Petrology and structure of the Palaeoproterozoic (1.9�Ga) Rytky nickel sulphide deposit, Central Finland: a comparison with the Kotalahti nickel deposit

M�kinen, Jari; Makkonen, Hannu V.

doi:10.1007/s00126-004-0413-4

Cited by 12 publications

(20 citation statements)

References 18 publications

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“…However, the D 2 thrusting has commonly disrupted the primary stratigraphy. Svecofennian thermal and tectonic activity was strong around the Archaean Kotalahti Dome, as indicated by the presence of allochthonous Archaean gneiss units and by the schollen-schlieren migmatites formed during D 2 (Mäkinen & Makkonen, 2004). Among the studied intrusions, Rytky and Kotalahti probably represent the deepest stratigraphical level, because they formed at the contact between the Archaean and Proterozoic rocks or within the Archaean rocks.…”

Section: Kotalahtimentioning

confidence: 85%

“…The Kotalahti Nickel Belt also lies close to the Archaean/Proterozoic boundary (Fig. 1, Häkli, 1971;Gaál, 1972;Häkli et al, 1979;Mäkinen & Makkonen, 2004;Peltonen, 2005). The magmatism that produced the ore-bearing intrusions was broadly coeval with the Svecofennian orogeny and the emplacement of the magma took place during the maximum intensity of deformation and metamorphism (Mäk-inen & Makkonen, 2004;Makkonen, 2005;Pelto-nen, 2005).…”

Section: Introductionmentioning

confidence: 94%

“…The rock types range from olivine cumulates to olivine-enstatite cumulates, orthopyroxenites, poiki litic gabbros, ophitic gabbronorites, and diorites (Papunen, 2003). Among the peridotitic rocks, coarse-grained lherzolite is found in the stratigraphic footwall and is overlain by medium-grained lherzolite (Mäkinen & Makkonen, 2004). Disseminated sulfides are common in ultramafic rocks and poikilitic gabbros whereas ophitic gabbros and diorites are almost barren.…”

Section: Kotalahtimentioning

confidence: 99%

“…On the basis of the three separate intrusive phases recognized, the rock types can be grouped as follows, beginning from the earliest phase: 1) coarse grained lherzolites and websterites/melagabbros, 2) mediumgrained lherzolites, websterites and gabbronorites and 3) subophitic gabbros (Mäkinen & Makkonen, 2004).…”

Section: Rytkymentioning

confidence: 99%

“…It has been suggested that the composition of the parental magma was basaltic with a MgO content of about 12 wt.% (Peltonen, 1995a(Peltonen, , 2005. Emplacement of magma was accompanied the gently dipping D 2 folding and thrusting event (Mäkinen & Makkonen, 2004;Makkonen, 2005), which was a response to convergence and thrusting of Svecofennian terranes over the Archaean cratonic foreland (Koistinen, 1981). During D 3 the subhorizontal D 1-2 structures were reoriented into steeper orientations (Mäkinen & Makkonen, 2004).…”

Section: Introductionmentioning

confidence: 99%

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Sm-Nd data for mafic-ultramafic intrusions in the Svecofennian (1.88 Ga) Kotalahti Nickel Belt, Finland - Implications for crustal contamination at the Archaean/Proterozoic boundary

Makkonen¹,

Huhma²

2007

Bull Geol Soc Finland

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Sm-Nd data were determined for eight mafic-ultramafic intrusions from the Svecofennian (1.88 Ga) Kotalahti Nickel Belt, Finland. The intrusions represent both mineralized and barren types and are located at varying distances from the Archaean/Proterozoic boundary. The samples for the 23 Sm-Nd isotope analyses were taken mostly from the ultramafic differentiates. Results show a range in initial ε Nd values at 1880 Ma from -2.4 to +2.0. No relaNo relationship can be found between the degree of Ni mineralization and initial ε Nd values, while a correlation with the geological domain and country rocks is evident. The Majasaari and Törmälä intrusions, which have positive ε Nd values, were emplaced within the Svecofennian domain in proximity to 1.92 Ga tonalitic gneisses, which have previously yielded initial ε Nd values of ca. +3. In contrast, the Luusniemi intrusion, which has an ε Nd value of -2.4 is situated close to exposed Archaean crust. Excluding two analyses from the Rytky intruArchaean crust. Excluding two analyses from the Rytky intru-. Excluding two analyses from the Rytky intrusion, all data from the Koirus N, Koirus S, Kotalahti, Rytky and Kylmälahti intrusions, within error limits, fall in the range -0.7 ± 0.3. The results support the concept of contamination by Archaean material in proximity to the currently exposed craton margin. The composition of the proposed parental magma for the intrusions is close to EMORB, with initial ε Nd values near +4.

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Section: Kotalahtimentioning

confidence: 85%

Section: Introductionmentioning

confidence: 94%

Section: Kotalahtimentioning

confidence: 99%

Section: Rytkymentioning

confidence: 99%