THE MAGNETIZATION OF THE MAGNETITE OREBODY NEAR CORTEGANA, SPAIN*

Abstract

AbstractThe magnetic ground survey of ΔZ across the orebody near Cortegana suggests that the direction of the magnetization of the orebody deviates from the present earth field direction in that area. Magnetic measurements of more than 500 specimens of drilling cores of several vertical and one nearly horizontal drill holes showed that the magnetization of the orebody points essentially to the north in the direction of the inclination of the orebody and the banding of the ore. In the central part of the orebody with an average magnetite content of about 50 vol% the magnetization amounts to 0.35 Gauss, the remanent and induced component having the same order of magnitude. The outer parts of the orebody have a much smaller magnetization according to both the smaller magnetite content and greater inhomogeneity of the remanent magnetization, also partly due to their reversed magnetization which is brought about by the stray field of the central part of the orebody. As all drilling cores have been chemically analyzed with respect to their Fe content a logarithmic relationship could be established between the magnetite content, ranging from 25 to 80 vol%, and the susceptibility.