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.

Coupled Process Models as a Tool for Analysing Hydrothermal Systems

“…There have been numerous analyses of this kind undertaken during the last decade, typically involving Mohr-Coulomb plasticity with Darcy flow to simulate dilation and fluid migration in complex multi-material geometries in 2D and 3D (Jiang et al 1997;Gow et al 2002;Oliver et al 2001;Ord et al 2002;Ord and Oliver 1997;Schaubs and Wilson 2002;Schaubs and Zhao 2002;Sorjonen-Ward et al 2002;Gessner et al 2006;McLellan et al 2004;Robinson et al 2006;Schaubs et al 2006;Upton et al 2007;Vos et al 2007;Zhang et al 2006aZhang et al , b, 2007. The ability to simulate fluid flow within 3D architectures has been crucial to successfully predict locations of mineralisation (Potma et al 2008).…”

Coupled Models of Brittle-plastic Deformation and Fluid Flow: Approaches, Methods, and Application to Mesoproterozoic Mineralisation at Mount Isa, Australia

“…Models In both cases there is a potential to drive flow upward in regions where fluid pressure departs from hydrostatic gradient, but the high pore pressure below the seal (in b) may favour tensile failure of the rock at the top of the reservoir are either purely elastic (Cox and Ruming 2004;Micklethwaite and Cox 2004), based on damage mechanics concepts (Sheldon and Micklethwaite 2007), or simulate plasticity by slip along interfaces of discrete elements representing weak fault systems (Ojala et al 1993;Holyland and Ojala 1997;Mair et al 2000). Other workers have used numerical models based on coupling Mohr-Coulomb plasticity with Darcy flow as implemented in the finite difference codes FLAC (Itasca 2000) and FLAC 3D (Itasca 2003;Cundall and Board 1988), to simulate dilation in complex multi-material geometries (Jiang et al 1997;Gow et al 2002;Ord et al 2002;Ord and Oliver 1997;Schaubs and Zhao 2002;Sorjonen-Ward et al 2002;Gessner et al 2006;McLellan et al 2004;Sheldon and Ord 2005;Robinson et al 2006;Schaubs et al 2006;Vos et al 2007;Zhang et al 2006aZhang et al , b, 2007Potma et al 2008). The latter technique is based on coupling Darcy flow to a Mohr-Coulomb constitutive model including plasticity.…”

The effects of basement faults on thermal convection and implications for the formation of unconformity‐related uranium deposits in the Athabasca Basin, Canada

“…It has been applied successfully to, for example, the fields of structural geology and fluid flow related to various types of deposits (e.g. Oliver et al 1999Oliver et al , 2006McLellan et al 2004;Vos et al 2007;Feltrin et al 2009;Sheldon 2009;Zhang et al 2011;Cui et al 2012b;Upton & Craw 2014;Li et al 2015b).…”