The Windimurra Igneous Complex is situated in the western part of the Archean Yilgarn Craton within the Youanmi Terrane. It is part of the plume-related and laterally extensive c. 2.81 Ga Meeline Suite, an anhydrous tholeiitic suite comprising five layered mafic–ultramafic intrusions 25–80 km in diameter. The intrusions also host significant V–Ti mineralization in their fractionated, Fe-rich upper zones. The Windimurra Igneous Complex is the only intrusion to contain two upper zones, separated by the Shephards Discordant Zone.
Recent mapping, aeromagnetic and gravity surveys, and the Youanmi seismic lines have provided unparalleled 3D constraints on the Windimurra Igneous Complex. These data have allowed direct assessment of the zone thicknesses and facilitated construction of a 3D model. This model was refined by forward modelling of potential field data and tested against a geophysical inversion. The results show that the complex is thicker than previously predicted, reaching approximately 11 km, which make it the thickest layered mafic–ultramafic intrusion identified worldwide.
Relative to the consistency of layered igneous units, three significantly discordant units are identified: 1) the Shephards Discordant Zone that separates the older, basal eastern lobe from the western lobe; 2) the base of the highly transgressive upper zone of the western lobe; 3) the roof zone and overlying Kantie Murdana Volcanics Member. The geometry of these three features provides constraints on a multistage genetic model for magma emplacement. In addition, the indication of a thick, subsurface ultramafic zone provides a potential target for Ni–Cr–PGE mineralisation. More information can be found in GSWA Record 2015/12.
For further information contact:
3D.geoscience@dmirs.wa.gov.au