Isotopic remobilization in the Mount Isa tuff beds

Abstract The water-laid tuff beds in the mine sequence at Mount Isa, Queensland, yield anomalous whole-rock isochron results. The RbSr “age” is significantly younger than expected, the apparent initial ratio is high, and the scatter about the regression line is significantly greater than experimental. In the UThPb system, the scatter is greater, the “age” is even lower, and the initial ratios approximate to the ore values. The results are interpreted in terms of continued mobility of minor elements in the water-rich sediments while deep-burial conditions persist.