## 6 Discussion  
### Distribution of Different Deposits Constrained from Zircon Hf-Isotopic Mapping  
Previous knowledge of the lithospheric structure and deep tectonic framework of the Sanjiang Tethys orogenic belt was mainly speculated by geophysical means [37; 173] but lacked material information support. Neutral-acid rocks are widely developed in the Sanjiang Tethys orogenic belt. These zircon Hf isotopes can be used as a \"rock probe\" to trace the petrogenesis, so as to reflect the material composition and temporal and spatial changes in different parts of the crust. In this study, based on the contour map of granitic zircon \(\epsilon\)Hf(t) values, we can demonstrate the spatial distribution and spatial transformation of the model ages of deep source rocks in the crust, and thus determine the spatial distribution and temporal evolution of different terranes. Zircon Hf isotope mapping shows that there are widespread negative \(\epsilon\)Hf(t) values in the Tengchong block, Baoshan block, and Changing-Menglian suture in the west of Sanjiang Tethys orogenic belt and Zhongzan block Yidun island arc belt in the east, which correspond to two-stage model ages TDM\({}^{\text{c}}\) > 1.2 Ga, suggesting that these terranes may be ancient, locally modified crustal blocks. Spatially, the higher \(\epsilon\)Hf(t) values correspond to a younger TDM\({}^{\text{c}}\) age in the east Qiangtong block, the southern part of the Yidun Island arc, the Simao block, and the southern margin of the South China Craton, which are located in the eastern part of the Sanjiang Tethys orogenic belt, indicating that the petrogenesis of these regions is dominated by newly formed mantle-derived components. Combining Hf isotope mapping results with geophysical exploration, we can construct a three-dimensional lithospheric structure at the scale of the terrane. [PERSON] [37] speculated that the crust of the southwest Sanjiang Tethys orogenic belt shows a \"stepwise\" thickening trend from west to east and from south to north. The 3D model map from the terrane to the South China Craton shows that the Tengchong-Baoshan block has an approximately 35 km thick crust with negative \(\epsilon\)Hf(t) values and old model ages (TDM\({}^{\text{c}}\) values), indicating the presence of older crustal components and remelted crustal components in the magmatic rocks of the region [17; 34]. In contrast, the continental crust of the eastern South China Craton is about 45 km thick and the magmatic zircons have positive \(\epsilon\)Hf(t) values and young model ages (TDM\({}^{\text{c}}\) values), indicating the incorporation of juvenile mantle-derived material in the magma source area of the region [17; 34]. Therefore, based on zircon Hf isotope regional mapping, the Sanjiang region shows temporal and spatial heterogeneity of the crust, which is bounded by the Longmucuo-Shuanghu suture and the Changning-Menglian suture. The ancient crust of negative \(\epsilon\)Hf(t) values is mainly in the west and the juvenile crust of positive \(\epsilon\)Hf(t) values is mainly in the east. The zircon Hf isotope mapping of granitic rocks in the Sanjiang region reveals that the mineralization system in the Sanjiang region is controlled by the crustal properties in the region, and the differences in crustal properties constrain the distribution pattern of different mineralizing elements (Figure 3). The results of zircon Hf isotope mapping prove that the properties and composition of the crust are closely related to the formation and spatial distribution of polymetallic deposits. Firstly, all porphyry Cu-(Mo-Au) are located within the juvenile crustal blocks with high \(\epsilon\)Hf values. This is consistent with the Cu-ore-forming magmas in the Jinshajiang-Ailaoshan suture mainly sourced from the juvenile lower crust [94].