The National Argon Map was an AuScope-funded pilot project (2020–2021). The project aimed to compile a national-scale map of and to analyse new samples to fill the gaps in national coverage in 40Ar/39Ar geochronology. This report provides the results from dated samples located in the eastern Gawler Craton, in the vicinity of the Olympic Dam deposit, and from the region in and around the Cairn Hill Fe-Cu deposit. Hydrothermal muscovite sampled from the drill core recovered from drillhole ASD 1 yielded a discordant age spectrum with upper limit of c. 952.8 Ma and lower limit of c. 496.6 Ma, suggesting overprinting during the Delamerian Orogeny. K-feldspar from drillhole Blanche 1, located around 6 km to the south-west of the Olympic Dam ore deposit, yielded a complex age spectrum that includes four age populations, 1500.6 ± 9.2 Ma, 1406.2 ± 5.7 Ma, 1153.7 ± 4.2 Ma, and c. 682.8 Ma, suggesting that multi-phase hydrothermal processes have affected this granite. Analysis of hornblende from a narrow vein of hornblende-magnetite alteration sampled within the Cairn Hill deposit yielded a plateau age of 1412.5 ± 3.7 Ma, which may record the timing of formation of this hornblende. Conversely, K-feldspar from the foliated granite that hosts this hornblende-magnetite vein yielded a step-wise age progression between an upper limit of 1278.9 ± 6.7 Ma and a lower limit of 995.0 ± 6.6 Ma, suggesting that Musgravian-aged thermal and or microstructural events have affected it. Biotite and K-feldspar were also analysed from a sample of foliated and partly altered granite in drill core from hole KDD005, located to the west of Cairn Hill. The biotite has a disturbed age spectrum, with an upper limit of 1506.5 ± 8.6 Ma and an intermediate limit of 1430.7 ± 4.1 Ma, suggesting overprinting during the regional c. 1465 – 1410 Ma thermal event documented previously across the northern Gawler Craton. The co-existing K-feldspar in contrast records an upper age limit of 1355 ± 5.6 Ma and a lower limit of 1206.2 ± 7.7 Ma, suggesting overprinting during a Musgravian-aged thermal or microstructural event, thereby further extending across the Gawler Craton the spatial distribution of rocks having evidence for the effects of Musgravian-age processes. Further work is required to produce a more complete interpretation of the data presented here, including analysis of diffusion parameters derived during the step-heating experiments.