Search

Mineral Resource downgrades can be prevented by integrating better structural geological interpretations into project evaluations. Geological modelling for Mineral Resource estimation is presented as a systematic process of structural geological analysis at the deposit-scale using drill-sampled grade data. The initial step in this process is to use Maximum Intensity Projection (MIP) rendering to interpret axial symmetry and its orientation from the grade interval mid-points at the deposit-scale, thus reducing the modelling process's degrees of freedom to only three—estimating the prolateness of the grade or lithological distribution. This approach contrasts with the brute-force methods for assessing modelling uncertainty because the axial direction is fixed to the down-plunge orientation, thus eliminating from the outset, structurally implausible geometric configurations and unrealistic geological scenarios common in brute-force methods. Adopting this new approach of creating geological models means moving away from conventional mining industry methods that prioritise operational considerations in constructing resource estimates but fail to explain the geometric complexities of mineral deposits. We use experiments and a practical case study of a historical gold mine in Western Australia to highlight the significance of analysing the structural control of a gold deposit at the deposit-scale using raw grade data. Our research is based on anecdotal evidence suggesting that erroneous geological modelling leads to unforeseen Mineral Resource downgrades. However, we cannot confirm this hypothesis because there have been few, if any, independent public inquiries into Mineral Resource downgrades. To establish the underlying reasons for significant resource downgrades with certainty, impartial investigations (modelled on accident investigations in the aviation industry) are imperative. There is a general lack of incorporating structural geological knowledge in creating resource models, which can lead to poor outcomes such as Mineral Resource downgrades. Structural geological analysis of drill-sampled raw grade data allows the structural controls on a deposit to be better understood. We offer a simple workflow for understanding and modelling these patterns. [ABSTRACT FROM AUTHOR]

Unless properly managed, acid sulphate soils can exert a range of negative environmental impacts, including soil acidification and mobilization of metals and metalloids. Incorporation of organic matter in the form of plant mulches can substantially neutralize sulphuric soils and prevent the oxidation of sulphidic soils. These positive effects of dead plants are largely mediated by bacterial reduction of sulphates to sulphides, using the organic matter as a microbial nutrient source. However, very little is known about the effects of live plants on acid sulphate soils. In this study, we compared pH, Eh and sulphate content of sulphidic and sulphuric soils that were not planted (i.e. unplanted) with those soils planted with the following three common wetland plants: Phragmites, Melaleuca and Typha. Each of these plants is capable of growth in aerobic and flooded soils. In all our experiments, the presence of plants correlated with an increase in soil acidification rather than neutralizing soil acidity when compared to unplanted controls. The mechanism for this appears to be transport of oxygen down the soil profile by aerenchymatous tissue formed in these species, and the release of oxygen into the rhizosphere. [ABSTRACT FROM AUTHOR]