Remanent magnetization in fresh xenoliths derived from combined demagnetization experiments: Magnetic mineralogy, origin and implications for mantle sources of magnetic anomalies

Fresh mantle xenoliths represent an exceptional opportunity to directly access Earth's interior. In particular, magnetic signals carried by upper mantle xenoliths may provide the only opportunity to determine the depth of remanent magnetization below the Moho boundary. In recent years, the nature, intensity and magnetic properties of the magnetic signal have been characterized by measurements of the 0020 induced magnetization in hysteresis loops. The natural remanent magnetization (NRM) intensity, despite providing the first indication of the magnetic nature of magnetite inclusions, has not been studied in detail. This study focusses attention on the number of recorded NRM directions and characteristics of the anhysteretic remanent magnetization (ARM) and saturation isothermal remanent magnetization (SIRM) demagnetization spectra. A collection of 17 extremely fresh mantle xenoliths has been subjected to AF demagnetization, characterizing samples with one, two or three populations of remanence carriers, with differing coercivities, that are potential carriers of magnetization at mantle depths.