Zinc isotope composition of the Proterozoic clastic-dominated McArthur River Zn-Pb-Ag deposit, northern Australia.

[Display omitted] • Zinc isotope characterisation of the giant McArthur River Zn-Pb-Ag deposit. • Sulfide ores show invariable whole rock δ66Zn typical for the continental crust. • Only subtle, localized covariation between δ66Zn and relative abundances of Zn, Pb and Ag. • Data indicate rapid Zn precipitation that suppressed (Rayleigh) Zn isotope fractionation. • Discussion of the applicability of Zn isotopes for ore exploration. This study provides a Zn isotope characterization (δ66Zn) of the c. 1,640 Ma clastic-dominated McArthur River Zn-Pb-Ag deposit. Dolomitic, siltstone-hosted sulfide ores were sampled in two separate drill cores. One intersects the stratiform, vertically stacked orebodies at the centre of the deposit, and the other one intersects the south-eastern periphery of the deposit. The analyzed ores show relatively invariable δ66Zn values typical of the continental crust (0.35 ‰ median with 0.05 ‰ standard deviation). This signature is consistent with (near-) quantitative sulfide (sphalerite) precipitation during ore formation, negligible Zn isotope fractionation during fluid transport, and perhaps muted fractionation associated with near-quantitative Zn extraction from the source. Hence, our data show that a pronounced Zn isotope fractionation pattern characterized by lower δ66Zn values closer to the hydrothermal source, as reported from other Zn-Pb deposits, is not developed within the McArthur River deposit. However, across some orebodies, we note a subtle Zn isotope fractionation trend that correlates with the relative abundances of several temperature-sensitive base and trace metals (Zn, Pb, and Ag). This trend can be explained by subtle influence of Rayleigh-type Zn isotope fractionation during fluid evolution and Zn sulfide precipitation. Previous studies have suggested that Zn isotopes may be useful in the exploration for economic mineralization, as these studies observed both a significant Zn isotope halo and δ66Zn values markedly different from the continental crust. However, because both characteristics are not observable at McArthur River, the Zn isotope system may not have been useful in finding this deposit. [ABSTRACT FROM AUTHOR]