[M-ZZ44] Geology and culture

[MZZ44-05] Measurement of magnetic susceptibility of simulated rocks and application to stone research

*Ayaha Emura¹, Tada-nori Goto¹, Kyohei Sano¹, Norihito Kawamura¹ (1.University of Hyogo)

Keywords:cultural geology, magnetic susceptibility, cultural property, stone

The magnetic susceptibility of sediments and soils is often used in investigations such as paleoenvironmental changes and environmental pollution (e.g., Torii, 2005). Since magnetic susceptibility measurement can be conducted easily and non-destructively, it can also provide information for cultural geological studies, such as estimating the origin of stone structures (Cho, 2015; Sakiyama, 2005). Although the grain-size dependency of magnetic susceptibility in magnetite has been discussed previously (Till et al., 2011), the magnetic susceptibility of samples containing magnetic grains larger than several hundred micrometers is rarely discussed. Additionally, systematic studies have not been conducted on the stability of magnetic susceptibility measurements for rock samples, the relationship between the size of rock samples and magnetic susceptibility measurements, and the relationship between the crystallinity of volcanic rocks and magnetic susceptibility. In this study, laboratory experiments were conducted to examine the influence of the size of rock samples and the amount of magnetic grains on magnetic susceptibility. Specifically, simulated rock samples with various masses of magnetite and hematite were created to measure magnetic susceptibility, and we also compared measurements by changing the thickness or area of the samples. As a result, a strong positive correlation was found between the mass of magnetic particles and magnetic susceptibility. It was also found that the relationship between the thickness and area of rock samples and magnetic susceptibility can be quantified. Based on these findings, appropriate measurement conditions were proposed. Furthermore, measurements of the magnetic susceptibility of stone, including those used in the stone bases of Himeji Castle, a UNESCO World Cultural Heritage site, were conducted to compile the required knowledge for investigations of stones in the field.