Department of Radiological Sciences, Tokyo Metropolitan University, 7-2-10 Higashiogu, Arakawa-ku, Tokyo, 116-8551, Japan; Environmental Radionuclides Research Group, National Institutes for Quantum and Radiological Sciences and Technology, 4-9-1 Anagawa, Inage-ku, Chiba, 263-8555, Japan.
Environmental Radionuclides Research Group, National Institutes for Quantum and Radiological Sciences and Technology, 4-9-1 Anagawa, Inage-ku, Chiba, 263-8555, Japan.
J Environ Radioact. 2021 Jun;232:106565. doi: 10.1016/j.jenvrad.2021.106565. Epub 2021 Mar 10.
The Kanyakumari coastal area in the southernmost part of Tamil Nadu, India is a well-known natural high background radiation area due to the abundance of monazite in beach placer deposits. In the present study, the concentrations of major oxides, rare earth elements (REEs), Th and U were measured to understand geochemical characteristics of these monazite sands. Based on the ambient dose rate, 23 locations covering an area of about 60 km along the coast were selected for sample collection. The concentrations of U and Th ranged from 1.1 to 737.8 μg g and 25.2-12250.6 μg g, respectively. The Th/U ratio ranged from 2.2 to 61.6, which clearly indicated that Th was the dominant contributing radionuclide to the enhanced natural radioactivity in this coastal region. The chondrite-normalized REEs pattern of the placer deposits showed enrichment in light REEs and depletion in heavy REEs with a negative Eu anomaly that indicated the monazite sands were derived from granite, charnockite, and granitoid rocks from the Nagercoil and the Trivandrum Blocks of the Southern Granulite Terrain.
印度泰米尔纳德邦最南端的坎亚库马里沿海地区是一个著名的天然高本底辐射区，这是由于海滩砂矿中富含独居石。在本研究中，测量了主要氧化物、稀土元素（REEs）、钍和铀的浓度，以了解这些独居石砂的地球化学特征。根据环境剂量率，在沿海水域约 60 公里的范围内选择了 23 个位置进行采样。铀和钍的浓度范围分别为 1.1 至 737.8μg/g 和 25.2 至 12250.6μg/g。钍/铀比值范围为 2.2 至 61.6，这清楚地表明，在该沿海地区，钍是增强天然放射性的主要贡献放射性核素。砂矿沉积物的球粒陨石标准化 REE 模式显示轻 REE 富集，重 REE 亏损，并有负铕异常，表明独居石砂来源于纳格尔科伊尔和特里凡得琅区块的南方麻粒岩带的花岗岩、片麻岩和花岗质岩石。
