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
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		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: 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
Ore miner. photo 4		Ore outcrop photo 2
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		Outcrop photo 1
Regional geol map 2		Outcrop photo 2
Local geology map 1		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
Structure photo 2		Vein photo 2
Structure photo 3		Vein photo 3
ALTERATION
General alteration	Tourmalinisation and biotitisation [1].
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
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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