## 5 Analytical Result
### Major and Trace Elements  
The major element data of the volcanic rocks are shown in Table S2. Among them, nine samples were collected from the Qiaoxiaha mining area and Kurt town on the north bank of the Ulungu River, and 18 samples were compiled from the literature [45; 49]. All samples were Early-Middle Devonian intermediate to basic volcanic rocks. The samples were corrected for loss on ignition and volatile content, and the geochemical diagrams were constructed after normalizing the data to 100%. The volcanic rocks showed SiO\({}_{2}\) levels in the range of 42.79-57.22% (\(n\) = 27), with Na\({}_{2}\)O + K\({}_{2}\)O values of 0.52-7.74%; most samples had low K\({}_{2}\)O and high Na\({}_{2}\)O contents. Samples had CaO values of 3.59-11.5%, MgO values of 2.83-7.08% and Mg# values of 35.60-56.92. In a plot of Na\({}_{2}\)O + K\({}_{2}\)O versus SiO\({}_{2}\) (Figure 7a), the samples were both subalkaline and alkaline series. Samples of the subalkaline series are mainly basaltic andesite and andesite, with little basalt. Samples of the alkaline series are mainly brachybasalt, basaltic trachyandesite, and trachyandesite. According to the recommendations of the IUGS, samples falling into trachybasalt, basaltic trachyandesite, and trachyandesite fields can be further divided based on whether their Na\({}_{2}\)O \(-\) 2 \(\geq\) K\({}_{2}\)O. Therefore, samples of trachybasalt, basaltic trachyandesite, and trachyandesite can be further divided into hawaitie, potassic trachybasalt, mugearite, shoshonite, and benmoreite. From the above, in combination with the characteristics of field occurrence, hand specimens, and petrography, the specific rock names are shown in Table S2. In the AFM diagram, the subalkaline samples are mostly  
Figure 6: Zircon U–Pb concordia diagrams for the volcanic and volcaniclastic rocks examined in the Fuyun–Qinghe area. (**a**) Sample FY-80418, (**b**) sample FY-80618, (**c**) sample FY-80703, (**d**) sample FY-80704. calc-alkaline series (Figure 7b). Alkaline series sample points are present as the basalt and MA series in the SiO\({}_{2}\)-MgO diagram, while most subalkaline samples are MA rocks, with a few HMA rocks (Figure 7c). In the A/CNK-A/NK diagram, all samples pertain to the metaluminous series rocks (Figure 7d). In the plot of K\({}_{2}\)O versus SiO\({}_{2}\), the subalkaline samples belong to the low-K and middle-K CA series (Figure 7e). The alkaline samples (in the TAS diagram) in the SiO\({}_{2}\)-(Na\({}_{2}\)O + K\({}_{2}\)O - CaO) diagram show characteristics of A and AC series, while the subalkaline samples (in the TAS diagram) show AC, CA, and C series features (Figure 7f). Figure 7: (**a**) Total alkali versus silica (TAS) diagram ([59]; the boundary line between the alkaline and subalkaline series is from [60]). (**b**) AFM diagram (the dashed separation line is from [60]; TH = tholeitic; CA = calc-alkaline. b = basalt; fb = ferro-basal; ab = andesite basalt; a = - andesite;  
d = dacite; r = rhyolite.). (**c**) SiO\({}_{2}\) versus MgO diagram [61]. (**d**) A/CNK versus A/NK diagram [62]. (**e**) SiO\({}_{2}\) versus K\({}_{2}\)O diagram [63]. (**f**) SiO\({}_{2}\) versus (Na\({}_{2}\)O + K\({}_{2}\)O - CaO) diagram ([64]; A = alkaline series; AC = alkali-calcie series; CA = calc-alkaline series; C = calcite series). (Data of shaded fields are from [26; 65; 66], while data of black circles are from [45; 49], solid circles represent alkaline series, and hollow circles indicate subalkaline series). In addition, there were special labeled rock types such as sub-boninite (FY-80704, SiO\({}_{2}\) = 54.36%, > 52%, MgO = 6.24%, <8%, but higher than the boundary between HMA/MA, with 0.5% < TiO\({}_{2}\) = 0.57% < 1%, so we define it as sub-boninite), adakite (A01-2, etc., SiO\({}_{2}\) > 56%, Al\({}_{2}\)O\({}_{3}\)\(\geq\) 15%, MgO \(\leq\) 6%, Sr \(\geq\) 400 ppm, Y < 18 ppm), NEAB (FY-80618, etc., Na\({}_{2}\)O > K\({}_{2}\)O, TiO\({}_{2}\) > 1%, Nb/La > 0.5, Nb/U > 10), and HMA and MA (see above).