Oltava - Gold Database

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Name	Oltava	DATA UPDATED	19.1.2007
Alternative names
Deposit summary	OLTAVA, in the Raahe-Haapajärvi area, has an in situ resource estimate of 22 kg gold for one of the lodes having a grade of 30 g/t Au. It is a Palaeoproterozoic orogenic or a granitoid-related (non-skarn) gold deposit, comprises a number of lodes with variable grades, and is characterised by arsenopyrite-bearing tourmaline-quartz veins in mica gneiss and quartz diorite. The deposit is located between two major NW-trending shear zones of the Raahe-Ladoga suture zone. Native gold as inclusions in arsenopyrite and löllingite and free gold with quartz. No arsenic in the lode with the resource estimate, where gold occurs as free in gangue.
LOCATION
Geological domain	Svecofennian	Belt	Raahe–Haapajärvi
Site photo		Regional map
Map sheet	243211
Northing (kkj)	7149307	Easting (kkj)	2532355
Latitude	64.44081N	Longitude	24.66809E
Municipality	Pyhäjoki
Nearest town, roads	20 km E from Pyhäjoki, 40 km SW from Oulu. A sealed road 6 km from the area, a gravel road to the area.
MINING
Exploration licence no	866, 942, 6809/1	Mining concession no
Present holder	Pyhäjärven Kehitys Oy (2003–)
Previous holders	Geological Survey of Finland (GTK) (1951–1953, 1997–2 001)
Infra Fig 1		Infra Fig 2
Mine photo 1		Mine photo 2
Mine photo 3		Mine photo 4
Status of development	Prospect
When mined
Resources	718 t @ 30 ppm Au: the most recently explored lode [8].
Deposit size (Mt)	0.000718	Reference (size)	[8]
Total in-situ gold (kg)	22	Reference (in-situ Au)	[8]
Total gold production (kg)		Reference (gold prod)
Production of other metals
Extent of mineralisation
Lodes	One of the lodes: length 6 m, width 2 m, open at depth of 30 m; quartz rock lode is in the contact zone between quartz diorite and mica gneiss [4,8,9,10].
Best sections	0.5 m @ 10.9 ppm, 1 m @ 69.6 ppm, 1.7 m @ 21.3 ppm, 2.3 m @ 18.5 ppm, 3 m @ 2.7 ppm Au, 17.6 m @ 1.15 ppm Au [1,2].
EXPLORATION
Discovery year	1951
Discovery	By GTK: gold-rich samples from boulders and outcrop, found during prospecting for Zn deposits and drilling in areas of electric anomalies [1,2].
Exploration history	GTK (1949–1953) [1,2,3]: Bedrock mapping, survey of glacial erratic boulders, electric and magnetic ground survey, thin and polished section investigations, diamond drilling. GTK (1998–2000) [4,8,9,10,11]: Bedrock mapping, percussion and diamond drilling, magnetic ground 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 (1951–1953) [1,2]: 20 diamond-drill holes, in total 2548 m. GTK (1998–2000) [8,9,10]: 30 diamond-drill holes, in total 1656 m, 2002 [11]: five diamond-drill holes, in total 860 m.
Elements analysed	Au, Ag, Cu, Ni, Zn [1,2]. Au, Bi, Sb, Te by GAAS, major elements, S, Co, Cr, Cu, Mo, Ni, Pb, and Zn by ICP–AES [11].
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, 1950's: T. Borg; GTK 1990's: Jarmo Nikander.
ORE
Siting of gold	Native gold as inclusions in arsenopyrite and loellingite and as free gold with quartz; no arsenic in the lode with the resource estimate, where gold occurs as free in gangue [1,2,4,8,9,10].
Fineness
Major opaques	Pyrite, chalcopyrite, molybdenite [4,8,9,10].
Minor opaques	Arsenopyrite, pyrrhotite, sphalerite, loellingite, native gold [1,2,4].
Gangue	Quartz, tourmaline, diopside, tremolite, garnet, graphite [1,2,8].
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	The mineralisation is in Svecofennian rocks, in the contact zone between a late-orogenic quartz diorite (1.88–1.87 Ga?) and a mica gneiss [4,8,9,10].
Major host rocks	Mica gneiss and quartz diorite [4,8].
Minor host rocks	Black schist, felsic schist, amphibolite, "skarn bands" [1,2].
