Day 0, Friday 15th August: Plan to arrive in Rovaniemi in the evening.
Day 1, Saturday 16th August:
08:00 Lecture: Suhanko-PGE prospect and the Portimo layered intrusion
09:30 Departure Rovaniemi
Stop 1: Suhanko, Among the layered intrusions of the Tornio-Näränkävaara belt, the Portimo Complex is exceptional in hosting a large variety of sulphide-PGE mineralization types. These include basal accumulations and stratiform horizons of PGE enriched sulphides. The Suhanko sulphide-PGE deposits represent the newly defined Contact-Type deposits being hosted by a thick basal marginal zone of layered intrusion and footwall lithologies right underneath. The Suhanko resources are distributed into two separate deposits, namely the Konttijärvi and Ahmavaara deposits located c. 2.5 km apart. The total resources at Suhanko are (cut-off 1.0 g/t 2PGE+Au) 7.5 million ounces (2PGE+Au) the Pd/Pt ratio being 4.2. In addition, the deposits contain significant concentrations of copper and nickel. The Konttijärvi deposit has a strike length of 1,000 metres. The thickness of open pitable mineralization varies from 30 to 100 meters. The orebody dips north at medium to gentle angle. The Ahmavaara deposit has a total strike length of 2,700 meters. The deposit comprises two slab-shaped mineralized units with a combined total thickness varying from 20 to 60 metres. The Ahmavaara deposit dips northeast at between 70° along the southwestern margin to 5° at the northeastern side of the deposit. The deepest known mineralization at Ahmavaara is approximately 500 m below surface.
The Portimo Complex belongs to the Tornio-Näränkävaara Belt of c. 2.44 Ga old layered intrusions and is composed of three separate layered intrusions, the Konttijärvi and Ahmavaara Intrusions being two of them. Both intrusions contain a marginal series and an overlying layered series. The marginal series of the Suhanko and Konttijärvi Intrusions is generally 20-50 in thickness, but may reach ~100 m locally. The marginal series proper is, especially at Konttijärvi, underlain by up to several tens of metres thick varitextured gabbro or 'hybrid zone', which is a mixture of gabbroic cumulate and semi-assimilated felsic footwall material showing also flow structures and banding. The overlying layered series (max. 500 m) is composed of entirely gabbroic cumulates.
Day 2, Sunday 17th August: Pahtavaara and Keivitsa (Overnight Luosto, Departure 08:00)
Stop 1: (9:00-11:00) Pahtavaara Gold mine. Pahtavaara is an active gold mine (in production 1996-2000, 2003-), with a total in situ size estimate of 15 t gold (production + resource, February 2006). It is sited in an altered komatiitic sequence at the eastern part of the Central Lapland greenstone belt. It comprises of a swarm of subparallel lodes; nearly all gold is free native. It has many of the alteration characteristics of amphibolite-facies orogenic gold deposits and an obvious structural control, but has an anomalous barite-gold association and a very high fineness (>99.5 % Au) of gold. The geometry of high-grade quartz-barite lenses and amphibole rock bodies relative to biotite-rich alteration zones is also anomalous, as is the δ13C of alteration carbonate minerals. Pahtavaara can be interpreted as a metamorphosed seafloor alteration system with ore lenses as either carbonate- and barite-bearing cherts or quartz-carbonate-barite veins. The gold may have been introduced later, but its grain size, textural position (nearly all is free, native, and occurs with silicates, not sulphides) and high fineness point to a pre-peak metamorphic timing which is highly anomalous for orogenic gold.
Stop 2: (13:00-17:00) Keivitsa. Keivitsa represents one of the largest mineral discoveries in Finland's history. The development-stage Kevitsa property hosts a measured and indicated resource of 141 million tons at a 0.2% nickel cut-off, together with a further 291 million ton inferred resource. The property is currently being developed by Canadian company Scandinavian Minerals Ltd, which has a 100% interest in the Kevitsa. The company is currently conducting a pre-feasibility study examining the economics of an open pit mining operation, mining up to 3.5 million tons of ore per year, with production of smelter-grade nickel and copper concentrates.
