## 2 Materials and Methods  
### Geological Settings  
The Mojiang area is located in Yunnan province in the southwest of China. It extends ca. 56 km in the east-west corresponding to the longitude from E 101.44\({}^{\circ}\) to E 101.99\({}^{\circ}\) and ca. 65 km in the north-south corresponding to the latitude from N 23.24\({}^{\circ}\) to N 23.83\({}^{\circ}\), covering an area of ca. 3626 km\({}^{2}\) (Figure 1). Public network data indicates that the topography slopes from north to south, with significant elevation differences in this area. The landforms are characterized by medium-cut middle mountain hills valleys. The climate features mild seasonal temperature differences, with no extreme heat in summer and no severe cold in winter. The average annual sunshine duration is ca. 90 days, and the average annual precipitation is ca. 1345 mm. Figure 1: Regional geological map of the Mojiang area (after the 1:1,000,000 geological map of F47 by China Geological Survey). (1) Quaternary: sand, gravel, clay; (2) Pliocene: clay, clayey limestone; (3) Lower Cretaceous: yellow-gray, purplish-red sandstone interbedded with purplish-red and gray-green mudstone, gravelly sandstone, calcareous mudstone; (4) Upper Jurassic: yellow-gray, grayish-purple sandstone, purplish-red, gray-green mudstone, calcareous mudstone interbedded with mudstone-limestone; (5) Middle-Upper Jurassic: purplish-red mudstone, siltstone, calcareous mudstone interbedded with gray-green mudstone and mudstone-limestone, sandstone; (6) Middle Jurassic: yellow-gray sandstone, mudstone, purplish-red mudstone, interbedded with calcareous mudstone, mudstone-limestone; (7) Triassic: gray-white sandstone, black shale interbedded with limestone, purplish-red mudstone, siltstone interbedded with mudstone-limestone, fine sandstone;  
(8) Triassic: meta-conglomerate, sandstone, phyllite; (9) Upper Triassic: mudstone (slate), limestone, sandstone interbedded with siltstone, mudstone-limestone; (10) Upper Triassic Waigucun Formation: purplish-red, gray-green conglomerate, sandstone, mudstone, occasionally interbedded with mudstone-limestone; (11) Paleozoic: slate, phyllite, quartzite interbedded with green schist, crystalline limestone; (12) Upper Permian: Sandstone, siltstone, mudstone with coal seams, occasionally with tuff and volcanic rocks; (13) Middle-Upper Permian: sandstone, siltstone, mudstone with limestone, tuff, and andesite, locally containing coal; (14) Carboniferous-Devonian: sandstone, shale interbedded with thin layers of limestone and tuff; (15) Middle-Upper Devonian: quartz sandstone, graywacke interbedded with siltstone shale; (16) Silurian: black and gray-green shale, sandstone with a small amount of limestone; (17) Upper-middle parts of Kunyang Group of Mesoproterozoic: lower purple slate, dolomite, slate, metamorphic sandstone, upper dolomite interbedded with calcareous slate; (18) Dahongshan Group of Paleoproterozoicoic: microcrystalline schist, quartzite, marble with slate and metamorphosed intermediate-basic volcanic rocks; (19) Ailaoshan Group of Paleoproterozoicoic: genesis, schist, marble interbedded with amphibolite, granulite, and graphite schist; (20) Granite; (21) Lhezolite; (22) Lithological boundary; (23) Fault; (24) Ni deposit. The exposed strata in the Mojiang area trend NW direction and include Paleoproterozoic, Silurian, Devonian, unclassified Paleozoic, Permian, Triassic, and Jurassic periods (Figure 1). The lithology of these strata is described briefly in Figure 1. The main magmatic rocks are felsic and ultramafic intrusions [18; 19]. The felsic intrusions are mainly distributed in the northeast of the area and distributed in the NW direction. The ultramafic intrusions include four ophiolite bodies extending in an NNW direction [19; 20]. The ultramafic ophiolite body located in the central is Jinchang ultramafic ophiolite body, which is mainly composed of serpentinized harzburgite [20; 21].