## 1 Introduction  
East China, towards the west Pacific Ocean (Figure 1a), was transformed into an active continental margin due to Palaeo-Pacific plate subducting under East Asia at a shallow angle, which was initiated at c. 180 Ma [1; 2; 3], following the collision of the North China Craton (NCC) with the Yangtze Craton (YC) in the Middle-Late Triassic (244-220 Ma) [4]. The latter orogenesis resulted in the formation of the Jiaodong Peninsula, by the combination of Jiaobei terrane in the northwest with Sulut retrane in the southeast by way of the NE- to NNE-trending lithospheric-scale Wulian-Qingdao-Yantai Fault (WQYF), on the East China continental margin (Figure 1a,b) [5; 6]. The Mesozoic tectonic evolution in the Jiaodong Peninsula was closely associated with the Palaeo-Pacific plate subduction [7; 8], the varying velocity, angle, and direction of which caused the crustal deformations and changed the geodynamics of the overlying East China continental margin [8; 9]. In particular, it has been suggested that a tectonic transition occurred in the Jiaodong Peninsula because of the changes in the direction of Palaeo-Pacific plate subducting during the late Early Cretaceous [8; 9; 10; 11]. A shift of this period from extension to transmission, corresponding to a change from SW to NW in the direction of Palaeo-Pacific plate subducting during c. 125-122 Ma [8], has been inferred from the development of basins, extension-related igneous rocks and gold deposits in the Jiaodong Peninsula [8; 10; 11]. However, it was suggested that the stress regimes shifted from transmission to extension at c. 120 Ma, which was indicated by the sinistral to normal movement that the Tan-Lu Fault (TLF) experienced [12]. Furthermore, fault-slip data from the Jiaobei terrane showed an overall extensional tectonic regime during Early Cretaceous only with the extensional direction rotating from E-W to NW-SE at c. 120 Ma [13], corresponding to a change of the Palaeo-Pacific plate subduction direction from WNW (139-122 Ma) to NW (121-95 Ma) [14]. Figure 1: (**a**) Simplified tectonic map of East China illustrating the locations of Palaeo-Pacific subduction zone and Jiaodong Peninsula. Adapted with permission from [15]. (**b**) Simplified geological map of the Jiaodong Peninsula illustrating the major faults, large-scale Mesozoic magmatism, and typical gold deposits. Adapted with permission from [6]. Main faults: TLF, Tan-Lu Fault; WQYF, Wulian-Qingdao-Yantai Fault. High Ba-Sr granitoids, occurring in Phanerozoic (especially Early Cretaceous and Tertiary) orogenic belts globally [16; 17; 18], were first defined by [16] based on their geochemical features, which are marked by high Ba (>500 ppm), Sr (>300 ppm), LREEs and K/Rb, as well as low Rb, U, Th, Ta, Y and HREEs, with strong Nb depletion and insignificant Eu anomaly [16; 19; 20]. It has been proposed that the genetic mechanisms for high Ba-Sr granitoids include the partial melting of subducted ocean plateau resulting from mafic high Ba-Sr magma underplating [16], partial melting of metasomatized lithospheric mantle by asthenosphere-derived carbonatitic [16] or continental slab-derived melts [19; 20], partial melting of mafic lower crust involving enriched mantle-derived magmas [18; 21], mixing of acid and basic magmas produced from lower crust and enriched mantle, respectively [22; 23], and crystal fractionation from the associated enriched lithospheric mantle-derived alkaline magmas accompanied with minor crustal assimilation [24; 25; 26]. The variable origins of high Ba-Sr granitoids play an important role in revealing the tectonic evolution of orogenic belts [27]. Mesozoic giant igneous magmatism in Jiaodong Peninsula is one of the principal geological events closely associated with Palaeo-Pacific plate subducting [28; 29]. In particular, the Cretaceous giant igneous magmatism was coincident with the shift of Palaeo-Pacific plate drifting [8]. Furthermore, it is noted that a great number of high Ba-Sr granitoids (c. 162-110 Ma) have been discovered in the Jiaobei terrane [30; 31].