The surface cross-section of the ore body is about 0.25 km2 and it extends to the depth of several hundreds of meters with the horizontal section becoming wider with the depth. The resources are distributed between two ore types, the 'main ore type' and the 'Ni-PGE type'. The later forms a vertical zone or pipe-like structure with a surface extent of 150 m by 5-20 m. The main difference between the ore types is that the nickel-PGE type has a higher Ni/Co ratio, and has a tendency towards lower sulphur and copper contents. The main ore type makes up 93 % of ore to a depth of 330 m. Mineralogically the two ore types have the same gangue and sulphide minerals – pyrrhotite, pentlandite and chalcopyrite.
The Keivitsa Intrusion has an areal extent of 3.7 * 4.9 km2. The igneous stratigraphy is mainly composed of ultramafic cumulates. The basal marginal chill zone is 0–8 m thick, and consists of microgabbro or contaminated quartz gabbros and quartz-rich pyroxenites. The overlying ultramafic zone is thickest in the northeast of the intrusion, where the mineral deposit is also located. The maximum thickness is not known, but it may be as much as 2 km. Gabbroic cumulates are follows these ultramafic cumulates. The topmost cumulate of the gabbroic zone, magnetite gabbro, grades rapidly into granophyre, the uppermost magmatic unit of the intrusion.
Day 3, Monday 18th August: Suurikuusikko and Kolari: Overnight (Sirkka/Levi) (Departure 08:00)
Stop 1: (09:00-12:00) Suurikuusikko. The Suurikuusikko gold deposit is the largest known gold resource in northern Europe. Current resource estimates identify over of 2 million ounces of gold, and clear potential exists for further ounces both at depth and along strike of the host structure. The deposit occurs in Kittilä Group rocks of the Early Proterozoic Central Lapland Greenstone Belt (CLGB). Suurikuusikko host rocks are dominantly mafic volcanic rocks. Individual ore lodes occur within a 25+-kilometre long strike-slip shear zone (Kiistala Shear Zone) active during the later stages of the orogenic development of the CLGB. Gold is refractory, occurring within arsenopyrite (majority) and pyrite as lattice-bound gold or inclusions.
Stop 2: (14:30-17:00) Hannukainen IOCG deposit. All gold occurrences in the Kolari area are spatially, and possibly also genetically, related to the N- to NNE-trending Pajala shear zone. They all best fit into the iron oxide-copper-gold class of mineralisation style; although in sensu lato, they also fit into skarn deposit category due to their gangue assemblages.
Hannukainen IOGC deposit was mined in 1978–1992 when 1.96 Mt iron, 40,000 t copper and 4300 kg gold were produced. The present (September 2007), NI43-101 compliant, in situ resource estimate is 15 t Au, 300,000 t Cu and 60 Mt Fe. 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 Pajala shear zone, 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 suggests epigenetic Au-Cu mineralisation postdating the monzonite by about 40 million years. Native gold is closely associated with chalcopyrite, magnetite and gangue: inclusions in pyrite with chalcopyrite, in cracks of magnetite and pyrite, or as inclusions in chalcopyrite.
Stop 3: (17:00-18:00) Limestone quarry, Äkäsjokisuu. Shallowly dipping, folded and sheared calcitic marble.
Day 4, Tuesday 19th August: Northern Sweden to Kiruna (Departure Kolari 07.30 (Finnish time))
Stop 1: (08:00-9:00) Sahavaara Fe deposit.
Stop 2: (10:00-11:00) Pahakurkio at Kalixriver, micaschist with 1,86-1,85 Ga metamorphism (7484800/1770220)
Svecofennian metasedimentary rocks:
a. Gently dipping, andalusite porphyroblastic mica schists. They are intruded by tourmaline-bearing pegmatite. Minor folds are consistently north-vergent. Towards the south the metamorphic grade increases and the aluminum silicate is sillimanite. Intercalations with intermediate metavolcanic rocks suggest that the metasedimentary rocks of the Pahakurkio group are of Svecofennian age.
b. Quartzite with layers rich in heavy minerals, cross bedding and ripple marks (7484800/1769100).
