Magnetic behavior transitions identified in natural rock formations


  • Colin Schultz


[1] How the magnetic properties of minerals such as magnetite change with grain size is of fundamental importance to understanding magnetic fields of the past and present, which are useful for tracking the movement of tectonic plates and in teasing out the histories of changing environmental factors. Materials ideal for experimental work on size-dependent properties are difficult to find, as natural materials tend to be messy mixtures of different magnetic minerals, with variable concentrations, chemical purities, and wide distributions of grain sizes, all of which serve to blur magnetic properties. However, on the western base of Yucca Mountain lies the Tiva Canyon Tuff, a 12.7-million-year-old deposit of volcanic material that provides an ideal study site for investigations of grain size-dependent magnetic properties. The ash deposits of the Tiva Canyon Tuff contain abundant volcanic glass, within which the average particle size of magnetite nanoparticles increases systematically with height above the base of the tuff.