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Paleomagnetism of Archean rocks potentially provides information about the early development of the Earth and of the geodynamo. Precambrian layered intrusive rocks are good candidates for paleomagnetic studies: such complexes are commonly relatively unaltered and may contain some single-domain magnetite ‘armored’ by silicate mineral grains. However, layered intrusives often have a strong petrofabric that may result in a strong remanence anisotropy. Magnetic anisotropy can have particularly disastrous consequences for paleointensity experiments if the anisotropy is unrecognized and if its effects remain uncorrected. Here we examine the magnetic anisotropy of an anorthosite sample with a well-developed magmatic foliation. The effect of the sample’s remanence fabric on paleointensity determinations is significant: paleointensities estimated by the method of Thellier and Thellier range from 17 to 55 μT …