Stop 3: (11:30-13:00) Masugnsbyn Skarn-iron ore with granite intruding ore, dolomite quarry. Skarn-rich iron formation and dolomite in the upper part of the Greenstone group.
a. Magnetgruvan (RT90 7497480/1767130), skarn iron ore, discovered in 1642, mine production until the early 19th century. Later investigations have shown a total tonnage of 60 Mt ore containing 30 % Fe. Magnetite affiliated with amphibole-pyroxene-serpentine skarn and some Fe-sulphide. Locally relatively large amounts of chondrodite. Uranium-mineralised fractures have been discovered.
b. Red, fine to medium grained granite (RT90 7497450/1768400) belonging to the Perthite Monzonite Suite. The U-Pb zircon age is 1858±9 Ma (Skiöld & Öhlander 1989). eNd(1.87)=-2.5. The Rb/Sr age is 1535±30 Ma, MSWD = 5.9, I.R. = 0.713±0.004 (Gulson 1972).
c. Dolomite quarry (RT90 7497380/1766900) run by Norrbottens Järnverk AB from 1952 to 1972, now run by LKAB. Dolomite is used as additive in pellets. The SiO2 content is as low as 1.5 %, which is essential for industrial purposes. Olivine, amphibole, chlorite, pyrite and calcite exist in low amounts. The normally 100-200 m thick dolomite is the uppermost unit in the Greenstone group, and occurs between the greenstones and the Svecofennian supracrustal rocks. At the quarry the dolomite is thickened, and the thickness exceeds 300 m.
Stop 4: (14:30-18:00) Kiirunavaara. The Kiirunavaara deposit was found in outcrop 1696, but regular mining did not start until 1900 when a railway was built from the coast to the town of Kiruna. Open pit mining ceased in 1962, with a total production of 209 Mt. Underground work started in small scale during the 1950:s and the ore is now mined by large scale sublevel stooping. The present main haulage level is at 1045 m and the total production from open pit and under ground was c. 1030 Mt at the end of 1999.
The tabular ore body is c. 5 km long, up to 100 m thick, and it extends at least 1300 m below the surface. It is situated in the middle part of the Kiirunavaara Group and follows the contact between a thick pile of trachyandesitic lava (Hopukka Fm.) and overlying pyroclastic rhyodacite (Luossavaara Fm.). Towards north the much smaller Luossavaara ore is situated in a similar stratigraphic position.
The trachyandesite lava occurs as numerous lava flows, which are rich in amygdules close to the flow tops. Minor pyroclastic intercalations exist between some of the flows. A thick sill varying in composition from gabbro to monzonite has intruded the lavas 1000 m stratigraphically below the ore. Several dykes of granophyric to granitic character cuts the ore and a larger body of K-rich granite is found at deeper levels in the mine on the footwall side of the ore.
Magnetite-actinolite breccias are developed both in the footwall and hanging wall along the contacts of the Kiirunavaara ore body. In the footwall larger breccia zones may show a change from veined trachyandesite to breccia with angular fragments of the wallrock. In some places there is a central part containing rounded pebbles of the wallrock set in a matrix rich in magnetite. Close to the hanging wall contact the ore is often rich in angular to subrounded clasts of rhyodacitic tuff. Veins of magnetite and actinolite may extend tens of meters into the hanging wall and locally form rich ore breccia or lenses of massive ore.
