Whole‐Rock U‐Th‐Pb and Rb‐Sr ages of the sybella microgranite and pegmatite, mount Isa, Qeensland

Abstract

Abstract Isochron data on the Sybella microgranite and pegmatite support recent age estimates on muscovite and monazite. From Rb‐Sr, the age is 1553 ± 29 m.y., initial ratio 0–7323 ± .0101; from the three U‐Th‐Pb isochrons the pooled age is 1565 ±52 m.y., initial ratios 17–530 ±.013, 15–639 ±.013, 36.443 ± .013. These lead ratios are so markedly different from those of the adjacent Ag‐Pb‐Zn orebody that they exclude any possible correlation between these components of the Sybella Granite and the mineralization.