On shearing, magmatism and regional deformation in Neoarchean granite-greenstone systems: Insights from the Yilgarn Craton I. Zibra a, * , K. Gessner a, c , H.R. Smithies a , M. Peternell b a Geological Survey of Western Australia, Perth, WA 6004, Australia b Johannes Gutenberg Universität Mainz, Institut für Geowissenschaften, Department of Earth Sciences, Tektonophysik, Becherweg 21, 55099 Mainz, Germany c School of Earth and Environment, The University of Western Australia, 35 Stirling Highway, Crawley WA 6009, Australia article info Article history: Received 10 March 2013 Received in revised form 7 October 2013 Accepted 21 November 2013 Available online xxx Keywords: Neoarchean Crustal-scale shear zone Syntectonic plutons Regional deformation Geophysics Geochemistry abstract The structure of the Neoarchean Yilgarn Craton is dominated by craton-scale high-strain zones, mostly associated with highly-deformed elongate granitic bodies and transposed greenstone belts. These shear zones developed during widespread and prolonged magmatic activity that led to a nearly complete reworking of the felsic continental crust. The spatial, temporal and genetic relationships between such a voluminous and protracted event of crustal reworking and the development of the craton-scale shear zone network are unclear. Here, we combine new structural, geophysical and geochemical data to investigate the relationship between crustal-scale shear zones and large syntectonic plutons in the Yilgarn Craton of Western Australia. We propose that Archean granite-greenstone systems may have commonly evolved through the interaction of three fundamental geological processes: (I) emplacement of large scale syntectonic plutons; (II) activity of crustal-scale shear zones; (III) pervasive, largely syn- metamorphic polyphase deformation in greenstone belts adjacent to syntectonic plutons. We propose that the concept of “Archean regional deformation event” need to be reassessed: a regional event is probably pluton- (or batholith-) size, and the structural/metamorphic evolution of adjacent greenstone belts might have proceeded quite independently and potentially in a time-transgressive way, if those belts were not spatially related to the same syntectonic pluton. Crown Copyright Ó 2013 Published by Elsevier Ltd. All rights reserved. 1. Introduction The understanding of Archean geodynamics largely hinges around the long-standing debate on the tectonic styles that were active on Early Earth (e.g. Condie and Benn, 2006). The two end- member processes that have been proposed for Archean tectonics are generally referred to as “horizontal tectonism” and “vertical tectonism” (Lin, 2005), reflecting the view that Archean geo- dynamics was dominated by uniformitarian or non-uniformitarian processes, respectively (e.g. Van Kranendonk, 2004 for a review; see also Van Kranendonk, 2010). In Western Australia, the Archean Pilbara and Yilgarn cratons show some contrasting first-order geo- metric and structural features that are only partly understood, of- fering the opportunity to contribute to this long-standing debate. The Neo- to Mesoarchean East Pilbara Craton represents the best- documented example of crustal evolution dominated by vertical tectonics (Van Kranendonk et al., 2004), and includes a well- preserved dome-and-keel architecture, with map-view geome- tries characterized by circular granite-migmatite domes wrapped by greenstone envelopes displaying a well-preserved stratigraphy and lateral continuity. Here, the combination of a thick and dense supracrustal greenstone layer overlaying a low-viscosity felsic mid- to lower crust led to large-scale gravitational instabilities, triggering a partial convective crustal overturn (Collins et al., 1998). This model satisfactorily explains most of the first-order structural, strati- graphic, petrologic and geochemical features observed in the East Pilbara Craton (Collins and Van Kranendonk, 1999). In contrast, the Neoarchean Yilgarn Craton is dominated by craton-scale, approxi- mately north-trending high-strain zones, mostly associated with highly-deformed elongate granite bodies and dismembered greenstone packages, superficially resembling Phanerozoic orogenic belts. These shear zones are also of economic significance (Vearncombe,1998), as they exert a crucial structural control on gold mineralization, particularly in the highly mineralized Kalgoorlie Terrane of the Eastern Goldfields Superterrane, but also in the Murchison Domain of the Youanmi Terrane. Together with a range of other factors, the presence of crustal-scale shear zones has been * Corresponding author. E-mail address: ivan.zibra@dmp.wa.gov.au (I. Zibra). Contents lists available at ScienceDirect Journal of Structural Geology journal homepage: www.elsevier.com/locate/jsg 0191-8141/$ e see front matter Crown Copyright Ó 2013 Published by Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jsg.2013.11.010 Journal of Structural Geology xxx (2013) 1e15 Please cite this article in press as: Zibra, I., et al., On shearing, magmatism and regional deformation in Neoarchean granite-greenstone systems: Insights from the Yilgarn Craton, Journal of Structural Geology (2013), http://dx.doi.org/10.1016/j.jsg.2013.11.010