The Fennoscandian or Baltic Shield (both names occur in the literature) occupies the northern part of Europe. Pre-cambrian areas are exposed in Norway, Sweden, Finland, and Russia and their continuation beneath the platform cover sequences to the east and south have been better understood through studies within the European “Euro-probe” project. The craton of which the exposed Fenno-scandian Shield forms a part is bordered to the west by the Caledonian orogenic belt. Precambrian rocks of the same craton outcrop again in the Ukrainian Shield and the Voronezh Massif (cf. Gee and Zeyen, 1996 ). The Fennoscandian Shield is composed of Archean to Neoproterozoic rocks (Fig. 1 ). It is beyond the scope of this guidebook to describe all the different settings in detail, but adjoining areas that both predate and postdate the Svecofennian rocks that are the main interest of this field trip will be briefly described. The term Svecokarelian is used for the orogeny that occurred between 1900 and 1800 Ma (i.e., emphasizing deformation and metamorphism as defining the orogeny), while the term Svecofennian is used for the supracrustal rocks that were emplaced during c. 1.95 Ga to 1.85 Ga. To the reader unfamiliar with literature on the Fennoscandian Shield it is important to remember that these terms are not used consistently in the literature. The pre-Svecokarelian crustal growth can be subdivided into Archean and Paleoproterozoic. During the Archean, greenstone belts and tonalite-trondhjemite-granodiorite (TTG) terranes formed, while crustal growth during the Paleoproterozoic involved rifting of the Archean

Abstract The Skellefte mining district occurs in an Early Proterozoic, mainly 1.90-1.87 Ga (Svecofennian) magmatic province of low to medium metamorphic grade in the Baltic Shield in northern Sweden. The district contains over 85 pyritic Zn-Cu-Au-Ag massive sulfide deposits and a few vein Au deposits and subeconomic porphyry Cu-Au-Mo deposits. The massive sulfide deposits mainly occur within, and especially along the top of, a regional felsic-dominant volcanic unit attributed to a stage of intense, extensional, continental margin arc volcanism. From facies analysis we interpret the paleogeography of this stage to have comprised many scattered islands and shallow-water areas, surrounded by deeper seas. All the major massive sulfide ores occur in below-wave base facies associations; however, some ores occur close to stratigraphic intervals of above-wave base facies associations, and the summits of some volcanoes that host massive sulfides emerged above sea level. Intense marine volcanism was superceded at different times in different parts of the district by a stage of reduced volcanism, uplift resulting in subregional disconformities, and then differential uplift and subsidence resulting in a complex horst and graben paleogeography. Uplift of the arc is attributed to the relaxation of crustal extension and the emplacement of granitoids to shallow crustal levels. A few massive sulfide ores formed within the basal strata of this second stage. The horst and graben system was filled by prograding fluvial-deltaic sediments and mainly mafic lavas, and during this stage the Skellefte district was a transitional area between renewed arc volcanism of more continental character to the north, and subsidence and basinal mudstone-turbidite sedimentation to the south. This whole volcanotectonic cycle occurred within 10 to 15 m.y. We define 26 main volcanic, sedimentary, and intrusive facies in the Skellefte district. The most abundant facies are (1) normal-graded pumiceous breccias, which are interpreted as syneruptive subaqueous mass flow units of pyroclastic debris, (2) porphyritic intrusions, and (3) mudstone and sandstone turbidites. Facies associations define seven main volcano types, which range from basaltic shields to andesite cones and rhyolite calderas. Despite this diversity of volcano types, most massive sulfide ores are associated with one volcano type: subaqueous rhyolite cryptodome-tuff volcanoes. These rhyolite volcanoes are 2 to 10 km in diameter, 250 to 1,200 m thick at the center, and are characterized by a small to moderate volume rhyolitic pyroclastic unit, intruded by rhyolite cryptodomes, sills, and dikes. Massive sulfide ores occur near the top of the proximal (near vent) facies association. The remarkable coincidence in space and time between the ores and this volcano type indicates an intimate, genetic relationship between the ores and the magmatic evolution of the volcanoes. Many of the massive sulfide ores occur within rapidly emplaced volcaniclastic facies and are interpreted to have formed by infiltration and replacement of these facies. Some of the ore deposits have characteristics of both marine massive sulfides and subaerial epithermal deposits. We suggest that massive sulfides in the Skellefte district span a range in ore deposit style from deep-water sea-floor ores, to subsea-floor replacements, to shallow-water and possibly subaerial synvolcanic replacements. Facies models are provided for the mineralized rhyolite volcanoes and volcanological guides are provided for exploration for blind ores within these volcanoes.

