Isotopic and geochemical constraints on the evolution of the 1.93-1.79 Ga Svecofennian crust and mantle in Finland

Lahtinen, Raimo; Huhma, Hannu

doi:10.1016/s0301-9268(96)00062-9

Cited by 113 publications

(67 citation statements)

References 48 publications

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“…Further evidence for a major contribution from such sources is provided by the 1.92 Ga juvenile felsic crust in the Kotalahti Nickel Belt, which is characterized by initial epsilon values of ca. + 3 (Lahtinen & Huhma, 1997). If the parental magma for the Svecofennian nickel-bearing intrusions was similar to the proposed magma in Table 2, then the intrusions could also have been derived from a depleted mantle source with initial epsilon values near + 4.…”

Section: Discussionmentioning

confidence: 93%

“…In the immediate vicinity of the Törmälä body occur 1.92 Ga tonalitic gneisses, which are the oldest known rocks in the Svecofennian domain, and which have yielded initial ε Nd values of ca. +3 (Lahtinen & Huhma, 1997 Luusniemi intrusion with ε Nd (1880) of -2.4 is located close to the exposed main Archaean basement. Another objective of the study is to compare the Sm-Nd isotope compositions of ore-bearing and barren intrusions.…”

Section: Sm-nd Investigationsmentioning

confidence: 97%

“…Rocks with distinctly positive initial values, including some of the mafic and ultramafic volcanics and the bulk of the 1.92 Ga crust within the Kotalahti Nickel Belt (Lahtinen & Huhma, 1997), suggest derivation from depleted mantle sources, without significant contributions from older LREE -enriched lithospheric material. In contrast, initial ε Nd values close to zero obtained on some mafic-ultramafic rocks suggest heterogeneity in mantle sources or assimilation of crustal material.…”

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: Discussionmentioning

confidence: 93%

Section: Sm-nd Investigationsmentioning

confidence: 97%

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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“…A combination of these settings was proposed by and Väisänen & Westerlund (2007). Older underlying continental crust below these units is supported by initial ε Nd values close to zero in some magmatic rocks both in Sweden (Valbracht et al, 1994) and in Finland (Huhma, 1986;Lahtinen & Huhma, 1997). In addition, recent ion microprobe zircon results include Archaean and 2.1 − 1.92 Ga inherited zircons in younger intrusive rocks, indicating crustal sources of these ages Ehlers et al, 2004;Andersson et al, 2006b).…”

Section: Geological Settingmentioning

confidence: 90%

“…The earliest stage of arc volcanism at 1895 Ma is bimodal with marbles and iron formations. Although controversial, some older hidden crust may have been involved with the formation of the early volcanism (Lahtinen & Huhma, 1997). The possible hidden crust has been referred to as "proto-Svecofennian" by Andersson et al (2006b).…”

Section: Regional Implicationsmentioning

confidence: 99%

U-Th-Pb zircon geochronology on igneous rocks in the Toija and Salittu Formations, Orijärvi area, southwestern Finland: Constraints on the age of volcanism and metamorphism

Väisänen¹,

Kirkland²

2008

Bull Geol Soc Finland

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Zircons from a felsic volcanic rock in the Toija Formation and a synvolcanic gabbro intrusion in the Salittu Formation within the Orijärvi area were dated by U-Th-Pb SIMS in order to provide depositional constraints on these formations. Zircon crystals from the felsic rock preserve a two-stage crystallisation history with zoned core domains and homogeneous rim domains. Inner domains yield a 1878 ± 4 Ma concordia age, interpreted to determine the crystallisation of this rock. Rims yield a 1815 ± 3 Ma concordia age interpreted to determine the regional metamorphism. Small rounded zircon grains from the Salittu gabbro, located within the Jyly shear zone, yield a concordia age of 1792 ± 5 Ma. We interpret the grain textures to suggest that they recrystallised from inherited zircon seeds during the heat and fluid flow into the shear zone. Although no direct ages for the Salittu Formation have been recovered, field relationships imply that it was deposited between 1878 − 1875 Ma.

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Mafic plutonic rocks in a continental‐arc setting: geochemistry of 1.87–1.78 Ga rocks from south‐central Sweden and models of their palaeotectonic setting

Rutanen

Andersson

2008

Geological Journal

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Mafic intrusive rocks (1.79-1.78 Ga) of the Transscandinavian Igneous Belt (TIB) and the c. 1.87 Ga Hedesunda Igneous Complex in the Fennoscandian Shield of south-central Sweden were studied using whole-rock and isotope geochemistry.Rock types vary from gabbros/norites (and leucogabbros) to quartz diorites, with Mg# between 76 and 49, and wt% SiO 2 between 43.6 and 59.7, indicating some variation in evolutionary levels and variable cumulus components. Geochemical signatures are calc-alkaline to shoshonitic, large ion lithophile elements and light rare earth elements enriched and high-field strength elements depleted of continental-arc type.e Nd (t) ranges between þ1.0 and þ2.7, and 87 Sr/ 86 Sr(t) between 0.7020 and 0.7038. There is no systematic correlation between chemical parameters and isotope ratios. These isotopic data overlap with other mafic plutonic TIB rocks; samples from the Dala Province (DP) tend to overlap with the c. 1.7 Ga basic Dala lavas of TIB at slightly elevated relative Sr/Nd ratios.With two exceptions, the e Nd (t) of þ1 to þ2 conform to an isotopically 'mildly depleted' source, typical for mafic TIB rocks and many Svecofennian rocks in the region. Reported values above e Nd (t) þ2.0 are scarce in the TIB. Mantle sources represent depleted mantle wedge material that was enriched by fluids/melts not long before (T DM c. 2.0 Ga), that is during subduction in the preceding Svecofennian (2.0-1.87 Ga) and/or during the TIB-0&1 event (1.85-1.78 Ga). The palaeotectonic settings inferred are active continental margins; N-S-directed convergence at 1.87 Ga and E-W-directed at 1.79-1.78 Ga.

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Isotopic and geochemical constraints on the evolution of the 1.93-1.79 Ga Svecofennian crust and mantle in Finland

Cited by 113 publications

References 48 publications

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

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

U-Th-Pb zircon geochronology on igneous rocks in the Toija and Salittu Formations, Orijärvi area, southwestern Finland: Constraints on the age of volcanism and metamorphism

Mafic plutonic rocks in a continental‐arc setting: geochemistry of 1.87–1.78 Ga rocks from south‐central Sweden and models of their palaeotectonic setting

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