Paleomagnetism of Paleoproterozoic Rocks from Lofoten, Norway: Can They Provide a Baltica Pole for 1.8 Ga?
Paleomagnetism of Paleoproterozoic Rocks from Lofoten, Norway: Can They Provide a Baltica Pole for 1.8 Ga?
Previously Published Material: 10% of the information (magnetic properties of the anorthosite samples) was published in a chapter of IAGA Special Sopron Book Series, Vol 1, in 2011.
Abstract ID#: 36558
English Abstract:
Paleoproterozoic rocks including paragneisses and AMCG suite rocks dominate the landscape in the southern Lofoten islands of Norway, sandwiched between the Scandinavian Caledonides to the east and offshore Mesozoic basins to the west. Published geochronology on the AMCG suite and the metamorphism of the gneisses they intrude range from 1.9 to 1.8 Ga, suggesting tectonic activity in this area was coincident with the formation of the supercontinent Columbia. Twenty-seven sites were drilled into these rocks from Moskenesøy and Flakstadøy to investigate their paleomagnetic character and possible determination of a Paleoproterozoic pole for Baltica. Magnetic susceptibility for all the 27 sites averages 6.95 x 10-2 SI, but only one site has a low susceptibility (5.4 x 10-4); all other sites have susceptibilities greater than 1 x 10-2. NRM values range from 0.5 A/m to 4.6 A/m, with an average of 2.0 A/m. Hysteresis properties of at least one sample per site indicate MD magnetite is the predominant oxide, but demagnetization studies show that a high coercivity phase is commonly present and is likely the source of the stable remanence. Both normal and reversed polarities, nearly antipodal, are observed, with a mean direction of I = -48.0° and D= 209.4° (α95 = 9.1°, N = 22) with a corresponding (inverted) paleopole at 47°N, 154°E. The paleolatitude from this study (61°) puts the current northwestern side of Baltica at high latitudes at this time, similar to published reconstructions for Columbia, although the Lofoten pole longitude is displaced some 65° from other Sveconorwegian poles.