Disequilibrium of the 238U series in basalt
Radioisotope analyses of basalt samples from Hawaii, Japan, and Iwo Jima show that: (1) 234 U and 238 U are virtually in radioactive equilibrium, (2) 230 Th exceeds equilibrium values in all these samples, (3) 210 Pb concentrations range from 10–200% of the equilibrium values and average 30% deficient, and (4) 226 Ra is probably not in equilibrium with 234 U. The source regions of the basalts or magma forming processes are open systems, chemically. The enrichment of some of the uranium-daughter nuclides is insufficient to account for the excess 206 Pb in volcanic rocks. The isotopic composition of lead and specific activity of 210 Pb in sublimates from Showa-shinzan, Japan are also reported.
Hawaii↗