Metamorphic peak geothermobarometry in the Furulund Group, Sulitjelma, Scandinavian Caledonides: implications for uplift

Boyle, A. P.; Westhead, R.K.

doi:10.1111/j.1525-1314.1992.tb00110.x

Cited by 14 publications

(12 citation statements)

References 25 publications

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“…At the garnet isograd, which lies within the Furulund Group to the east of the orebodies, PT conditions have been determined as 480~ and 5 kbar. Temperature and pressure rise westwards within the Furulund Group reaching about 620 ~ and 9-10 kbar to the west of the orebodies in Sjr (Burton et al, 1989;Boyle and Westhead, 1992). 'Peak' metamorphic conditions were attained during or just after D 2.…”

Section: Geological Settingmentioning

confidence: 99%

“…Current views on the geological setting and tectonic evolution of the Sulitjelma region can be found in Boyle et al(1985), Boyle (1980Boyle ( , 1987, Stephens (1986), Burton et al (1989), and Pedersen et al (1991). A map of the region compiled by Kollung (1989Kollung ( , 1990) at a scale of 1:100000 has recently been published.…”

Section: Geological Settingmentioning

confidence: 99%

“…During this process, inversion of the stratigraphy in the lower limb of the nappe took place so that the sedimentary cover sequence now underlies the ophiolite at the present level of exposure (Boyle, 1987). The deformation (D2) which accompanied nappe emplacement caused strong simple-shear resulting in the development of sheath folds, rotation of porphyroblasts in matrix, and overturning of the metamorphic zones which range from biotite to kyanite grade in a broadly Barrovian sequence (Boyle et al, 1985;Boyle, 1987;Burton etal., 1989). All of the significant orebodies lie within the garnet isograd or rocks of higher grade.…”

Section: Geological Settingmentioning

confidence: 99%

“…The deposits to the north of Langvatn in the northern field ( Fig. 1) show elongation in a NW-SE direction which is parallel to the D 2 stretching lineation in the host rocks (Vogt, 1952;Kautsky, 1953;Wilson, 1973;Boyle, 1987). Cook (1987) has suggested that this elongation may also reflect the primary morphology of the sulphide bodies which could have been formed in parallel trough-like features on the sea floor related to the fracture systems which fed the hydrothermal system.…”

Section: Massive Sulphides 69mentioning

confidence: 99%

“…The Sulitjelma region contains three major rock associations lying within the K61i Nappe Complex of the Upper Allochthon of the Central Scandinavian Caledonides (Stephens et al, 1985). These include a major metabasic igneous complex, the Sulitjelma ophiolite (Boyle, 1980), the plutonic parts of which intrude an older unit of predominantly metasedimentary rocks, the Skaiti Supergroup (Boyle etal., 1985;Kollung, 1989Kollung, , 1990). This association is stratigraphically overlain by a sequence of metasediments and calc-alkaline volcanic rocks, the Furulund and Sjcnst~ Groups .…”

Section: Geological Settingmentioning

confidence: 99%

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Deformation and metamorphism of massive sulphides at Sulitjelma, Norway

1993

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The copper-bearing stratabound pyritic massive sulphide bodies contained in metamorphosed basic eruptives of Ordovician age at Sulitjelma in Nordland County, Norway, form one of the important fields of sulphide mineralisation within the Krli Nappe Complex. The sulphide bodies and their enclosing rocks were subject to successive stages of penetrative deformation and recrystallisation during the cycle of metamorphism and tectonic transport caused by the Scandian Orogeny. Textures within the ores and the immediate envelope of schists show that strain was focused along the mineralised horizons. The marked contrast in competence between the massive pyritic sulphides and their envelopes of alteration composed dominantly of phyllosilicates, and the metasediments of the overlying Furulund Group, led to the formation of macroscale fold and shear structures. On the mesoto microscale, a variety of textures have been formed within the pyrite-pyrrhotite-chalcopyritesphalerite sulphide rocks as a result of strain and recrystallisation. Variations in pyrite:pyrrhotite ratios and in the texture and proportions of associated gangue minerals evidently governed the strength and ductility of the sulphide rocks so that the same sulphide mineral can behave differently, displaying different textures in different matrices. In massive pyritic samples there is evidence of evolution towards textural equilibrium by recrystallisation, grain growth and annealment during the prograde part of the metamorphic cycle. Later, brittle deformation was superimposed on these early fabrics and the textural evidence is clearly preserved. By comparing published data on the brittle-ductile transformation boundaries of sulphide minerals with the conditions governing metamorphism at Sulitjelma, it is concluded that most of the brittle deformation in the sulphides took place during or after D3 under retrograde greenschist conditions. Grain growth of pyrite in matrices of more ductile sulphides during the prograde and early retrograde stages of metamorphism produced the coarse metablastic textures for which Sulitjelma is well-known. In some zones of high resolved shear stress, pyrite shows ductile behaviour which could be explained by a dislocation flow mechanism operating at conditions close to the metamorphic peak. In those horizons in which pyrrhotite is the dominant iron sulphide, the contrast in ductility between silicates, pyrite and pyrrhotite has led to the development of spectacular tectonoclastic textures in which fragments of wall rock have been broken, deformed, rolled and rotated within the ductile pyrrhotite matrix.

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Section: Geological Settingmentioning

confidence: 99%

Section: Geological Settingmentioning

confidence: 99%

Section: Geological Settingmentioning

confidence: 99%

Section: Massive Sulphides 69mentioning

confidence: 99%

Section: Geological Settingmentioning

confidence: 99%

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Deformation and metamorphism of massive sulphides at Sulitjelma, Norway

1993

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Petrographic evidence for diachronous metamorphism of the Skaiti Supergroup, Köli Nappe Complex, Arctic Scandinavian Caledonides

Westhead

Boyle

1995

Geological Journal

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The Skaiti Supergroup is the uppermost major tectono-stratigraphic unit of the Koli Nappe Complex, which comprises Precambrian to Lower Palaeozoic rocks immediately north of the Arctic Circle in Scandinavia. This complex was derived from within the Iapetus Ocean and emplaced during the Scandian phase of the Caledonian Orogeny. Petrographic evidence along a hinterland to foreland traverse of the Skaiti Supergroup demonstrates that garnet, staurolite and kyanite porphyroblastesis was diachronous with respect to fabric development, becoming later towards the hinterland. The hinterland rocks experienced two discrete phases of heating, whereas the foreland rocks only experienced one. These observations are consistent with a recent tectonic model for diachronous burial and exhumation of the Koli Nappe Complex during emplacement.

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