Mapping the Gawler Craton-Musgrave Province interface using integrated heat flow and magnetotellurics

Abstract

The approximate position of a terrane boundary between the Archean-Mesoproterozoic Gawler Craton and the Meso-Neoproterozoic Musgrave Province, central Australia, is currently inferred from magnetic and gravity anomalies. However, its precise location, structural architecture and tectonic attributes are poorly understood. Thick overlying sediments of the Neoproterozoic Officer Basin restrict outcropping basement, and the number of basement-intersecting drill holes across the proposed boundary is limited. The Gawler Craton-Musgrave Province interface is critical to interpreting the tectonic relationship between these adjacent terranes, providing insights into the mechanism of Australian Proterozoic assembly. To assist its geophysical identification, we present 14 new heat flow estimates from the Nawa and Mount Woods Domains of the Gawler Craton, along with the first heat flow value calculated from the eastern Musgrave Province. These estimates are integrated with a magnetotelluric (MT) profile that transects the study area. The new datasets show that a transition exists from heat flow values of 68–89 mW m⁻² in the eastern Musgrave Province and northern Nawa Domain, through to higher heat flow values of 93–112 mW m⁻² in the southern Nawa and Mount Woods Domains. This transition corresponds to a highly resistive region located between two subvertical conductive bodies observed in the MT data; seismic interpretations from the Gawler Craton–Officer Basin–Musgrave Province–Amadeus Basin (GOMA) profile indicate that it corresponds to a region located between the Sarda Bluff Fault and Karari Shear Zone within the Nawa Domain. We therefore argue that the transition from Musgrave Province to Gawler Craton lithosphere can be mapped on the basis of higher heat flow and electrical conductivity, providing sufficient contrast to constrain this interface more accurately than previous geophysical models based on magnetic and gravity data alone.