The Archean Windimurra Igneous Complex consists of distinct components, including a thick layered series, with a cumulate mineral stratigraphy similar to the zones identified in the well-studied Bushveld Complex, South Africa. The complex is part of the plume-related and laterally extensive 2.81 Ga Meeline Suite, the intrusive component of a large igneous province. It is an anhydrous tholeiitic suite consisting of five layered mafic–ultramafic intrusions 25–85 km in the long dimension. These intrusions host significant V–Ti mineralization in their fractionated, Fe-rich upper zones. Recent mapping, combined with aeromagnetic, gravity and seismic surveys, has provided unparalleled three-dimensional constraints on the largest of these intrusions. The results of three-dimensional modelling show that it is thicker than previously recognized. At c. 11 km, it is the thickest layered mafic–ultramafic intrusion identified globally and one of the largest such intrusions volumetrically. The mineral zone stratigraphy and many other features associated with this complex share similarities with the c. 800 myr younger Bushveld Complex. On a large scale, three discordant units are delineated geometrically, providing fundamental constraints on a multi-stage genetic model for magma emplacement. The indication of a thick, subsurface Ultramafic Zone provides a potential target for Ni–Cr–platinum group element mineralization.
In 1974, the Australian Bureau of Mineral Resources, Geology and Geophysics completed a 15-year systematic reconnaissance gravity survey of Australia with stations spaced at 11 km. The 1976 Gravity Map of Australia was a seminal product; half a century later, the data still provide the only coverage for substantial parts of the continent. In 2005, the Geological Survey of Western Australia, supported by Geoscience Australia, commenced a program of regional ground gravity surveys with 2.5 km station spacing, a sixteen-fold improvement of resolution over the 'first generation' BMR data. In 2013, GSWA declared its aim of completing 'second-generation' reconnaissance gravity coverage of WA by 2020. In 2016, with 45% of the State yet to be surveyed in the north and east, and ground access issues slowing progress and making uniform coverage increasingly difficult, GSWA and GA undertook the first government-commissioned regional aerogravity survey in Australia, using the Sander Geophysics AIRGrav system. The 38,000 line-km survey covering 84,000 km 2 in the East Kimberley region was flown at 2.5 km line-spacing for compatible spatial resolution with GSWA's regional ground surveys. We compare airborne with ground gravimetry in the context of the East Kimberley project and conclude that, for reconnaissance surveys: aerogravity costs now approach those of ground surveys; spatial resolution is equivalent; data precision is not a critical factor; and airborne and ground data can be merged seamlessly for interpretation. Consequently, new aerogravity surveys were commissioned over 264,000 km 2 of northern WA in the Tanami, northeast Canning and Kidson regions.
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