TY - JOUR

T1 - Transitioning from Svecofennian to Transcandinavian Igneous Belt (TIB) magmatism in SE Sweden

T2 - Implications from the 1.82 Ga Eksjö tonalite

AU - Åhäll, Karl-Inge

AU - Connelly, James N.

AU - Brewer, Tim S.

N1 - Funding Information: ated assistance during planning and evaluation, and to Frank Beunk, Per-Olof Persson and Joakim Mansfeld for valuable review comments. R. Kelly, E. Mansley and N. Marsh are thanked for assistance with geochemical analyses at the University of Leicester. The study was financially supported by the Geological Survey of Sweden, grant 03-1101/2000 (KIÅ).

PY - 2002

Y1 - 2002

N2 - The Eksjö intrusion forms a major tonalitic body in the Oskarshamn-Jönköping belt (OJB), SE Sweden. This is a NW-SE unit of dominantly intermediate granitoid intrusions, bound by felsic rocks of the Transscandinavian Igneous Belt (TIB). Previous U-Pb data for the Eksjö tonalite (1754±10 Ma) implied that subduction-related magmatism occurred in SE Sweden during a period of time when other data required that such magmatism had already moved further west. New U- Pb zircon dating establishes that the Eksjö tonalite crystallised at 1823±2 Ma and that subduction-related, granitoid magmatism of the OJB occurred in the 1834-1823 Ma interval. Field observations and geochemistry implies fractional crystallisation in either a continental arc or a mature island arc system. Although major portions of the Eksjö intrusion are well preserved, it is cut by NW-trending shear zones attributed to block-related movements that remained active until at least 1.80 Ga. Available constraints for the OJB support models of recurring convergent-margin tectonism along the southwestern margin of Baltica between 1.85-1.82 Ga and, hence, prior to onset of voluminous TIB 1 magmatism (1.81-1.77 Ga). Such a scenario accounts for recurring deformation in SW Finland (1.84-1.80 Ga), broadly coeval deformation in south-central Sweden, and apparent steps in Moho depths between the OJB and the pre-1.85 Ga margin of Baltica.

AB - The Eksjö intrusion forms a major tonalitic body in the Oskarshamn-Jönköping belt (OJB), SE Sweden. This is a NW-SE unit of dominantly intermediate granitoid intrusions, bound by felsic rocks of the Transscandinavian Igneous Belt (TIB). Previous U-Pb data for the Eksjö tonalite (1754±10 Ma) implied that subduction-related magmatism occurred in SE Sweden during a period of time when other data required that such magmatism had already moved further west. New U- Pb zircon dating establishes that the Eksjö tonalite crystallised at 1823±2 Ma and that subduction-related, granitoid magmatism of the OJB occurred in the 1834-1823 Ma interval. Field observations and geochemistry implies fractional crystallisation in either a continental arc or a mature island arc system. Although major portions of the Eksjö intrusion are well preserved, it is cut by NW-trending shear zones attributed to block-related movements that remained active until at least 1.80 Ga. Available constraints for the OJB support models of recurring convergent-margin tectonism along the southwestern margin of Baltica between 1.85-1.82 Ga and, hence, prior to onset of voluminous TIB 1 magmatism (1.81-1.77 Ga). Such a scenario accounts for recurring deformation in SW Finland (1.84-1.80 Ga), broadly coeval deformation in south-central Sweden, and apparent steps in Moho depths between the OJB and the pre-1.85 Ga margin of Baltica.

KW - Arc magmatism

KW - Baltica

KW - Eksjö tonalite

KW - Geochemistry

KW - Paleoproterozoic growth

KW - Sweden

KW - U-Pb geochronology

U2 - 10.1080/11035890201244217

DO - 10.1080/11035890201244217

M3 - Journal article

AN - SCOPUS:3843150730

VL - 124

SP - 217

EP - 224

JO - G F F

JF - G F F

SN - 1103-5897

IS - 4

ER -