Geology of the Setesdalen Area, South Norway: Implications for the Sveconorwegian Evolution of South Norway

Home , Bygland, Bygland (village), Evje, Evje (village), Gautestad, Gothian orogeny

Geology of the Setesdalen area, South Norway: Implications for the Sveconorwegian evolution of South Norway

SVEND PEDERSEN & JENS KONNERUP-MADSEN

Pedersen, S. & Konnerup-Madsen, J. 2000–02–10: Geology of the Setesdalen area, South Norway: Implications for the Sveconorwegian evolution of South Norway. Bulletin of the Geological Society of Denmark, Vol. 46, pp. 181–201, Copenhagen. https://doi.org/10.37570/bgsd-1999-46-15

Crust forming processes in the Setesdalen area in the central part of southern Norway are dominated by the development of pre-Sveconorwegian supracrustal rocks (immature clastic sediments and bimodal volcanics) with an assumed depo- sitional age of 1150–1100 Ma and by the emplacement of scattered infracrustal granitoids. The supracrustal rocks were deposited on a partly older than 1300 Ma gneissic basement including rocks which may have suffered one or more pre- Sveconorwegian orogeneses. During the Sveconorwegian orogeny, with the main upper greenschist to middle amphibolite facies high-temperature metamorphism and deformational phases in the period 1060–970 Ma, igneous activity comprising K-rich rocks high in elements such as P, Ti, La, Sr, Zr, and LREE and Ba was dominant. Significantly younger than this activity is the development of many REE pegmatites which are so characteristic for the region. The Precambrian geological activity terminated (at about 830 Ma?) with the development of E-W trending tholeiitic dolerites.

Key words: Geochronology, granites, metagabbros, Norway, Precambrian, REE pegmatites, Sveconorwegian orogeny

Svend Pedersen & Jens Konnerup-Madsen, Geologisk Institut, Copenhagen Uni- versity, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark. 22 June 1999.

Southern Norway and Sweden make up the Sveco- 1998) with extensive polyphase deformation, meta- norwegian Province of the Baltic Shield and consist morphism and magmatism. of rocks formed during the Sveconorwegian orogeny The Sveconorwegian Province in southwestern and pre-existing rocks which were tectonically re- Scandinavia includes several Proterozoic crustal seg- worked and metamorphosed during this tectonother- ments separated by thrust and shear zones (Fig. 1A), mal event. some of which show evidence of sinistral strike-slip The Sveconorwegian orogeny – the Scandinavian movements (Hageskov 1997). West of Oslo Fjord the counterpart to the Grenvillian – has determined the dominant thrust zone, the Kristiansand-Bagn shear structural pattern observed west of the Sveconorwe- zone (the Bamble and Kongsberg shear zones, Fig. 1) gian Front (Fig. 1) and plausibly developed at the (Hageskov 1980) divides southwestern Norway into margin of a larger continent (Laurentia and Baltica) two main crustal segments, the Kongsberg-Bamble and as a result of oblique collision(s) with another un- the Telemark-Vest Agder-Rogaland segments. The known continent (Romer & Smeds 1996). The present Mandal-Ustaoset lineament (Sigmond 1985) has more level of exposure in southern Norway has been con- recently also been considered to be a significant thrust sidered to represent the deep roots of a Cordilleran (e.g. Starmer 1993) and to divide the Telemark-Vest type convergent plate margin and a subsequent colli- Agder-Rogaland segment into a Telemark sector and sion zone which is often indicated to have formed in a Vest Agder-Rogaland sector (Fig. 1); the geological the period 1100–900 Ma. The Vest Agder-Rogaland history of the individual segments and sectors prob- area (Fig. 1) is by many authors described as being ably differs. situated in the core zone of the orogen (e.g. Falkum & The crustal evolution between Oslo Fjord and the Petersen 1980, Falkum 1985, Bingen & van Bremen Mylonite zone is dominated by Gothian (1710-1570

Pedersen & Konnerup-Madsen: Geology of the Setesdalen, Norway 181

DGF Bulletin 46-2.p65 181 17-01-00, 13:26 lified geological map of South lified Gneiss Region, and the extent of and the extent Gneiss Region, Caledonian and younger cover. Abbreviations: SZ: shear zone; MU SZ: the Mandal Ustaoset shear zone. The right map (B) is a simp SZ: shear zone; MU the Mandal Ustaoset zone. Abbreviations: Caledonian and younger cover. the location of Setesdalen area. showing Norway Fig. 1. The left map (A) shows the major structural divisions of the basement in South Norway and Southwest Sweden, the Western and Southwest Sweden, the of the basement in South Norway divisions the major structural The left map (A) shows Fig. 1.

182 Bulletin of the Geological Society of Denmark

DGF Bulletin 46-2.p65 182 17-01-00, 13:26 Ma) orogenic processes (Gaál & Gorbatschev 1987, uplift histories (e.g. Bingen et al. 1998) and suggest Graversen & Pedersen 1999) and widespread post- that the Sveconorwegian orogeny was not one con- Gothian intracratonic magmatism during several tem- tinuous orogeny but different orogenies, one ending porally and spatially distinct episodes in the period at around 1100 Ma and the other around 980 Ma. 1530–1130 Ma (Åhäll & Connelly 1998) before the Rocks of pre-Sveconorwegian, unequivocal supra- Sveconorwegian (1100–900 Ma) overprinting. The crustal origin are especially known from the Telemark Kongsberg and Bamble sectors were also affected by region, where large areas are covered by volcanic rocks the Gothian orogeny, the widespread influence of and clastic sediments belonging to the so-called which has not been convincingly demonstrated in ar- Telemark supracrustals (Dons 1960, Sigmond et al. eas west of the Kristiansand-Bagn shear zone, where 1997) and have only been affected by low to medium Sveconorwegian crust-forming processes appear to be grade metamorphism in its central part. The Telemark the determining event. supracrustals are divided into four groups: the Rjukan Sveconorwegian magmatic activity is far less im- (oldest), Seljord, Heddal and Bandak (youngest) portant east than west of the Kristiansand-Bagn shear groups (Dahlgren 1996). The age of the Telemark su- zone where magmatic activity contemporaneous with pracrustals is somewhat uncertain but recent studies and later than the Sveconorwegian orogenic evolu- suggest ages and deposition of the volcanic dominated tion is widespread, particularly west of the Mandal- Rjukan and Bandak groups of about 1500 Ma and 1120 Ustaoset lineament (Fig. 1B). Emplacement of most Ma, respectively (Dahlgren 1996). Dating of detrital of the late- to post-Sveconorwegian granites appears zircons from a metasandstone-arkose in the top of the to have occurred along several N-S to NNE-SSW line- Bandak group suggests deposition ages as young as aments which might represent zones of crustal weak- 1045±22 Ma (Bingen et al. 1999). The age of deposi- ness reflecting the orientation of the Sveconorwegian tion of the intermittent, essentially clastic sedimen- collision (Fig. 1). Judged from age determinations of tary Seljord group is not known but parts of it are con- younger intrusions and pegmatites not influenced by strained by an age of 1145 Ma obtained on a gabbroic Sveconorwegian deformations (e.g. Falkum 1998), a sill emplaced in the sediments (Dahlgren et al. 1990) lower limit to the Sveconorwegian orogeny of around and being in agreement with U/Pb ages of detrital zir- 980–970 Ma is favoured by the authors. cons of about 1350 Ma (Bingen et al. 1999). The metamorphic rock complex in southern Nor- Basement relations for the Telemark supracrustals way is generally divided into two main lithological are not well established, but it is commonly inferred suites, a granitic gneiss suite and a banded gneiss suite, that (parts of) the gneisses exposed in the Vest Agder- comprising several mappable units (Falkum 1998). Rogaland sector and in the southern part of the The former suite includes several types of granitic Telemark sector are plausible basement candidates. gneiss units including granitic orthogneisses and augen gneisses with a plutonic precursor. The banded gneiss suite comprises a series of generally banded gneisses with alternating mafic and felsic layers and amphibolite facies mineral assemblages. Parts of the banded Geology of the Setesdalen area gneiss suite are of an indisputable supracrustal origin The Setesdalen area is situated in the southern part of and represent metamorphosed clastic sediments and the Telemark sector, south of the principal area of the basaltic tuffs. Rb-Sr whole rock age determinations Telemark supracrustals and just east of the Mandal- and U-Pb zircon dating of the gneisses mostly give Ustaoset lineament/shear zone as defined by Sigmond ages around 1130–1030 Ma (e.g, Knudsen et al. 1997, (1985) (Fig. 2). The 1:250,000 geological map Bingen & van Bremen 1998) believed to reflect Sve- MANDAL (Falkum 1982) covers part of the area, and conorwegian metamorphism, but ages of 1190–1130 additional geological information may be obtained Ma on metaplutonic rocks with A-type geochemical from the 1:50,000 preliminary map EVJE (Pedersen signatures indicate pre-Sveconorwegian crustal addi- 1985). In addition, various aspects of the geology of tions (e.g. Bingen & Bremen 1998). Even older ages parts of the area have been presented by Andersen have been obtained (e.g. Birkeland et al. 1997) and (1931), Barth (1947), Bjørlykke (1934, 1937, 1947), suggest local (?) Gothian and pre-Gothian igneous Teisseyre (1970), Pedersen (1975, 1981), Pedersen & activity as well. However, the actual amount of pre- Konnerup-Madsen (1994) and Hansen et al. (1998). Sveconorwegian rocks in the Vest Agder-Rogaland Based on these previous studies and more recent sector is still largely unknown. In the Bamble sector, detailed field and geochemical studies, the present Sveconorwegian (granulite facies) metamorphism is knowledge of the geological evolution of the Setes- indicated to have ended around 1095 Ma (Kullerud & dalen area may be summarised chronologically under Dahlgren 1993), whereas in the Vest Agder-Rogaland the headings (Fig. 3): sector the last Sveconorwegian deformation and metamorphism occurred around 990-980 Ma (Falkum (1) Formation of the Setesdalen metamorphic base- 1998). The differences in age between these sectors ment complex consisting of pre-Sveconorwegian are substantiated by similar differences in cooling and basement gneisses which host a series of calc-al-

