Palaeomagnetism of Metamorphic Rocks: Errors owing to Intrinsic Anisotropy

Summary It is shown that palaeomagnetic errors owing to anisotropy can be expressed in terms of Fisher'sstatistics and so can be directly applied to the estimation of errors in directions and poles. The high coercive force components (those that are palaeomagnetically useful) in visibly foliated gneissic rocks are deflected from the ambient field by about 5° compared with 1° in essentially isotropic diabase. The deflections show no systematic relationship to the foliation, and anisotropy merely introduces a small component of random noise. This result is typical of many from metamorphic rocks, and there seems to be no technical impediment to using a wide range of metamorphic rocks for the accurate determination of palaeomagnetic poles.