Temperature dependence of coercivity for chondrites: Allende, Allan Hills-769, and Nuevo Mercurio

概要

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Temperature dependence of the hysteresis parameters (saturation magnetization J_S, saturation remanent magnetization J_R (SIRM), coercive force H_C, remanent coercive force H_<RC> and initial susceptibility X_i) was examined from 30℃ to 750℃ for Allende (CV3), ALH-769 (L6) and Nuevo Mercurio (H5) chondrites. The NRMs of these chondrites were thermally demagnetized for determination of the NRM blocking (T_B) temperature. The hysteresis parameters were compared with the T_B in order to identify which parameter is the most sensitive to the high coercivity grains. The J_S-T and X_i-T curves showed almost the same transition temperature (Θ_<JS>, Θ_<Xi>), but the Θ_<JS> andΘ_<Xi> were not coincident with the T_B for these chondrites. On the other hand, the main transitions of theΘ_<JR>, Θ_<HC> andΘ_<HRC> in the J_R-T, H_C-T and H_<RC>-T curves were coincident with the T_B. Consequently the temperature dependency of the J_R, H_C and H_<RC> is useful for the determination of the high coercivity grains which carry the stable NRM. The reliable NRMs are carried by tetrataenite in ALH-769,and Nuevo Mercurio, although their main magnetic mineral is kamacite.
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