Intrusives	Synorogenic, 1.89–1.88 Ga, quartz diorites and granites, aplite and pegmatite dikes, late-orogenic, 1.88–1.87 Ga, diorites and gabbros, and post-orogenic dolerites [1,2,6].
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	Progressive metamorphism after mineralisation (?): loellingite envelops arsenopyrite [1,2].
Metamorphic grade	Lower- to mid-amphibolite facies (garnet-staurolite-andalusite grade) [4,7].
Metamorphic mineral assemblage	Mica schist: quartz–biotite–muscovite±plagioclase, baryte, tourmaline, pyrrhotite, chlorite [2,4]. Amphibolite: hornblende–plagioclase–biotite±quartz, pyrrhotite, titanite [2,4].
Metamorph photo 1		Metamorph photo 2
STRUCTURE
Structural style	Ductile(?).
Closest major shear	The mineralisation is located between NW-trending major (>100 km long) shear zones of the Raahe–Ladoga suture zone [4,5].
Controlling structure	A set of dextral faults or shear zones [4].
Deformation history
Ore fabric
Veins	Auriferous, arsenopyrite-bearing tourmaline-quartz veins in an area covering about 2 ha [1,2,3].
Structure photo 1		Vein photo 1
Structure photo 2		Vein photo 2
Structure photo 3		Vein photo 3
ALTERATION
General alteration
Proximal alteration	Quartz veins have commonly hornblende or actinolite selvages [1,2]. Intense silicification of mica schist [4].
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	The mineralisation post-dates the late-orogenic diorite [4].
GENETIC MODEL	A mesothermal mineralisation with a distinct structural control [4]. Gold mineralisation and granitic pegmatites have a genetic connection? [2,8].
GENETIC TYPE	Granitoid-related (non-skarn	References	[8]
Alternative genetic type 1	Orogenic	References	[8]
Alternative genetic type 2		References
References 1. Borg, T. 1952, 1953, 1954. Geol. Surv. Finland, Reports M/52/PJ-52/1, M/17/PJ-53/2, M/17/PJ-54/1. 1 p., 5 p., 6 p. (in Finnish) 2. Pehkonen, E. 1953. Selostus Pyhäjoen Polusjärven alueen geologiasta. Geol. Surv. Finland, Report M/17/PJ-53/3. 70 p. (in Finnish) 3. Stigzelius, H. 1953. Pyhäjoen Oltavan kultamalmiaihe. Comments on the Geol. Surv. Finland, Report M/17/PJ-53/2. Report M/17/PJ-53/4, Ministry of Trade and Industry. 5 p. (in Finnish) 4. Nikander, J. 1998. Personal communication 29/9/1998. 5. Korsman, K., Koistinen, T., Kohonen, J., Wennerström, M., Ekdahl, E., Honkamo, M., Idman, H. & Pekkala, Y. (eds.) 1997. Suomen kallioperäkartta = Berggrundskarta över Finland = Bedrock map of Finland 1:1 000 000. Geol. Surv. Finland. 6. Mäkelä, M. 1984. Raahen Laivakankaan kvartsi–arseenikiisu–kultaesiintymä. Unpublished MSc thesis. University of Turku. 105 p. (in Finnish) 7. 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. 8. Nikander, J. 2001. The Oltava Gold Prospect, Pyhäjoki, Finland. Appendix to an international tender notice by the Finnish Ministry of Industry and Trade. www.gtk.fi/explor/tender/Oltava/oltava.htm 9. Nikander, J. 1999. Exploration report on gold ore exploration carried out in Pyhäjoki Commune, expl. lease Oltava 1 (mine reg. NR. 6809/1), years 1998 and 1999. Geol. Surv. Finland, Report C/M 06/2432/-99/1/10. (in Finnish with English summary) 10. Nikander, J. 1999. Gold exploration in Oltava, Pyhäjoki, map sheet 2432 11 under years 1998 and 1999. Geol. Surv. Finland, Report C/M 19/2432/-99/1/10. (in Finnish) 11. Makkonen, H., Kontoniemi, O., Lempiäinen, R., Lestinen, P., Mursu, J. & Mäkinen, J. 2003. Raahe–Laatokka-vyöhyke, nikkelin ja kullan etsintä –hankkeen (2108001) toiminta vuosina 1999–2 003. English summary: Exploration for nickel and gold in the Raahe–Ladoga Zone during 1999–2003, GTK Project 2108001. Geol. Surv. Finland, Report M 10.4/2003/5/10. 90 p. (26.4 MB)
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