Tectonic framework of the southern Mount Isa Province

Abstract

The North Australian Craton consists of a series of latest Archean to Paleoproterozoic cratonic blocks including several orogenic belts. The Mount Isa Province and the Tennant Creek-Davenport Terrane are two components of the North Australian Craton. These regions are interpreted to be adjacent west and south west of the Mount Isa Inlier. However, there is limited understanding of the tectonic architecture of this relationship. At best, conclusions drawn from studies of outcropping relationships can be extrapolated undercover. This study uses recently collected magnetotelluric data, combined with deep crustal seismic, to directly investigate the relationship between the Mount Isa Province and the Tennant Creek–Davenport Terrane. The deep crustal seismic was collected along two orthogonal profiles capturing the relationship between the two regions, while the magnetotelluric (MT) data were collected in a regional grid over the junction between seismic lines, extending further west. The MT data underwent inversion before being jointly interpreted with the seismic data. Magnetotelluric inversion shows a highly resistive mid to lower crust beneath the Kalkadoon-Leichhardt domain. In contrast, the mid to lower crust for the Ardmore May Downs (Tennant Creek-Davenport equivalent) display several discrete conductors. The Leichhardt River domain displays characteristics similar to both the Ardmore-May Downs and Kalkadoon-Leichhardt domains. The seismic data show a reversal in the dip of the primary structures which is consistent with a transition between two geologically distinct terranes. The variation in MT and seismic character within the project area suggests significantly different geology or tectonic histories between the Kalkadoon-Leichhardt and Ardmore-May Downs/Leichhardt River domains.