The Skellefte district is best known as a major massive sul-fide mining district. Many of the massive sulfide ores are relatively gold rich, and some are extremely rich (Boliden and Holmtjärn; Fig. 1 ; see metal grades listed in Allen et al. [1996] and reprinted in this volume). The Boliden massive sulfide deposit produced 123 tonnes of gold at an average grade of 15.5 g/t. The deposit contains pyrite-rich massive sulfide ore, gold- and arsenopyrite-rich massive sulfide ore, and an underlying zone of gold-bearing quartz and tourmaline veins. The most gold-rich parts of the deposit were the 1 million tonnes of massive arsenopyrite within the massive sul-fide body. This deposit was interpreted by Bergman Weihed et al. (1996) as an ancient, high sulfidation epithermal type deposit. However, the deposit has a complex assemblage and paragenesis of ore types and alteration zones, and shows some similarities with both submarine volcanogenic massive sulfide deposits and epithermal deposits. This combination of deposit characteristics at Boliden and several other massive sulfide deposits in the Skellefte district led Allen et al. (1996) to suggest that volcanogenic sulfide deposits in the district span a range from deep-water sea-floor ores, to sub-sea-floor replacements, to shallow water-subaerial synvolcanic replacements with a mixture of volcanic-hosted massive sul-fide (VHMS) and epithermal characteristics. In the Skellefte district gold also occurs in porphyry-style Cu-Au deposits and in gold lodes (Fig. 1 ), and it is these two deposit styles that are the focus of this contribution.

This Field Day provides an overview of the rock types, structure and geological interpretations of the Skellefte district. Some history of exploration and mining in the district is also covered. Papers in this volume by Weihed and Allen et al., 1996 (reprint 2004) provide background information and relevant maps and diagrams. More field stops are included than can be visited in one day, because due to the uncertainties of river levels and forest road conditions a couple of the locations may be inaccessible (Fig. 1 ). The Skellefte mining district, one the most important mining districts in Sweden and Europe, is a 120 × 30 km belt of mineralized 1.90 to1.88 Ga Early Proterozoic volcanic, intrusive and sedimentary rocks. This belt is characterized by abundant moderately to strongly deformed, gray, diagenetically and hydrothermally altered, marine volcanic rocks. The belt has an apparently conformable boundary to the south with an extensive metasedimentary region with abundant granitoids (Bothnian basin). To the north the Skellefte district has a poorly defined boundary with an extensive region of less deformed, less altered, mainly brown continental felsic volcanic rocks, intrusions and minor sediments (Arvidsjaur Group). The Skellefte district has a first-order regional stratigraphy consisting of a >3-km-thick volcanic unit (Skellefte Group) overlain by a >4-km-thick, sediment-dominated succession (Vargfors Group; Allen et al., 1996 ). Provenance of the sedimentary rocks and radiometric dating indicate that the Vargfors Group is contemporaneous with at least part of the Arvidsjaur Group to the north.

