Laivakangas-N - Gold Database

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Name	Laivakangas-N	DATA UPDATED	16.3.2006
Alternative names	Näädänmaa, Näädänmalmi
LOCATION
Geological domain	Svecofennian	Belt	Raahe-Haapajärvi
Site photo		Regional map
Map sheet	244107
Northing (kkj)	7160400	Easting (kkj)	2528200
Latitude	64.54068N	Longitude	24.58394E
Municipality	Raahe
Nearest town, roads	16 km SSE from Raahe, 50 km SW from Oulu. A sealed road 8 km from the area, a narrow gravel road to the area.
MINING
Exploration licence no	3181/1, 3463/1, 3649/1, 6122/1, 6571/1–5, 7803/1, 7979/1–2, 7992/1–3, 8045/1–5	Mining concession no
Present holder	Nordic Mines AB (2005–)
Previous holders	Outokumpu Oy (1980's), Endomines Oy (1997–2005)
Mine photo 1		Mine photo 2
Mine photo3		Mine photo 4
Status of development	Test mine [13].
When mined	1985 [13].
Resources	Indicated + inferred: 3.1 Mt @ 2.6 ppm Au [15]. Indicated 0.3 Mt @ 3.3 ppm + inferred 0.2 Mt @ 5 ppm (cutoff 2 ppm) [12]. 0.7 Mt 4 ppm Au [5].
Deposit size (Mt)	3.1	Reference (size)	[15]
Total in-situ gold (kg)	8060	Reference (in-situ Au)	[15]
Total gold production (kg)	28	Reference (gold prod)	[13]
Production of other metals
Extent of mineralisation	A few metres wide and a few tens of metres long at surface [3], open at the depth of 60 m [10,11,12].
Lodes	The number of lodes reported is 18; they are 10–100 m long, on average 2.4 m wide, and have an ENE strike [12].
Best sections	1 m @ 92 ppm Au [15]. 14.85 m @ 1.9 ppm, 4 m @ 2.9 ppm, 1.9 m @ 3.3 ppm Au [14]. 2.2–13.4 m sections at 2.7–24.2 ppm Au [8].
EXPLORATION
Discovery year	1982
Discovery	By Outokumpu. The first indication was an sample from a glacial erratic boulder found by an amateur prospector on 1980 [2,4].
Exploration history	Outokumpu Oy (1980's) [2,3,4,6,10,11,12]: bedrock mapping, till and stream sediment geochemical survey, survey of glacial erratic boulders, till stratigraphy, magnetic and IP ground survey, percussion and diamond drilling, pilot plant tests, thin section studies. Endomines Oy [10,11,12,14]: diamond drilling, pilot plant tests. Nordic Mines [15]: diamond drilling, test mining, pilot plant tests.
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	Outokumpu Oy (1980's): diamond drilling, total 6200 m in the area [2], 77 diamond-drill holes in Laivakangas-N [12]. Drilling in profiles, information from two profiles where each hole is about 20-30 m apart and the distance between profiles is 25 m [4]. Endomines: 11 diamond-drill holes, total 803 m [12]. Total drilling by end of September 2005: 6957 m [15].
Elements analysed	SiO2, TiO2, Al2O3, Fe2O3, MnO, MgO, CaO, Na2O, and K2O by XRF; Ag, As, Au, Bi, Co, Cu, Fe, Hg, Ni, Pb, Te, Zn: by AAS; S by Leco [3].
Primary dispersion	Good correlation between Au, As, Bi and Sb [2,3,6]. Other element pairs showing good mutual positive correlation are: Cu and Ag, As and Sb, and Te and Bi [3].
Secondary dispersion	A distinct stream sediment Au, As and Sb anomaly, and Au and As anomaly 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
Economic evaluations	Feasibility study by Outokumpu Oy on 1990(?) [4]. Resource estimates for Endomines by GTK in 1999–2001 [10,11,12]. Feasibility study by Nordic Mines planned for 2006 [15].
