Magnetic susceptibility measurements are a non-destructive and cost effective method of determining the presence of iron-bearing minerals within the sediments. Individual sediment samples are exposed to an external magnetic field which causes the sediments to become magnetized according to the amount of Fe-bearing minerals present in the samples.
Magnetic susceptibility is a measure of the ease with which particular sediments are magnetized when subjected to a magnetic field. The ease of magnetization is ultimately related to the concentration and composition (size, shape and mineralogy) of magnetizable material contained within the sample. Magnetizable minerals include the ferromagnetic minerals (strongly magnetizable) and any of the paramagnetic (moderately magnetizable) minerals and other substances. The former include magnetite, hematite, iron titanium oxides, pyrrhotite, maghemite, greigite and goethite, minerals capable of acquiring remnant magnetization and useful for paleomagnetic studies. The latter include a broad array of substances all of which contain Fe2+, Fe3+, or Mn2+ ions. These paramagnetic minerals may include clay minerals (chlorite, smectite and glauconite), iron and manganese carbonates (siderite, rhodochrosite), ferromagnesian silicates (olivine, amphiboles, pyroxenes, etc.), as well as a variety of ferric-oxyhydroxide mineraloids.
Soil samples are exposed to a susceptibility loop in which a magnetic field is generated that magnetizes the samples susceptible substances (minerals or mineraloids) within the sediment. Samples that are rich, per unit volume, in magnetizable substances will yield high readings. Samples that are poor in magnetizable substances, or contain diamagnetic minerals, will yield lower or negative values.
Magnetic Susceptibility measurements determine the actual magnetic particle content of the soil samples. These measurements are unaffected by any nearby iron or steel objects and can be used to effectively study the distribution of diagenetic magnetic minerals. Magnetic particles are left as by products from magnetotactic bacteria in near surface sediments.
Magnetic Susceptibilty Example 1
Magnetic Susceptibility Example 2
Magnetic Susceptibility Example 3