Abstract The Skellefte mining district in northern Sweden contains over 85 pyritic Zn-Cu-Au-Ag massive sulfide deposits of which 27 have been producers. The Renström area contains three major and two minor zinc-and gold-rich deposits, comprising at least 12 ore lenses, within an area of 4 km 2 . The deposits are massive to semimassive pyrite-sphalerite dominated ores with local stringer-type pyrite-chalcopyrite ± pyrrhotite mineralization. Following an extensive regional and within-mine geological mapping and drilling program, recent exploration has extended the ore resource in the Renström main lens down to the 1750 m level, has defined the new Simon lens between 950 and 1170 m levels, and has intersected the new “Ren-ström Deep zone” between the 1260 and 1750 m levels. The Renström area is divided by major faults and intrusions into four structural blocks. Each structural block contains massive sulfide mineralization within a multiply deformed and volcanically complex rock sequence. The area has two main generations of folding with a complex interference pattern, and several generations of faults and intrusions. The Renström and Kyrkvägen deposits lie within a corridor of deformation adjacent to the Renström fault zone, which is a 400-m-wide zone of steeply west-dipping shears and faults, intruded by high Mg basaltic andesite dikes. At the Renström deposit, the A-B lenses, the Deep zone and the Simon lens occur on different limbs of a refolded, tight to isoclinal anticline and syncline. The Petiknäs North and Petiknäs South deposits occur below and above a moderately south-dipping thrust fault, and parts of both deposits are truncated by the fault. Most rocks in the Renström area are moderately to strongly foliated and lineated, and all have been metamorphosed to greenschist facies. Due to the complex geology it is difficult to identify, correlate, and map out stratigraphic units. Considerable effort has been expended on defining and characterizing each volcanic facies and stratigraphic unit. Forty-four volcanic facies can be distinguished using a combination of phenocryst mineralogy, rock texture and lithogeochemistry. These facies are subalkaline, basaltic andesites to rhyolites and include at least four magmatic suites. The suites appear to belong to transitional to calc-alkaline and tholeiitic magma series. A suite of immobile element ratios has been developed in order to help distinguish tex-turally similar facies and strongly altered rocks. The ratios Ti/Zr and Al 2 O 3 /TiO 2 have proven most useful. Coherent (nonclastic), juvenile clastic, and reworked clastic volcanic facies of the same initial mag-matic composition, all display different patterns and degrees of geochemical variation. Variation patterns, even of immobile element ratios, are especially complex in the clastic facies due to mechanical fractionation of pumice, ash, and crystals during eruption, transport, and deposition. Stratigraphic correlation suggests that the Renström, Kyrkvägen, and Petiknäs South ore deposits occur at approximately the same stratigraphic level, whereas the Renström East deposit occurs in the footwall rocks and the relative stratigraphic position of the Petiknäs North deposit is uncertain. The foot-wall mainly comprises more than 1 km of stratified andesitic breccias and an upper, chemically distinct, 10- to120-m-thick interval of high Ti dacitic pumiceous volcaniclastics, all intruded by andesitic and dacitic sills. Erosion surfaces, traction current bed forms and local red coloration, indicate shallow-water to subaerial depositional conditions near the top of this footwall sequence. The footwall rocks are conformably overlain by the ore host unit, a 20- to 70-m-thick succession of alternating rhyolitic vitric silt-stone-sandstone and pumice deposits, intruded by several different rhyolites. Three of the rhyolites are interpreted to be comagmatic with three of the pumice facies in the ore host unit. The pumiceous strata include subaqueous pyroclastic fall beds, laterally transported clastic mass flows, and beds of pumiceous lava blocks that floated off rhyolite domes and then became waterlogged and sank. Bed forms indicate subaqueous deposition, with water depths of probably 100 m or more. The ore lenses are scattered through these pumiceous strata and are interpreted to have formed by subseafloor replacement. The ores are associated with strong chlorite, dolomite, sericite, and silica alteration. The ore-host package is overlain by gray to black mudstone and sandstone, more than 200 m of rhy-olitic and dacitic pumiceous subaqueous mass flow units, and in turn by more than 200 m of andesitic breccias, lavas and sills. The hanging-wall andesitic rocks are texturally and chemically similar to the foot-wall andesites. Both are interpreted as parts of marine fissure-fed andesitic cones or ridges. The ore host unit is interpreted as one or more small to moderate volume, low relief, submarine rhyolite volcanoes. The proximal (near-vent) part of the volcano is characterised by a moderately thick sequence of pumiceous deposits and porphyritic rhyolite sills and cryptodomes. Thinner sections of the ore host unit with no associated rhyolite intrusions and a thin sequence of pumice deposits are interpreted as distal margins of the volcano. The Renström and Kyrkvägen ore deposits occur in the proximal part of one volcano. The Petiknäs South deposit is interpreted to occur in the proximal part of a nearby, ?second small rhyolite volcano at the same stratigraphic level. The Petiknäs North deposit is interpreted to occur in the proximal facies association of a third small rhyolite volcano. These small rhyolite volcanoes could be related dispersed centers of a larger multivent volcanic system. The Renström ores are thus related to the evolution of one or more rhyolitic centers between periods of andesitic volcanism. A combination of volcanological, structural and geochemical analysis enables correlation of the prospective rhyolitic package both within and away from the Renström mine. A coincidence of proximal volcanic facies associations within this favourable stratigraphic interval and strong hy-drothermal alteration in the host-package or footwall rocks are important exploration targets.

