b'2.5D AEM inversionFeatureFigure 20.2.5D Forward model resistivity and mesh geometry and ore type property legend.The survey was designed to map geology, minerals and groundwater in the Greater Cobar area and was flown as part of the MinEx Cooperative Research Centres (MinEx CRC) National Drilling Initiative. The NRG Xcite survey could not be flown over the known Elura deposit because the cultural disturbance at the mine is too extensive to obtain noise-free data. The nearest line is 1 km north of the orebody extremities.The Elura orebody is clearly visible in the last 10 channels of the Z component forward modelled data, and is well above noise levels. The X component is more heavily affected by noise, but the orebody response is visible at early to mid-time, see Figure21. With the addition of motion noise to the X component, which is not included in these estimates, this response may be difficult to identify.Elura takeawayWe can conclude from the forward model of section 5750N that the Elura orebody would be recognisable in the Z component of the Xcite data if a survey line had crossed over the main massive sulphide lens, which has a strike length of 150 m. It is unlikely that a response would have been seen in a line 100 m to the south, as the mineralisation cuts out quickly in that direction.Conversely, had a survey line been flown 200 m further to the north, where the top of mineralisation is 320 m below surface and the massive sulphide lenses are smaller, the survey would have been unlikely to detect the conductor. Note, it was beyond the scope of the modelling exercise to forward model heliborne systems with larger dipole moments (and therefore broader footprint), although this may be attempted at a later date.The conductive cover in the northern part of the Cobar Basin, where Elura is located, is generally thicker than further to the south. Clearly thinner regolith would enhance detectability. Nevertheless, to ensure detection of this deposit style (very steeply plunging, short strike length sulphides) a close line spacing (200 m) is probably required.Operational challengesAEM data processing, including 2.5D inversions comes with a number of challenges. These challenges can be broadlyFigure 21.2.5D Xcite forward model; section 5750N, flown from left grouped as relating to system complexity and geological noise. toright.AUGUST 2020 PREVIEW 44'