Lokkiluoto - Gold Database

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Name	Lokkiluoto	DATA UPDATED	24.5.2007
Alternative names	Lokki
Deposit summary	LOKKILUOTO, in the Kuhmo greenstone belt, is an Archaean orogenic gold occurrence in an islet on a lake, with no resource estimate available. It is formed by a single lode in mafic metatuffite close to the main, NW-trending, shear zone of the greenstone belt. Native gold as inclusions and in margins of arsenopyrite and chalcopyrite grains.
LOCATION
Geological domain	Archaean	Belt	Kuhmo
Site photo		Regional map
Map sheet	441302
Northing (kkj)	7115520	Easting (kkj)	4463870
Latitude	64.13751N	Longitude	29.25463E
Municipality	Kuhmo
Nearest town, roads	12 km W from Kuhmo. Two small islets on the lake Ontojärvi, 4 km from sealed road, 1.5 km over the lake to a gravel road at the lake shore.
MINING
Exploration licence no	4969/1	Mining concession no
Present holder	OPEN FOR ACQUISITION
Previous holders	Kajaani Oy, Geological Survey of Finland (GTK).
Mine photo1		Mine photo2
Mine photo3		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	N-S trending, 1 m wide, 80 m long [2].
Lodes	One lode [8].
Best sections	5.6 m @ 4.2 ppm Au [1].
EXPLORATION
Discovery year
Discovery	The mineralised outcrop was found by an amateur prospector [2].
Exploration history	Kajaani Oy (pre-1990) [2]: bedrock mapping, diamond drilling. GTK (1990–1998) [2,8] : bedrock mapping, low-altitude airborne magnetic, electric, gravity and radiometric 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	Kajaani Oy [2]: two diamond-drill holes. GTK (1992) [2]: 8 diamond-drill holes, total 343 m.
Elements analysed	Ag, As, Au, Co, Cu, Fe, Ni, Pb, S, Te, and Zn [2].
Primary dispersion	Au and As anomaly, at least, in the hanging wall [2].
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: Timo Heino.
ORE
Siting of gold	Gold as inclusions and in margins of arsenopyrite and chalcopyrite [2,8].
Fineness
Major opaques	Arsenopyrite [2,8].
Minor opaques	Pyrrhotite, chalcopyrite, ilmenite, pyrite, a telluride, gold, molybdenite [2,8].
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	Diamond-drill core [1]: 3.90 ppm Au, 0.225 ppm Ag, 8500 ppm As, 7.5 ppm B, 271 ppm Ba, 1.3 ppm Bi, 73 ppm Co, 319 ppm Cu, 150 ppb Hg, 2.0 ppm Mo, 55 ppm Ni, <2 ppm Pb, 51 ppm Rb, 10300 ppm S, 8.9 ppm Sb, 0.32 ppm Se, 148 ppm Sr, 0.150 ppm Te, 2.6 ppm Th, 1.3 ppm U, 280 ppm V, 5.0 ppm W, 235 ppm Zn; 49.7% SiO2, 2.12% TiO2, 12.1% Al2O3, 18.6% Fe2O3, 3.25% MgO, 7.99% CaO, 1.63% Na2O, 1.04% K2O, 0.36% P2O5, 1.16% LOI. Within the entire mineralisation: 1–9 ppm Au [2].
Enriched elements	Au, As, Bi, S, Sb, Te, W [1].
Ore fluid
Stable isotopes
Pb isotope data
GEOLOGY
Geological setting	The deposit is conformable; it is in the SW part of the late Archaean Kuhmo Greenstone belt, in the contact zone of the mafic to ultramafic-dominated Petäjäniemi Formation and the mica schist-dominated Kokkoniemi Formation [2,4].
Major host rocks	Mafic metatuff(ite) [1,2].
Minor host rocks
Intrusives	The greenstone belt is largely bounded by 2739–2697 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 very weak, unevenly distributed Palaeoproterozoic overprint [5].
Metamorphic grade
Metamorphic mineral assemblage
Metamorph photo 1		Metamorph photo 2
STRUCTURE
Structural style
Closest major shear	The NW-trending main shear zone of the Kuhmo greenstone belt [8].
Controlling structure	D4-structure(s) [2]. The deposit is between two NW-trending, mylonitised shear zones [2].
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 [3,7]. Age of D2 is probably 2820±15 Ma [8] or 2843±18 Ma [9].
Ore fabric
Veins
Structure photo 1		Vein photo 1
Structure photo 2		Vein photo 2
Structure photo 3		Vein photo 3
ALTERATION
General alteration	Biotitisation, weak sulphidation and precipitation of quartz [2,8].
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	Late Archaean [3].
GENETIC MODEL	Orogenic "mesothermal" deposit formed during late-Archaean cratonisation [6].
Genetic type	Orogenic	References	[6]
Alternative genetic type 1		References
Alternative genetic type 2		References
References 1. Nurmi, P. A., Lestinen, P. & Niskavaara, H. 1991. Geochemical characteristics of mesothermal gold deposits in the Fennoscandian Shield, and a comparison with selected Canadian and Australian deposits. Geol. Surv. Finland, Bulletin 351. 101 p. 2. Heino, T. & Kilpelä, M. 1995. Tutkimustyöselostus valtausalueella Lokki 1, kaivosrekisterinumero 4969/1 suoritetuista tutkimuksista. Geol. Surv. Finland, Report M06/4413/1995/1/10. 5 p. (in Finnish, 770 KB) 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. (in Finnish) 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. 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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