Geochronology and geochemistry of late Archean adakitic plutons from the Taishan granite–greenstone Terrain: Implications for tectonic evolution of the eastern North China Craton

Three groups of coeval plutonic rocks with different petrogenetic histories and geochemical features have been recognized in the Late Archean Taishan granite–greenstone terrain (TSGT) in the Eastern Block of the North China Craton. Zircon U–Pb dating indicate that they were emplaced contemporaneously at around 2.54 Ga. Geochemically, all of the three groups have high Al2O3 and Sr concentrations, low Y and Yb concentrations, and high Sr/Y and La/Yb ratios. They have high-SiO2 concentrations ranging from 57.56 to 67.98 wt%, indicating that they are typical high-SiO2 adakites. Granodiorites from the Taishan area and monzodiorites from the Zoucheng area have similar geochemistries. However, the Zoucheng monzodiorites have wider ranges in element concentrations than the Taishan granodiorites, with the latter having higher Mg numbers. The Yishui monzodiorites have higher MgO, Cr, and Ni concentrations, higher Mg numbers, and lower SiO2 concentrations, but similar REE and spidergram patterns to the Zouchang and Taishan intruisions. These geochemical features indicate that their parental magmas were all derived from the partial melting of a downgoing oceanic slab. The Zoucheng high-SiO2 adakitic rocks were probably produced by this process alone; however, the Taishan and Yishui high-Si adakite groups were formed by interaction between primary adakitic melts and overlying peridotitic mantle. In combination with coeval sanukitoid or low-SiO2 adakitic magmatism in the study area, the rock association indicates partial melting of a peridotitic mantle wedge that was metasomatized by adakitic melts and aqueous fluids derived from the subducting slab, the presence of these three high-SiO2 adakite groups supports a genetic model involving slab subduction in the Late Archean (∼2.54 Ga). The adakitic intrusions and associated rocks in the region postdate the earlier (∼2.7–2.6 Ga) voluminous TTG rocks suggesting that the angle of subduction changed from flat or shallow subduction, to steeper subduction likely related to the arrival of an oceanic plateau or thickened lithospheric keel at the subduction zone.

► The Eastern Block of the North China Craton (NCC) experienced an important magmatic event at ∼2.54 Ga. ► Geochemically, all granitoid rocks in the Taishan area have an affinity to adakites. ► The ∼2.54 Ga adakitic magmatism in the Taishan area are subduction-related. ► New data presented in this paper provide insights into the mechanism of crustal growth of the NCC in the late Archean.