Preliminary report on magnetic susceptibility measurements on rocks within the Zaria granite batholith, Nigeria

Abstract

Low field magnetic susceptibility measurements have been carried out within the Zaria granite batholith. The result has shown that magnetic susceptibility within the batholith varies between 29 ´ 10–6 SI to 3506 ´ 10–6 SI, with an average value of 684 ´ 10–6 SI. The large variation in the measured values of the susceptibility is as a result of large variation of magnetic mineral content within an outcrop and the diversity of rock types within individual suite. Thin section observation of representative samples shows the major mineral to be feldspar, quartz and biotite, while magnetite, ilmenite and hematite occur as trace minerals. The frequency distribution shows a bimodal distribution, which is typical of granites due to a low-k peak for paramagnetic dominated specimens and high-k peak for magnetite/hematite dominated specimens. The occurrence of hematite and ilmenite may be due to the alteration of magnetite.