## 3 Geologic Setting  
The Sanjiang (Three Rivers) region is named due to it being drained by three major rivers: the Jinshajiang, Lancangjiang, and Nujiang [17; 30]. The region is the eastern segment of the Tethys-Himalayan tectonic domain, covering the southeastern part of the Tibetan Plateau and the western part of Yunnan Province (Figure 1) [28; 30; 31; 32; 33; 37]. The Sanjiang region lies adjacent to the South China block and Songpan-Garze accretionary complex in the east and the West Burma block in the west [17; 30; 31]. It is composed of seven blocks, including the Simao block, Baoshan block, Tengchong block, Zhongza block, East Qiangtang block, West Qiangtang block, and Lhasa block (Figure 2). Some sutures are preserved in the Sanjiang region as evidence of the tectonic evolution of the Tethys Ocean, such as Longmucuo-Shuanghu Changning-Menglian, Jinshajiang, Ailaoshan, Garze-Litang, and Nujiang (Figure 2). Among them, the Longmucuo-Shuanghu suture, Changning-Menglian suture, Jinshajiang suture, and Ailaoshan suture are all north-south sutures (Figure 2) [18; 30; 38; 39; 40; 41; 42].  
Along with the process of Tethys accretionary orogen and collisional orogen, a series of minerals associated with the Tethys orogenic belt developed in the southwestern Sanjiang Tethys orogenic belt. The main mineral types can be divided into eight categories, including volcanogenic massive sulfide (VMS) Pb-Zn-Cu-Ag deposits, porphyryv Cu-(Mo-Au) deposits, porphyryv Mo-W(-Cu) deposits, magmatic-hydrothermal Sn-W deposits, magmatic-hydrothermal Pb-Zn-Cu-Ag deposits, Mississippi Valley Type (MVT) Pb-Zn deposits, hydrothermal Au deposits and orogenic Au deposits (Figure 1) [17; 34]. The porphyry Cu-(Mo-Au) deposits concentrate in the Jinshajiang-Honghe alkali-rich porphyry Cu-(Mo-Au) deposits belt and the Garze porphyryv Cu-(Mo-Au) deposits belt on the southern edge of the Yidun Island arc [43; 44; 45]. The mineralization era of the Jinshajiang-Honghe alkali-rich porphyry Cu-(Mo-Au) deposits belt was concentrated in the Cenozoic and can be divided into the Jinshajiang porphyry belt in the north and the Honghe porphyry belt in the south. The porphyry deposits in the North belt are mainly Cu-(Mo-Au) deposits [46; 47; 48]. The porphyry deposits in the south belt are mainly Au-(Cu-Mo) deposits [49; 50; 51; 52]. The mineralization age of the Garze porphyry Cu-(Mo-Au) deposits belt on the southern edge of the Yidun Island Arc is Late Triassic [45; 53]. Porphryv Mo-W(-Cu) deposits are developed in the southern margin of the Yidun Island Arc of the Sanjiang orogenic belt and the contact position is between the Garze-Litang combined zone and the Xiangcheng-Lijiang land margin depression at the western margin of the South China Craton [45; 54]. These Late Cretaceous deposits distributed in a nearly north-south direction are large porphyry Mo-W(-Cu) deposits [45; 54; 55; 56]. The magmatic-hydrothermal Sn-W deposits are located in the Tengchong-Baoshan block, the northern part of the Yidun volcanic arc, and the Changning-Menglian suture. The age span of the deposits ranges from Early Cretaceous, Late Cretaceous, and Paleocene [29; 57].  
Figure 2: Geological map of the Sanjiang Tethyan Orogen showing the distribution of Early Paleozoic to Cenozoic igneous rocks and major ore deposit. Adapted with permission from Ref. [17]. Copyright 2016 ELSEVIER.