129I in iodyrite and marshite

Abstract

The concentrations of 129I incorporated in iodyrite (AgI) and marshite (CuI) are determined by measurements of radiogenic 129Xe. In addition to radiogenic 129Xe, some of these iodine-rich minerals contain excesses of 128Xe, 126Xe and 124Xe which are assigned to ( n, γβ −), ( n, 2 nβ −) and spallation reactions on 127I, respectively. The concentrations of radiogenic 129Xe indicate that the initial isotopic composition of iodine in iodyrite was (1.48±0.33)10 −14 ≤ 129 I 127 I ≤ (9.8±2.2)10 −14 and in marshite it was (0.32±0.24)10 −14 ≤ 129 I 127 I .