Controls on the formation of the Magdala gold deposit at Stawell, Western Victoria, Australia

Abstract

The Stawell goldfield lies within a reworked portion of the Delamerian Fold Belt in western Victoria and has a structural complexity and a gold-lode style that is markedly different from similar ca 440 Ma aged deposits in the Lachlan Fold Belt such as Bendigo or Ballarat. Comparisons with these other turbidite-hosted gold deposits in Victoria suggest four major differences: (1) presence of a tholeiitic basaltic pile; (2) ductile deformation (D1-4) over at least 60 million years prior to gold mineralisation; (3) a preferential and localised reactivation of pre-existing structures within a progressively rotating stress field and (4) highly evolved hydrothermal alteration. Of these differences a key element has been the nature of the basaltic pile, which may have promoted alteration of onlapping sedimentary rocks, thereby creating a basis from which a high sulphur turbidite-hosted orogenic gold deposit was formed.