Louhiniemi - Gold Database

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Name	Louhiniemi	DATA UPDATED	24.5.2007
Alternative names
Deposit summary	LOUHINIEMI, in the Kuhmo greenstone belt, is an Archaean orogenic gold occurrence with no resource estimate available. It comprises several narrow lodes in mylonitic, N-trending, late-D3 or D4 structures near the main, N-trending shear zone of the greenstone belt. The occurrence is hosted by mafic volcanic rocks. No information on siting of gold.
LOCATION
Geological domain	Archaean	Belt	Kuhmo
Site photo		Regional map
Map sheet	441210
Northing (kkj)	7137500	Easting (kkj)	4456800
Latitude	64.33383N	Longitude	29.10308E
Municipality	Kuhmo
Nearest town, roads	30 km NW from Kuhmo. Three km to a sealed road, gravel roads adjacent to the area, 15 km from railway.
MINING
Exploration licence no	6822/1	Mining concession no
Present holder	OPEN FOR ACQUISITION
Previous holders	Geological Survey of Finland (GTK) (1999–2002)
Claim Fig 1		Claim Fig 2
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	Open along strike and at the depth of a few tens of metres [1].
Lodes	Apparently, several 1 m wide lodes [1,7].
Best sections	0.9 m @ 6.2 ppm Au, 1 m @ 1 ppm Au [1].
EXPLORATION
Discovery year	1998
Discovery	By GTK; the first indications were the several auriferous glacial erratic boulders discovered in the area by amateur prospectors in 1997; ground geophysical and till geochemical surveys led diamond drilling into the deposit [1,7].
Exploration history	GTK (1997-1999) [1,7]: bedrock mapping, ground magnetic, slingram and IP survey, till geochemical 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 (1999): seven diamond-drill holes, total 507 m [1].
Elements analysed
Primary dispersion	The regional Au-As anomaly seems to evelop the Au mineralisation [1,7].
Secondary dispersion	The prospect is within an area covered by an extensive As anomaly in till [1].
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: Markku Tenhola
ORE
Siting of gold
Fineness
Major opaques	Pyrrhotite [1,7].
Minor opaques	Arsenopyrite, pyrite, chalcopyrite [1,7].
Gangue
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
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 mica schists and mafic tholeiitic metavolcanic rocks with thin ultramafic (komatiitic?) interlayers [1].
Major host rocks	Mafic metavolcanic rock [1].
Minor host rocks	Quartz porphyry [1].
Intrusives	A few m wide quartz porphyry dykes cut across the supracrustal sequence [1]. 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 region [7].
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]
Closest major shear	The main, N-trending, shear zone of the Kuhmo greenstone belt [7].
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 [2,6]. D2: 2850–2837 Ma, D3: 2701–2697 Ma, D4: peaked at 2657±32 Ma [6]. Age of D2 is probably 2820±15 Ma [7] or 2843±18 Ma [8].
Ore fabric
Veins
Structure photo 1		Vein photo 1
Structure photo 2		Vein photo 3
ALTERATION
General alteration
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 [6].
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. Tenhola, M. & Niskanen, M. 2001. Tutkimustyöselostus Kuhmon kaupungissa valtausalueella Louhiniemi 1 (Kaivosrekisteri No 6822/1) suoritetuista kultamalmitutkimuksista vuosina 1998–1999. English summary: The Louhiniemi gold prospect in Kuhmo, eastern Finland in 1998–1999 (register number of claim: Louhiniemi 1, 6822/1) Geol. Surv. Finland, Report M 06/4412/2001/2/10. 7 p.(1.8 MB) 2. 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. 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. 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. 7. 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) 8. 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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