ALLEN ET AL. (1996) interpreted the Kyrkvägen ore horizon to be a structural repetition of the Renström horizon. Further work has shown that the Renström A-B lenses, the Renström Deep Zone, the Simon lens and the Kyrkvägen deposit all occur in the same 20- to 200-m-thick stratigraphic unit (the “Renström ore host unit”). However, Allen et al. (1996) showed that the stratigraphies that enclose each of the three major massive sulfide deposits in the area (Renström, Petiknäs South and Petiknäs North) have significant differences. They concluded that these three deposits occur at three slightly different strati-graphic levels, at the top of the proximal volcanic facies association of three separate rhyolite volcanoes. Further work ( Allen, 1999 ; Allen and Svenson, 1999 ; Allen and Svenson, 2004 ) has identified two important stratigraphic marker units at the Ren-ström mine, which also occur at the Petiknäs South deposit: the upper footwall high Ti dacite pumice breccia and the large (up to 8 mm) quartz crystal-bearing member of the ore host package. Correlation suggests that the Petiknäs South deposit also lies in the Renström ore host unit, and within tens of meters of the stratigraphic level of the Renström deposits. The differences in the rock successions enclosing the deposits are attributed to the complex structure and volcanic architecture, and lateral changes in facies and stratigraphic thicknesses. The Renström East deposit is interpreted to lie in the stratigraphic footwall to the Kyrkvägen deposit. The relative stratigraphic position of

Abstract The Maurliden area in the central part of the Skellefte mining district, northern Sweden, contains four Zn-Pb-Cu-Au-Ag deposits. They range in style from massive sulfide deposits to semimassive, disseminated and vein-type mineralizations. The host succession consists of moderately feldspar porphyritic rhyolites, quartz-feldspar porphyritic rhyolites, mudstones, volcaniclastic sandstones and conglomerates. Based on field relationships, petrographic and textural evidence, all four Maurliden deposits are interpreted to be hosted in the same strongly quartz-feldspar porphyritic rhyolite. This rhyolite is generally strongly altered, massive, moderately homogeneous and has the appearance of a porphyry intrusion. However, drill core from the central, least altered part of the rhyolite displays normal graded bed forms and relict pumice textures, which indicate the unit is a thick juvenile pumice deposit. The Maurliden sulfide deposits show some features typical of sea-floor volcanic-hosted massive sulfide (VMS) deposits, such as well-developed stringer zones, metal zonation, a potential ore-host subaqueous sedimentary horizon, collo-form pyrite and polymetallic composition. However, the location of most of the mineralization within a pumice deposit and relict quartz phenocrysts within the ore imply that the four Maurliden deposits formed mainly below the sea floor by replacement of the pumice deposit.

