title: Determination of thorium concentrations and activity ratios in silicate rocks by alpha spectrometry.
abstract: A detailed radiochemical procedure for alpha spectrometry measurements of thorium concentrations and of 230Th/232Th activity ratios in silicates is presented. The Th behaviour, during each step of the chemical process, was investigated by using a 234Th tracer, which is a gamma-ray emitter. The described chemical processing provides relatively high thorium yields, which varied between 56% and 88%, in the analysis of GB-1 (granite) and BB-1 (basalt) Brazilian geological standards. Also, the application of the established radiochemical method allowed a determination of both Th concentrations and activity ratios with high reproducibility, on the order of 2%. The estimation of the concentration result accuracy is also about 2%, which was calculated by using published data obtained from neutron activation analysis as reference values.
authors.affiliation: Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo, Rua do Matão, 1226; São Paulo, Brazil.
authors.forename: R N
authors.initials: RN
authors.lastname: dos Santos
authors.forename: L S
authors.initials: LS
authors.lastname: Marques
authors.forename: S H A
authors.initials: SH
authors.lastname: Nicolai
authors.forename: F B
authors.initials: FB
authors.lastname: Ribeiro
mesh_terms: D000512:Alpha Particles; D019015:Geologic Sediments / Q000032:analysis; D055593:Geological Phenomena; D005844:Geology; D008722:Methods; D012015:Reference Standards; D017640:Silicates / Q000032:analysis*; D013057:Spectrum Analysis; D013910:Thorium / Q000032:analysis* / Q000592:standards
chemical_list: D017640:Silicates; D013910:Thorium