R8：変成岩とテクトニクス

14:00 〜 14:15研究発表優秀賞エントリー

[R8-09] Assessment of Natural Radionuclide Concentrations and Radiogenic Heat Production in Granulite-Facies Rocks of the Rundvågshetta, East Antarctica, Using Gamma-Ray Spectrometry

*DEVIKA S PANICKER¹, Jun Goto², Tomokazu Hokada³, Toshiro Takahashi⁴, Satish Kumar Madhusoodhan⁴ (1. GSST, Niigata Univ., 2. IRA, Niigata Univ., 3. NIPR, Japan, 4. Dept. of Geology, FoS, Niigata Univ.)

キーワード：

Natural Radionuclide Concentrations、Radiogenic Heat Production、Granulite-Facies Rocks、Rundvågshetta、Gamma-Ray Spectrometry

Radiogenic heat generated from the decay of uranium (U), thorium (Th), and potassium (K) plays a crucial role in regulating the Earth's internal thermal structure. While this has been extensively studied in many continental terrains, East Antarctica remains one of the most underexplored regions in terms of radiogenic heat production (RHP) data. Particularly, the Rundvågshetta region of the Lützow-Holm Complex (LHC), composed of high-grade metamorphic rocks, lacks detailed heat production characterization. To address this gap, the purpose of this study is to quantify natural radionuclide concentrations and estimate the associated RHP across key lithologies in this region. Understanding the radioactive heat production of this region is crucial not only to assessing present-day radioactive heat production in Antarctica, but also for back-calculating the thermal regime during the time of Gondwana. We have analysed twenty representative rock samples, including pyroxene granulite, garnet-bearing gneiss, felsic gneiss, mafic gneiss, and pyroxene gneiss. Radionuclide concentrations were determined using direct gamma-ray spectrometry with a high-purity germanium detector. This non-destructive technique allows precise measurement of U, Th, and K directly from whole rock samples, which is ideal for Antarctic terrain. Our results show a wide range of radionuclide content: U from 0.03 to 14.87 ppm, Th from below detection to 40.1 ppm, and K from 0.16 to 4.47%, with calculated RHP values ranging from 0.05 to 7.01 µW/m³. Notably, felsic gneisses exhibit elevated U and Th, indicating zones of high heat production. This study delivers the first detailed RHP dataset for Rundvågshetta, offering critical new insights into the crustal heat regime of East Antarctica. Overall, this research offers essential insights into the natural radioactivity and radiogenic heat production of the Rundvågshetta bedrock, underscoring the crucial role of Earth's internal heat in shaping crustal processes. Ongoing radiometric investigations aim to further expand these findings and generate radioactive heat maps, which will be presented at the upcoming conference.