Pedersen & Konnerup-Madsen: Geology of the Setesdalen, Norway 183

DGF Bulletin 46-2.p65 183 17-01-00, 13:26 Fig. 2. Geological map of the Setesdalen area.

184 Bulletin of the Geological Society of Denmark

DGF Bulletin 46-2.p65 184 17-01-00, 13:26 Fig. 3. Schematic lithological and chronological column for the rock types in the Setesdalen area.

kaline granodiorites and granites, as well as basic the Setesdalen area is shown in Figure 2, and a gener- igneous rocks with a continental margin arc sig- alised lithological-chronological diagram in Figure 3. nature (e.g. the Iveland-Gautestad metagabbro). Subsequently this basement complex was metamorphosed under upper amphibolite facies conditions during a pre-Sveconorwegian tectonothermal The Setesdalen metamorphic basement event. complex (2) Formation of pre-Sveconorwegian supracrustal Remnants of the metamorphic basement complex have and infracrustal rocks (the Byglandsfjorden mainly been identified in the southern part of Setes- group), comprising deposition of immature clas- dalen, around and south of Evje village. Banded tic sediments and igneous activity related to bi- gneisses dominate and consist of alternating cm-dm modal anorogenic volcanic and plutonic complexes thick felsic and mafic bands. The individual bands as well as the emplacement of minor bodies of comprise mainly amphibolites, granodioritic biotite- gabbros and diorites. hornblende gneisses, alkalifeldspar-garnet gneisses, (3) Sveconorwegian regional amphibolite facies meta- and cummingtonite-rich gneisses, but occasionally morphism, possibly with associated synorogenic patches of mafic two-pyroxene, garnet-bearing emplacement of calc-alkaline granites and ferro- gneisses occur. These mineral assemblages indicate diorites (e.g., the Flåt Complex). the attainment of upper amphibolite to lower granu- (4) Late- to post-Sveconorwegian emplacement of a lite facies conditions. highly potassic granitoid suite of bimodal (gran- The minimum age of metamorphism is indicated ite-monzodiorite) igneous complexes. from dating on igneous rocks crosscutting folds in this (5) Formation of the Iveland-Evje REE pegmatite field, series of banded gneisses. The oldest age obtained has and emplacement of post-Sveconorwegian E-W been on a metagranodiorite of calc-alkaline affinity, trending tholeiitic dykes. the Sletthei augen gneiss, which yields a Rb-Sr whole rock age of 1350 ± 80 Ma (Pedersen 1981) (MSWD:

In this paper, a summary of the geological evolution 3.58); a SrIR of 0.701±0.003 precludes significant in- of the Setesdalen area will be presented, with the main volvement of older crustal components. Rocks simi- emphasis placed on the character of magmatic activ- lar in composition and age to the Sletthei augen gneiss ity as time markers in the area. The geological map of occur scattered in the Vest Agder-Rogaland,

Pedersen & Konnerup-Madsen: Geology of the Setesdalen, Norway 185

DGF Bulletin 46-2.p65 185 17-01-00, 13:26 Fig. 4. Geological map of the area around Evje and Iveland in the southern part of the Setesdalen showing the relationships between the Iveland-Gautestad metagabbro and other metabasic bodies and basement gneisses.

186 Bulletin of the Geological Society of Denmark

DGF Bulletin 46-2.p65 186 17-01-00, 13:26 Kongsberg, and Bamble sectors (Falkum, 1985; (hornblendite and pyroxene-hornblendite lenses or Sigmond, 1978). Their actual proportion of the pre- boudins), a massive gabbronoritic unit, and a layered Sveconorwegian rocks within the Agder Complex is series of predominantly diorites, all of which are cut still not fully elucidated, but they form an important by dykes or plugs of gabbronoritic, tonalitic and gab- type. broic compositions. The ultramafic bodies clearly be- Another indication is provided by the Iveland- long to the same stratigraphic level within the intru- Gautestad metagabbroic complex described below sion. Further south and more central in the intrusion, which is the most important indication of pre-Sveco- larger bodies of hornblende pyroxenites and peridotites norwegian igneous activity prior to the formation of occur with up to 50% olivine in addition to smaller the Byglandsfjorden group. scattered occurrences of lenses, schlieren or bands of hornblende pyroxenite within the gabbronoritic unit (Bertelsen 1984). Occasionally rounded bodies of harzburgitic pyroxene-hornblende peridotite with The Iveland-Gautestad metagabbroic complex olivine (Fo86), orthopyroxene, spinel and hornblende The main occurrence of basic rocks in Setesdalen is occur within the hornblende pyroxenite. The ultra- the Iveland-Gautestad metagabbroic complex (see Fig. mafic series is considered to represent various types 2) which was originally termed the Iveland-Evje am- of peridotitic and in particular pyroxenitic cumulates. phibolite by Barth (1947). The amphibolite is a large A weakly foliated, coarse-grained to pegmatitic unit body covering 160 km2 and stretching 30 km in the (essentially a hornblende diorite) was mapped out in N-S direction and up to 15 km in the E-W direction. the central part of the intrusion by Bertelsen (1984) It was originally described by Barth (1947) as a tho- and suggested to represent a largely continuous peg- roughly reworked, metamorphosed and metasomatised matite-rich layer occasionally crosscutting the layered norite now present as various types of hornblende gabbroic series at a low angle. gabbros, diorites and amphibolites, and with only Within the intrusion a number of small and uneco- minor noritic patches being preserved. The strongest nomic Fe-Ni-Cu sulphide showings are known. Min- argument for the originally noritic character was the eralization occurs in irregular zones up to 25 meters occurrence of several nickel deposits. Recent studies wide with intervening zones lacking mineralization; have shown it to be composed of several distinctly all gradations from finely disseminated ore, through different bodies, the composite and layered Iveland- ore forming a network to cm-dm-sized rounded blebs, Gautestad metagabbroic complex, and the somewhat aggregates and bands of sulphides are seen. The min- younger Evje amphibolite (previously termed evjeite eralization displays textural, mineralogical and chemi- by Barth (1947)) and Mykleås ferrodiorite, which is cal characteristics similar to those of orthomagmatic now regarded as part of the Flåt complex (see below) deposits of segregative origin associated with mafic- (M. Pedersen 1993) (Fig. 4). ultramafic compositions and to those described for The Iveland-Gautestad intrusion is a composite similar types of mineralization from the Bamble area body which consists of igneous rocks ranging in com- (Brickwood 1986). position from ultramafic to felsic, and which has been In the eastern part of Lake Høvringsvatn and in an partly metamorphosed under static conditions. The area towards the southeast, coarse-grained amphibo- dominant rock types are gabbronorites, occasionally lite is found as xenoliths in the fine-grained olivine-bearing, grading into diorites and quartz metabasites of the Iveland-Gautestad body. The diorites. Tonalitic and leucotonalitic (trondhjemitic) xenoliths have suffered stronger deformations than the rock types occur in subordinate amounts. Field obser- gneissic host rocks and complicated fold patterns in- vations and gravimetry (Smithson 1963) indicate the cluding sheath folds can be seen. Calc-silicate like shape of the intrusion to be that of a folded flat bowl, lenses are seen in the metabasic xenoliths. the thickness of which is in the order of 1-2 km at Representative analyses of the main rock types in maximum, and that the present level of erosion is close the Iveland-Gautestad intrusion are given in the Ap- to the roof of the intrusion. The intrusion was em- pendix. placed discordantly into highly deformed and isocli- The observed trends in variation diagrams (Fig. 5)

