New U–Pb geochronology for the South Nicholson region and implications for stratigraphic correlations

The Mesoproterozoic South Nicholson Basin sits between, and overlies, the Paleoproterozoic Mount Isa Province to the east and the southern McArthur Basin to the northwest. The McArthur Basin and Mount Isa Province are well studied and highly prospective for both mineral and energy resources. In contrast, rocks in the South Nicholson region (incorporating the Mount Isa Province, the Lawn Hill Platform and the South Nicholson Basin, and geographically straddling the Northern Territory and Queensland border) are mostly undercover, little studied and consequently relatively poorly understood. A comprehensive U-Pb sensitive high-resolution ion microprobe (SHRIMP) zircon and xenotime geochronology program was undertaken to better understand the stratigraphy of the South Nicholson region and its relationship to the adjacent, more overtly prospective Mount Isa Province and McArthur Basin. The age data indicate that South Nicholson Basin deposition commenced ca. 1483 Ma, with cessation at least by ca. 1266 Ma. The latter age, based on U-Pb xenotime, is interpreted as the timing of postdiagenetic regional fluid flow. The geochronology presented here provides the first direct age data confirming that the South Nicholson Group is broadly contemporaneous with the Roper Group of the McArthur Basin. Some rocks, mapped previously as Mesoproterozoic South Nicholson Group and comprising proximal, immature lithofacies, have detrital spectra consistent with that of the late Paleoproterozoic McNamara Group of the western Mount Isa Province; this will necessitate a revision of existing regional stratigraphic relationships. The stratigraphic revisions and correlations proposed here significantly expand the extent of highly prospective late Paleoproterozoic stratigraphy across the South Nicholson region, which, possibly, extends even further west beneath the Georgina and Carpentaria basins. Our data and conclusions allow improved regional stratigraphic correlations between Proterozoic basins, improved commodity prospectivity and targeted exploration strategies across northern Australia. Citation: Carson, C.J., Kositcin, N., Anderson, J.R., Cross, A. and Henson, P.A., 2020. New U–Pb geochronology for the South Nicholson region and implications for stratigraphic correlations.. In: Czarnota, K., Roach, I., Abbott, S., Haynes, M., Kositcin, N., Ray, A. and Slatter, E. (eds.) Exploring for the Future: Extended Abstracts, Geoscience Australia, Canberra, 1–4.