## 3 Results
### Elemental Within-Object Separability  
Figure 12 gives the object-based map of dimension (\(D_{2}\)) for the I-series and S-series elemental associations, respectively. We note that as the geochemical behaviors of the I-series elements are quite different from those of the S-series elements [30], so the object-based \(D_{2}\) map for all elements was not calculated here. From Figures 12 and 13, we have delivered three important observations as follows:  
1. The \(D_{2}\) values of the image objects containing the known ore spots vary in a wide range. For the I-series ore spots, the relevant dimension values fluctuate between 2 and 116 with a peak at 18 (The original \(D_{2}\) values were normalized to [0, 255]), and if we set \(D_{2}=116\) as the binarization threshold, the obtained anomalous area accounts for 98.63% of the total area. For the S-series ore spots, the relevant dimension values fluctuate between 1 and 32 with a peak at 14, and if we set \(D_{2}=32\) as the threshold, the obtained anomalous area will account for 78.93%.
2. As the histogram of the \(D_{2}\) map is usually right-skewed, so we empirically set the binarization threshold as the mode value + 1 \(\times\) standard deviation (for a standard normal distribution, 68.3% of data falls within one standard deviation of the mean, so we suppose that most, if not all, of the ore-spots would fall within the objects with the \(D_{2}\) value \(\leq\) mode + 1 \(\times\) standard deviation). For I-series elements, the threshold is 36, and for S-series, it is 34. Our purpose of image binarization is not to delineate the anomalous regions like Figures 9-11 do, but to delineate some highly confident non-anomalous objects. That is why in Figure 12, very few ore-spots fall in the colored patches. Naturally, by removing these non-anomalous objects from Figures 9 and 10, we can obtain a moderately reduced prospecting-target-area as shown in Figure 13.
3. In Figure 13 (upper), the anomalous area of I-series elements decreases to 43.045% of the total area, and the buffered anomalous area decreases to 61.608%. Only 5 ore-spots fall outside the reduced anomalous target area, which are Au, Pb-Zn, and Ag-Zn mineral spots. In Figure 13 (lower), the anomalous area of S-series elements decreases to 43.172% of the total area, and the buffered area decreases to 61.534%. Only 2 ore-spots fall outside the target area, which are fluorite and Pb-Zn spots.  
Figure 12: (**upper**) the object-based D\({}_{2}\) map for I-series elements with relevant ore spots (red squares) overlaid on it. (**lower**) the D\({}_{2}\) map for S-series elements with relevant ore spots overlaid on it. The green colored patches represent the delineated non-anomalous regions.  
Figure 13: (**upper**) the buffered anomalous regions (green colored patches edged with white, delineated by the 50% quantile) for I-series elements with relevant ore spots overlaid on it. (**lower**) the buffered anomalous regions for S-series elements with relevant ore spots overlaid on it. The ore spots not falling in the anomalous regions are labelled with their mineral species. Other legends in this figure are consistent with those in Figures 9 and 10.