## 2 Geological Settings
### Deposit Geology  
Due to the harsh working environment, the basic geological work in the study area has been limited to small-scale investigations, with only some detailed geological mapping conducted on the already discovered ore deposits. Figure 2 is a simplified geological map of the study area, modified from a 1:250,000 regional geological map. The geological features shown in Figure 2 are relatively rough and can only display larger geological units and structural backgrounds, lacking detailed information on ore deposit scales. The exposed strata in the area mainly include the pre-Ordovician Songduo Group (AnOsd), the Paleogene Linzizong Group Pana Formation (E\({}_{2}\)P), and Quaternary loose deposit, flood, and fluvial sediments (Q). The AnOsd is distributed in the southeastern part of the study area, with rock types mainly consisting of quartzite, quartz-mica schist, and others. The strata have undergone deep metamorphism, with hard and resistant rocks that are less susceptible to weathering, often forming steep and rugged terrain. E\({}_{2}\)P is only distributed in the northeastern corner of the study area, consisting of a suite of intermediate-acidic volcanic rocks and volcaniclastic rocks. The volcanic rocks unconformably overlie the older strata and rocks, with an angular relationship. Large areas of intrusive rocks have developed in the study area, roughly bounded by a diagonal line from the southwestern to the northeastern corner. Except for Quaternary cover, almost the entire northwestern part of the study area is composed of Mesozoic intermediate-acidic intrusive rocks, with rock types mainly consisting of biotite granite and gabbro. This suite of intrusive rocks is the source rock for the mineralization of the already discovered ore deposits in the area. Structurally, the mining area is located in the middle part of the Pangduo thrust fault zone [20], which is characterized by a set of near-NE-trending faults in the study area. Thanks to the many years of exploration work at the DZL deposit, the geological map of the DZL mining area (Figure 3a) provides more detailed geological information compared to Figure 2. The exposed strata in the mining area mainly include the Ordovician Songduo Formation (Songduo Fm. ), the Triassic Lubodaui Formation (Luobadui Fm. ), and Quaternary fluvial, flood, and glacial deposits. The Songduo Fm. is mainly distributed in the southeastern part of the mining area, with rock types primarily consisting of quartzite; the Lubodaui Fm. is distributed in the central and eastern parts of the mining area, with a main rock assemblage of slate, limestone, and dolomite, and a dip direction mainly towards the southeast, with dip angles between 60\({}^{\circ}\) and 85\({}^{\circ}\). A large area of Mesozoic intermediate-acidic intrusive rocks is exposed in the northwestern part of the mining area, with rock types mainly consisting of quartz porphyry, granite porphyry, and diorite. The main structural direction in the mining area is near-NE-trending, with a set of secondary structures developed in the SE and near-SN directions later on, and no obvious folds are observed on the surface. Figure 1: The location of the study area and its tectonic outline map (modified from [7]). (**a**) The location of the Himalayan orogenic belt. (**b**) The location of the Gangdese metallogenic belt. (**c**) The location of the Lhasa terrane and the characteristics of ore deposit distribution. IYZSZ—Yarlung Zangbo suture zone; BNSZ—Bangong–Nujiang suture zone; JSSZ—Jinsha River suture zone; SNMZ—Shiquanhe–Nam Too Melange zone; LMF—Luobadui–Milashan fault zone; SLS–southem Lhasa subterrane; CLS—central Lhasa subterrane; NLS—northern Lhasa subterrane. DZL—Dongzhongla deposit; LML—Longmala deposit; MYA—Mengya’a deposit; YGL—Yaguila deposit; SR—Sharang deposit. All the discovered ore bodies in the mining area are mainly hosted in the contact zone between the quartz porphyry or granite porphyry and the surrounding rocks (limestone or dolomite, etc.) (Figure 3b).