Self-Reversal of Thermo-Remanent Magnetization in Pyroclastics from the 1991 Eruption of Mt. Pinatubo, Philippines

Abstract

We studied magnetic properties of the pyroclastics of the 1991 eruption of Mt. Pinatubo. At one locality of the pyroclastics flows, the directions of natural remanent magnetizations (NRMs) of dacite pumice fragments are dispersed, indicating that these fragments settled after their temperature reached their Curie points. At another locality, almost all dacite pumice fragments show reversed NRMs, indicating that these settled before their temperature reached the Curie point thereby acquiring a self-reversed thermo-remanent magnetization in the ambient geomagnetic field. Almost all the dacite pumice samples from both localities acquied self-reversed TRMs in the laboratory. Detailed examination revealed that these dacite pumice samples in the pyroclastic flows of the 1991 eruption of Mt. Pinatubo have characteristics of the Haruna-type self-reversal of thermo-remanent magnetization. © 1992, Society of Geomagnetism and Earth, Planetary and Space Sciences. All rights reserved.