| 1. |
- Ahl, M, et al.
(författare)
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The Dala granitoids
- 2004
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Ingår i: The Transscandinavian Igneous Belt (TIB) in Sweden; a review of its character and evolution. ; , s. 70-74
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Bokkapitel (refereegranskat)
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| 2. |
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| 3. |
- Andersson, U. B., et al.
(författare)
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Ancient and juvenile components in the continental crust and mantle : Hf isotopes in zircon from Svecofennian magmatic rocks and rapakivi granites in Sweden
- 2011
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Ingår i: Lithosphere. - 1941-8264 .- 1947-4253. ; 3:6, s. 409-419
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Tidskriftsartikel (refereegranskat)abstract
- The sources of igneous rocks in the continental crust are elusive, but they may be traced by radiogenic isotopes, which convey a message about the age and composition of the concealed parts of the continent. We investigated the Hf-isotope composition of zircon in ten rocks from central and southern Sweden. Two felsic metavolcanic rocks and two metagabbros (ca. 1.89 Ga) from Bergslagen, southern Sweden, show epsilon(Hf)(t) ranges of -1.8 to +5.1 and +2.6 to +6.8, respectively, suggesting that juvenile sources have contributed to both. A 1.85 Ga granite from southern Bergslagen shows a epsilon(Hf)(t) range of -2.6 to +4.6 for magmatic zircons, but both highly negative and positive values for inherited grains, providing evidence for both Archean and juvenile crustal sources. These and previous data confirm the existence of juvenile proto-Svecofennian crust (<2.2-1.9 Ga) with a minor Archean component, from which later crustal magmas were generated. The Hf-isotope evolution curve for this crust can be approximated by epsilon(Hf)(1.90) = 3 +/- 3 and (176)Lu/(177)Hf = 0.018. Similarly, the present data, together with data for younger mafic intrusions, can be used to infer the presence of a "mildly depleted" sub-Svecofennian mantle evolution curve with epsilon(Hf)(1.90) = 4.5 +/- 2.5 and (176)Lu/(177)Hf = 0.0315. Zircons from four out of five rapakivi intrusions (1.53-1.50 Ga) in central Sweden yield negative epsilon(Hf)(t) in the range -9.8 to -4.6, suggesting mixed Archean and juvenile Svecofennian sources. One intrusion farther south ranges between epsilon(Hf)(t) of -4.1 and -1.6, and has a larger contribution from Svecofennian crust. The data suggest that the crust in Bergslagen, southern Sweden, is dominantly Paleoproterozoic, while higher proportions of Archean material are present below central Sweden.
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| 5. |
- Andersson, U.B., et al.
(författare)
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Characterization of the Paleoproterozoic Mantle beneath the Fennoscandian Shield : Geochemistry and Isotope Geology (Nd, Sr) of ~ 1.8 Ga Mafic Plutonic Rocks from the Transscandinavian Igneous Belt in Southeast Sweden
- 2007
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Ingår i: International Geology Review. - : Informa UK Limited. - 0020-6814 .- 1938-2839. ; 49:7, s. 587-625
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Forskningsöversikt (refereegranskat)abstract
- Geochemistry and Sr-Nd isotope geochemistry of ca. 1.8 Ga, mafic intrusions of the Transscandinavian Igneous Belt (TIB-1) in the Fennoscandian shield were studied in southeastern Sweden. These rocks show LILE-LREE-enriched, HFSE-depleted, calc-alkaline, continental arc signatures in the north, grading to slightly less enriched, oceanic affinities southward.εNd(1.80) values range from +2.0 to +0.7 and 87Sr/86Sr(1.80) from 0.7022 to 0.7029 (with one outlier at 0 and 0.7033), without correlation to fractionation (e.g., Mg#) or crustal contamination, indicating sources that are mildly depleted. The most depleted ratios occur in the south, trending with the geochemistry toward more enriched compositions northward. The sources represent depleted mantle wedge material that was subjected to enrichment not long before (TDM ca. 2.0 Ga), i.e., during the preceding arc subduction (2.1-1.82 Ga), and/or during the TIB-1 magmatism itself, by hydrous fluids with a sediment and/or melt input increasing northward. The TIB-1 magmatism occurred above a south(west)ward-retreating subduction zone along the continental margin of the juvenile Svecofennian continent at 1.81-1.76 Ga.
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| 6. |
- Andersson, U.B, et al.
(författare)
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Foreword – A note on nomenclature
- 2004
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Ingår i: The Transscandinavian Igneous Belt (TIB) in Sweden. ; , s. 3-4
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Bokkapitel (refereegranskat)
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