Palaeomagnetism of the dyke swarms of the Gardar Igneous Province, south Greenland

Details Palaeomagnetism of the dyke swarms of the Gardar Igneous Province, south Greenland Palaeomagnetism of the dyke swarms of the Gardar Igneous Province, south Greenland

Jul 1977

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1977pepi...14..345p&link_type=abstract

Physics of the Earth and Planetary Interiors, Volume 14, Issue 4, p. 345-358.

Physics

8

Scientific paper

In the western part of the Gardar Igneous Province of southern Greenland, lamprophyre dykes intruded at ca. 1276-1254 m.y. Rb-Sr biotite ages yield a palaeomagnetic pole at 206.5°E,3°N (nine sites, dψ = 5.1°, dχ = 10.1°) Slightly younger dolerite dykes with Rb-Sr biotite ages in the range 1278-1263 m.y. give a pole at 201.5°E,8.5°N (24 sites, dψ = 4.7°, dχ = 9.4°), and the syeno-gabbro ring dyke of the Kûngnât complex (Rb-Sr isochron age 1245 +/- 17 m.y.) cutting both of these dykes swarms, gives a pole at 198.5°E, 3.5°N (four sites, dψ = 2.3°,dχ = 4.4°). All these rock units have the same polarity and the poles are identical to those from Mackenzie and related igneous rocks of North America (1280-1220 m.y.) after closure of the Davis Strait; they confirm that this part of the Gardar Province is a lateral extension of the Mackenzie igneous episode within the Laurentian craton. In the Tugtutôq region of the eastern part of the Gardar Province 47 NNE-trending dykes of various petrologic types, and intruded between 1175 +/- 9 and 1168 +/- 37 m.y. (Rb-Sr isochron ages) yield a palaeomagnetic pole at 223.9° E, 36.4°N (dψ = 4.1°, dχ = 6.1°). Fifteen other dykes in this swarm were intruded during a transitional phase of the magnetic field which, however, does not appear to have achieved a complete reversal over a period of several millions of years. The majority of dykes studied are highly stable to AF and thermal demagnetisation and contain single high blocking temperature components with single Curie points in the range 380-560°C. Palaeomagnetic poles from the Gardar Province between ca. 1330 and 1160 m.y. in age define the earlier part of the Great Logan apparent polar-wander loop; they correlate closely with contemporaneous North American results and confirm the coherence of the Laurentian craton in Upper Proterozoic times.

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