nally folded, predominantly mafic, middle to upper are typical for low- to medium-K2O, tholeiitic to calc- amphibolite facies banded gneisses (locally granulite alkaline basaltic rock suites. facies). Subsequent to its plausibly syn-kinematic The ultramafic unit is high in MgO, Ni and Cr, and

emplacement the Iveland-Gautestad body was de- low in major elements such as K2O, P2O5 and TiO2 formed together with the enclosing banded gneisses. indicating an early stage of fractionation of Mg-rich The contact is sharp although the presence of mafic phases such as olivine and pyroxenes. High Ni and Cr layers in the gneiss may obscure the contact relations. contents support this. Streaks and wedges of gneissic material are sand- Attempts to determine the tectono-magmatic envi- wiched between gabbroic layers in the contact zone. ronment using the mantle normalised hygromagma- In the northern part of the intrusion Rønholt (1990) tophile element diagram of Wood et al. (1979) lead to was able to distinguish between an ultramafic unit trends strongly resembling those typical of low-po-

Pedersen & Konnerup-Madsen: Geology of the Setesdalen, Norway 187

DGF Bulletin 46-2.p65 187 17-01-00, 13:26 Fig. 5. Selected chemical relations illustrating some basic chemical characteristics of the Iveland-Gautestad metagabbroic complex. The upper left diagram presents the Hughes (1973) screening off of altered samples; only samples within the Hughes’ igneous spectrum have been plotted in the other diagrams. Other discimination lines in the diagrams are taken from Miyashiro (1974), Pearce & Gale (1977) and Irvine and Barager (1971).

Fig. 6. Sm-Nd and Rb-Sr isotopic characteristics for the Iveland-Gautestad metagabbro and the Evje amphibolite as discussed in the text.

188 Bulletin of the Geological Society of Denmark

DGF Bulletin 46-2.p65 188 17-01-00, 13:26 tassium tholeiites from destructive plate margins and ture sediments. Together with the volcanics, granitic

the trends in the TiO2-K2O-P2O5, Ti-Zr-Sr and Ti-Zr- intrusions are found. Y diagrams further give a continental margin signature. The Byglandsfjorden group The Byglandsfjorden group is dominated by supra- Isotope signature and age of the Iveland- crustal rocks of both volcanic and sedimentary ori- Gautestad metagabbro gin. The early volcanism is clearly bimodal and in- U/Pb dating on euhedral and unzoned zircons sepa- cludes metarhyolitic lavas, pyroclastic rocks or vol- rated from a sample of coarse-grained (pegmatitic) canic sediments and metabasic tuffs and/or lavas, as diorite from the southern part of the complex gave an well as plutonic (granitic) equivalents, which together age of 1279±3 Ma, considered to be the emplacement constitute the Bygland formation. The metavolcanic and cooling age of the complex. A lower intercept age sequence contains interlayered metasediments vary- of 228 Ma indicates isotope disturbance at a later time. ing in composition from arkoses to quartzites and con- In addition, eight samples were analysed for Rb/Sr glomerates. The amount of metasedimentary layers and Sm/Nd isotopes and the results are summarized increases towards the stratigraphic top of the volcanic in Figure 6. The Sm/Nd data do not constrain an age. sequence; on top of the volcanic sequence a metasedi- A 1350 Ma reference line has been added to Figure 6 mentary unit is seen. Likewise, metavolcanics are and represents the best fit to six of the eight samples found interlayered with the metasedimentary unit near analysed; however, the scatter in data points indicate the base of the sedimentary sequence indicating that that the data do not represent an isochron but more there is a transitional evolution from the volcanic likely reflect assimilation of older crustal material by Bygland formation to the overlying sedimentary units the basic melt which is plausibly from a depleted man- of the Jordalsvatn formation. In the northern part of tle source. The Rb/Sr isotopes on the same samples Setesdalen, the Jordalsvatn formation corresponds to appear to define an 1040 Ma isochron (Figure 6). Ac- the lowermost part of the Bandak group. cepting the age of 1279 Ma as the emplacement age, the age obtained from the Rb/Sr data may represent a The Bygland formation. The volcanic-dominated metamorphic (Sveconorwegian) event. Bygland formation consists of an often banded sequence of pink, fine- to medium-grained metarhyolites forming up to m-thick units interlayered with up to dm-thick amphibolites and biotite schists. Between Other occurrences of basic bodies individual layers grey to white, coarse-grained rocks In addition to the Iveland-Gautestad metagabbroic representing different kinds of psammites are seen. complex, a number of smaller basic bodies have been Leucocratic veining often parallels the foliation of the discovered and show that basic magmatism was more metarhyolites but locally discordances are seen. extensive than earlier recognised. Most of these bod- Within the Bygland formation, metagranites be- ies are rather small but may collectively cover several lieved to represent intrusive (sub-volcanic ?) analogues square km. The smaller bodies are usually fine- to to the extrusives occur. One such example is the medium-grained and homogeneous. They show clear Syrtveit gneiss (metagranite) described earlier by Pe- intrusive features and in places exhibit igneous layer- dersen (1981). The Syrtveit gneiss has been dated by ing and contain ultramafic units. the Rb-Sr whole-rock method (11 samples) to 1120 ±

31 Ma with a SrIR of 0.706 ± .002. This age is considered to reflect the time of emplacement and cooling of the granitic precursor of the Syrtveit gneiss. The Syrtveit gneiss is a foliated and lineated, reddish to The pre-Sveconorwegian Byglandsfjorden greyish, leucocratic, medium- to coarse-grained gneiss of granitic to granodioritic composition, with linear supracrustal and infracrustal units and planar structures defined by mm-thin aggregates The metabasic units of the metamorphic basement of biotite and hornblende. Antiperthite has been ob- complex are discordantly overlain by rocks of what served in several samples. Accessories are titanite, tentatively has been termed the Byglandsfjorden apatite, zircon, allanite and opaque minerals. group. Detailed mapping has shown that a major part Both the acid metavolcanic and metaplutonic rocks

of what was previously described as heterogeneous are characterised by rather high SiO2 contents and high gneisses belonging to the Agder Complex are actu- FeOTotal/MgO ratios (>8) considered characteristic of ally distinguishable pre-Sveconorwegian metasu- North American anorogenic granites, e.g. Anderson pracrustal units. In the Setesdalen area these include (1983). a series of interlayered metavolcanic rocks and metasediments, and a sequence of metamorphosed imma- The Jordalsvatn formation. The metasediments of the

