## 4 Result
### Alteration Types
#### 4.1.1 Porphyry Alteration  
Potassic Alteration usually occurs in the central part of alkaline porphyry (Figure 4), which typically displays a pale red color (Figure 5A) and mainly contains hydrothermal orthoclase (K-feldspar) and hydrothermal biotite (Figure 5B,C), as well as a small amount of quartz, sericite (Figure 5B,C) and some metal minerals such as pyrite, chalcopyrite, molybdenite, native gold, etc. The potassic alteration has certain characteristics: (1) plagioclase or orthoclase phenocysts are replaced by hydrothermal orthoclase or hydrothermal biotite, forming a ring edge of hydrothermal orthoclase (Figure 5B) and even replacing them completely; (2) hydrothermal orthoclase or hydrothermal biotite replace groundmass; (3) hydrothermal orthoclase or hydrothermal biotite fill in fractures (Figure 5C); (4) a small degree of sericitic and pyrite alteration telescopes on potassic alteration. Figure 4: The mineralization-alteration zones of selected geological sections in the Beiya deposit. The description of the mineralization and alteration zones identified numerically is given in the text (C1 and C2 sections are modified after [PERSON] et al. [31]). Figure 5: Alteration characteristics in the Beiya deposit. (**A**)—potassic alteration QSP, with light red to pink in color; (**B**)—hydrothermal orthoclase (K-feldspar) and hydrothermal biotite occur, and the hydrothermal orthoclase are replaced by the later sextictics; (**C**)—hydrothermal biotite fill in fracture; (**D**)—phyllic alteration QSP; (**E**)—quartz occur in fracture and cut the previous orthoclase; (**F**)—quartz, sericide, and pyrite are developed in phyllic zone; (**G**)—propyl alteration QSP, with light greenish in color; (**H**)—chloride and some carbonate minerals are developed in propylitic zone; (**I**)—chlorite replace groundass; (**J**)—argilic alteration QSP; (**K**)—kaolinite metsonamidine orthoclase along the edge; (**L**)—kaolinite completely metsonamidine plagioclase; (**M**)—endoskarn, with greenish-gray in color; (**N**)—template are developed in skarn; (**O**)—tremolite and magnetite are developed in skarn; (**P**)—unaltered limestone of the Beiya Fm. ; (**Q**)—magnetization and limonization limestone of the Beiya Fm. ; Bt = Biotite, Or = Orthoclase, Beriya Fm. ; (**R**)—silicification and calcification limestone of the Beiya Fm. Bt = Biotite, Or = Orthoclase, Ber = Sericide, Qtz = Quartz, Chl = Chlorite, Cb = Carbonate mineral, KIn = kaolinite, Tr = Tremolite, Py = Pyrrite, Mag = Magnetite. copyrite, bornite, native gold, etc. The phyllic alteration is characterized by (1) lots of sericite and quartz occurring, replacing mineral phenocryst and groundmass; (2) sericite or quartz in veins or veinlet fillings (Figure 5E,F); (3) large amounts of pyrite disseminated or in quartz sulfide veins or veinlets. Phyllic alteration is later than potassic alteration, in which the new hydrothermal alteration minerals are cut by those of the former. For instance, the quartz vein that formed in the fracture cut the previous hydrothermal orthoclase (Figure 5E). Propylitic alteration usually occurs on the outside of phyllic alteration (Figure 4). These propylitic rocks are characterized by a light green color (Figure 5G), mainly containing epidote and chlorite (Figure 5H,I), with a small amount of carbonate minerals (Figure 5H), sericite, quartz, pyrite, etc. The propylitic alteration has the following characteristics: (1) many chlorites and epidotes are generated, replacing mineral phenocryst and groundmass (Figure 5H,I); (2) some carbonate minerals such as siderite and calcite occurred; (3) the content and variety of metal minerals are reduced, while pyrite veins or veinlets are dominant. Argillic alteration occurs on the outside and upside of porphyry alteration (Figure 4). The argillic rocks are predominantly light white (Figure 5J) and contain mainly kaolinite (Figure 5K,L), as well as a little sericite and quartz.