Report from IUGG Assembly: IAGA session on rock magnetism of fine particles



As a frontier science, rock magnetism provided crucial evidence for plate tectonics, but that was two decades ago and skeptics might ask whether the subject can still generate excitement, innovation, and controversy. They would have been reassured at the recent IAGA session on fine particles, the only meeting at Canberra that was devoted to rock magnetism per se, where 14 papers were presented.

One of the few topics on which rock magnetists seem generally agreed is that the stable remanence, important in paleomagnetism, resides in effectively singledomained (SD) grains. However, their mode of occurrence and relationship to multidomained (MD) grains in rocks is not understood. For example, is SD caused by submicroscopic particles or by effective subdivision of much larger grains, or both? Other contentious questions raised at Canberra concern the role of grains that carry viscous remanence (VRM) and of superparamagnetism (SP) as a cause of magnetic instability.