Pedersen & Konnerup-Madsen: Geology of the Setesdalen, Norway 189

DGF Bulletin 46-2.p65 189 17-01-00, 13:26 Jordalsvatn formation consist mainly of immature Evje amphibolite) and ferrodiorites (the Flåt diorites). coarse arkosic metasediments but more mature The later magmas, belonging to the younger part of (quartzitic) units and conglomeratic units also occur. the province, were emplaced around 970-900 Ma Some of the units are sufficiently characteristic to be (preferentially in the older end of the interval) as small mappable, such as a green spotted quartzite (where plutons and accompanying dykes, in dyke systems and the green spots consist of an intergrowth of amphi- as minor bodies. Magma compositions of these are bole, biotite and epidote), orthoquartzites interlayered bimodal with one component being granitic and the with amphibolites, a metaarkose and a metaconglom- other ranging from monzodiorite over monzonite to erate. syenite. Four (perhaps five) such bimodal complexes The psammites are grey, fine-grained, often com- have been identified (see Fig. 2). The associated dykes positionally laminated (mm-cm scale) and foliated often exhibit pronounced foliated/lineated fabrics. with the foliation parallel to the lamination. Less fre- quent are biotite schists and ultramafic rocks now present as talc-rich lenses/boudins. Metabasic rocks with a mineral assemblage containing cordierite, an- The early Sveconorwegian igneous activity thophyllite, sillimanite and garnet are observed locally. Representatives of the early Sveconorwegian igneous Clasts of quartzite, metagranite and different types of activity in Setesdalen are a deformed granodiorite (the gneisses can be recognised in the metaconglomerates Fennefoss augen gneiss) and granite (Grimsvatn augen and indicate the presence nearby of an eroded gneissic gneiss) and a dioritic phase dominated by highly basement during deposition of the Jordalsvatn forma- evolved rocks some of which are described as ferro- tion. diorites (i.e. the Flåt diorite comprising the Mykleås The Jordalsvatn formation in places has clearly dis- diorite and the so-called ore diorite). The Fennefoss cordant contact relationships to the Bygland forma- augen gneiss is an approximately 45 km long folded tion, but mostly it is concordant with a gradation as body stretching in a NNE-SSW direction, and the cur- described above. rent mapping has demonstrated that it actually con- In the southern part of the Setesdalen, orthoquartzite sists of two bodies, the Fennefoss augen gneiss and units are seen interlayered with amphibolites and the Grimsvatn augen gneiss (Fig. 2). The Fennefoss metarhyolites and in direct contact with metarhyolite augen gneiss is briefly described by Pedersen (1981). from the Bygland formation. Further to the north, the The presence of crenulate to cuspate contacts indi- orthoquartzite changes laterally into more impure feld- cate that the time between emplacement of the spathic gneisses, and thins out and is gradually re- ‘Fennefoss granodiorite’ and the Mykleås diorite was placed by amphibolites and biotite-schists. The short; the occurrence of hybrids in the contact zone orthoquartzite unit apparently dies out toward the between the two complexes indicates that the grano- south. This whole sequence seems to be discordantly dioritic rocks were not fully consolidated at the time cut by the granitic gneiss of the Syrtveit type. of emplacement of the diorites. This observation is Thick layers of mafic rocks (amphibolite and biotite supported by zircon datings of both rock types. U/Pb schists) locally occur between the Jordalsvatn and dating on separated zircons from the Mykleås diorite Bygland formations and the Fennefoss augen gneiss give ages of 1034 (±2) Representative chemical analyses of the Syrtveit and 1031 (±2) Ma, respectively. The age obtained on granitic gneiss, metarhyolites and psammites are given the Fennefoss augen gneiss is in close agreement with in the Appendix. the previously obtained U/Pb zircon age of 1035 Ma (Bingen 1998) and the 1026 (± 26) Ma Rb-Sr whole- rock age of Pedersen (1981).

Sveconorwegian magmatic activity in the The Flåt dioritic rocks. The Mykleås diorite body consists of different types of diorites. The main type is a Setesdalen area plagioclase-phyric rock with abundant phenocrysts. Following deposition of the Byglandsfjorden group The ore diorite, which is more equigranular but does and emplacement of infracrustal granitic rocks, the not differ in mineralogy or chemistry from the Mykleås Setesdalen area was subjected to an event of highly diorite, hosts the ore body of the Flåt nickel mine diffentiated and mostly potassic to ultrapotassic mag- (Bjørlykke, 1947), at one time the largest nickel mine matism from about 1030 Ma to possibly around 900 in Europe. The mining was stopped in 1944. The ore Ma. Together this igneous activity constitutes the is very heterogeneous and ranges from ore diorite with Setesdalen Igneous Province which falls into two dis- disseminated sulphides to nearly 100 % sulphide ore. tinctly different periods. The ore minerals are mainly pyrite, pyrrhotite, pent- The earliest magmas were emplaced around 1030 landite and chalcopyrite. Ma as large elongated composite complexes consist- Representative chemical relations of the igneous ing of granodiorite and granite (‘feldspar porphyritic’ complexes of the early Sveconorwegian activity are augen gneisses) and different types of diorites (the shown in Figure 7. The calc-alkaline, high-K charac-

190 Bulletin of the Geological Society of Denmark

DGF Bulletin 46-2.p65 190 17-01-00, 13:26 Fig. 7. Selected chemical relations illustrating some basic chemical characteristics of the Fennefoss and Grimsvatn augen gneisses (see Fig. 4) and the Flåt diorites. See text for further discussion.

ters of this early Sveconorwegian activity is clearly contents of Y, Zr and Nb and slightly lower Rb, Sr and seen. Cr. Chemically, it strongly resembles enriched MORB or oceanic island tholeiites; discrimination diagrams

The Evje amphibolite. The Evje amphibolite, named of TiO2-K2O-P2O5, Ti-Zr-Sr and Ti-Zr-Y also give an after the village Evje (Fig. 4), was originally described oceanic signature for the Evje amphibolite (Pedersen as a gabbro with primary hornblende and called evjeite 1993). by Barth (1947). Field evidence shows the Evje amphibolite to be a composite body that mostly occurs as xenoliths within the Fennefoss augen gneiss. Some of these xenoliths themselves contain xenoliths of rocks from the Byglandsfjorden group. The late- to post-Sveconorwegian igneous The typical Evje amphibolite is a black fine-grained Setesdalen activity dioritic rock with thin, a few mm thick veins of pure The magmatic character of the plutons emplaced dur- hornblende. It typically contains plagioclase, horn- ing the younger part of the Setesdalen igneous activ- blende and opaque phases as the main minerals, but ity is established from studies of four intrusive com- occasionally minor amounts of garnet and biotite are plexes, their accompanying dyke systems and single, present and probably reflect the results of assimila- irregular dykes. Intrusive rocks comparable – and in tion of older gneisses. At a few localities corona tex- many cases identical – to those found in the complexes tures after pyroxene can be observed in some of the can be observed as smaller dykes and plugs elsewhere basic rocks which may belong to the Evje amphibo- in the Setesdalen area indicating that further similar lite. intrusive complexes may occur at depth. Smaller mon- The Evje amphibolite is clearly distinguished chemi- zonitic dykes have also been observed outside Setes- cally from the Iveland-Gautestad complex by higher dalen.

Pedersen & Konnerup-Madsen: Geology of the Setesdalen, Norway 191

DGF Bulletin 46-2.p65 191 17-01-00, 13:26 Fig. 8. Geological maps of the Åraksbø and Høvringsvatn bimodal granite-monzonite complexes.

