## 5 Disscussion
### Two Mesozoic Stages of Magmatism and Mineralization in XHLOF
#### 5.3.2 Two Mesozoic Stages of Magmatism in XHLOF  
The Jianfengling and Laiziling plutons are representative intrusions of the XHLOF and are also the main metallogenic granites. The ages of the deep coarse-grained biotite granite and the shallow albite granite of the Laiziling pluton are 155 \(\pm\) 2 Ma (MSWD = 0.77) [29] and 150.88 \(\pm\) 0.55 Ma (MSWD = 0.77) [28]. The zircon U-Pb weighted mean age of the Jianfengling biotite granite is 160.7 \(\pm\) 2.2 Ma (MSWD = 0.8) [65]. The weighted mean age of zircons from the concealed biotite granite in the Xianghualing tin deposit is 150.37 \(\pm\) 0.94 Ma (MSWD = 0.113) [28]. The metallogenic ages ranged from 161 Ma to 154 Ma using polyhedente Re-Os dating and mica Ar-Ar dating [20; 21]. The above data indicate that the magmatism related to the mineralization in the XHLOF mainly took place during 160-150 Ma.  
The zircon U-Pb dating yielded a Concordia age of 87.75 \(\pm\) 1 Ma for the concealed granite in the Laohuya deposit, which is completely different from the existing age data. According to the observed cut-through relationship that the steep hydrothermal vein-type orebody cut through the stratiform-like cassiterite-sulfide orebody (Figure 14), this paper  
Figure 13: Discrimination diagrams of magmatic zircon and hydrothermal zircon.  
suggests that another magmatic-metallogenic activity may exist in the XHLOF, which is represented by the Late Cretaceous LG and the steep hydrothermal vein-type orebody.  
Even extended to the entire Nanling region, the Late Jurassic stage is the main stage of tungsten-tin-related magmatism and mineralization, which is also concentrated in the 160-150 Ma range and is fully consistent with the XHLOF, such as the Qianlishan intrusion and the adjacent Shizhuyuan tungsten-polymeretallic deposit [4; 5; 6; 7], the Qitianling intrusion [24] and related Furong tin deposit [23], the Yaogangxian intrusion [19] and the related tungsten deposit [18], the Xihuashan intrusion [8; 10] and the related tungsten deposit [9], and the Taoxikeng intrusion and the related tungsten deposit [14]. Deposits formed during the Cretaceous stage (130-90 Ma) include the Jiepailing tin deposit (91-89 Ma, [17; 66]), the Shanhu tin deposit [67], and the Yanbei tin deposit (133-130 Ma, [68]). Among these, the Jiepailing is the closest to the XHLOF in distance, which is about 70 km east of the XHLOF. The chronological data of the two phases in the XHLOF and the Nanling area are highly consistent, which indicates that the magmatism of the Late Cretaceous stage in the XHLOF is reasonable, and it is the product of the same specific tectonic setting in the Nanling region.  
Figure 14: Photos of the cut-through relationship between the steep sulfide-bearing quartz vein and the stratiform-like cassiterite–sulfide orebody in the Laohuya mining area.  
In the XHLOF, the structural and stratigraphic conditions in the Late Cretaceous were basically the same as those in the Late Jurassic, and the magmatism in the Late Cretaceous was also highly evolved A-type granitic magmatism that was similar to the magmatism relating to tin-polymeretallic mineralization in Late Jurassic, which probably contributed to another tungsten-tin polymetallic metallogenic system with the Late Cretaceous granitoid as the metallogenic center.