# Genesis and Magmatic Evolution of the Gejiu Complex in Southeastern Yunnan, China
## 4 Results  
### Petrography  
Based on field observations, structural characteristics, and petrographic features such as mineralogical and lithological compositions under the microscope (Figure 3), all samples were classified into four categories. The following is a summary of the petrological analysis. (1) Granite and granite enclaves: The granites within the study area were primarily classified into two types: equigranular and porphyritic varieties. Equigranular granites were characterized by medium-to-coarse-grained textures and hypodiomorphic equigranular fabrics. Porphyritic granites exhibited medium-to-coarse-grained textures with hypodiomorphic inequigranular or porphyritic fabrics. Additionally, medium-to-coarse-grained pinkish K-feldspar granites, located east of the Shenxianshui area, displayed extensive alteration features, including K-feldspathization, chloritization, and intense kaolinization. All analyzed granite samples shared similar mineralogical compositions, dominated by quartz (\(\sim\)30%), K-feldspar (10-25%), plagioclase (\(\sim\)10%), amphibole (\(\sim\)15%), and biotite (\(\sim\)10%), with accessory minerals (\(\sim\)10%) such as zircon, apatite, titanite, and magnetite (Figure 3a). Granitic enclaves, which are predominantly distributed in the Jiasha area, displayed coarse-grained textures and euhedral-to-subhedral fabrics. Their mineral assemblages consisted of quartz (\(\sim\)40%), plagioclase (\(\sim\)30%), amphibole (\(\sim\)15%), and biotite (\(\sim\)10%), with minor accessory phases including zircon, apatite, and monazite (Figure 3b).  
(2) Gabbro: The gabbro samples were gray-black in color. The Shenxianshui gabbro was primarily composed of pyroxene (40%), plagioclase (40%), and biotite (20%), displaying a granular texture (Figure 3c). The Jiasha gabbro contained pyroxene (35%), plagioclase (40%), amphibole (15%), and biotite (10%). Amphibole exhibited fibrous textures, and plagioclase showed alteration features.  
(3) Diorite and monzonite: The diorite samples were gray-black, predominantly exhibiting a medium-to-fine-grained texture and a massive structure. The main minerals were plagioclase (40%), amphibole (25%), biotite (15%), K-feldspar, and quartz (20%). Minor alteration minerals such as chlorite and sericite were also present. Plagioclase was hypodiomorphic granular, with some grains showing intense sericitization, and amphibole was partially chloritized (Figure 3d). Monzonite displayed a gray-black medium-grained texture and a massive structure, with quartz (20%), plagioclase (50%), K-feldspar (25%), and amphibole (5%). Occasionally, large feldspar grains were observed, along with tourmaline, calcite, and fluorite nodules (Figure 3e).  
(4) Syenite: Nepheline sysenite exhibited a gray-green medium-to-coarse-grained texture and massive structure. The primary minerals were nepheline (50%), alkaline amphibole (20%), K-feldspar (20%), alkaline pyroxene (5%), and biotite (5%). Accessory minerals included titanate, zircon, and ilmenite. Nepheline formed tabular anhedral crystals with cloudy surfaces and microfractures (Figure 3f). Amphibole was euhedral to subhedral, alkaline feldspar was subhedral granular, and biotite was euhedral to subhedral.