The complexes are up to 35 km2 large and usually Representative chemical relations of the four igne- have an elongated or ellipsoidal form. They exhibit ous complexes of the late- to post-Sveconorwegian different characteristics regarding magmatic evolution activity are shown in Figure 9. A high-K to shoshonitic but all contain a characteristic monzonitic-monzodi- character for both monzonites and granites and a oritic phase and a granitic phase which is occasion- within-plate granite setting is clearly seen. ally porphyric. Associated minor bodies, mostly of monzonitic composition, but also of granitic and mixed The Neset intrusion. The Neset intrusion (N in Fig. 2) bimodal compositions are characteristic. In the smaller is elliptical with a NW-SE orientation of the longest bodies and dykes, cuspate and crenulate contacts typi- axis; it developed as a ring intrusion. The intrusion cal of coexisting basic and felsic melts are often ob- seems to be cut by the Grendi Complex (see below). served and indicate the coexistence of monzodioritic Near the northern contact small scale igneous layer- and granitic melts in the evolution of these complexes. ing with alternating monzonitic and granitic layers is In the smaller monzonitic dykes a pronounced fabric found. The monzonitic layers are of a dark grey me- is usually observed as well as special structures of dium-grained equigranular type and are a few cm deformation. These minor intrusions are treated by thick. Often the transition to granite is abrupt, but in Skjernaa & Pedersen (this volume). other cases a small transition zone with phenocryst- The complexes of the Setesdalen Igneous Province bearing monzonite is developed. Some massive sheets occur aligned in a NNW-SSE direction, even though of a coarse-grained granite crosscut the fine the individual ellipsoid complexes may have a differ- layering.The granite which alternates with the mon- ent elongation. The mapping of the individual com- zonite is of a red medium-grained type. plexes has revealed the emplacement of different mag- Some hundred meters south of the northern contact matic pulses of monzonitic and granitic compositions. the type of layering changes and the layers become In one of the complexes (the Neset complex) mag- several meters, up to around 10 meters, thick. All lay- matic layering is a pronounced feature. All complexes ers start with a dark medium-grained equigranular except one may have been slightly deformed. In the monzonite and, towards the centre of the intrusion, following the complexes will be briefly treated. Geo- K-feldspar phenocrysts (and in some cases phenocrysts logical maps illustrating the form of observed struc- consisting of antiperthitic plagioclase) become in- tures are shown in Figure 8 for two of the complexes, creasingly abundant until a red granitic rock with only the northernmost Åraksbø complex and the Høvrings- few dark minerals takes over. In many of the layers vatn complex emplaced in the northernmost part of the evolution stops before ‘the granitic end member’. the Iveland-Gautestad metagabbroic complex. Crosscutting the layering are medium- to coarse-

192 Bulletin of the Geological Society of Denmark

DGF Bulletin 46-2.p65 192 17-01-00, 13:26 Fig. 9. Selected chemical relations illustrating some basic chemical characteristics and the possible tectonic setting of the four bimodal granite- monzonite complexes described in the text. Empty symbols represent granites; filled symbols monzonites and monzodiorites. See text for further discussion.

grained granitic bodies (‘dykes’) and thin monzonitic erosion is close to the roof as indicated by the many dykes, most probably cone sheets. xenoliths and roof pendants. Most of the rocks in the intrusion have a contact- The monzonites are of a dark grey, medium-grained parallel fabric. A large number of thin granitic veins type, and a light grey type which often forms hybrids cut the fabric especially in the monzonitic and the in contact with granite. Both rock types are homoge- phenocryst-bearing parts. neous and generally without any preferred orientation In the western part of the intrusion the layered se- of the minerals. The granite in the central part is me- ries form only part of the exposed rocks. The ring dium- to coarse-grained and contains phenocrysts of structure here is defined by the presence of cone sheets alkali feldspar. The phenocrysts usually become larger and individual rock types which fit into the ring struc- towards the centre of the intrusion and are absent close ture as screens. Further to the west the ring structures to contact. In addition, a fine-grained aphyric granite are still defined by thin monzonitic cone sheets but it type is present in the south-eastern part of the com- is significant that different rocks of true granitic complex and in places within the coarser type. The gran- positions also form ring structures. Outside the intru- ite usually has a weakly developed fabric of parallel sion small bodies and/or dykes of monzonite and gran- arranged biotite or flattened aggregates of biotite and ite are present often as irregular dyke-shaped bodies. hornblende. This fabric becomes more and more pro- A Rb-Sr whole rock age (based on 6 samples) for nounced towards the marginal parts of the intrusion, the emplacement of the monzonites in the complex of and in the outer cone sheet system (see below) a 969 ± 18 Ma (MSWD: 1.59) has been obtained (Pe- streaky rock is seen.

dersen & Konnerup-Madsen 1994) with a SrIR of Cone sheets are present in three major systems. The 0,70381 (± 0.00006). inner cone sheet system consists of different types of fine grained monzonite similar to those seen as dykes and minor bodies in other places within the intrusion. The Høvringsvatn complex. The Høvringsvatn com- The intermediate and outer cone sheet systems con- plex (in Fig. 2 and Fig. 8) is an elliptical ring complex sist of several individual sheets of both granitic and consisting of a monzonitic and a granitic component. monzonitic composition. In places, between 10–20 or A unique feature of the complex is the development even more individual sheets lying close to each other of well-defined cone sheet systems as well as a bell can be counted. Also sheets of compositions interme- jar system indicating its emplacement at a high level diate between granite and monzonite are found. The in the crust (Anderson 1936). The complex is elon- monzonitic sheets are mostly of a spotted type (biotite gated approximately north-south. The present level of or biotite + amphibole aggregates form the spots) with

Pedersen & Konnerup-Madsen: Geology of the Setesdalen, Norway 193

DGF Bulletin 46-2.p65 193 17-01-00, 13:26 sheets, veins and marginal veins of granitic aplite The Åraksbø complex. The Åraksbø complex (A in material. Fig. 2 and Fig. 8) is divided into two parts by Lake The cone sheet systems are the dominant ring form- Byglandsfjorden (Fig. 8) and covers an area of 35 km2. ing structures. However, other dyke systems include It contains abundant xenoliths of psammites of the a horizontal system interpreted as a bell jar feature, Jordalsvatn formation. To the north the complex com- and a radial system with only a few dykes developed. prises a dark grey quartz monzonite and red granitic In addition to these well-defined dyke systems, a large rocks which are generally porphyric. This composite number of irregular dykes and smaller bodies of mon- part of the complex includes several intrusive pulses zonitic composition occur throughout the intrusion. of granite and monzonite with irregular contact rela- Within the complex, a large number of pegmatites tions, and between the monzonite and the granite a are found especially in the south-eastern part. The transition zone of several hundred meters with hybrid pegmatites belong to the Iveland-Evje pegmatite field rocks is observed. (see below). The monzonitic rocks comprise several types. The

