Insights into factors that control gold mineralisation: numerical modelling of the western Hodgkinson Province, northeast Queensland, Australia

Abstract

Results of coupled mechanical and fluid flow modelling provide insights into some of the factors that controlled gold mineralisation and deformation in the Hodgkinson Province in northeastern Queensland, Australia. These results aid in resolving why many north-south to northwest-southeast trending, second-order fault zones throughout the Hodgkinson province are spatially associated with gold deposits. The simplified, regional-scale model geometry used in this study permitted variation of boundary conditions, material properties and stress regimes. This included variation of lithological properties, the absence of fault zones in some models, and the application of plane strain or transpression. The model outcomes illustrate the importance of a listric fault geometry for focusing deformation and fluid flow in zones of relatively high permeability and / or low rock strength. Also, the orientation of fault zones with respect to the dominant far-field compressive stress regime is shown to be a key factor controlling deformation and fluid flow. In addition, fault bends and terminations are shown to influence significantly the distribution of deformation and fluid flow in our models. Our results provide an improved understanding of first-order factors that may have controlled localisation of deformation and fluid flow in the regional geological architecture of the Hodgkinson Province. Focused fluid flow arising from localised dilation and permeability increase plays an important role in the formation of ore deposits, hence the outputs of our modelling may be of significant value for future exploration in the Hodgkinson Province, and analogous regions elsewhere. Moreover, our study illustrates the usefulness of numerical modelling as a tool for testing multiple scenarios, leading to improved conceptual understanding of geological systems.