Exploration geologist in charge	Outokumpu: Esa Sandberg, Endomines Oy: Jaakko Liikanen.
ORE
Siting of gold	Gold occurs as native inclusions in quartz and other silicates (34% of all gold), and arsenopyrite and loellingite (64%; grain size 1–40 μm), minor gold (2%) is in maldonite and as inclusions in chalcopyrite; most of gold is in the quartz veins [2,3,6,12].
Fineness	95% Au, 1.7% Ag (avg.) [2, 6].
Major opaques	Arsenopyrite, loellingite [2,3,6].
Minor opaques	Pyrrhotite, chalcopyrite, pyrite, cubanite, marcasite, sphalerite, maldonite, bismuth, hedleyite, gold, molybdenite [2,3,6]
Gangue	Quartz, diopside, K-feldspar, plagioclase, biotite, scheelite [2,3,6].
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	Diamond-drill core [1]: 4.95 ppm Au, 2.100 ppm Ag, 2200 ppm As, 5.6 ppm B, 283 ppm Ba, 14.2 ppm Bi, 71 ppm Co, 451 ppm Cu, 52 ppb Hg, 2.0 ppm Mo, 36 ppm Ni, <1 ppm Pb, 66 ppm Rb, 2800 ppm S, <0.3 ppm Sb, 2.2 ppm Se, 202 ppm Sr, 1.850 ppm Te, 1.7 ppm Th, 0.5 ppm U, 280 ppm V, 28 ppm W, 92 ppm Zn; 54.1% SiO2, 0.80% TiO2, 15.2% Al2O3, 10.4% Fe2O3, 6.14% MgO, 8.51% CaO, 2.82% Na2O, 1.56% K2O, 0.14% P2O5, 0.85% LOI.
Enriched elements	Ag, As, Au, Bi, Hg, K (in mafic rock only), S, Se, Si(?), Te, W [1,3]
Ore fluid
Stable isotopes
Pb isotope data
GEOLOGY
Geological setting	The deposit is in a late-orogenic(?) quartz diorite and mafic metavolcanic rock [2,3,5,6,12]. The deposit is in a sequence of Palaeoproterozoic metavolcanic rocks intruded by synorogenic dykes, sills and plutons [5,6].
Major host rocks	Quartz diorite and mafic metavolcanic rock [1,3]
Minor host rocks
Intrusives	Quartz diorite dikes from the 1.89–1.87 Ga [9] synorogenic pluton cross cut the metavolcanic rock, but predate mineralisation. Up to 20 cm wide, late-orogenic(?), granite dikes cut across the quartz diorite dikes and gold mineralisation [1,2,3,5,6], and a large granite body is immediately to the west of the mafic rock and the deposit [12].
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
Metamorphic grade	Amphibolite facies, 575±50°C, 5±0.5 kbar [3]. On the other hand, the presence of diopside indicates mid-amphibolite facies conditions. "Medium-grade" metamorphism in the reference [2].
Metamorphic mineral assemblage	Mafic metavolcanic rock: plagioclase-hornblende-biotite ± quartz, K feldspar, titanite, epidote, ilmenite [3]. Quartz diorite: plagioclase-hornblende-quartz-biotite ± K feldspar, titanite [3].
Metamorph photo 1		Metamorph photo 2
STRUCTURE
Structural style	Brittle-ductile [2,3].
Closest major shear	The mineralisation is located between NW-trending major (>100 km long) shear zones of the Raahe-Ladoga suture zone [5,6,7].
Controlling structure	A set of parallel, 1–150 cm wide, E- or ENE-trending, subvertical shear zones [2,12].
Deformation history
Ore fabric
Veins	Auriferous arsenopyrite-quartz veins [1,2,3] which have a dip of 70–85° to the ENE [10].