Rb-Sr whole-rock ages of 945 ± 53 Ma (SrIR : 0,7041 main type is a homogeneous dark grey, medium ± 0.0007) ; MSWD: 0.88) and 900 ± 53 Ma (SrIR : grained rock without phenocrysts but locally a light, 0,7041 ± 0.0002; MSWD: 0.78), respectively, for the finer-grained massive type is seen. The hybrid zone emplacement of the granites and monzonitic dykes in between the two principal rock types varies greatly in the complex have been obtained (Pedersen 1981, Pe- appearance, from a complex (mechanical) mixture dersen & Konnerup-Madsen 1994). where it is possible to identify features from both end members to monzonitic rocks which nevertheless con- The Grendi complex. The Grendi complex (G; Fig. tain varying amounts of often rounded alkali feldspar 2), about 15 km2 in size and elongated in an east-west phenocrysts/xenocrysts. These hybrid rocks cover direction, has been interpreted as a giant south dip- considerable areas of the intrusion and also occur as ping sheet. The Grendi complex is younger than the dykes. Neset Complex. Towards the southeast, a body of fine-grained mon- A dark grey medium-grained monzonite is the domi- zonite crosscuts the composite part of the complex nant rock although variations are seen. The dominant resulting in intricate structures especially between the monzonite shows gradual transitions to more felsic porphyric granite and the fine-grained younger mon- rock types which sometimes grade into coarse-grained zonite. The complex here is clearly deformed appar- granitic rocks. ently exhibiting fold axes parallel to the regional axes The complex consists of a lower part of medium in the supracrustal host rocks. grained monzonite and an upper part dominated by Two fundamental intrusive features can be noted: alternating fine-grained granitic and monzonitic rocks. some major NNW-SSE trending dykes up to 50–100 Also within the lower series some south dipping sheets m wide of porphyric granite which can be followed of fine-grained granitic and monzonitic compositions for several hundreds of meters, and different types of are observed which intruded lit-par-lit into the monzonitic dykes some of which apparently form cone monzonites. A foliation in all sheets parallelling the sheets. These dykes can only be followed over short contacts is thought to be primary and formed during distances. Other dykes exhibit a pronounced radial consolidation. pattern. The dykes comprise both medium-grained In the western part an evolution from the dark grey dark monzonite and a fine-grained spotted monzonite medium-grained monzonite through a light alkali feld- similar to that seen in the other complexes. The cone spar-porphyric monzonite to a light porphyric granite sheet systems are cut by subhorizontal dykes of is observed. To the east a similar evolution is not monzonites with deformation structures similar to the present. In addition, outside the intrusion abundant structures from the subhorizontal dykes described by small monzonitic and granitic dykes are seen. The term Skjernaa & Pedersen (this volume). monzonite includes rocks ranging from quartz mon- A Rb-Sr whole rock age for the emplacement of the zonite to monzodiorite, quartz monzodiorite and porphyritic granites and the monzonites in the com-

syenite. plex of 971 ± 16 Ma (MSWD: 2.54) with a SrIR value Rb-Sr whole-rock ages for the emplacement of the of 0.7036 (± 0.0002) has been obtained (Pedersen & medium/coarse-grained granites and the fine-grained Konnerup-Madsen 1994).

granites in the complex of 973 ± 74 Ma (SrIR: 0.7037 ± 0.0003; MSWD: 2.37) and 1004 ± 200 Ma (SrIR: The Rustfjellet granite. Northwest of the Åraksbø com- 0.7036 ± 0.0006; MSWD: 0.69), respectively, have plex, another complex, the Rustfjellet granite (R; Fig. been obtained (Rasmussen 1993). Field relationships 2), which may be comparable to the Åraksbø com- similarly suggest that only the coarser-grained gran- plex, has been observed. Around the complex, mon- ites form part of the complex whereas the fine-grained zonitic dykes are observed but the intrusion has not granites may be representatives of melts generated been investigated in any detail and will not be treated during the Sveconorwegian orogeny. further in this paper.

194 Bulletin of the Geological Society of Denmark

DGF Bulletin 46-2.p65 194 17-01-00, 13:26 1986) where an age of about 835 Ma has been sug- The Iveland-Evje REE pegmatite field gested (Maijer & Verschure 1998). However, an age The Setesdalen area is well known for the Iveland- of 616 ± 3 Ma was obtained by Bingen et al. (1998). Evje REE pegmatites which have been described in A chemical analysis of one of these dykes is included detail by Andersen (1931), Barth (1931) and Bjørlyk- in the Appendix. ke (1934, 1937). In addition to their REE- and U/Th- bearing minerals, the pegmatites have been quarried primarily for quartz, micas and feldspars. The pegmatites occur in an approximately 5 km wide Structural considerations: the possible and about 30 km long N-S trending belt extending significance of the Mandal-Ustaoset southward from the Høvringsvatn complex. Most pegmatites are hosted by the Iveland-Gautestad lineament metagabbroic complex and appear to have been em- The importance of the Mandal-Ustaoset lineament for placed along pre-existing zones of weakness deter- the geological evolution of the Setesdalen area has mined by the previous structural history of the Iveland- not been touched upon in this paper. However, de- Gautestad metagabbroic complex and the emplace- tailed geological mapping of various regions previ- ment of the Høvringsvatn complex. Both steep N-S ously thought to cover parts of the suggested shear and E-W striking as well as sub-horizontal orientations zone, and preliminary structural analyses do not sup- are seen and occasionally mushroom-shaped pegma- port its presence at the present level of erosion. Thus, tite bodies are developed (Fougt 1993) due to a high the direct influence of a shear zone on the geological level of emplacement (Brisbin 1986). Most of the peg- evolution of southern Norway – as indicated by e.g. matites consist of an outer wall zone composed of a Sigmond (1985) and Sigmond et al. (1997) – will be coarse-grained graphic intergrowth of quartz and al- restricted to periods before the deposition of the Byg- kali feldspar, several intermediate zones with hetero- landsfjorden group supracrustals, that is before about geneous textural developments, and an inner quartz 1120 Ma. However, its existence as a deep-going zone core with blocks of alkalifeldspar and euhedral me- of crustal weakness may have been influential for em- ter-sized alkalifeldspar crystals. placement of the later magmas and pegmatitic melts. The mineralogy and the peraluminous bulk composition of the Iveland-Evje pegmatites is typical of the mixed-type REE pegmatites (Cerný 1991), for which an origin by partial melting of lower crustal litholo- gies is often favoured. No regional distribution of peg- Concluding remarks and summary matite minerals is seen. The geological studies summarized in this paper In earlier descriptions it has been inferred that the clearly indicate a long and complex mid- to late-Pro- pegmatitic activity marked the terminal stages of the terozoic crustal evolution in the Setesdalen area, with late- to post-Sveconorwegian igneous activity in Setes- both an important Sveconorwegian history as well as dalen and was closely related to the Høvringsvatn clear indications of older orogenies and intermittant complex. However, a Rb-Sr mineral age of 845 ± 12 tectonically quiet periods. Based on our present knowl-

Ma (SrIR: 0,70628 ± 0,00013; MSWD: 1,46; 9 sam- edge the authors suggest the following framework for ples) does not support such a relationship (Pedersen, the evolution of the Setesdalen area and possibly for a unpublished data; Stockmarr 1994). In addition, a pre- more general model for the evolution of southern liminary age obtained by step-wise leaching of gar- Norway: nets from another of the pegmatites indicated an age of about 800 Ma (R. Frei, pers. comm. 1998). 1. Formation of a pre-Sveconorwegian basement. This Besides the Iveland-Evje pegmatite field, important consists of heterogeneous gneiss intruded by the pegmatite areas are also found in the gneissic com- younger calc-alkaline granitoids (1350–1300 Ma) plex outside the Iveland-Gautestad metagabbro body. and by the Iveland-Gautestad gabbroic complex (1279) Ma). The geochemical characteristics of both of these suites of rocks suggest a continental margin setting and the possible initiation of a stage of subduction around 1350–1300 Ma followed by Dolerite dykes regional metamorphism. Emplacement of a minor swarm of generally only 2. Uplift, erosion and peneplanization, and anoro- meter-thick basaltic dykes trending E-W occurred in genic conditions. During this period, rifting oc- the northernmost part of the area (Fig. 2) and repre- curred allowing bimodal volcanism and later depo- sents the last sign of genuine magmatic activity in the sition of clastic sediments (the Byglandsfjorden Setesdalen region. These dykes are tholeiitic and thus group). The ages indicated for associated infrac- similar in composition to those described from the rustal granites constrain this event to 1150–1100 Rogaland area in SW-Norway (Venhuis & Barton, Ma. Diorites, e.g. the Evje amphibolite, and gab-

