Abstract
This paper reports a nonlinear controlling function of geological features on magmatic–hydrothermal mineralization, and proposes an alternative method to measure the spatial relationships between geological features and mineral deposits using multifractal singularity theory. It was observed that the greater the proximity to geological controlling features, the greater the number of mineral deposits developed, indicating a nonlinear spatial relationship between these features and mineral deposits. This phenomenon can be quantified using the relationship between the numbers of mineral deposits N(ε) of a D-dimensional set and the scale of ε. The density of mineral deposits can be expressed as ρ(ε) = Cε−(De−a), where ε is the buffer width of geological controlling features, De is Euclidean dimension of space (=2 in this case), a is singularity index, and C is a constant. The expression can be rewritten as ρ = Cεa−2. When a < 2, there is a significant spatial correlation between specific geological features and mineral deposits; lower a values indicate a more significant spatial correlation. This nonlinear relationship and the advantages of this method were illustrated using a case study from Fujian Province in China and a case study from Baguio district in Philippines.
Highlights
The formation of magmatic–hydrothermal ore deposits is strongly controlled by geological features, such as intrusions and faults; these provide the heat sources and hydrothermal pathways required for magmatic–hydrothermal mineralization
The spatial associations between Yanshanian intrusions/C–P Formation and mineral deposits were more significant than in the case of NNE–NE-trending faults. When comparing these singularity indices with the Student’s t values, it can be noted that the greater the Student’s t value (>1.96), the lower the singularity index a (
Log–log plots of the buffer width of these geological features versus the density of mineral deposits (Fig. 3) show that the gradients of the fitted lines were −0.42, −0.08, −0.41, and −0.46; the obtained values of the singularity indices for NE-trending faults/fractures, NW-trending faults/fractures, batholithic pluton margins, and porphyry pluton contacts were 1.58, 1.92, 1.59, and 1.54, respectively (Table 1). These results suggest that the controlling functions of NE-trending faults/fractures, batholithic pluton margins, and porphyry pluton contacts on Au mineralization are nonlinear, and these three geological features are spatially correlated with Au mineralization due to their singularity indices being
Summary
The formation of magmatic–hydrothermal ore deposits is strongly controlled by geological features, such as intrusions and faults; these provide the heat sources and hydrothermal pathways required for magmatic–hydrothermal mineralization. The methods used to express and quantify the controlling function of these geological features on magmatic–hydrothermal mineralization are critical for understanding the formation of ore deposits and for assigning the weights to these features. These methods have not been extensively researched. C is equal to W+−W−; W+ and W− are positive and negative weights used when a geological controlling feature is present or absent, respectively; S(c) is the standard deviation of c Calculation of these parameters is described by Bonham-Carter et al.[2]. The aim of this paper is to report a nonlinear controlling function of geological features on magmatic–hydrothermal mineralization, and to describe an alternative method to measure the spatial association between geological features and mineral deposits using multifractal singularity theory
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