## 5 Discussion  
### Petrological Classification and Petrogenesis  
As mentioned above, the large scale Early Cretaceous intrusive rocks (130-110 Ma) occurred in the Jiaodong Peninsula (Figure 1) [8; 33; 49]. Based on the lithology, geochemistry and geochronology, as well as their attitudes and spatial relationships, they can be traditionally divided into two subgroups [33; 49; 65; 73]: (a) the middle Early Cretaceous granitoids (132-122 Ma), mainly consisting of quartz monzonite, granodiorite and porphyritic-like monzogranite, and trending E-W to ENE (Figure 1b); and (b) the late Early Cretaceous granitoids (118-110 Ma), mainly including porphyritic-like monzogranites, granodiorite and ysenogranites, and trending NE to NNE (Figure 1b). The LA-ICP-MS zircon U-Pb ages obtained in this study provide the first precise geochronology on granitoids of the Dazeshan pluton and show ages of 119.6 \(\pm\) 1.3 to 120 \(\pm\) 1 Ma, which are between those of middle Early Cretaceous granitoids and late Early Cretaceous granitoids. Given that the granitoids in this study have the same petrology (Figure 3), attitude (Figure 1b), major-element composition (Figure 5), and REE and trace-element distribution patterns as those of the late Early Cretaceous granitoids (Figures 6 and 7), it is logical to infer that the Dazeshan pluton belongs to the late Early Cretaceous granitoids, and the crystallization age of c. 120 Ma probably represents the lower limit of emplacement ages for the late Early Cretaceous granitoids in the Peninsula. In addition, the LA-ICP-MS zircon U-Pb age of 119 \(\pm\) 2 Ma obtained for the dioritic microgranular enclaves is the same as those of the host granitoids (119.6 \(\pm\) 1.3 to 120 \(\pm\) 1 Ma), suggesting that the felsic and intermediate magmas were coeval. All the analyzed samples for granitoids of the Dazeshan pluton and their enclaves produced very low LOI (0.42-1.33 wt.%), as well as low La/Th ratios (1.0-6.4) and low to medium K/Sr ratios (49-160), suggesting that their element composition was not modified by the element migration [74; 75]; therefore, all the major- and trace-element data obtained can be used to interpret their petrogenesis. All the samples for granitoids of the Dazeshan pluton in this study have higher alkali contents (Na\({}_{2}\)O + K\({}_{2}\)O = 7.29-9.00%), and lower Al\({}_{2}\)O\({}_{3}\) (13.91-15.70%) and MgO values (0.76-1.11%) (Table A1; Figure 5) and flatter HREE patterns (Figure 7a) as compared to the calc-alkaline geochemical features that the typical adakitic rocks possess. In addition, they reflect a dominant calc-alkaline trend in the Na-K-Ca plot, instead of the trendhjemitic affinities of the adakitic rocks (Figure 9a). Furthermore, they show high Ba (>629 ppm), Sr (>451 ppm), K/Rb (>320) and LREEs (>132 ppm), as well as low Rb (<137 ppm), Th (<29 ppm), U (<2.4 ppm), Nb (<9.7 ppm), Ta (<0.9 ppm), Y (<10.9 ppm) and HREEs (<9.6 ppm) (Table 2), have no clearly negative Eu anomalies (Figure 6a) and are depleted in Nb in spidergrams (Figure 7a), which separate them from the traditional A-, M-, S- and I-type granites. However, the very high Sr (451-638 ppm) and Ba (1157-2842 ppm) contents indicate Dazeshan granitoids are similar to the high Ba-Sr granitoids proposed by [16], which are characterized by high Sr (>300 ppm) and Ba (>500 ppm) concentrations. Based on the difference in Sr and Ba contents, in the Sr-Rb-Ba plot, all the analyzed Dazeshan granitoids plot inside the domain of the high Ba-Sr granite [16], which is different from the low Ba-Sr granite (Figure 9b). Furthermore, the lack of clearly negative Eu anomalies (Figure 6a), the apparent fractionated REE patterns (Figure 6a) as well as the prominent depletion in Ti, P, Nb and Ta (Figure 7a), together with the very low Yb and Y concentrations against high (La/Yb)\({}_{\rm N}\) (32-50) and Sr/Y (50-79) ratios, are also similar to the typical geochemical characteristics of high Ba-Sr granitoids (Figures 6d and 7d) [20; 76]. Therefore, it is logical to classify the Dazeshan granitoids as high Ba-Sr granitoids.