metakomatiite [1,2].
Intrusives The greenstone belt is largely bounded by 2739–2697 Ga tonalites and trondhjemites [4]. NW-trending Palaeoproterozoic dolerite cut arcoss the deformed Archaean rocks in the rergion [8].
Regional geol map 1 kuhmo_map_thumb Outcrop photo 1  
Regional geol map 2   Outcrop photo 2  
Local geology map 1 muje_aitto_harma_jousi_kair_th Outcrop photo 3  
Local geology map 2  
METAMORPHISM
Metamorphic history A very weak, unevenly distributed Palaeoproterozoic overprint [5].
Metamorphic grade Transitional between greenschist and amphibolite facies [1].
Metamorphic mineral assemblage  
Metamorph photo 1   Metamorph photo 2  
STRUCTURE
Structural style Ductile(–brittle).
Closest major shear Ductile, N–S trending, subvertical, several hundreds of metres wide shear zone = the main shear zone of the Kuhmo greenstone belt [1,8].
Controlling structure The mineralisation is in the eastern margin of the N-trending major shear zone [1,2,8].
Deformation history At least, six 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 and/or D4 stages [3,7]. D2: 2850–2837 Ma, D3: 2701–2697 Ma, D4: peaked at 2657±32 Ma [7]. Age of D2 is probably 2820±15 Ma [8] or 2843±18 Ma [10].
Ore fabric  
Veins Arsenopyrite-rich quartz-tourmaline veins up to 50 cm wide, quartz-tourmaline breccia [1].
Structure photo 1   Vein photo 1 aittoranta1_thumb
Structure photo 2   Vein photo 2 aittoranta2_thumb
Structure photo 3   Vein photo 3 aittoranta_sample2_thumb
ALTERATION
General alteration Tourmalinisation and biotitisation [1].
Proximal alteration  
Intermediate alteration  
Distal alteration  
Zonation figure   Prox alteration photo 1 aittoranta_sample4_thumb
Alteration photo 1   Prox alteration photo 2  
Alteration photo 2   Intermed alteration photo  
Alteration photo 3   Distal alteration photo 1  
Post-mineralisation modifications  
TIMING During ca. 2700–2650 Ma [7].
GENETIC MODEL Clearly epigenetic, "mesothermal" mineralisation with a distinct structural control, formed during late-Archaean cratonisation [1,3,6]. Fluid inclusions suggest a single-event mineralisation at about 2.5–3.5 kbar, 450–500°C [9].
GENETIC TYPE Orogenic References [6]
Alternative genetic type 1   References  
Alternative genetic type 2   References  

References

1. Pietikäinen, K. 1998. Personal communication 14/9/98.
2. Luukkonen, E. 1998. Personal communication 27/10/98.
3. 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.
4. 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.
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. 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.
7. Luukkonen, E. 2001. Lentiiran kartta-alueen kallioperä. Summary: Pre-Quaternary rock of the Lentiira map-sheet area. Suomen geologinen kartta 1:100 000. Kallioperäkarttojen selitykset, 4414 + 4432 Lentiira. 68 p.
8. 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)
9. Poutiainen, M. and Partamies, S. 2003. Fluid inclusion characteristics of auriferous quartz veins in Archean and Paleoproterozoic greenstone belts of eastern and southern Finland. Econ. Geol. 98, 1355–1369.
10. 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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