West Maurliden mine was opened in 2000 and is the most recent mine to come into production in the Skellefte district. It is one of four polymetallic sulfide deposits in the Maurliden area. The area lies in the center of the Skellefte district, which has been a type area for several important studies of the district ( Grip, 1951 ; Kautsky, 1957 ; Helfrich, 1971 ; Claesson, 1985 ; Dumas, 1986) due to the relatively good outcrop (more than the 1% average for the district!) and the lower degree of deformation and metamorphism compared with the western and eastern parts of the district. The area has also been important for recent research into the stratigraphy and volcanology of the Skellefte district ( Allen et al., 1996 ; Montelius et al., 2004 ). The Maurliden area is dominated by volcanic rocks of the Skellefte Group and borders the overlying sedimentary successions of the Vargfors Group (fig. 1 in Montelius et al., 2004 ). The area is characterized by coherent felsic intrusions, lavas and their clastic facies, diffusely stratified conglomerates, sandstones and mudstones (Fig. 1 ). The diffusely stratified conglomerates have locally derived clasts and are interpreted as traction current deposits emplaced in shallow-water environments. Dark gray mudstones with graded turbiditic sandstone beds occur locally and indicate that the depositional environment fluctuated from shallow to deep water (from above to below wave base). The four sulfide deposits are associated with a quartz-feldspar porphyritic rhyolite intrusion. The

The Laisvall disseminated Pb-Zn deposit, located along the Caledonian front just south of the Arctic Circle in northern Sweden, was an underground mining operation run by Boli-den Mineral AB. The ore deposit was discovered in 1939 through boulder tracing and subsequent diamond drilling, and development started in 1941 ( Grip, 1954 ). Production ceased at the end of year 2001 because of a declining ore reserve. During the life of the mine, a total of 64.256 Mt of ore at 0.6 percent zinc, 4.0 percent lead and 9 g/t AG was extracted. The deposit was mined using the room and pillar method and the ore is milled at Laisvall, where separate Pb and Zn concentrates were produced.

The Lower part of the autochthonous sequence including the sandstone hosted Pb-Zn mineralization crops out east of the Laisvall mine, and the possibility of studying the basement/autochthonous sediment relationship exists along a profile in this area (stop 1, for location see fig. 1 in Willdén, 2004 ). At Laisvall (stop 2), mining is presently retreating from west to east and it is unclear which parts of the mine will be accessible at the time of the field trip. A complement to the mine visit will be provided by the examination of a drill core through the deposit (stop 3).

