The nature of Paleoproterozoic basement in the northern Yangtze and its geological implication

Archean-Paleoproterozoic crystalline basements are sporadically distributed in the Yangtze Craton, but the fundamental problems about the formation and evolution of these Precambrian basements have not been completely solved. In this study, Precambrian basement rocks in the Feidong Complex provide an excellent opportunity for inspecting the evolution of the Yangtze Craton. It is composed mainly of Paleoproterozoic granitic gneiss (2470-2434 Ma), amphibolite (2482-2461 Ma) and potassic granite (2002-1963 Ma). Granitic gneisses show typical I-type affinity, their relatively enriched Nd-Hf isotopic components (epsilon Nd(t) = -1.3 to -1.2; epsilon Hf(t) = -5.2 to 1.1) indicate the Archean crustal growth (3.3-3.1 Ga) and subsequent reworking during Early Paleoproterozoic. Meanwhile, the arc-like geochemical signature as well as epsilon Nd(t) (3.1-3.8) and epsilon Hf(t) (-1.9-3.0) values in amphibolite reveal the interaction between lithospheric mantle wedge peridotite and slab-derived fluids. Early Paleoproterozoic magmatic activities in the Feidong Complex most likely occurred at convergent continental margin related to a subduction event. Furthermore, a comparison of crustal evolution in various Precambrian continental blocks scattered in the Yangtze Craton proves their independence prior to Paleoproterozoic. The potassic granites show typical S-type granites affinity with high Sr/Y, Rb/Sr ratios, their negative epsilon Nd(t) (-15.5 to -11.5) and epsilon Hf(t) (-12.8 to -7.7) values indicate the reconstruction of Archean continental crust related to continental collision. In conjunction with broadly coeval magmatism and metamorphism events distributed in Yangtze Craton, it is speculated that the orogeny is linked to the internal assembly and convergence event of Yangtze and Columbia supercontinent, respectively.

Automated summary

This study examines the Precambrian basement rocks in the Feidong Complex to understand the evolution of the Yangtze Craton. The results show that the granitic gneisses and amphibolites reflect the growth and reworking of the Archean crust, while the potassic granites are related to continental collision events.