Modelling the giant, Zn–Pb–Ag Century deposit, Queensland, Australia

Abstract

This paper presents a combination of geometric reconstructions of the Century Zn–Pb–Ag deposit, and finite-difference modelling of coupled deformation and fluid flow. Our intention is to demonstrate that these computer-based applications represent a new approach in testing ore genesis models. We use a “visiometric” approach, utilising GoCad 3D structural and property modelling. Computer visualisation is applied to reveal metal zonations, fault distributions and timing, stratigraphic influence on zoning, and the nature and extent of metal redistribution during basin evolution and deformation. We also examine possible links between fluid flow, deformation, and mass transfer using the numerical code FLAC3D. Numerical modelling results suggest that subsurface fluid flow during basin inversion is compartmentalised, being focussed within more permeable fault zones, thus accounting for the secondary redistribution of base metals identified using the 3D reconstructions. However, the results do not explain the broad metal zonation observed. Both the spatial and numerical models suggest that Century is syngenetic, with further diagenesis and deformation producing 1–100 m-scale (re)mobilisation.