Hannukainen - Gold Database

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Name	Hannukainen	DATA UPDATED	30.1.2008
Alternative names	Laurinoja
Deposit summary	HANNUKAINEN, in the western margin of Central Lapland greenstone belt (CLGB), is a deposit mined in 1978–1992 when 1.96 Mt iron, 40,000 t copper and 4300 kg gold was produced. The present in situ resource estimate is 16 t Au, 125,000 t Cu and 26 Mt Fe (no JORC-compliant resource is available). It is a Palaeoproterozoic iron oxide-copper-gold deposit including five main ore bodies all variably enriched in Au, Ca, Cu, K, Mg, Na, Fe, and S. The ore is hosted by massive to banded diopside-hornblende- and magnetite rocks in a bend in the crustal-scale, N- to NNE-trending Pajala Shear Zone (aka Kolari Shear System), in the contact zone between a 1.86 Ga monzonitic intrusion and the supracrustal CLGB rocks. Sulphides and gold postdate diopside, hornblende and magnetite, and the age dating at site suggest epigenetic Au-Cu mineralisation postdating the monzonite by ca. 40 Ma. Native gold, all or most of it, closely associated with chalcopyrite, magnetite and gangue: inclusions in pyrite with chalcopyrite, in cracks is magnetite and pyrite, inclusions in chalcopyrite.
LOCATION
Geological domain	Lapland	Belt	Central Lapland
Site photo		Regional map
Map sheet	271410
Northing (kkj)	7496350	Easting (kkj)	2499300
Latitude	67.55461N	Longitude	23.97931E
Municipality	Kolari
Nearest town, roads	25 km NE of Kolari. One km to a sealed road, gravel roads to the mine site. Seven km to railway.
MINING
Exploration licence no		Mining concession no	2436/1b
Present holder	Northland Resources Ab (2005–)
Previous holders	Suomen Malmi (1956–1960), Otanmäki Oy (1960–1967), Rautaruukki (1967–1985), Outokumpu (1985–)
Mine photo 1		Mine photo 2
Mine photo 3		Mine photo 4
Status of development	Open pit, closed
When mined	1978–1992
Resources	166.2 Mt @ 35.1 % Fe, 0.17 % Cu, 0.065 ppm Au (cut-off grade 15 % Fe) [15]. Laurinoja ore body, mined: 4.5 Mt @ 43% Fe, 0.88% Cu, 0.95 g/t Au [4,9]. Entire Laurinoja 43 % Fe, 0.36 % Cu, 0.15 ppm Au [11].
Deposit size (Mt)	170.7	Reference (size)	[15]
Total in-situ gold (kg)	15080	Reference (in-situ Au)	[15]
Total gold production (kg)	4300	Reference (gold prod)	[4]
Production of other metals	40,000 t Cu, 1.96 Mt Fe [4]
Extent of mineralisation	N-S extent 2.5 km, E-W extent at least 2 km; open at depth: extends further to the W below the monzonite [1]. The lodes Kuervaara, Vuopio, Laurinoja, Lauku, Kivivuopio form an area measuring approximately 1.3 km by 2.7 km [15].
Lodes	Several ore bodies, oriented along the regional dominant lineation, at least: Kuervaara, Vuopio, Laurinoja, Lauku, Kivivuopio [1,11]. They are flat lenses dipping at 0-35° to the W and plunging at 0-30° to the SW, 500-1200 m long, 100-500 m wide and 5-40 m thick [1,11]. Au-Cu ore body detected in 2005: horizontal extent >600 m x >850 m, avg thickness 17.5m, dip from horizontal to 15°, open to the NE and SW [8,10,12]. Another, 15 m thick, Au-Cu ore body detected in the hangingwall in 2007 [12].