The phosphorus content of the ore exhibits a pronounced bimodal distribution with either < 0.05 % P or > 1.0 % P. Most of the apatite-poor ore (B-ore) is found close to the footwall as a slightly irregular and branching body of massive magnetite ore. It is usually 40–70 m thick and contains up to 15 % of disseminated actinolite in a 5–20 m wide zones along the borders. The magnetite is mostly very fine-grained (<0.3 mm) but in the central part of the B-ore, zones of coarser magnetite (up to 2 mm) occur in places together with minor calcite and small amounts of pyrite. Apatite-rich ore (D-ore) is mainly found towards the hanging wall and in the peripheral parts of the ore body, but also occurs in varying amounts in the footwall contact. The D-ore in places has a banded structure and the proportions of apatite and magnetite is variable. The age relationship between B- and D-ore is ambiguous, and both ore types can be seen cutting each other. Columnar and dendritic magnetite are locally developed textures that suggest rapid crystallization in a supercooled magma (Geijer 1910, Nyström 1985, Nyström and Henriquez 1989). Veins of anhydrite, anhydrite-pyrite-magnetite and coarse-grained pyrite are locally encountered in the ore and wall rocks.
Extensive albitization is developed in the footwall to the Kiirunavaara deposit. The area of most intense albitization surrounds the gabbroic to monzonitic sill, which itself is strongly altered. Especially the amygdaloidal parts of the lava flows are strongly altered and the albitization is accompanied by secondary magnetite, actinolite, titanite, and locally some tourmaline (Geijer 1910). A U-Pb age of 1876±9 Ma was obtained from titanite in albitized trachyandesite lava, which is considered to be the age of albitization (Romer et al. 1994). Actinolite is a common alteration mineral both in the footwall and hanging wall contacts and it in places form massive skarn bordering the ore. Actinolite also replaces, partly or completely, clasts of wallrocks in the ore and in the ore breccia. Besides actinolite and magnetite veining close to the ore, the hanging wall is in some areas affected by biotite-chlorite alteration, which commonly is accompanied by disseminated pyrite and a weak enrichment of Cu, Co, and Mo. Sericite schist with some tourmaline is locally found in the footwall contact of the ore (Geijer 1910), and may be related to post-ore shearing.
Day 5, Wednesday 20th August: Kiruna-Gruvberget (Gällivare)-Aitik-Kemi. Gruvberget-Aitik (Departure Kiruna 08:00)
Stop 1: (9:30-11:00) Gruvberget. The Gruvberget apatite iron ore is 1300 m long and up to 65 m thick. It is calculated to contain 64.1 Mt with 56.9 % Fe and 0.87 % P to a depth of c. 300 m where the ore still has approximately the same thickness as at the surface (Frietsch, 1966). The bedrock consists of strongly altered volcanic rocks of mainly mafic composition. The metavolcanic rocks have a granoblastic texture and are altered by albite, scapolite, and microcline. Locally remnats of plagioclase phenocrysts are found. Several dykes of metadiabase with a NE direction cut the ore and its wallrocks. A strong N–S foliation and shear zones are situated in the footwall to the ore and deformed dykes indicate a sinistral movement on the shear zones (Lindskog, 2001).
The apatite iron ore is mostly massive and consists of magnetite in the northern part and hematite in the middle and southern part of the deposit. Within a transition zone of a few meters magnetite is gradually replaced along grain boundaries and crystallographic planes into hematite. Apatite and calcite are gangue minerals that occur as disseminations and in veinlets also including garnet in the hematite ore. Accessory minerals are quartz, diopside, amphibole, biotite, epidote, and orthite. The eastern part of the magnetite ore is rich in calcite clots and irregular aggregates. The calcite is partly leached leaving vugs lined with magnetite crystals. The northern part of the ore is bordered by a narrow zone of garnet, amphibole, and epidote towards the hanging wall. An extensive ore breccia is developed in the footwall at the middle part of the deposit. It consists of veins and schliren of magnetite, hematite, apatite, and amphibole. The richer part of the breccia is calculated to contain 9.7 Mt with 40.9 % Fe and 0.88 % P (Frietsch, 1966). A breccia of a probably tectonic origin is situated in the middle part of the deposit in a 400x20 m large area. It consists of up to 20 cm large and angular to subrounded clasts of hematite ore and smaller amounts of sericite schist. The matrix is dominated by hematite and chlorite with minor quarts and calcite (Frietsch, 1966).
