Archean diapirism recorded by vertical sheath folds in the core of the Yalgoo Dome, Yilgarn Craton

Abstract

In Archean granite-greenstone terrains, both vertical and horizontal tectonic processes can generate the typical dome-and-keel structural geometries. One of the classic Archean domes interpreted to result from a horizontal tectonic regime is the Yalgoo Dome in the Yilgarn Craton of Western Australia. In this contribution, we reassess the structural evolution of the Yalgoo Dome by detailing the structures exposed in the migmatitic core. The core contains multi-scale domes-and-basins. These structures were previously interpreted as the result of superposed folding. Our structural mapping shows that the dome-and-basin patterns result from vertical sheath folds developed in a single, progressive deformation event (D1). This first event most likely resulted from diapiric ascent of a buoyant partially molten tonalitic crust and was overprinted by two contractional episodes (D2–D3) both reflecting bulk EW shortening. The structural evolution proposed here points towards a shift from an early history of vertical tectonics dominated by diapirism to a regional regime dominated by horizontal tectonics.