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Orogenic Gold Deposits of the Agnew Gold Camp

Orogenic (and not so orogenic) gold deposits of the Agnew Gold Camp - Yilgarn Craton, Western Australia

Nicolas Thébaud

Western Australia’s Archean gold deposits are commonly considered to be orogenic. However, as seen with Phanerozoic examples, these deposits often form in close proximity to and coeval with intrusion-related gold systems. In the Agnew Gold Camp (Yilgarn Craton, Western Australia), recent field investigation has allowed delineation of the structural framework and mineral paragenesis associated with mineralisation in four individual deposits – the Songvang, Crusader, Waroonga and New Holland-Genesis deposits. Mineralisation in all four was controlled by the formation of the Lawlers Antiform during regional E-W contraction. Geochronological constraint for the systems interpreted in the context of structural and paragenetic relationships indicate mineralisation developed during two discrete episodes with contrasting fluid sources. The initial event is related to onset of folding, and presents characteristics of magmatic intrusion related mineralisation. The second mineralisation episode is more akin to typical Archean orogenic-type gold mineralisation, and has occurred during a late developmental stage of the Lawlers Anticline. This close spatial and temporal correlation of intrusion-related and orogenic style deposits may hold significant implications for the delineation of future exploration strategies in the Agnew Gold Camp.