Pedersen & Konnerup-Madsen: Geology of the Setesdalen, Norway 195

DGF Bulletin 46-2.p65 195 17-01-00, 13:26 bros may possibly have been emplaced at this stage øvre grønskifer til mellem amfibolit facies høj-tem- too. peratur metamorfose og hoveddeformationsfaserne i 3. Subsequently, the area was again subjected to gran- perioden 1060-970 Må, prægedes den magmatiske ite emplacement, regional deformation and meta- aktivitet af K-rige bjergarter med høje indhold af P, morphism. Based on studies elsewhere in SW Nor- Ti, La, Sr, Zr, de lette sjældne jordsartselementer, og way, where more distinctly calc-alkaline granitic Ba. Emplacering af de sjældne jordartselementholdi- melts occur (Bingen & van Bremen 1998), Setes- ge pegmatitter som området er kendt for, er yngre og dalen is at a larger distance from the suggested site ikke genetisk tilknyttet denne magmatiske aktivitet. of subduction, implying a probable east-dipping Setesdalens magmatiske aktivitet sluttede omkring 830 position off the present west coast of South Nor- Må før nu med dannelsen af Ø-V strygende tholeiitiske way. Ages of about 1031 Ma for the deformed doleritgange. Fennefoss augen gneiss, the Rb-Sr age of metamor- Resultaterne viser, at det Sydnorske grundfjeldsom- phic resetting of about 1040 Ma for the Iveland- råde også vest for Oslo feltet har en lang og vigtig Gautestad metagabbroic complex, and ages ob- præ-Svekonorvegisk historie. tained further west in south Norway indicate an age of 1060-1040 Ma for the initiation of the Sveco- norwegian orogeny. 4. The end of the Sveconorwegian orogeny is marked by emplacement of a series of K-rich igneous, bi- Acknowledgements modal complexes with a clear within-plate signa- The authors are indebted to Tom Andersen (Oslo Uni- ture in Setesdalen. The ages for their emplacement versity) for Sm-Nd analyses on the Iveland-Gautestad around 980–975 Ma, their largely undeformed na- and evjeiite basic rocks, and to J.C. Bailey, Peter Ihlen ture, and their high crustal level define an intermit- (NGU) and Feiko Kalsbeck for constructive criticism tent stage of the post-Sveconorwegian uplift and and valuable comments to the manuscript. Peter C. peneplanization of the area. Lightfood (Inco Limited) is acknowledged for pro- 5. Post-Sveconorwegian events. Finally, emplacement viding U/Pb-zircon datings. of the Iveland-Evje REE pegmatites and E-W trending tholeiitic dykes occurred around 835–800 Ma and possibly as late as around 620 Ma, respectively; they represent a tensional stage possibly reflecting one or more attempted early break-up of References the continent. The presence of basic melts may have Åhäll, K.-I. & Connelly, J. 1998: Intermittent 1.53-1.13 been influential in generating higher heat flows at Ga magmatism in western Baltica; age constraints and this stage (Hansen et al. 1996) and provoking the correlations with a postulated supercontinent. Precam- formation of the crustally derived REE-rich peg- brian Research 92, 1–20. matitic melts. Andersen, O. 1931: Feltspat II. Norges Geologiske Under- søkelse 128b, 107pp. 6. Following this final igneous activity in Setesdalen, Anderson, E.M. 1936: The dynamics of the formation of continued uplift and peneplanization occurred (e.g. cone-sheets, ring-dykes and cauldron subsidence. Pro- Hansen et al. 1996). ceedings of the Royal Society of Edingburgh 56, 128– 157. Anderson, J.L. 1983: Proterozoic anorogenic granite plu- tonism of North America. Geological Society of Ameri- ca Memoir 161, 133–154. Dansk Sammendrag Barth, T.F.W. 1931: Feltspat III. Norges Geologiske Un- Den geologiske udvikling i Setesdalen i Sydnorge re- dersøkelse 128b, 107pp. Barth, T.F.W. 1947: The nickeliferous Iveland-Evje am- præsenterer mindst 500 millioner års udvikling, fra phibolite and its relation. Norges Geologiske Undersø- tidligere end ca. 1300 Må til ca. 800 Må før nu, der kelse 168a, 71 pp. belyser væsentlige aspekter af den Proterozoiske ud- Bertelsen, S. 1984: A geological description of the basic vikling i Sydskandinavien. rocks in the southern part of the Iveland-Gautestad com- De skorpedannende processer i Setesdalen domi- plex (south Norway). Unpublished M.Sc. Thesis, Uni- neres af præ-Svekonorvegiske suprakrustaler (umodne versity of Copenhagen, 231 pp. (in Danish). klastiske sedimenter og bimodale vulkanitter) med en Bingen B. 1998: Geochemistry of Sveconorwegian augen formodet aflejringsalder på 1150–1100 Må, samt af gneisses from SW Norway at the amphibolite-granulite emplaceringen af spredte infrakrustale granitter og facies transition. Norsk Geologisk Tidsskrift 69, 177– granodioritter. De suprakrustale bjergarter aflejredes 189. Bingen, B. & van Bremen, O. 1998: Tectonic regimes and på et allerede tidligere deformeret og metamorfoseret terrane boundaries in the high-grade Sveconorwegian nederoderet grundfjeld, der er ihvertfald delvis ældre belt of SW Norway, inferred from U-Pb zircon geo- end 1300 Må. chronology and geochemical signature of augen gneiss Under den senere Svekonorvegiske orogenese, med

