## 2 Materials and Methods  
### Geological Settings  
The Mufushan area is situated on the borders between Hunan, Jiangxi, and Hubei provinces in China, and has an area of ca. 13,750 km\({}^{2}\) (Figure 1) ranging from E 113\({}^{\circ}\)10\({}^{\prime}\) to E 114\({}^{\circ}\)19\({}^{\prime}\), and from N 28\({}^{\circ}\)35\({}^{\prime}\) to N 29\({}^{\circ}\)43\({}^{\prime}\), in this study, and is in a subtropical monsoon climate zone with humid climate. The average annual temperature is ca. 11 \({}^{\circ}\)C and the annual rainfall is ca. 1979 mm, most of which falls in summer according to the public network data. The topography in the Mufushan area is characterized by mountainous and hilly regions, with the main peak reaching an elevation of 1599 m.a.s.l. Soils are thinly developed, and the regolith thickness commonly varies from 0.5 to 5 m depending on the relief. The strata are mainly Neoproterozoic basement rock series, Paleozoic and Mesozoic sedimentary rock series, and Cenozoic alluvial sands [25]. The Neoproterozoic base rock series is mainly the Lengjiaxi Group, which is a set of low-grade metamorphic rocks such as sandy silty slate, metamorphic siltstone, and metamorphic complex sandstone. Sedimentary rocks are mainly distributed from northeast to southwest, and the main lithology is limestone, dolomite, siliceous rocks, sandstone, and siltstone. The alluvial sands are also distributed from northeast to southwest [25]. The lithology of these strata is described briefly in Figure 1.  
Figure 1: Location of the Mufushan studied area in China (**a**) and its geological map sketched after the H49 and H50 geological map from China Geological Survey (**b**). 1—Quaternary gravel, clay, sub sandy soil, and sub clay; 2—Tertiary conglomerate sandstone and quartz sandstone; 3—Cretaceous sandstone and gravel rock; 4—Triassic limestone, dolomite, and shale; 5—Devonian–Perman limestone, sandstone, siltstone, and shale; 6—Silurian silty shale, argillaceous sandstone, and fine sandstone; 7—Ordovician shale, shale, and siliceous rock; 8—Cambrian limestone, dolomite, siltstone, and shale; 9—Sinian siliceous rocks, carbonaceous shale, and limestone; 10—Neoproterozoicoic Lengiáxi Group slate, sandstone, phyllite, and metamorphic siltstone; 11—Mesoproterozoicoic Anlelin Formation tuff, tuffaceous slate, tuffaceous sandstone, and siltstone; 12—Late Yanshanian granite third stage intrusion; 13—Late Yanshanian granite second stage intrusion; 14—Late Yanshanian granite first stage intrusion; 15—Early Yanshanian granite; 16—Early Yanshanian graniodiorite; 17—Neoproterozoicoic two-mica plagioclase granite; 18—pegmatite; 19—fault; 20—water system; 21—Li deposit; 22—study area; 23—country; 24—township. Faults are very common in the study area, mainly trending N-E, NE-E, and N-W. The main N-E faults are the Yuetian-Wuli-Tongcheng fault and the Nanjing-Magang-Maishi fault in the center of the area. The main NE-E fault is the Renli-Hongqiao-Shiao fault in the southeast and the main N-W fault is the Nanjing-Yuetian-Changtang fault (Figure 1b). The magmatic activity is extensive in the area, with a granite outcrop area of ca. 2350 km\({}^{2}\). The Mufushan complex granite batholith is the main part of the regional magmatic rocks, and the main lithology is biotite granodiorite, two-mica monzogranite, and muscovite granite [26; 27] with multiple evolution stages [28]. The early Yanshanian granodiorites (\(\gamma\)\(\xi\)\({}_{5}^{2}\)) are mainly located in the eastern area of the Mufushan complex and the early Yanshanian granites (\(\gamma\)\({}_{5}^{2}\)) are mainly situated in the northeastern and the southwestern areas. The first stage of the late Yanshanian granites (\(\gamma\)\({}_{5}^{3}\)) is the main body of the complex, which is distributed in the central and the northwestern areas, while the second and the third stage of the late Yanshanian granites (\(\gamma\)\({}_{5}^{3}\) and \(\gamma\)\({}_{5}^{3}\)) are exposed sporadically in the complex (Figure 1b).