Geochemical characterization of monazite sands based on rare earth elements, thorium and uranium from a natural high background radiation area in Tamil Nadu, India

N Veerasamy; R Murugan; S Kasar; K Inoue; N Kavasi; S Balakrishnan; H Arae; M Fukushi; S K Sahoo

doi:10.1016/j.jenvrad.2021.106565

Geochemical characterization of monazite sands based on rare earth elements, thorium and uranium from a natural high background radiation area in Tamil Nadu, India

J Environ Radioact. 2021 Jun:232:106565. doi: 10.1016/j.jenvrad.2021.106565. Epub 2021 Mar 10.

Authors

N Veerasamy¹, R Murugan², S Kasar², K Inoue³, N Kavasi², S Balakrishnan⁴, H Arae², M Fukushi³, S K Sahoo⁵

Affiliations

¹ 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.
² Environmental Radionuclides Research Group, National Institutes for Quantum and Radiological Sciences and Technology, 4-9-1 Anagawa, Inage-ku, Chiba, 263-8555, Japan.
³ Department of Radiological Sciences, Tokyo Metropolitan University, 7-2-10 Higashiogu, Arakawa-ku, Tokyo, 116-8551, Japan.
⁴ Department of Earth Sciences, Pondicherry University, R Venkat Raman Nagar, Kalapet, Puducherry, 605014, India.
⁵ Environmental Radionuclides Research Group, National Institutes for Quantum and Radiological Sciences and Technology, 4-9-1 Anagawa, Inage-ku, Chiba, 263-8555, Japan. Electronic address: sahoo.sarata@qst.go.jp.

PMID: 33714078
DOI: 10.1016/j.jenvrad.2021.106565

Abstract

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^-1 and 25.2-12250.6 μg g^-1, 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.

Keywords: Beach placer deposit; HBRA; Monazites; Rare earth elements; Thorium; Uranium.

MeSH terms

Background Radiation
India
Metals, Rare Earth* / analysis
Radiation Monitoring*
Sand
Thorium / analysis
Uranium* / analysis

Substances

Metals, Rare Earth
Sand
monazite
Uranium
Thorium