Quantification of magnetic coercivity components by the analysis of acquisition curves of isothermal remanent magnetisation

A new method of analysing isothermal remanent magnetisation (IRM) acquisiti on curves based on cumulative log Gaussian analysis [Robertson and France, Phys. Earth Planet. Inter. 82 (1994) 223-234] is proposed. It is based on t he curve fitting of the IRM acquisition curve versus the logarithm of the a pplied field with: (i) the acquisition curve on a linear scale, (ii) the ac quisition curve expressed as a gradient, and (iii) the acquisition curve on a probability scale. Even when a sample is not saturated, its magnetic pro perties can be defined, although with less certainty. The number of magneti c components required for an optimal fit to a measured IRM acquisition curv e is evaluated statistically. The method discriminates on the basis of diff erent mineral coercivity. Therefore, additional rock-magnetic tests are sti ll required to separate minerals with similar coercivities. (C) 2001 Elsevi er Science B.V. All rights reserved.