Best sections	Han-089: 21.5 m @ 0.56 ppm Au, 0.87 % Cu, 35.5. % Fe, Lau-251: 32.4 m @ 0.38 ppm Au, 0.91 % Cu, 37.8 % Fe, Lau-177: 31.9 m @ 0.23 ppm Au, 0.47 % Cu, 34.6 % Fe [8]. 33.1 m @ 0.33 ppm Au, 0.77 % Cu, 37.7 % Fe; 29.1. m @ 0.75 ppm Au, 0.81 % Cu, 39.7 % Fe; 9.6 m @ 0.99 ppm Au, 1.11 % Cu, 46.9 % Fe [10]. 11.25 m @ 51.39 % Fe, 1.09 ppm Au, 0.75 % Cu; 6.2 m @ 53.41 % Fe, 0.27 ppm Au, 4.75 % Cu [12].
EXPLORATION
Discovery year	1974
Discovery	By Rautaruukki [1], by low-altitude airborne magnetic survey. This survey indicated four magnetite ore bodies.
Exploration history	Several small companies (early-1600's to 1930's) [1]: bedrock mapping and attempt to mine the Juvakaisenmaa Fe-only deposit 15 km SW of Rautuvaara. Vuoksenniska (1940–1945) [1]: Ground magnetic surveys, bedrock mapping. Suomen Malmi (1956–1960) [1]: Airborne magnetic and electromagnetic surveys, bedrock mapping, diamond drilling. Otanmäki Oy (1960–1967) [1]: Ground geophysical surveys, bedrock mapping, diamond drilling. Rautaruukki (1967–1985) [1,11]: Ground geophysical surveys, low-altitude airborne magnetic, electromagnetic and radiometric survey, till geochemical survey, trenching, bedrock mapping, diamond drilling. Northland [8,10,12,13,14,15]: re-logging and re-assaying historic drill core, diamond drilling, metallurgical test work.
Section figure 1		Plan figure 1	Click here (pdf 108 KB)
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	Good response on magnetic and gravity methods for all magnetite-rich ore bodies [1].
Drilling	Rautaruukki Oy, Rautuvaara and Hannukainen combined: >400 diamond-drill holes between 1974–1980 [1]. Northland (2006–2007): 42 diamond-drill holes [10,12]; 2007: 72 diamond-drill holes [12,15].
Elements analysed	By XRF: Si, Ti, Al, Fe, Mn, Mg, Ca, K, P, Cr, Cu, S, V, Zr, and Na by AAS [1].
Primary dispersion	Au, Ca, Cu, K, Mg, Na, Fe, and S seem to form haloes of enrichment around the deposit [1].
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	Feasibility study by Rautaruukki by 1970's [11]. Resource calculation during 2006–2007 based on 104 holes drilled by Northland and re-evaluation of 236 historic holes [13,14,15].
Exploration geologist in charge	Rautaruukki: A. Hiltunen
ORE
Siting of gold	Associated with chalcopyrite, magnetite and silicate gangue: inclusions in pyrite with chalcopyrite, in cracks is magnetite and pyrite, inclusiuons in chalcopyrite [1,9]. Native gold as 0.1-0.3 mm grains associated with chalcopyrite [11].
Fineness
Major opaques	Magnetite, pyrite, pyrrhotite, chalcopyrite [1,5,9,11].
Minor opaques	Native gold, molybdenite, tellurides [1,5,9,11].
Gangue	Diopside, quartz, hornblende, biotite, calcite, albite, microcline, titanite, scapolite, andradite, epidote [1,5].
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
Ore composition table 1	Click here	Ore composition table 2
Enriched elements	Au, Ca, Cu, K, Mg, Na, Fe, S ± Ag, Bi, Ba, Co, LREE, Mo, Sb, Te, Zn [5,9].
Ore fluid	Early L-V-halite, 45-48 % NaCl eq, later L-V-halite 32-56 % NaCl eq, late CO2-rich [9].
