Determination of thorium concentrations and activity ratios in silicate rocks by alpha spectrometry.
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.
dos Santos
R N
RN
Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo, Rua do Matão, 1226; São Paulo, Brazil.
Marques
L S
LS
Nicolai
S H A
SH
Ribeiro
F B
FB
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
D017640:Silicates; D013910:Thorium