## 4 Results and Discussion
### Geochemical Anomaly Map on Seven Levels Classification Method  
To contour the geochemical anomaly maps, which focus on the relatively high values (or the anomaly values) of elemental concentrations or other geochemical indices, the elemental concentrations are converted on the method of seven levels of classification using GBAL 1.0 software [16] into nine levels ranging from \(-1\) to 7. Here, the value of \(-1\) indicates that the concentration is less than the background value of a sample, and 0 indicates that the concentration is between the background value and the first anomaly level. Values of 1 to 7 represent the first to seventh levels, and the 7 th level indicates that the concentration is greater than or equal to the cutoff grade [16]. Then the data of anomaly levels are gridded with an interval space of 2 km. The grid parameters, including search radius, and interpolation method, were consistent with those used in the aforementioned 19-level fixed-value method for drawing the geochemical map. The anomaly grid data are contoured to derive the geochemical anomaly maps of Ni, Sn, and Li, respectively, with the same legend ranging from 1 to 7 (Figure 4). The background values (i.e., \(-\)1 and 0) are not illustrated in the geochemical anomaly maps. In Figure 4a, the anomaly regions of Ni are distributed as a belt in the NNW direction. The maximum anomaly level reached 7, indicating that Ni concentrations in certain stream  
Figure 4: Geochemical anomaly map of Ni (**a**) Sn (**b**) and Li (**c**) on the method of seven levels classification along with the geological map (**d**) in the Mojiang area. Detailed legend information is in Figure 1.  
sediments exceeded the defined cutoff grade (i.e., 2000 \(\mu\)g/g). The anomaly belt is consistent with the outcropped regions of the four ultramafic ophiolite bodies. This consistency indicates that the mineralization of Ni in the Mojiang area is closely related to the ultramafic ophiolite bodies. The two known Ni deposits, the Jinchang Ni-Au deposit, and the Mili Ni deposit, are located in the anomaly regions with the maximum anomaly levels of 6 and 4, respectively. However, in some regions with the anomaly level of 7, no Ni deposits have been reported till now although the Ni concentrations of stream sediments in these regions are higher than the cutoff grade. In addition, three anomaly regions have been delineated with an anomaly level up to 7 (Figure 4a), whose locations are consistent with those delineated from the Ni geochemical map (Figure 3a). Therefore, the three anomaly regions can be predicted as the Ni resource potential, which is also spatially consistent with the outcropped regions of the other three ultramafic ophiolite bodies except the Jinchang ultramafic ophiolite body, which formed the Jinchang Ni-Au deposit. Due to the research conducted by numerous experts and scholars, it has been confirmed that the Jinchang ultramafic ophiolite body is the ore-bearing ophiolite body of the Jinchang Ni-Au deposit [18; 19; 20; 21]. Therefore, the other three ultramafic ophiolite bodies that form an NNW linear distribution with the Jinchang ultramafic ophiolite body are predicted to be possible regions with Ni mineralization. In Figure 4b,c, the anomaly regions of Sn and Li are delineated sporadically. The maximum anomaly level of Sn is only 1 (Figure 4b), and the maximum level of Li is only 2. The results of Sn and Li are consistent with the geological facts that no deposits of Sn and Li have been discovered in this area. For a comparison with the Mufushan area, in which a geochemical anomaly map of Li was also drawn on the seven levels classified method [12], the highest anomaly level reaches level 4, and all known Li deposits are located in areas with anomaly levels not less than level 2. In a word, the four ultramafic ophiolite bodies are closely related to the Ni deposits.