Over the last couple of decades, structural schemes proposed for the Yilgarn Craton largely derived from the structural record acquired in gold and nickel deposits. Such structural schemes present complex deformation paragenetic tables (i.e. local paleo-stress history tables) pointing towards with 4 to 10-stage structural schemes (e.g. Duuring et al., 2012). The problems associated with such an approach is that it commonly ignores (i) the partitioning of protracted, convergent deformation that generated large-scale (10-100 km) finite strain patterns; (ii) the importance of critically defining regional deformation phases with respect to major tectonic events or and/or significant changes in tectonic conditions; and (iii) the fact that the first-order geometric and kinematic characteristics of upper-crustal deformation in wide, hot orogens, can be explained by orogen-parallel gradients in crustal strength. In this contribution we focus on the tectono-magmatic evolution of the Agnew-Wiluna Greenstone Belt (AWB) in the Yilgarn Craton. We present a coherent structural history for the AWB constructed using regional geophysical data, seismic reflection data, lithostratigraphic compilation, and structural data from surface exposures. We propose that the feedback between inhomogeneous, E-W-directed bulk crustal shortening and magmatism in a transpressive deformation regime induced cyclic weakening-then-hardening of the continental crust between ca. 2680 and 2630 Ma, ultimately resulting in the observed finite strain pattern. Collectively the body of data collected in the AWB depict a tectonic evolution similar to that documented in other geological domains/terranes across the Yilgarn Craton (e.g. Zibra, 2020).

Reference(s)

Duuring, P, Bleeker, W, Beresford, SW, Fiorentini, ML, Rosengren, NM 2012. Structural evolution of the Agnew–Wiluna greenstone belt, Eastern Yilgarn Craton and implications for komatiite-hosted Ni sulphide exploration: Australian Journal of Earth Sciences, v. 59,765–791.

Zibra, I 2020. Nearchean structural evolution of the Murchison Domain (Yilgarn Craton): Precambrian Research 343:105719.