EarthRef.org Reference Database (ERR) -- Morimoto et al. 1997

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Morimoto et al. 1997

Morimoto, C., Otofuji, Y., Miki, M., Tanaka, H. and Itaya, T. (1997). Preliminary palaeomagnetic results of an Archaean dolerite dyke of west Greenland: Geomagnetic field intensity at 2.8 Ga. Geophysical Journal International 128(3): 585-593.

The geomagnetic field intensity during Archaean times is evaluated from a palaeomagnetic and chronological study of a dolerite dyke intruded into the 3000 Ma Nuuk Gneisses at Nuuk (64.2 degrees N, 51.7 degrees W), west Greenland. Plagioclase from the dolerite dyke yields a mean K-Ar age of 2752 Ma, Palaeomagnetic directions after thermal demagnetization of the dyke and the gneiss reveal a positive baked-contact test, indicating that the high-temperature-component magnetization of the dyke is primary. Thellier experiments on 12 dyke specimens yield a palaeointensity value of 13.5 +/- 4.4 mu T The virtual dipole moment at ca. 2.8 Ga is 1.9 +/- 0.6 x 10(22) Am-2, which is about one quarter of the present value. The present study and other available data imply that the Earth's magnetic field at 2.7 similar to 2.8 Ga was characterized by a weak dipole moment and that a fairly strong geomagnetic field similar to the present intensity followed the weak field after ca. 2.6 Ga.

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Keywords
archaean, earth's core, geomagnetic field, greenland, k-ar age, palaeomagnetism, paleomagnetic data, isotopic evidence, greenstone-belt, godthabsfjord, geochronology, expansion, evolution, gneisses, earth, core

Journal
Geophysical Journal International
http://www.blackwell-synergy.com/servlet/useragent?func=showIssues&code=gji&journal=gji

Publisher
Blackwell Science Ltd.
Osney Mead
Oxford OX2 0EL
U.K.
+44-1865-206206
+44-1865-721205
journals.cs@blacksci.co.uk