The Gruvberget Cu-deposit, located close to Svappavaara, is one of the oldest Cu-mines in Norrbotten. It was discovered in 1654 and during 1657–1684 about 1000 tonnes of Cu were produced (Tegengren 1924). The Cu-deposit is situated close to the Gruvberget Fe-ore, which is an apatite iron ore (see above). Cu-sulphides are scattered throughout the Gruvberget area, but higher grade mineralisation is mainly developed in the footwall to the iron ore.
Chalcopyrite and some bornite are the main ore minerals, occurring disseminated together with magnetite in altered rocks, or as rich ore shoots at the contact to the iron ore. Druses with epidote, magnetite, pyrite, Cu-sulphides, and stilbite are common within the bornite bearing sulphide mineralisation. Locally veins consisting of quartz, minor K-feldspar, amphibole, garnet, and small amounts of magnetite, chalcopyrite, and bornite are found. Molybdenite may occur in small amounts (Frietsch, 1966). Cu is the only economic metal and the Au content is generally very low. Several of the small mines are found close to metadiabases and Cu-mineralisation seems to be controlled by the same structures as the dykes. As the dykes cut the iron ore Cu-mineralisation is probably younger and genetically unrelated to the apatite iron ore. However, the competent iron ore probably has acted both as a tectonic and chemical trap for later Cu-bearing fluids.
Close to the Cu-ores the bedrock is mainly affected by scapolitization and shows an enrichment of Fe and to some extent Mn and K. The altered host rocks contain scapolite with 25–57 mol% meionite, garnet, and pyroxene rich in Mn and some epidote as characteristic minerals (Lindskog, 2001). Strong K-feldspar alteration is mainly developed east of the iron ore, resulting in a high K2O (up to 9.8 %) and Ba content, while Na and Ca are depleted. However, intense K-feldspar alteration replacing earlier scapolite is locally developed in association with mineralisation of bornite in late structures.
Stop 2: (12:00-16:00) Aitik. Aitik is Sweden’s largest sulphide mine and one of Europe’s most important copper producers. The mine has an annual production of 18 Mt of ore with 0.38 % Cu and 0.22 ppm Au and a total production between 1968-2005 of 429 Mt of ore (Pers. Comm. R.Nordin). Current proven and probable reserves are 219 Mt and measured & indicated mineral resources are 875 Mt, with an additional 110 Mt of resources in the inferred category.. Mineralisation is inferred to a depth of at least 800-m in the northern part of the open pit and is drill indicated to about 400 m below surface in the southern part. The deposit is situated 15 km southeast of Gällivare, close to the regionally important and NW-SE striking Nautanen Deformation Zone.
The host rock to the ore comprises garnet-bearing biotite schist and gneiss towards the footwall, and quartz-muscovite (sericite) schist towards the hanging wall (Zweifel, 1976; Monro, 1988). These rocks are strongly deformed and altered which obscure their primary character. However, the chemical character of the rocks suggests a magmatic precursor of intermediate composition, and based on the knowledge from areas outside the mine, a volcaniclastic origin is suggested (Wanhainen and Martinsson 1999). A subvolcanic, multiphase intrusion of intermediate composition occurs in the footwall to the Aitik deposit. This intrusion, classified as a quartz monzodiorite, is weakly mineralised, with chalcopyrite, pyrite, and magnetite as veins and disseminations. It has an age of c. 1.87 Ga and undeformed pegmatite dykes crosscutting the ore zone and the hanging wall units are c. 1.75 Ga in age (Witschard 1996).
Chalcopyrite and pyrite are the main ore minerals and occur as disseminations and in veinlets. Minor components are magnetite, pyrrhotite, bornite, and molybdenite. Veins consisting of quartz and sulphides are common, as are sulphides concentrated in veinlets of amphibole and biotite. These mineralised veins contribute to locally higher ore grades. Locally more intense veining from quartz-sulphide stockworok zones. Baryte veins containing varying amounts of pyrite, chalcopyrite, magnetite, and actinolite are partly abundant. Pegmatite dykes within the ore zone are often mineralised with remobilized sulphides, while those in the hanging wall are barren. Stilbite and chabazite, sometimes together with sulphides, represent late mineralisation phases. The zeolites occur as crystals in drusy vugs in some of the pegmatite dykes and quartz veins. Mineralisation of copper extends in subeconomic grades into the footwall rocks, while the hanging wall contact of the ore is sharp and tectonically controlled (Drake 1992). The sulphur isotopic composition for the sulphides is close to zero.
