Preservation and detectability of shock‐induced magnetization

Abstract

An understanding of the effects of hypervelocity impacts on the magnetization of natural samples is required for interpreting paleomagnetic records of meteorites, lunar rocks, and cratered planetary surfaces. Rocks containing ferromagnetic minerals have been shown to acquire shock remanent magnetization (SRM) due to the passage of a shock wave in the presence of an ambient magnetic field. In this study, we conducted pressure remanent magnetization (PRM) acquisition experiments on a variety of natural samples as an analog for SRM acquisition at pressures ranging up to 1.8 GPa. Comparison of the alternating field (AF) and thermal demagnetization behavior of PRM confirms that AF demagnetization is a more efficient method for removing SRM overprints than thermal demagnetization because SRM may persist to unblocking temperatures approaching the Curie temperatures of magnetic minerals. The blocking of SRM to high temperatures suggests that SRM could persist without being eradicated by viscous relaxation over geologic timescales. However, SRM has been rarely observed in natural samples likely because of two factors: (1) other forms of impact-related remanence (e.g., thermal remanent magnetization from impact-related heating or chemical remanent magnetization from postimpact hydrothermal activity) are often acquired by target rocks that overprint SRM, and (2) low SRM acquisition efficiencies may prevent SRM from being distinguished from the underlying primary remanence or other overprints due to its low magnetization intensity.

Domain State and Temperature Dependence of Pressure Remanent Magnetization in Synthetic Magnetite: Implications for Crustal Remagnetization

“…Our results compare well (Figure ) with the results for pure magnetite in Tikoo et al () and Gattacceca et al (). However, the pressure used in these studies was a lot higher.…”

“…However, the pressure used in these studies was a lot higher. Therefore, assuming a continuous increase in α with pressure, our values are smaller compared to the values reported in (Tikoo et al, ). These earlier studies used AF demagnetization (2 mT) to remove any low‐coercivity viscous magnetizations, which in our study are negligible (i.e., M ( T 0 , P 0 )).…”

Shock‐induced deformation phenomena in magnetite and their consequences on magnetic properties

“…Static pressure experiments have consistently documented that all magnetic minerals substantially demagnetize at pressures of a few GPa and that the degree of demagnetization depends strongly on magnetic mineralogy and magnetic domain state [ Gilder et al ., ; Bezaeva et al ., ; Louzada et al ., ]. In an ambient magnetic field, rocks with ferromagnetic, minerals can acquire a shock remanent magnetization (SRM) during the passage of a shock wave, which can persist to unblocking temperatures near the Curie point [e.g., Tikoo et al ., , and references therein].…”

Volume 364: Chicxulub: Drilling the K-Pg Impact Crater

“…These measurements will also allow us to evaluate whether hydrothermal circulation is the source of the strong magnetic anomaly recorded at the surface and whether a component of the natural remanent magnetization (NRM) in peak-ring lithologies is shock induced (Tikoo et al, 2015). We will also investigate detrital remanent magnetizations held by post-impact sedimentary rocks, following previous investigations of Borehole Yax-1 (Rebolledo-Vieyra and Urrutia-Fucugauchi, 2004).…”