Magnetite rods in plagioclase as the primary carrier of stable NRM in ocean floor gabbros

The ubiquitous occurrence of magnetite rods in plagioclase may account for the stable, intense magnetization of ocean floor gabbros. These single-domain grains are formed by the subsolidus exsolution of Fe²⁺ and Fe³⁺ incorporated into the plagioclase at higher temperatures. We expect that this process will be particularly important in the upper portions of the oceanic gabbro unit because of the relative paucity of femic minerals at these levels. The geometry of accretion prohibits a constructive contribution to marine magnetic anomalies by the lower olivine-rich gabbros. As a result of the presence of these rods, ocean floor gabbros may constitute an important source for marine magnetic anomalies.