Seismic Reflection and Potential Field Constraints on Imbrication and Exhumation of the Paleoarchean Narryer Terrane, Yilgarn Craton

Abstract

AbstractThe Narryer Terrane, which is located on the northwest margin of the Yilgarn Craton, is one of the oldest preserved blocks of continental crust on Earth with rocks as old as 3.73 Ga and detrital zircons up to 4.4 Ga. In 2010‐11, three deep seismic reflection profiles were acquired over the terrane, and interpreted to show that during the Neoarchean the Narryer Terrane was thrust over the northwest edge of the Youanmi Terrane, which represents the core of the Yilgarn Craton, and in turn underthrust from the north by the Glenburgh Terrane during the Paleoproterozoic. We have reprocessed the seismic data to improve the imaging, extract 3D reflector orientations, and determine near‐surface velocity models. We locate the shear zone along which the Narryer Terrane was exhumed and correlate upper crustal faults interpreted in the seismic data with near‐surface faults and shear zones identified in a regional map of the first vertical derivative of the total magnetic field. One >150 km and two ∼50 km long shear zones divide the exposed Narryer Terrane into distinct structural domains that were probably juxtaposed relatively late in the thrusting of the Narryer Terrane over the Youanmi Terrane in the Paleoproterozoic. While most supracrustal rocks occur in the Northern and Southern domains, the Western Domain where magmatic ages are <3.0 Ga, high mass density, consistent with exhumation from the middle‐lower crust, and is made up of four blocks that exhibit differing patterns of seismic reflectivity, indicating they were likely combined prior to their exhumation.