Remanent, induced, and total magnetism of a suite of serpentine specimens from the Sierra Nevada, California

The remanent magnetism of a suite of serpentine specimens from the western part of the Sierra Nevada has an average declination of 32° and a dip angle of 84°. The average intensity is 80×10−5 emu/cm3. The induced magnetism has an intensity of 218×10−5 emu/cm3 and a declination of 17° at +62° as calculated from susceptibility data and from the intensity and direction of the earth's magnetic field. The resultant of remanent and induced magnetism is the total magnetism, which has a declination of 17° at +66° and an average intensity of 320×10−5 emu/cm3. A curve for total magnetism as determined from individual specimens is found to correlate with a measured ground magnetometer profile of the area, which has a maximum anomaly of 6000 γ. Comparison of the magnitudes of remanent, induced, and total magnetism suggests that the total magnetism is primarily a function of induced magnetism. The maximum anomaly is, however, related to large components of both remanent and induced magnetism. Comparison of magnetic properties with chemical analyses of the rocks suggests a lack of correlation between the two. It appears that the variance in magnetic intensity is generally related to the grain size of the magnetite.