The world-class Wallaby gold deposit, Laverton, Western Australia: An orogenic-style overprint on a magmatic-hydrothermal magnetite-calcite alteration pipe?

Abstract

Gold mineralisation at the Wallaby gold deposit is hosted by a 1,200 m thick mafic conglomerate. The conglomerate is intruded by an apparently comagmatic alkaline dyke suite displaying increasing fractionation through mafic-monzonite, monzonite, syenite, syenite porphyry to late-stage carbonatite. In the mine area, a pipe-shaped zone of actinolite-magnetite-epidote-calcite (AMEC) alteration overprints the conglomerate. Gold mineralisation, associated with dolomite-albite-quartz-pyrite alteration, is hosted in a series of sub-horizontal, structurally controlled zones that are largely confined within the magnetite-rich pipe. The deposit has a current ore reserve of 2.0 Moz Au, and a total resource of 7.1 Moz Au.