Abstract The geology of the northern Norrbotten region includes an Archean granitoid-gneiss basement, which is unconformably overlain by Paleoproterozoic greenstones, porphyries, and sedimentary successions. The Archean basement is dominated by c. 2.8 Ga tonalite-granodiorite intrusions. In the Kiruna area the deformed and metamorphosed Archean basement is covered by a volcanosedimentary pile with 2.5 to 2.0 Ga Karelian units and a c. 1.9 Ga Svecofennian succession of volcanic and sedimentary rocks. The oldest Karelian unit is the Kovo Group, comprising rift-related clastic sediments and basaltic to andesitic volcanic and volcaniclastic rocks. The subsequent Kiruna Greenstone Group was generated during a second rifting event at c. 2.1 Ga. The lower part of the greenstones is dominated by basaltic volcanic rocks and komatiites, with clastic sediments and evaporites as minor constituents at the base of the pile. Vol-caniclastic sediments with intercalations of graphitic schist and carbonate rocks are found in the middle and upper parts. Midocean ridge basalt-type pillow lava occurring in the Kiruna area represents a locally developed deeper marine facies formed within a north-northeast–directed failed rift arm. The Karelian units are overlain by andesitic volcanic rocks and related clastic sediments in a continental arc setting. Comagmatic to these volcanic rocks is the Haparanda Suite. The younger Kiirunavaara Group is mainly restricted to the western part of northern Norrbotten and it is comagmatic with the Perthite Mon-zonite Suite. The volcanic rocks are generally porphyritic and show a bimodal character with a mainly basaltic lower part and a dacitic to rhyolitic upper part. An intraplate origin is indicated by the chemical composition of the porphyries and related intrusions. Later uplift and erosion of the area resulted in the formation of the arenitic sediments within the Hauki Quartzite. The c. 10-km-thick pile of volcanic and sedimentary rocks was deformed and metamorphosed at c. 1.88 Ga. A second event of metamorphism and deformation occurred at 1.81 to 1.78 Ga and was temporally associated with gabbroic to monzonitic intrusions and minimum melt granites and pegmatites. Northern Norrbotten is a province characterized by regionally developed scapolitization and albitization and mineral deposits dominated by Fe and Cu, with Au as an economically important constituent of some sulfide deposits. Stratiform to stratabound mineralizations with Fe and base metals occur in volcaniclastic units in the middle and upper parts of the Kiruna Greenstone Group and include base metal sulfide deposits (Cu or Zn-Pb) and iron formations. Apatite iron ores are mainly restricted to the Kiruna and Gäl-livare areas and are spatially related to the Kiirunavaara Group. Epigenetic Cu-Au mineralizations are mainly found in the Paleoproterozoic greenstones and porphyries. Two major events of mineralization are distinguished at c. 1.87 and 1.77 Ga and include disseminated and vein styles of mineralization. The ore-forming fluids are interpreted to have had high salinity, and this is probably the most important feature of this ore district and the explanation of its metallogeny and regional alterations. Evaporitic sediments at the base of the 2.1 Ga greenstones might have acted as a source for Na and Cl during synvolcanic, diagenetic, magmatic and metamorphic processes. The saline character of the hydrothermal fluids is manifested by the extensive formation of scapolite and albite in the Paleoproterozoic rocks and the high salinity in fluid inclusions from stratiform and epigenetic sulfide deposits in this region. Another important feature is the large-scale 1.9 to 1.8 Ga deformation zones controlling the location of many epigenetic Cu-Au deposits. The most prominent structure is the north-northeast–directed Karesuando-Arjeplog deformation zone that represents a reactivated major crustal structure initially formed as a failed rift arm during the breakup of the Archean continent at c. 2.1 Ga. This deep crustal structure and the occurrence of evapor-ites within the Paleoproterozoic pile of volcanic and sedimentary rock may also be features of genetic importance for the generation of apatite iron ores in this region.

Abstract The Gällivare area is an important producer of Fe, Cu and Au. The Cu-Au deposits are hosted by Sve-cofennian successions of volcanic and sedimentary rocks formed in an arc environment. Apatite iron ores are restricted to overlying intermediate to felsic volcanic units with intraplate characteristics. Most of the Cu-Au occurrences are spatially related to the Nautanen Deformation zone, which is a major north-northwest–oriented crustal structure. A large-scale zoning pattern is outlined by the metal association and alteration along the Nautanen Deformation zone and to some extent across it. In the northwestern part, magnetite and locally apatite are important constituents indicating a relation to the nearby apatite iron ores. The host rock is strongly altered by K feldspar and scapolite. Towards the southeast pyrite becomes an important ore mineral, while magnetite is less abundant. This change is accompanied by an increasing Au/Cu ratio and alteration dominated by biotite or sericite. Mineralization within the Nautanen Deformation zone is mainly disseminated in character and may represent an early phase of mineralization related to synorogenic 1. 9 Ga intrusions of intermediate composition. Vein style mineralization occurs as late phases in disseminated deposits and outside the Nauta-nen Deformation zone. This mineralization may to some extent represent remobilized products of older disseminated sulfide occurrences. The common occurrence of tourmaline in the veins and locally also molybdenite or scheelite suggests a relation to the granites of the 1.8 Ga Lina Suite. Thus, the present zoning pattern along the Nautanen Deformation zone is the product of several hydrothermal events with the 1.9 Ga mineralization possibly outlining the large-scale features.

