Numerical modelling of structural controls on fluid flow and mineralization

Abstract

This paper presents the results of a set of numerical models focussing on structural controls on hydrothermal mineralization. We first give an overview of natural phenomena of structurally-controlled ore formation and the background theory and mechanisms for such controls. We then provide the results of a group of simple 2D numerical models validated through comparison with Cu-vein structure observed near the Shilu Copper deposit (Yangchun, Guangdong Province, China) and finally a case study of 3D numerical modelling applied to the Hodgkinson Province in North Queensland (Australia). Two modelling approaches, discrete deformation modelling and continuum coupled deformation and fluid flow modelling, are involved. The 2D model-derived patterns are remarkably consistent with the Cu-vein structure from the Shilu Copper deposit, and show that both modelling approaches can realistically simulate the mechanical behaviours of shear and dilatant fractures. The continuum coupled deformation and fluid flow model indicates that pattern of the Cuveins near the Shilu deposit is the result of shear strain localization, development of dilation and fluid focussing into the dilatant fracture segments. The 3D case-study models (with deformation and fluid flow coupling) on the Hodgkinson Province generated a number of potential gold mineralization targets. ª 2011, China University of Geosciences (Beijing) and Peking University. Production and hosting by Elsevier B.V. All rights reserved.

An overview of hydrodynamic studies of mineralization

“…However, in recent years, there have been increasing attempts in using numerical modeling to guide selection of exploration targets (e.g., Ord et al, 2002;Schaubs et al, 2006;Potma et al, 2008;Liu et al, 2010;Zhang et al, 2010Zhang et al, , 2011. It is known that many mineral deposits are controlled by structures, especially faults or fracture zones, but it is also known that mineral deposits only occur in some of the structures, while most structures are barren.…”

“…Generally, it is thought that the structures or segments of structures where fluid flow are focused for a prolonged period of time are favorable for mineralization, and 2D or 3D numerical modeling can predict such areas. As explained by Zhang et al (2011), a general practice is to compare the numerical modeling results with the occurrences of known mineral deposits, and try to find areas that have similar hydrodynamic attributes as the mineralized areas as targets.…”

“…A home-made program similar to Basin2 but with additional capacity taking into consideration the effect of hydrocarbon generation on fluid overpressure development has been developed and used in the study of various sedimentary basin-related mineralization systems (Chi and Savard, 1998;Chi, 2001;Chi et al, 2010;Xue et al, 2011). TOUGH2 and TOUGHREACT have been used in various hydrothermal systems, especially those involving multiple phases and watererock interactions (e.g., Todesco et al, 2003;Mannington et al, 2004), FEFLOW for modeling various fluid convection systems (e.g., Cui et al, 2010;Ju et al, 2011), and FLAC2D and FLAC3D mainly for modeling coupled deformation and fluid flow (Zhang et al, 2006(Zhang et al, , 2011Ju and Yang, in press).…”

Introduction to thematic section on hydrodynamic studies of mineralization

“…One of the main purposes of numerical modeling of fluid flow is to predict which structural locales are favorable for mineralization in a given area. Zhang et al (2011), after summarizing the principles of numerical modeling of fluid flow in relation to rock deformation, demonstrates how numerical modeling can be used to help the selection of exploration targets. Both discrete deformation model and continuum coupled deformation-fluid flow model are examined, and an example of 3D numerical modeling with a focus on mineral exploration is provided.…”

“…Nevertheless, a number of studies have been carried out regarding the hydrodynamics of fluid flow associated with ore mineralization (e.g., Cathles, 1981Cathles, , 1997Garven and Raffensperger, 1997;Cathles and Adams, 2005;Cox, 2005;Ingebritsen et al, 2006), and it is timely to evaluate our current understanding on this topic and gaps in knowledge to be addressed in further studies. This special section on "Hydrodynamics of mineralization" contains four papers Xue et al, 2011;Zhang et al, 2011;Ju et al, 2011), which summarize the current status of study in the field, and present a few case studies to highlight the importance of hydrodynamics in the research of mineral deposits. Chi and Xue (2011) summarizes the principles of fluid flow related to mineralization.…”