Structure photo 1		Vein photo 1
Structure photo 2		Vein photo 2
Structure photo 3		Vein photo 3
ALTERATION
General alteration	Formation of epidote, biotite, K feldspar, quartz and arsenopyrite [3]. Alteration is, apparently, more intense in the mafic metavolcanic rock than in the quartz diorite [3].
Proximal alteration	Diopside-biotite-hornblende-plagioclase-K-feldspar-biotite-quartz-epidote assemblage; a diopside band forms the most proximal subzone, next to the veins, this is followed by a hornblende-dominated subzone [2,3,6].
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 deposit post-dates the intrusion of synorogenic quartz diorite, but predates late-orogenic(?) granite dikes [3].
GENETIC MODEL	Loellingite is surrounded by a arsenopyrite rim: the deposit is formed at temperatures where loellingite is stable, although arsenopyrite thermometry only gives 370°C [2]. Features described in [2,3,4,5,6] indicate an orogenic "mesothermal" mineralisation formed under amphibolite-facies PT conditions.
GENETIC TYPE	Orogenic 'mesothermal'.
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. Mäkelä, M. & Sandberg, E. 1985. Raahen Laivakankaan kultaesiintymä. The gold occurrence at Laivakangas, Raahe. Geologi. 37, 5–8. 3. Mäkelä, M. 1984. Raahen Laivakankaan kvartsi-arseenikiisukultaesiintymä. Unpublished MSc thesis. University of Turku. 105 p. (in Finnish) 4. Korkalo, T. 1991. Kaivoslain 19 pyk. mukainen tutkimustyöselostus: Raahen kaupunki: Pirttihaudankangas, Siljanneva, Pirttivaara, Kauniinhaudansuo. Outokumpu Oy, Report 080/2441, 2432/TTK/91. 3 p. (in Finnish) 5. Mäkelä, M., Sandberg, E. & Rantala, O. 1988. Proterozoic, gold-bearing vein occurrences associated with the granitoids in western Finland. In: A. D. T. Goode et al. (comp.) Bicentennial Gold 88, Melbourne, Victoria, May 16–20, 1988: Extended abstracts. Poster programme. 1. Geological Society of Australia. Abstracts Series 23, 153–155. 6. Mäkelä, M., Sandberg, E. & Rantala, O. 1988. Geochemical exploration of gold-bearing veins associated with granitoids in western Finland. In: D. R. MacDonald & K. A. Mills (eds) Prospecting in Areas of Glaciated Terrain – 1988: Papers presented at the Eighth International Symposium on Prospecting in Areas of Glaciated Terrain, Halifax, Nova Scotia, August 28 – September 3, 1988: Canadian Institute of Mining and Metallurgy. 255–270. 7. 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. 8. Endomines Oy. 1999. www.endomines.fi on 09/12/99 9. 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. 10. Parkkinen, J. 1999. Ilomantsin Hoskon ja Raahen Laivakangas: mineraalivarantoarvioiden menetelmätarkistus Endomines Oy:lle. English summary: The Hosko gold prospect at Ilomantsi and the Laivakangas gold occurrence at Raahe: technical revision of evaluations for Endomines Oy. Geol. Surv. Finland, Report CM10/-99/1. 19 p. 11. Parkkinen, J. 2000. Laivakankaan kulta-aihe. Mineraalivarantoarvion tarkistus. Geol. Surv. Finland, Report C/M19/2441/2000/1. 7 p. 12. Parkkinen, J. 2001. Quality control of mineral resource estimates: Laivakangas, Hosko, Kuivisto E, Other, Osikonmäki, Pirilä, Housuvaara, Pahkalampi. Geol. Surv. Finland, Report. 27 p. 13. Puustinen, K. 1995. Suomen malmikaivokset vuosina 1530–1994. Geol. Surv. Finland, Report M10.1/-95/1. 96 p. (in Finnish) 14. Endomines Oy. 2005. www.endomines.fi in 12/12/2005. 15. Nordic Mines Ab. 2006. www.nordicmines.se/laiva.php in 16/03/2006 .
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