Palaeomagnetism of the Palaeoproterozoic ultramafic intrusion near Lake Konchozero,Southern Karelia,Russia |
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Affiliation: | 1. Department of Geology, University of Turku, FI-20014 Turku, Finland;2. Geological Survey of Finland, P.O. Box 96, FI-02151 Espoo, Finland;3. Department of Geology and Mineralogy, Åbo Akademi University, FI-20500 Turku, Finland |
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Abstract: | New palaeomagnetic results are presented from the recently dated Palaeoproterozoic ultramafic Konchozero sill, and associated basalts (three sites, 38 oriented samples). Three stable components of remanence have been isolated during thermal and alternating field demagnetisation. The component I, with a mean direction of D=103°, I=40°, k=18, α95=11° (N=11 samples), pole position of 14°S, 282°E, has been obtained from the unaltered deeper part of the sill and from baked schists. The study of the baked contact confirms the conclusion that component I is supposed to be primary and corresponds to the Sm–Nd age of the sill of 1974±27 Ma. The palaeopole of component I is not consistent with the accepted Fennoscandian apparent polar wander path (APWP) for the period 2120–1880 Ma, and for that part the Fennoscandian APWP should be revised. Two other components (component II: D=349°, I=39°, k=35, α95=6°, N=19 samples, pole position 49°N, 231°E; and component III: D=17°, I=41°, k=44, α95=5°, N=19 samples, pole position 50°N, 190°E) fit the APWP well, with palaeomagnetically estimated ages of ca. 1860 and 1760 Ma respectively. |
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