Sepponen - Gold Database

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Name	Sepponen	DATA UPDATED	24.5.2007
Alternative names
Deposit summary	SEPPONEN is a Palaeoproterozoic orogenic gold occurrence with no resource estimate available. It is in a small greenstone fragment (amphibolite) surrounded by high-grade granite-gneiss terrain SE from the Kuhmo greenstone belt proper. The occurrence is controlled by a local, NW-trending, dextral shear zone. Native gold associated with arsenopyrite.
LOCATION
Geological domain	Archaean	Belt	Kuhmo
Site photo		Regional map
Map sheet	432408
Northing (kkj)	7083900	Easting (kkj)	4488950
Latitude	63.85559N	Longitude	29.77001E
Municipality	Kuhmo
Nearest town, roads	32 km SSE from Kuhmo, 45 km NE from Nurmes. 4 km to asealed road, a gravel road to the area.
MINING
Exploration licence no		Mining concession no
Present holder	Karelian Diamond Resources (2004–)
Previous holders	Geological Survey of Finland (GTK)
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	Several ppm Au per metre in channel sampling on outcrop [2].
EXPLORATION
Discovery year	1992
Discovery	By GTK: The first indications were the auriferous glacial erratic boulders detected during regional till geochemical survey; this led to the discovery of the mineralisation in outcrop [2,7].
Exploration history	GTK [1,2,7]: Detailed bedrock mapping, trenching, ground slingram and IP 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
Elements analysed
Primary dispersion
Secondary dispersion
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: Timo Heino.
ORE
Siting of gold	Gold is associated with arsenopyrite [2,7].
Fineness
Major opaques	Arsenopyrite, pyrrhotite [2].
Minor opaques
Gangue	Quartz, hornblende, K feldspar, calcite [1,2].
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	A sequence of banded amphibolites and micagneisses within a granitoid-dominated area, to the SE of the main area of the Late-Archaean Kuhmo Greenstone belt [1,7].
Major host rocks	Amphibolite [1,2].
Minor host rocks
Intrusives	The small piece of a greenstone belt is bounded by 2739–2 697 Ga tonalites and trondhjemites [4].
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 relatively strong, but unevenly distributed Palaeoproterozoic overprint [5].
Metamorphic grade	Mid- or upper-amphibolite facies [2,7].
Metamorphic mineral assemblage	Amphibolite: hornblende-plagioclase [2].
Metamorph photo 1		Metamorph photo 2
STRUCTURE
Structural style	Ductile [2].
Closest major shear
Controlling structure	An Archaean D4, strike-oblique-slip, NW-trending, dextral shear and fault zone [1,2,3].
Deformation history	At least, six deformation stages during the late Archaean and two deformation stages during the Palaeoproterozoic time detected in the area; D3 peaked at 2697±10 Ma and D4 at 2657±32 Ma; gold mineralisation is related to the Archaean D4 stage [1,2,3,6,7]. Age of D2 is probably 2820±15 Ma [7] or 2843±18 Ma [8].
Ore fabric
Veins	Auriferous quartz ± K feldspar, calcite, hornblende, arsenopyrite veins [1,2,7].
Structure photo 1		Vein photo 1
Structure photo 2		Vein photo 2
Structure photo 3		Vein photo 3
ALTERATION
General alteration	Biotitisation, sulphidation [2].
Proximal alteration	Hornblende selvages, 1–3 cm wide, on the mineralisation-related quartz veins [2].
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	Late Archaean [3].
GENETIC MODEL	Orogenic "mesothermal" deposit.
GENETIC TYPE	Orogenic	References
Alternative genetic type 1		References
Alternative genetic type 2		References
References 1. Luukkonen, E. 1993. Kultamineralisaatio Suomussalmen ja Kuhmon vihreäkivivyöhykkeellä. In: P. Nurmi (ed.) Itä-Suomen kultaesiintymät. Ekskursio-opas. Vuorimiesyhdistys, Sarja B, no. 54, 33–3 5. (in Finnish) 2. Pietikäinen, K. 1998. Personal communication 14/9/1998. 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. 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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