Galena lead isotopes from the eastern part of the Nabberu Basin, Western Australia

Pb isotope assays are reported for galena found in undeformed stromatolitic dolomite of the eastern Earaheedy Sub‐basin of Western Australia. This sequence comprises the youngest group of sedimentary rocks in the Nabberu Basin, and lies directly on rocks of the Yilgarn Block. Two of three hand‐specimens yield concordant ratios and a model age in reasonable agreement with the 1.7 Ga K‐Ar dates on stratigraphically related glauconites. The Earaheedy Group and its iron formations can not therefore be correlated with the significantly older (2.5 Ga) Hamersley Group. The third hand‐specimen is isotopically heterogenous. Regression through the data indicates a source region of age similar to the youngest components of the underlying Yilgarn Block. Derived parameters suggest the high source‐U/Pb typical for the NW of Western Australia in this age range, and a less usual low source‐Th/U. By contrast the added radiogenic component revealed in the third specimen suggests an unusually high Th/U for its source rock.