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Abstract: This paper presents numerical investigation on the ore-forming fluid migration driven by tectonic deformation and thermally-induced buoyancy force in the Chanziping ore district in South China. A series of numerical scenarios are considered to examine the effect of meteoric water precipitation, the dip angle of the faults, unconformity surface, and thermal input on the ore genesis. Our computations reveal that the downward basinal fluid flow driven by extensional stress mixes with the upward basal fluid driven by the thermal input from depth at the junction of two faults at a temperature of about 200 °C, triggering the precipitation of the Chanziping uranium deposit. [Copyright &y& Elsevier]

Abstract: Fluid flow is an integral part of hydrothermal mineralization, and its analysis and characterization constitute an important part of a mineralization model. The hydrodynamic study of mineralization deals with analyzing the driving forces, fluid pressure regimes, fluid flow rate and direction, and their relationships with localization of mineralization. This paper reviews the principles and methods of hydrodynamic studies of mineralization, and discusses their significance and limitations for ore deposit studies and mineral exploration. The driving forces of fluid flow may be related to fluid overpressure, topographic relief, tectonic deformation, and fluid density change due to heating or salinity variation, depending on specific geologic environments and mineralization processes. The study methods may be classified into three types, megascopic (field) observations, microscopic analyses, and numerical modeling. Megascopic features indicative of significantly overpressured (especially lithostatic or supralithostatic) fluid systems include horizontal veins, sand injection dikes, and hydraulic breccias. Microscopic studies, especially microthermometry of fluid inclusions and combined stress analysis and microthermometry of fluid inclusion planes (FIPs) can provide important information about fluid temperature, pressure, and fluid-structural relationships, thus constraining fluid flow models. Numerical modeling can be carried out to solve partial differential equations governing fluid flow, heat transfer, rock deformation and chemical reactions, in order to simulate the distribution of fluid pressure, temperature, fluid flow rate and direction, and mineral precipitation or dissolution in 2D or 3D space and through time. The results of hydrodynamic studies of mineralization can enhance our understanding of the formation processes of hydrothermal deposits, and can be used directly or indirectly in mineral exploration. [Copyright &y& Elsevier]

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 Cu-veins 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. [Copyright &y& Elsevier]