## 4 Result
### Element Migration of Mineralization and Alteration Zone  
We adopting the equation of rock composition changing with volume change in the process of hydrothermal alteration proposed by [PERSON] [34] and [PERSON] [35; 36], to estimate the introduction and removal of elemental components from different alteration zone. [PERSON] [34] considered that some components in the rock were stable during the process of hydrothermal alteration, and [PERSON] [35; 36] established the corresponding equation of rock volume change, i.e., Equation (1):  
\[{\rm C_{i}}^{\rm A}={\rm M}^{\rm O}/{\rm M}^{\rm A}\ ({\rm C_{i}}^{\rm O}+ \Delta{\rm C_{i}}) \tag{1}\]  
For the immobile component, \({\rm M}^{\rm O}/{\rm M}^{\rm A}\) ratio is constant and \(\Delta{\rm C_{i}}=0\), so it can obtain Equation (2):  
\[{\rm C_{i}}^{\rm A}=({\rm M}^{\rm O}/{\rm M}^{\rm A})\ {\rm C_{i}}^{\rm O} \tag{2}\]  
\({\rm C_{i}}^{\rm A}\) and \({\rm C_{i}}^{\rm O}\) represent the concentration of a component in the rock after and before alteration, respectively; \({\rm M}^{\rm A}\) and \({\rm M}^{\rm O}\) represent the equivalent mass of rock after and before alteration, respectively; \(\Delta{\rm C_{i}}\) represents the change in concentration of a component in the rock after alteration. Assuming that the volume and mass of rock remain constant before and after hydrothermal alteration and immobile components in the rock do not vary in concentration, by plotting the values of the bivariable \({\rm C_{i}}^{\rm A}\) and \({\rm C_{i}}^{\rm O}\), we can create a straight line of the immobile component through the origin with a slope of \(\rm M^{O}/M^{A}\) and \(\rm\Delta C_{i}=0\), i.e., the Isocon line [35; 36]. As mentioned above, with the exception of propylitic, exoskarn, and endoskarn zones, the content of \(\rm P_{2}O_{5}\) is essentially constant between fresh rocks and altered rocks. For instance, the contents of \(\rm P_{2}O_{5}\) from unaltered and altered or mineralized limestones are 0.050 wt.% (n = 6) and 0.053 wt.% (n = 14), respectively; the same features are also shown between unaltered and altered quartz syenite porphyry, showing 0.060 wt.% (n = 3) of \(\rm P_{2}O_{5}\) in the former and 0.061-0.067 wt.% in the potassic, phyllic, and argillic zones. Therefore, \(\rm P_{2}O_{5}\) is selected as the immobile component by comparing unaltered samples with altered samples. The element migrations of six mineralization and alteration zones, including the wall-rock alteration zone, contact alteration zone, potassic zone, phyllic zone, propylitic zone, and argillic zone, are plotted by the Isocon method in Figure 7.  
Figure 7: Element migration characteristics of different alteration zones in the Beiya deposit. The slope of the solid line is 1, and the slope of the dashed line is seen in each diagram (**A**–**F**). In the wall-rock alteration zone, the Na\({}_{2}\)O, MgO, and CaO contents significantly decrease, while Fe\({}_{2}\)O\({}_{3}\)\({}^{*}\), SiO\({}_{2}\), K\({}_{2}\)O, and Al\({}_{2}\)O\({}_{3}\) increase. Compared to unaltered limestone, the content of metallogenic elements from altered or mineralized limestones increases, particularly for Pb and Zn, as well as rare earth elements. In the potassic zone, K\({}_{2}\)O, MgO, and Fe\({}_{2}\)O\({}_{3}\)\({}^{*}\) are slightly enriched, while SiO\({}_{2}\), Al\({}_{2}\)O\({}_{3}\), and CaO slightly decrease; the Cu, Mo, and Bi contents significantly increase, whereas Pb and Zn slightly increase; there is little change in the content of Na\({}_{2}\)O and rare earth elements. In the phyllic zone, Na\({}_{2}\)O, SiO\({}_{2}\), and Fe\({}_{2}\)O\({}_{3}\)\({}^{*}\) are enriched; however, K\({}_{2}\)O, Al\({}_{2}\)O\({}_{3}\), CaO and MgO decrease; it is similar to the potassic zone in that the Cu, Mo, and Bi contents significantly increase, while Pb and Zn slightly increase, as well as rare earth elements.