Stable isotopes	Calcite: δ13C = -7 – -3 permill, δ18O = +10 – +14 permill, fluid δ18O = +8 – +13 permill [9]. No lithologic correlation for δ34S values: vary at +1 – +7 permill, peak at +4 [1].
Pb isotope data
GEOLOGY
Geological setting	The variably Au- and Cu-enriched iron deposits at Kolari are at the contact zone between supracrustal rocks of the 2.20-2.05 Ga Matarakoski Formation and a synorogenic, 1.86 Ga, monzonitic pluton [2,9,16]. All ore bodies are hosted by the country rocks of the pluton, apparently are stratiform lenses, and seem to have a structural control [1,4]. The hosting supracrustal sequence is 70-140 m thick, dips at 15° to the W, and comprises quartzite, quartz-feldspar schist, calcitic marble and amphibolite. Alteration and gangue are characterised by diopside-hornblende exoskarns [1]. Endoskarns are minor, are known to host only low-grade sulphide mineralisation, and are characterised by the formation of albite with minor hornblende and diopside in the (monzo)dioritic marginal unit of the pluton [1].
Major host rocks	Magnetite skarn or ironstone (1,16].
Minor host rocks	Hornblende-diopside skarn [1,16].
Intrusives	A 1860 Ma synorogenic, mainly monzonitic, partially mineralised (sulphidised), intrusion in the hanging wall of the deposit, ca. 1.80 Ga granites a few km from the deposit, and cross-cutting, post-mineralisation granitic pegmatites [1,2,9,16].
Regional geol map 1		Outcrop photo 1
Regional geol map 2		Outcrop photo 2
Regional geol map 3		Outcrop photo 3
Local geology map 1		Outcrop photo 4
Local geology map 2
METAMORPHISM
Metamorphic history
Metamorphic grade	Lower-amphibolite facies conditions [1].
Metamorphic mineral assemblage	Amphibolite: hornblende-plagioclase ± biotite, titanite, magnetite, epidote [1]. Quartzite: quartz-feldspar ± sillimanite [1]. Quartz-feldspar schist: quartz-K feldspar-plagioclase-biotite ± graphite [1].
Metamorph photo 1		Metamorph photo 2
STRUCTURE
Structural style	Ductile [1].
Closest major shear	The E-trending overthrust and transpressional zone, D3 age, 10 km wide and 250 km long Kolari Shear System [3] which is also called the Pajala Shear Zone [8].
Controlling structure	Sheared(?) contact between the synorogenic granitoid and its country rocks, possibly also related to NE- and NW-trending faults next to the deposit [1]. Bend in reverse thrust fault [9].
Deformation history	D1: bedding-parallel foliation, possible gentle folding; D2: tight isoclinal folding, thrusting and faulting peak regional metamorphism; D3: reactivation of D2 thrusting; the latest stage was the brittle D4 [9,16]. Mineralisation is a late- to post-D3 event within the Pajala-Kolari Shear Zone, unrelated to Haparanda suite intrusions [16].
Ore fabric	Banded to massive magnetite with sulphides as dissemination and veinlets [1].
Veins	Late sulphide veins indicating remobilsation [1].
Structure photo 1		Vein photo 1
Structure photo 2		Vein photo 2
Structure photo 3	$laurinoja_ore_latefractures_th$	Vein photo 3
ALTERATION
General alteration	Na alteration (albitisation) in hanging wall, Ca-Fe alteration (diopside-hornblende-magnetite) in ironstone-skarn zone, K alteration (biotitisation) in footwall [5]. Exoskarn: magnetite-diopside-amphibole-plagioclase ± scapolite, sulphides, epidote, garnet, gold [1]. Endoskarn: 20-200 m wide zone, albite to oligoclase-quartz ± hornblende, diopside, scapolite, epidote, biotite, magnetite, pyrite, chalcopyrite, hornblende and eventually diopside appear and their contents increase towards the contact [1].
Proximal alteration	Diopside - actinolite or hornblende - magnetite ± scapolite, calcite, biotite, albite [9].
