Palaeomagnetism and U – Pb geochronology of c. 1570 Ma intrusives from Åland archipelago, SW Finland – implications for Nuna

A1 Originalartikel i en vetenskaplig tidskrift (referentgranskad)


Interna författare/redaktörer


Publikationens författare: Johanna M. Salminen, Robert Klein, Satu Mertanen, Lauri J. Pesonen, Sören Fröjdö, Irmeli Mänttäri, Olav Eklund
Förläggare: Geological Society of London
Förlagsort: London
Publiceringsår: 2015
Tidskrift: Geological Society Special Publications
Tidskriftsakronym: Geol Soc spec publ
Volym: 424
eISSN: 2041-4927


Abstrakt

We report new palaeomagnetic and isotope age data of Early Mesoproterozoic (i.e. Subjotnian) intrusions from the Åland archipelago, SW Finland. The palaeomagnetic results reveal dual-polarity magnetizations with a pronounced reversal asymmetry occurring in dykes. We explain the asymmetry by an unremoved secondary component, which is affecting more N-polarity dykes. Other explanations, such as the age difference of magnetization between normal and reversed polarity dykes, are discussed. The primary nature of magnetization in dykes for both normal (N) and reversed (R) groups is verified by positive baked contact tests. A dyke showing reversed polarity from Korsö is dated 1575.9±3.0 Ma (U–Pb) in this study. This and previous U–Pb data tighten the magmatic activity in Åland to 1580–1570 Ma. We combined new palaeomagnetic data with those from earlier studies to provide a new key-palaeomagnetic pole for Baltica. Our data positions Baltica on equatorial latitudes, supporting the NENA (North Europe–North America) connection between Baltica and Laurentia at 1.59–1.58 Ga. Palaeomagnetic data support that NENA was valid at 1.75, 1.58, 1.46, and 1.26 Ga, forming the core of Mesoproterozoic Nuna (a.k.a. Columbia) supercontinent.

Senast uppdaterad 2020-23-01 vid 05:25