Zircon U–Pb dating of Early Palaeozoic monzonitic intrusives from the Goonumbla area,New South Wales

Zircon U–Pb ages measured on four small intrusions into the succession of Ordovician volcanic rocks that hosts Northparkes Cu–Au mine northwest of Parkes, New South Wales, place limits on the age of the volcanic sequence. The basal Nelungaloo Volcanics are constrained by a cross‐cutting monzodiorite to be ≥484.3 ± 2.9 Ma (Early Ordovician). Similarly, the overlying basal Goonumbla Volcanics are constrained by another cross‐cutting monzodiorite to be ≥450.8 ± 4.2 Ma (Middle Ordovician). A later generation of monzonites intruded into the middle and upper Goonumbla Volcanics yield ages of 439.1 ± 4.5 and 438.9 ± 4.7 Ma (Siluro‐Ordovician). These various ages are consistent with the ages of fossiliferous sediments within the volcanic sequence, and indicate that both the intrusive and volcanic rocks span an appreciable period of time—neither are the product of a single magmatic episode. Intrusion of the youngest monzonites and mineralisation was virtually contemporaneous.