196 Bulletin of the Geological Society of Denmark

DGF Bulletin 46-2.p65 196 17-01-00, 13:26 suites. Journal of the Geological Society, London, 155, Fougt, H. 1993: A geological study of the pegmatites in 143–154. the area around Einerkilen-Ånestølkilen, south Norway Bingen, B., Boven, A., Punzalan, L., Wijbrans, J.R. & (in Danish). M.Sc. Thesis, Copenhagen University, 88 Demaiffe, D. 1998: Hornblende 40Ar/39Ar geochronol- pp. ogy across terrane boundaries in the Sveconorwegian Gaál, G. & Gorbatschev, R. 1987: An outline of the Pre- Province of S. Norway. Precambrian Research 90, 159– cambrian evolution of the Baltic shield. Precambrian Re- 185. search 35, 15–52. Bingen, B., Birkeland, A., Nordgulen, Ø., Sigmond, E. & Graversen, O. & Pedersen, S. 1999: Timing of Gothian Whitehouse, M. 1999: Detrital zircon ages from sedi- structural evolution in SE Norway: A Rb-Sr whole-rock ments in Hardangervidda, Telemark and Kongsberg, S age study. Norsk Geologisk Tidsskrift 79, 47–56. Norway, and implications for Proterozoic crustal bould- Hageskov, B. 1980: The Sveconorwegian structures of the ing in the Sveconorwegian Province. EUG 10, Abstract Norwegian part of the Kongsberg-Bamble-Østfold seg- Volume, 126. ment. Geologiske Föreningen Stockholms Förhandlinger Bingen, B.: Demaiffe, D. & van-Breemen, O. 1998: The 102/2, pp. 150–155. 616 Ma old Egersund basaltic dike swarm, SW Norway, Hageskov, B. 1997: Geochemistry and tectonic significance and late Neoproterozoic opening of the Iapetus Ocean. of late Gothian mafic dikes in the Østfold-Marstrand belt Journal of Geology 106, 565–574 of S.E. Norway and W. Sweden. Precambrian Research Birkeland, A., Sigmond, E.M.O., Whitehouse, M.J. & 82, 287–309. Vestin, J. 1997: From Archean to Proterozoic on Har- Hansen, K., Pedersen, S., Fougt, H. & Stockmarr, P. 1996: dangervidda, South Norway. Norges geologiske Under- Post-Sveconorwegian exhumation and cooling history søkelse Bulletin 433, 4–5. of the Evje area, southern Setesdal, Central South Nor- Bjørlykke, H. 1934: The mineral paragenesis and classifi- way. Norges geologiske undersøkelse Bulletin 431, 49– cation of the granite pegmatites of Iveland, Setesdal, 58. southern Norway. Norsk Geologisk Tidsskrift 14, 211– Hughes, C.J. 1973: Spilites, keratophyres and the igneous 311. spectrum. Geological Magazine 109, 513–527. Bjørlykke, H. 1937: The granite pegmatites of southern Irvine, T.N. & Barager, W.R.A. 1971: A guide to the chemi- Norway. The American Mineralogist 22, 241–255. cal classification of the common volcanic rocks. Cana- Bjørlykke, H. 1947: Flaat nickel. Norges Geologiske Un- dian Journal of Earth Sciences 8, 523–548. dersøkelse 168b, 39 pp. Knudsen, T.-L., Andersen, T., Whitehouse, M.J. & Vestin, Brickwood, J. D. 1986: The geology and mineralogy of J. 1997: Detrital zircon ages from Southern Norway – some Fe-Cu-Ni sulphide deposits in the Bamble area, implications for the Proterozoic evolution of the south- Norway. Norsk Geologisk Tidsskrift 66, 189–208. western Baltic Shield. Contributions to Mineralogy and Brisbin, W.C. 1986: Mechanisms of pegmatite intrusion. Petrology 130, 47–58. American Mineralogist 71, 644–651. Kullerud, L. & Dahlgren, S.H. 1993: Sm-Nd geochronol- Cerný, P. 1991: Rare-element granitic pegmatites. Part II. ogy of Sveconorwegian granulite facies mineral assem- Regional to global environments and petrogenesis. blages in the Bamble shear belt, south Norway. Precam- Geoscience Canada 18, 68–81. brian Research 64, 389–402. Dahlgren, S.H. 1996: An introduction to the geology of Maijer, C. & Verschure, R.H. 1998: Petrology and isotope the Telemark crustal block. A Guide to the SNF Excur- geology of the Hunnedalen monzonoritic dyke swarm, sion, 9pp. SW Norway: a possible late expression of Egersund anor- Dahlgren, S.H., Heaman, L. & Krogh, T. 1990: Geological thosite magmatism. Norges geologiske undersøkelse evolution and U-Pb geochronology of the Proterozoic Bulletin 434, 83–107. central Telemark area, Norway. Geolognytt 17, Oslo Uni- Miyashiro, A. 1974: Volcanic rock series in island arcs and versity, 38–39. active continental margins. American Journal of Science Dons, J.A. 1960: The stratigraphy of supracrustal rocks, 274, 321–355. granitization and tectonics in the Precambrian Telemark Pearce, J.A. & Gale, G.H. 1977: Identification of ore-depo- area, southern Norway. International Geological Con- sition environment from trace element geochemistry of gress, XXI Session, Norden. Guidebook to Excursion associated igneous host rocks. Geological Society Spe- A10, Norges geologiske Undersøkelse 212h, 30pp. cial Publication 7, 14–24. Falkum, T. 1982: Geologisk kart over Norge, berggrunds- Pearce, J.A., Harris, N.B.W. & Tindle, A.G. 1984: Trace kart Mandal 1:250,000 Norges Geologiske Undersøkelse. element discrimination diagrams for the tectonic inter- Falkum, T. 1985: Geotectonic evolution of southern Scan- pretation of granitic rocks. Journal of Petrology 25, 956– dinavia in light of a late-Precambrian plate collision. In 983. Tobi, A.C. & Touret, J.L.R. (eds): The Deep Proterozoic Pedersen, M. 1993: A geological study of the Flåt com- Crust in the North Atlantic Provinces, NATO Advanced plex, Aust-Agder, Norway. M.Sc. Thesis, Copenhagen Science Institutes Series, Series C, 158, 309–322. Reidel, University, 128pp. (in Danish). Dordrecht. Pedersen, S. 1975: Intrusive rocks of the northern Iveland- Falkum, T. 1998: The Sveconorwegian magmatic and Evje area, Aust-Agder. Norges geologiske undersøkelse tectonometamorphic evolution of the high grade Prot- 322, 1–11. erozoic Flekkefjord complex, south Norway. Norges geo- Pedersen, S. 1981: Rb-Sr age determinations of Late Prot- logiske undersøkelse, Bulletin 434, 5–33. erozoic granitoids from the Evje area, south Norway. Bul- Falkum, T. & Petersen, J.S. 1980: The Sveconorwegian letin of the Geological Society of Denmark 29, 129–143. Orogenic Belt, a case of Late-Proterozoic plate-collision. Pedersen, S. 1985. Geologisk kart over Norge, berggrunds- Geol. Rundshau 69, 622–647. kart Evje 1:50,000. Norges Geologiske Undersøkelse.

Pedersen & Konnerup-Madsen: Geology of the Setesdalen, Norway 197

DGF Bulletin 46-2.p65 197 17-01-00, 13:26 Pedersen, S. & Konnerup-Madsen, J. 1994: Geology of the Setesdal Region. Excursion Guide to the SNF Excursion, August 1994, Copenhagen University, 55 pp. Rasmussen, T. 1993: Geochemistry and petrogenesis of the Grendi complex – a Late Proterozoic intrusion in the Setesdalen Province, South Norway. Unpublished M.Sc. Thesis (Copenmhagen University), 133 pp. (in Danish). Romer, R.L. & Smeds, S.-A. 1996: U-Pb columbite ages of pegmatites from Sveconorwegian terranes in southwestern Sweden. Precambrian Research 76, 15–30. Rønholt, K.P. 1990: A geochemical and mineralogical description of metagabbros from the Åvesland area, the Iveland-Gautestad complex, south Norway. M.Sc. The- sis, Copenhagen University, 137 pp. (in Danish). Sigmond, E.M.O. 1975: Geologisk kart over Norge, berg- grunnskart Sauda 1:250,000. Norges Geologiske Under- søkelse. Sigmond, E.M.O. 1978: Beskrivelse til det berggrunns- geologiske kartbladet Sauda 1:250,000. Norges Geolo- giske Undersøkelse, Skrifter 23, 94pp. Sigmond, E.M.O. 1985: The Mandal-Ustaoset line, a newly discovered major fault zone in south Norway. In A.C. Tobi & J.L.R. Touret (eds): The Deep Proterozoic Crust in the North Atlantic Provinces, NATO Advanced Sci- ence Institutes Series, Series C 158, 323–331. Reidel, Dordrecht. Skjernaa, L. & Pedersen, S., 1999. Late Sveconorwegian monzonitic dykes in the Setesdalen area of Central South Norway: Examples of structures in dykes and their indications of accumulated strain. Bulletin of the Geologi- cal Society of Denmark 46, ??–??. Sigmond, E.M.O., Gjelle, S. & Solli, A 1997: The Rjukan Proterozoic rift basin, its basement and cover, volcanic and sedimentary infill, and associated intrusions. Norges geologiske undersøkelse. Bulletin 433, 6–7. Smithson, S.B. 1963: Granite studies: I. A gravity investi- gation of two Precambrian granites in South Norway. Norges Geologiske Undersøkelse 214b, 53–140. Starmer, I.C. 1993: The Sveconorwegian Orogeny in southern Norway, relative to deep crustal structures and events in the North Atlantic Proterozoic Supercontinent. Norsk Geologisk Tidsskrift 73, pp. 109–132. Stockmarr, P. 1994: A description of the pegmatites near Åvesland, Evje, south Norway. M.Sc. Thesis, Copenha- gen University, 133 pp. (in Danish). Teisseyre, J.H. 1970: Geological investigations in the Byg- landsfjorden-Gyvatn area. Norges Geologiske Undersø- kelse 266, 206–229. Venhuis, G.J. & Barton, M. 1986: Major element chemistry of Precambrian dolerite dykes of tholeiitic composition from Rogaland/Vest Agder, SW Norway. Norsk Geologisk Tidsskrift 66, 277–294. Wood, D.A., Joron, J.L. & Treuil, M. 1979: A reappraisel of the use of trace elements to classify and discriminate between magma series erupted in different tectonic set- tings. Earth and Planetary Science Letters 45, 326–336.

198 Bulletin of the Geological Society of Denmark

DGF Bulletin 46-2.p65 198 17-01-00, 13:26 Pedersen & Konnerup-Madsen: Geology of the Setesdalen, Norway 199

DGF Bulletin 46-2.p65 199 17-01-00, 13:26 200 Bulletin of the Geological Society of Denmark

DGF Bulletin 46-2.p65 200 17-01-00, 13:26 Pedersen & Konnerup-Madsen: Geology of the Setesdalen, Norway 201

DGF Bulletin 46-2.p65 201 17-01-00, 13:26