The Gällivare area was first recognized for its iron deposits in the eighteenth century. When the railway from Luleå was built in 1888 to exploit the large iron resources, it initiated extensive exploration activities for other deposits in the surrounding areas. In 1898 copper ore was discovered at Nau-tanen and within a few years a number of Cu mineralizations had been found northeast and east of Gällivare. The Nautanen Copper Ore company was founded in 1900 and mining started in 1902 but lasted only until 1907 ( Geijer, 1918 ). Some other small Cu mines (Likavaara, Ferrum) were active during the same period in the Nautanen area, and a prospector was working a small gold mine (Fridhem). The Aitik deposit was discovered in 1932 by drilling on geophysical targets in an area where a rich ore boulder and a mineralized outcrop had been found. Further drilling was carried out in 1960 through 1965, and this delineated a low-grade but large Cu deposit suitable for large-scale open pit mining ( Malmqvist and Parasnis, 1972 ; Zweifel, 1976 ). Mining started in 1968 with an annual production of 2 Mt of ore, which has successively increased to c. 18 Mt in 2004. Most of the Cu deposits in the Gällivare area are hosted by volcaniclastic sediments varying in composition from aren-ites to pelites. These sediments are intruded by synorogenic diorites and late orogenic to postorogenic granites and pegmatites. The ore deposits occur within or close to the Nauta-nen Deformation zone, which

In the central Kiruna area the apatite iron ores are mostly strata-bound in character and show only minor signs of deformation and metamorphic recrystallization. However, apatite iron ores from Gällivare and Svappavaara exhibit a large variation in mineralization style and postore modification by deformation and metamorphism. Several major deposits occur in these areas; Malmberget, Leveäniemi, Gruvberget, and Mertainen are the most important. The Mertainen deposit has the character of a large ore breccia, while the other three are more stratabound in character with tabular and massive ore and only minor ore breccia. However, at Leveäniemi and Malmberget the ores are strongly affected by ductile deformation that modified the original shape of the orebodies. These two deposits are also affected by strong metamorphic recrystallization, resulting in a coarser grain size compared to better preserved deposits in areas of lower metamorphic grade. This strong postore modification probably results from the proximity of large granite intrusions of the 1.8 Ga Lina Suite. Except for typical apatite iron ores there are also minor iron occurrences of a more unusual type in northern Nor-rbotten. One of these is the Saivo Fe-Ti mineralization in the Jukkasjärvi area. It is a lens-shaped body situated within a monzonitic intrusion, and comprises very coarse grained pyroxene rock with magnetite, and titanite in the marginal part. Preliminary data suggest a U-Pb titanite age of c. 1.8 Ga (Kjell Billström, pers. commun., 2001). Differences between this deposit and typical apatite iron ores include the intrusive host rock, the extremely coarse grained

Kiruna is the type area for apatite iron ores. Eight economically significant deposits are known, of which seven have been mined. Kiirunavaara is the largest and best known. Mining of iron ore in the Kiruna area started in the eighteenth century with very small scale production from Luos-savaara. Kiirunavaara has been mined since 1900, and most of the other deposits were found at that time and mined for various periods during the twentieth century. The ores occur in the middle and upper parts of the Kiirunavaara Group. They are mainly massive, tabular bodies of magnetite-hematite with varying amounts of apatite. Magnetite breccia ore and banded apatite rich ore are morphological forms of minor importance. The Kiirunavaara and Luossavaara ores occur at a similar stratigraphic level between trachyandesite and overlying rhyodacite. These ores are mostly high grade with a rather low apatite content, but low-grade ore breccia is developed both in the footwall and the hanging wall. Ores in the upper part of the Kiirunavaara Group are generally referred to as the “Per Geijer Ores” ( Geijer, 1910 ). They include the Nukutus, Henry, Rektorn, Haukivaara, and Lappmalmen deposits and are rich in apatite with an average P content of 4 to 5 percent. Ore breccia is lacking or mainly restricted to the footwall, while banded ore may be common towards the hanging wall. The Tuolluvaara deposit is situated in rhyo-dacitic rocks 6 km northeast of Kiirunavaara. The ore mainly has the character of a large ore breccia and the content