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AbstractIn 2011 a review of an historical TEMPEST airborne electromagnetic survey in the Murchison Region of Western Australia identified a number of discrete bedrock conductor anomalies potentially associated with base metal mineralisation. One of the anomalies identified was in close proximity to a known gossan at Hollandaire, within rocks of the Archaean Mt Eelya Complex. The Hollandaire gossan had been previously investigated during the mid-late 1970’s using a variety of geological, geochemical and geophysical methods, including ground magnetics, induced polarisation, magnetic induced polarisation and time-domain electromagnetics.A single line of time-domain in-loop transient electromagnetic data was collected at Hollandaire during 2011, in order to follow up the TEMPEST bedrock conductor. A strong time-domain EM anomaly was identified, with a very high time-constant of 107 ms. Plate modelling of the in-loop data resulted in a target at depth-to-top 100 m, dipping at 45 degrees to the west- northwest, and with conductance 5000 S. The nine initial holes drilled to test the electromagnetic target all intersected sulphide mineralisation. The inferred resource now totals 2.8 million tonnes at 1.6% Cu, 0.4 g/t Au and 5 g/t Ag, with the supergene zone averaging 4.7% Cu. Subsequent downhole electromagnetic (DHEM) surveys have identified an off-hole electromagnetic conductor to the south of the known mineralisation, which has not yet been tested by drilling.KeywordsTEMPESTTime-domain electromagnetic methodCrone PEMHollandaire AcknowledgmentsThe majority of this work was performed when JR was employed by Geoforce Pty Ltd and Groundprobe Geophysics. Initial modelling of the MLTEM and DHEM data was conducted by Ian James of ASST Pty Ltd. We thank Silver Lake Resources for permission to publish these results.