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

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.ε Nd (1.80) values range from +2.0 to +0.7 and 87 Sr/ 86 Sr(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 (T DM 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.ANDERSSON ET AL.

Trans-Baltic Palaeoproterozoic correlations towards the reconstruction of supercontinent Columbia/Nuna

“…In Sweden, the northernmost margin of the ESL is marked by the 1.83-1.82 Ga Oskarshamn-Jönköping belt (O-J in Figs. 1 and 9) of juvenile mafic and felsic volcanics, calc-alkaline intrusions and coarse clastic metasedimentary rocks related to an assumed northward subduction zone (Mansfeld et al, 2005;Andersson et al, 2007). This agrees well with interpretations of the BABEL seismic reflection line B (e.g.…”

Reconstruction of palaeoinfiltration during the Holocene using porewater data (Laxemar, Sweden)

“…The Små-land-Värmland Belt comprises a suite of granite-syenitediorite-gabbro intrusions and related volcanic equivalents and spans a time period from about 1.85 Ga to 1.65 Ga similar to rocks elsewhere in the TIB (e.g. Mansfield, 1996;Å häll and Larson, 2000;Andersson et al, 2007;Sö derlund et al, 2005Sö derlund et al, , 2008. The dominant intrusive rocks in the Laxemar-Simpevarp investigation area are an equigranular quartz-monzodiorite and a mineralogically and texturally more heterogeneous Ä vro granite, both dated to about 1.8 Ga (Wahlgren et al, 2004) and a larger body of finegrained diorite towards the coast (Fig.…”

Multi-stage emplacement of the Götemar Pluton, SE Sweden: new evidence inferred from field observations and microfabric analysis, including cathodoluminescence microscopy

“…The country rocks that surround the Götemar Pluton belong to the Transscandinavian Igneous Belt (TIB; Fig. 1a; Andersson et al 2007;Söderlund et al 2008), an up to 1,600-km-long and 130-km-wide batholithic complex (Hjelt and Daly 2004) that formed during several phases of magmatic activity on the western boundary of the Svecofennian Domain between 1.81 and 1.65 Ga (e.g. Andersson et al 2007 and references therein ;Hjelt and Daly 2004).…”

“…1a; Andersson et al 2007;Söderlund et al 2008), an up to 1,600-km-long and 130-km-wide batholithic complex (Hjelt and Daly 2004) that formed during several phases of magmatic activity on the western boundary of the Svecofennian Domain between 1.81 and 1.65 Ga (e.g. Andersson et al 2007 and references therein ;Hjelt and Daly 2004). The area represents a deep structural level of the southernmost part of the now-exposed TIB, where syn-to postkinematic 1.81-to 1.65-Ga-old granitoids (Wikman and Kornfält 1995;Kornfält et al 1997;Å hall and Larson 2000;Högdahl et al 2004;Wahlgren et al 2006) intruded into the previously folded and metamorphosed 1.88-to 1.85-Ga sediments of the Västervik Formation (Sultan et al 2005;Sultan and Plink-Björklund 2006).…”

“…Högdahl et al 2004;Andersson et al 2007;Å hall and Conelly 2008). Recent studies draw special attention to Mesoproterozoic (1.45 Ga) granites (e.g.…”