Mujesuo - Gold Database

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Name	Mujesuo	DATA UPDATED	24.5.2007
Alternative names
Deposit summary	MUJESUO, in the Kuhmo greenstone belt, is an Archaean orogenic gold occurrence with no resource estimate available. It is hosted by mafic or ultramafic volcanic rocks, defined by quartz veins and altered host rock, and controlled by 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)	7141500	Easting (kkj)	4455000
Latitude	64.36948N	Longitude	29.06464E
Municipality	Kuhmo
Nearest town, roads	35 km NW from Kuhmo. A sealed road across the area, seven km from railway.
MINING
Exploration licence no	5412/1	Mining concession no
Present holder	GTK (2004–2005)
Previous holders	Geological Survey of Finland (GTK) (1994–1998), Ilmari Exploration (2002–2003)
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
Best sections	1 m @ 9.06 ppm Au [6,8]; 0.05–0.5 m @ 2–100 ppm Au [5].
EXPLORATION
Discovery year	1994
Discovery	By GTK [1,2,6,8]: first indication was an auriferous sample from a glacial erratic boulder, provided by an amateur prospector in 1993; the deposit was detected by trenching and drilling by GTK.
Exploration history	GTK (1993–1998) [1,6,8]: bedrock mapping, trenching, diamond drilling, ground magnetic, electromagnetic and IP survey, till geochemical and stratigraphy survey.
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 [1,6]: 17 diamond-drill holes, total 997 m.
Elements analysed
Primary dispersion
Secondary dispersion	Regional and local Au, As and Ni anomalies in till [6].
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
Primary anomaly fig 6		Secondary anomaly fig 6
Economic evaluations
Exploration geologist in charge	GTK: Erkki Luukkonen.
ORE
Siting of gold
Fineness
Major opaques	Pyrrhotite, pyrite [1,6,8].
Minor opaques	Chalcopyrite, native gold [6,8].
Gangue	Tremolite-actinolite, quartz, chlorite [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	Ag, As, Au, Cu, Pb, S [6].
Ore fluid
Stable isotopes
Pb isotope data
GEOLOGY
Geological setting	Located in the central part of the Late-Archaean Kuhmo Greenstone Belt, in a sequence dominated by mafic metavolcanic rocks with thin ultramafic (komatiitic?) interlayers [1,6].
Major host rocks	Mafic or ultramafic metavolcanic rock [1,6]
Minor host rocks
Intrusives	The greenstone belt is largely bounded by 2739–2697 Ga tonalites and trondhjemites [3]. 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 [4].
Metamorphic grade	Upper-greenschist facies [1].
Metamorphic mineral assemblage
Metamorph photo 1		Metamorph photo 2
STRUCTURE
Structural style	Ductile [1,2]
Closest major shear	The main, N-trending, shear zone of the Kuhmo greenstone belt [8].
Controlling structure	N–S trending mylonites which are late-D3 or D4 structures [1,2].
Deformation history	At least, six deformation stages during the late Archaean and two deformation stages during the Palaeoproterozoic detected in the area; gold mineralisation is related to the Archaean late D3 and/or D4 stages [2,7]. 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 [9].
Ore fabric
Veins	Auriferous quartz vein, generally 5–10 cm wide [1].
Structure photo 1		Vein photo 1
Structure photo 2		Vein photo 2
Structure photo 3		Vein photo 3
ALTERATION
General alteration	Formation of Ca-amphibole [8].
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 [1], formed during late-Archaean cratonisation [5].
GENETIC TYPE	Orogenic	References	[5]
Alternative genetic type 1		References
Alternative genetic type 2		References
References 1. Pietikäinen, K. 1998. Personal communication 14/9/98. 2. Luukkonen, E., Pajunen, M. & Poutiainen, M. 1992. Kuhmo–Suomussalmen alueen arkeeisen kallioperä rakenne-evoluutio ja Au-aiheet. In: E. Ekdahl (ed.) Suomen kallioperän kehitys ja raaka-ainevarat. Vuorimiesyhdistys, Sarja B, 51, 11–12. 3. 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. 4. 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. 5. 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. 6. Tenhola, M. & Niskanen, M. 2001. Tutkimustyöselostus Kuhmon kaupungissa valtausalueilla Aitto 1 (Kaivosrekisteri No 5032/1), Mujesuo 1 (Kaivosrekisteri No 5412/1), Jousijärvi 1 (Kaivosrekisteri No 5333/1) sekä Härmäkangas 1 (Kaivosrekisteri No 6108/1) suoritetuista kulta- ja sinkkimalmitutkimuksista vuosina 1992–1999. English summary: The gold and zinc prospects in Kuhmo, Eastern Finland in 1992–1999 (register number of claims: Aitto 1, 5032/1; Mujesuo 1, 5412/1; Jousijärvi 1, 5333/1; Härmäkangas 1, 6108/1) Geol. Surv. Finland, Report M 06/4412/2001/3/10. 8 p. (in Finnish, 3.7 MB) 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. 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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