R7: Petrology, Mineralogy and Economic geology (Joint Session with Society of Resource Geology)

[R7-12] Searching for Dark Matter Using Geological Samples: Techniques and Preliminary Results

*Natsue ABE^1,2, Shigenobu Hirose¹, Qing CHANG¹, Takeshi Hanyu¹, Noriko Hasebe², Yasushi Hoshino³, Takashi Kamiyama⁴, Yoji Kawamura¹, Kohta Murase⁵, Tatsuhiro Naka⁶, Kenji Oguni¹, Katsuhiko Suzuki¹, Seiko Yamazaki⁷ (1. JAMSTEC, 2. Kanazawa University, 3. Kanagawa University, 4. Hokkaido University, 5. Penn State University, 6. Toho University, 7. AIST)

Keywords:Paleo-detectors, Dark Matter, Geoneutrino, Cosmic rays

The traces of cosmic rays from inside and outside the Earth recorded in geological samples can be effectively used for geological and astrophysical research. For instance, studies using Antarctic ice cores have estimated the number and age of supernova explosions and observed geoneutrinos from Earth's interior. Research utilizing seabed samples to measure cosmic ray intensity is also expected to provide insights into various events over long geological periods. Only about 5% of the matter in the universe can be directly observed, including such cosmic rays. In contrast, approximately 70% is dark energy, and the remaining 25% or more is dark matter. To search for such unknown matter or energy, large detectors using xenon are typically employed for dark matter detection. However, their scalability could be improved, making it challenging to improve detection limits. Considering this situation, we are exploring methods other than large detectors. For example, natural minerals like mica have been around for geological time scales, providing plenty of exposure even in small samples. These minerals can retain nuclear recoil tracks—evidence of dark matter interactions—for periods longer than the Earth's age. When etched, these tracks appear as observable pits. In 1995, Snowden-Ifft and colleagues studied natural Muscovite that was 500 million years old and covered an area of just 0.08 square millimeters. We propose using natural minerals (such as olivine and mica) that have long formation periods and are collected from deep within the ocean floor or continents with minimal surrounding radioactive substances. We are developing the necessary observational techniques to identify traces of dark matter as "Paleo-detectors" in these samples. Although there is still a long way to go before making an actual observation, this presentation will share our current efforts and discuss more efficient observation methods.