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Purpose: The objective of this paper is to establish a solution strategy for obtaining dual solutions, namely trivial (conventional) and nontrivial (unconventional) solutions, of coupled pore-fluid flow and chemical dissolution problems in heterogeneous porous media. Design/methodology/approach: Through applying a perturbation to the pore-fluid velocity, original governing partial differential equations of a coupled pore-fluid flow and chemical dissolution problem in heterogeneous porous media are transformed into perturbed ones, which are then solved by using the semi-analytical finite element method. Through switching off and on the applied perturbation terms in the resulting perturbed governing partial differential equations, both the trivial and nontrivial solutions can be obtained for the original governing partial differential equations of the coupled pore-fluid flow and chemical dissolution problem in fluid-saturated heterogeneous porous media. Findings: When a coupled pore-fluid flow and chemical dissolution system is in a stable state, the trivial and nontrivial solutions of the system are identical. However, if a coupled pore-fluid flow and chemical dissolution system is in an unstable state, then the trivial and nontrivial solutions of the system are totally different. This recognition can be equally used to judge whether a coupled pore-fluid flow and chemical dissolution system involving heterogeneous porous media is in a stable state or in an unstable state. The proposed solution strategy can produce dual solutions for simulating coupled pore-fluid flow and chemical dissolution problems in fluid-saturated heterogeneous porous media. Originality/value: A solution strategy is proposed to obtain the nontrivial solution, which is often overlooked in the computational simulation of coupled pore-fluid flow and chemical dissolution problems in fluid-saturated heterogeneous porous media. The proposed solution strategy provides a useful way for understanding the underlying dynamic mechanisms of the chemical damage effect associated with the stability of structures that are built on soil foundations. [ABSTRACT FROM AUTHOR]

This paper deals with how to implement perturbations in the computational simulations of chemical dissolution‐front instability (CDFI) problems in fluid‐saturated porous media. On the basis of theoretical analysis, it is found that the application of a perturbation to the chemical dissolution front is equivalent to the application of an alternative perturbation to the dimensionless pore‐fluid normal velocity (relative to the planar chemical dissolution front) in the chemical dissolution zone, where the chemical dissolution front is located. This avoids the difficulty to find the spatial coordinates of the chemical dissolution front locations in the computational simulations of CDFI problems. Based on this new finding, a novel algorithm for implementing perturbations in the computational simulations of CDFI problems is proposed. The key point of the proposed algorithm is that the perturbed pore‐fluid normal velocity (relative to the planar chemical dissolution front) is used to directly replace the original pore‐fluid normal velocity (relative to the planar chemical dissolution front) in the related mathematical governing equations (MGEs), so that the proposed algorithm works for the porosity‐velocity‐concentration scheme when it is used to solve CDFI problems in fluid‐saturated porous media. In addition, the related theoretical analysis in this study has answered the previous unanswered question why the application of a perturbation to porosity works in the porosity‐pressure‐concentration scheme but does not work in the porosity‐velocity‐concentration scheme for solving the same CDFI problems in fluid‐saturated porous media. Through solving two illustrative examples with two different distributions of initial porosity, in which one is homogeneous and another is heterogeneous in the chemical dissolution system, the validity and usefulness of the proposed algorithm for implementing perturbations in the computational simulations of CDFI problems have been demonstrated. [ABSTRACT FROM AUTHOR]

Abstract: Mass and energy should be conservative in nature and ore forming systems within the upper crust of the earth are no exception. Thus, the mass conservation law is valid not only for a closed system, but for an open system as well. In the latter case, exchange between the system and its surroundings must be considered. Based on the mass conservation law, this paper considers a number of different roles of geofluid flow in ore forming systems. Due to the concurrence of these roles, interactions between fluid flow, heat transfer, mass transport and chemical reactions need to be considered in a comprehensive manner. Through theoretical analysis and computational simulations of several typical generic models for ore forming systems, it can be demonstrated that for an ore forming system in chemical equilibrium, the aqueous species of which are produced by the chemical dissolution reactions, the approximate form (i.e. the rock alteration index and the improved rock alteration index) of the mineralization rate can be used to predict mineralization patterns in the ore forming system. However, for a chemically non-equilibrated ore forming system, the detailed interaction between solute advection, solute diffusion/dispersion and chemical kinetics needs to be considered to determine potential mineralization patterns in the ore forming system. [Copyright &y& Elsevier]

Graphical abstract Highlights • 3D computational simulation methods can improve the efficiency of 3D prospectivity modeling. • 3D prospectivity modeling can integrate lots of different methods and multi-source data. • 3D prospectivity modeling effectively delineated new targets for Fe-Cu mineralization at depth. Abstract The Yueshan orefield is one of the best-known Fe–Cu orefields in China and is located within the central Yangtze metallogenic belt ofin Anhui Province, China. The recent discovery of the skarn-type Zhuchong Fe–Cu deposit at depth within the orefield has highlighted the prospectivity of this area to host deep-seated skarn-type mineralization. However, the effectiveness of traditional geophysical exploration techniques is reduced with increasing depth. This, combined with recent developments in 3D mineral prospectivity modeling has led to the use of a 3D targeting approach for exploration for deep-seated and concealed mineralization in this area. However, to date the usefulness of this approach has been limited by a lack of an approach that could generate more useful 3D predictive maps. This study presents a 3D computational simulation based mineral prospectivity modeling approach that identified several exploration targets for concealed and deep-seated skarn-type mineralization within the Yueshan orefield. These prospective targets include areas of known mineralization as well as a number of new targets for future mineral exploration. In addition, the analysis of the resulting data using a capture-efficiency curve indicates that these 3D computational simulation approaches can provide additional predictive information for mineral exploration, indicating that 3D computational simulation should have a key role in the development and use of future 3D prospectivity modeling techniques during exploration targeting. [ABSTRACT FROM AUTHOR]