Laboratory-induced self reversal of thermoremanent magnetisation in pillow basalts

Abstract

CONSIDERABLE attention has been paid to the changes in the magnetic properties of pillow lavas with distance from a ridge¹. It has been found^2,3 that the originally stoichiometric titanomagnetites are altered at sea-floor temperatures to cation-deficient titanomagnetites (titanomaghaemites). The degree of cation deficiency—the fraction of initial Fe²⁺ oxidised to Fe³⁺—is described by the parameter ‘z’ (ref. 4). As the titanomaghaemite evolves, all the magnetic properties (for example, Curie point, saturation magnetisation, coercive force) change, but though the changes cause a decrease in the intensity of magnetisation, the direction is preserved.