Intermediate alteration	Biotite - K feldspar ± albite, scapolite [9].
Distal alteration	Albite ± scapolite [9].
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	Local remobilsation of sulphides during the latest, D4, brittle, stages of deformation [5,9,16].
TIMING	The 1797±5 Ma U-Pb age of zircon in skarn, and 1810–1780 Ma ages of metamorphic titanite in altered wallrocks and skarn, suggest that the mineralisation took place around 1800 Ma [9,16]. Mineralisation took place between 1.86 and 1.76 Ga [1].
GENETIC MODEL	Mineralisation took place from hypersaline fluids at ca. 1800 Ma, under conditions of 450–550°C, 1.5–3.5 kbar [9].
GENETIC TYPE	IOCG	References	[9]
Alternative genetic type 1	Skarn	References	[9]
Alternative genetic type 2		References
References 1. Hiltunen, A. 1982. The Precambrian geology and skarn iron ores of the Rautuvaara area, northern Finland. Geol. Surv. Finland, Bulletin 318. 133 p. 2. Lehtonen, M. I., Airo, M-L., Eilu, P., Hanski, E., Kortelainen, V., Lanne, E., Manninen, T., Rastas, P., Räsänen, J. & Virransalo, P. 1998. Kittilän vihreäkivialueen geologia. Lapin vulkaniittiprojektin raportti. Summary: The stratigraphy, petrology and geochemistry of the Kittilä greenstone area, northern Finland. A report of the Lapland Volcanite Project. Geol. Surv. Finland, Report of Investigation 140. 144 p. 3. Väisänen, M. 2002. Structural features in the central Lapland greenstone belt, northern Finland. Geol. Surv. Finland, Report K 21.42/2002/3. 20 p. (32.8 MB) 4. Eilu, P. (ed.) 2004. Iron oxide-copper-gold excursion and workshop, Northern Finland and Sweden 31.5.–4.6.2004. Geol. Surv. Finland, Report M 10.3/2004/1/10. 93 p. (53.9 MB) 5. Niiranen, T. 2004. Locality 2. Hannukainen. In: Eilu, P. (ed.) Iron oxide-copper-gold excursion and workshop, Northern Finland and Sweden 31.5.–4.6.2004. Geol. Surv. Finland, Report M 10.3/2004/1/10. 42–57. 6. Geol. Surv. Finland. 2004. Ore Deposit Data Base. 7. Puustinen, K. 2003. Suomen kaivosteollisuus ja mineraalisten raaka-aineiden tuotanto vuosina 1530–2001, historiallinen katsaus erityisesti tuotantolukujen valossa. Geol. Surv. Finland Report M 10.1/2003/3, 578 p. (in Finnish) 8. Northland Resources Inc. 2005. Press release 7 November 2005. 9. Niiranen, T., Poutiainen, M., and Mänttäri, I., (in press). Geology, geochemistry, fluid inclusion characteristics, and U–Pb age studies on iron oxide–Cu–Au deposits in the Kolari region, northern Finland. Ore Geology Reviews. 10. Northland Resources Inc. 2006. Press release 13 September 2006. 11. Hugg, R. & Heiskanen, V. 1983. Suomen rautamalmiesiintymät, malmiutumat ja malmiviitteet. Rautaruukki Oy OU 2/79, RAETSU Report 8.2.1983. 412 p. (in Finnish) 12. Northland Resources Inc. 2007. Press release 27 February 2007. 13. Northland Resources Inc. 2007. Press release 27 April 2007. 14. Northland Resources Inc. 2007. Press release 17 July 2007. 15. Northland Resources Inc. 2007. Press release 23 August 2007. 16. Niiranen, T. & Eilu, P. 2007. Day 3, Stop 2 Hannukainen, Kolari. Geol. Surv. Finland,Guide 54. 63–69. (15.4 MB)
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