Towards a high resolution Late Palaeoproterozoic ‐ earliest Mesoproterozoic apparent polar wander path for northern Australia

Abstract

Seven new primary poles upgrade the apparent polar wander path for northern Australia for the period 1730–1590 Ma. This brings the total number of primary poles to sixteen, of which nine have well‐defined SHRIMP U–Pb zircon ages. The upgraded path provides a tool for dating and correlation of tectonic events as well as fluid migration episodes for one of the most important periods of base‐metal mineralisation in Australia. Other new primary and overprint poles allow the path to be extended tentatively forward in time to ca 1500 Ma and back to ca 1770 Ma. The 1730–1590 Ma path comprises five quasilinear segments or tracks, each terminated by a sharp bend. The bends can be related to major (supersequence) boundaries in the northern Australian superbasins and to the initiation of sub‐basins that host the base‐metal deposits. Most bends are also associated with magnetic overprints related to episodes of fluid circulation, and three appear to be associated with the expulsion of metal‐rich brines that formed the world‐class Broken Hill, Mt Isa and HYC Pb–Zn deposits. According to the pole path, the movement of the region in the period 1730–1590 Ma can be described as series of clockwise‐counterclockwise rotations about mostly similar Euler poles located southwest of Australia, suggesting that the lithosphere may have been coupled alternately to oppositely convecting cells in the mantle. This mode of movement was terminated at the onset of the Isan Orogeny. The oldest track spans a period of igneous activity from 1740 Ma to 1710 Ma that left a 1000 km‐long trail of volcanics with a decreasing age trend to the northwest. Palaeomagnetic data are consistent with the interpretation that this trail was caused by the movement of the plate over a thermal anomaly in the upper mantle.