Similar to the ore minerals, alterations present within the ore zone probably formed during several generations of hydrothermal activity. Most extensive is biotite alteration, which often is accompanied by garnet porphyroblasts. Towards the hanging wall, sericite is abundant and occur mainly in sericite schist that may be rich in pyrite. K-feldspar alteration and epidotization are most extensive along the footwall and hanging wall contacts, but occur locally within the ore zone. Tourmalinization is less common and mainly restricted to the immediate wall rocks of quartz-tourmaline veins and pegmatites. Scapolitization and amphibole-pyroxene veinlets are less important and mainly restricted to the footwall.
The Aitik Cu-Au ore has been interpreted as a deformed and metamorphosed equivalent to porphyry-copper deposits (Yngström et al. 1986, Monro 1988) or is suggested to be hybrid between IOCG and porphyry-copper-type deposits, based on the character of the high salinity ore fluids (Wanhainen et al., 2003). The mineralised quartz monzodiorite in the footwall to the ore is suggested to represent an apophyse from a larger intrusion at depth consistent with this model (Drake 1992). However, all features of the main ore zone are not typical for porphyry systems and the deposit might therefore have a more complex origin. Several phases of remobilization have probably led to the present irregular distribution of sulphides within the ore zone. A copper-rich area in the strongly deformed rocks towards the footwall of the ore, and gold-rich areas correlating with high quartz vein frequency and high pyrite content have formed due to remobilization processes (Wanhainen et al., 2004). The sulphur isotopic composition close to zero for most sulphides irrespective mineralisation style favour this interpretation although minor additional overprinting mineralisation events might also have taken place contemporaneously with remobilization (Wanhainen and Martinsson, 2003).
Day 6, Thursday 21st August: Kemi
Stop 1: Kemi Crome Mine. The Kemi chrome ore is world-class in size and outstanding with respect to the economic cluster it has created in the area (Tornio stainless steel plant of Outokumpu Oyj). The mine's proven ore reserves total some 50 million tons. In addition, it is estimated that there are 90 million tons of mineral resources. The annual production during recent years has amounted to over one million tons of ore. The mining started as open pit mining, but changed to an underground operation as the pit reached a depth of c. 200 m a few years ago. The Kemi main chromitite layer, which is located in the lower, ultramafic part of the intrusion, can be followed along strike over the entire length of the intrusion for more than 15 km. Laterally, it varies in thickness from a few mm up to ~90 m at the thickest part of the intrusion, where the mine is located. The whole length of the mineable portion of the layer is 4.5 km. The main chromitite is separated stratigraphically from the lower contact of the intrusion by 50 to 100 m of pyroxenite. Furthermore, a chromite-bearing feeder dyke beneath the thickest part of the intrusion has recently been discovered.
The Kemi Intrusion is part of the Tornio-Näränkävaara belt of layered intrusions. The Tornio-Näränkävaara Belt is a discontinuous zone of layered intrusions crossing northern Finland almost along the Arctic Circle and extending some kilometres into Sweden (Tornio intrusion) and several tens of kilometers into Russia (the Olanga Complex). The belt contains roughly half of the 2.4–2.5 Ga layered igneous complexes within the Fennoscandian Shield. The intrusion has an Archaean basement complex on its footwall side and is capped by supracrustal rocks. The intrusion has a lenticular shape and is ~15 km long and 2 km wide at the middle. The lower part of the layered body comprises up to 500 m of peridotites overlain first by various pyroxenitic cumulates. The ultramafic zone of the Kemi intrusion is characterized by the presence of at least 15 chromitite interlayers that, apart from the exceptionally thick main chromitite, range in thickness from a few centimeters to 2.5 m. The upper half of the ~2 km total section is composed of gabbros with anorthosites at the top.