Natural remanent magnetization of Rumanova chondrite (H5) acquired by the shock metamorphisms S3

概要

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The natural remanent magnetization (NRM) of Rumanova (H5) chondrite was studied to focus on the shock remagnetization characterized by shock level S3. The NRM was examined by AF and thermal demagnetization, temperature dependencies of magnetization and coercivity, magnetic anisotropy, microscopic features using magnetic fluid technique and chemical compositions. Based on these results, Rumanova carries the stable NRM by a fine-grained taenite with 48 wt% Ni in cloudy taenite, although large amount of the soft NRM component with the magnetic anisotropy is overprinted. These taenite grains were produced by disorder from tetrataenite due to heating between 525℃ and 950℃ during shock metamorphism when the parent body collided with the asteroids. Rumanova was remagnetized below 530℃ in the cooling stage by the local magnetic field from strongly magnetized FeNi grains. From these viewpoints, the NRM of Rumanova was not original, but it was remagnetized during shock metamorphism.