Numerical modelling of the western Hodgkinson Province, northeast Queensland: implications for gold mineralisation

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. These results aid in resolving why the north – south-striking segment of the terrane-bounding Palmerville Fault is barren, while 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. The 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 the modelling may be of significant value for future exploration in the Hodgkinson Province and analogous regions elsewhere. The study illustrates the usefulness of numerical modelling as a tool for testing multiple scenarios, leading to improved conceptual understanding of geological systems.

Key words:

• deformation
• fluids
• gold
• mineralisation
• numerical modelling
• Hodgkinson Province

Acknowledgements

This study forms part of a PhD project carried out by IMAV at the Australian Crustal Research Centre at Monash University. Research has been funded by the Cooperative Research Centre for predictive mineral discovery (pmd∗CRC) and this paper is published with the permission of the CEO, pmd∗CRC. An International Postgraduate Research Scholarship from Monash University is gratefully acknowledged. The numerical modelling could not have been conducted successfully without the assistance of Peter Schaubs, Klaus Gessner and Thomas Poulet at CSIRO. Roberto Weinberg and Klaus Gessner are thanked for comments on the manuscript. The authors are indebted to J. McLellan and S. Cox for feedback and thorough formal reviews of the manuscript. Fractal Technologies is acknowledged for its support in using the FracSIS software package.