Magnetic susceptibility of a saprolite and a soil profile developed on pyroxenite at Mont-Saint-Bruno, Quebec, Canada

Magnetic susceptibility (chi) measurements were performed with a recording magnetic susceptivimeter on a pyroxenite and its alteration products, i.e., a saprolite and the horizons of a soil profile. Pyroxenite contains a rela tively high percentage of opaque minerals that, under alteration, transform ed partly into Fe oxides with a high magnetic susceptibility. In the saprol ite and the soil, chi values varied according to depth in the profile, part icle size, mineralogical and chemical composition. Significant correlations between chi values and Fe and Ti oxides indicated the importance of opaque minerals, magnetite, maghemite and ilmenite to the magnetic susceptibility of the alteration products of the pyroxenite. This method provided additio nal information on the intensity of the alteration of the rock, especially on the formation of secondary Fe oxides at the expense of the ferromagnesia n minerals.