Crustal maturation of the Yangtze Block during the Meso-Neoarchean

Abstract

The transition in felsic magmatism from Na-rich TTG suites to K-rich granites during the Mesoarchean to Neoarchean varies from craton to craton, marking the crustal maturation of the ancient continental crust. However, the crustal maturation history of the Yangtze Block is less well constrained due to poor exposure of Archean igneous rocks. In this study, we report a suite of late Mesoarchean mozo-granites from the SW Yangtze Block by providing new whole-rock major and trace element data, along with zircon U-Pb-Hf-O isotopic analyses, to constrain their petrogenesis. Zircon U-Pb dating shows that the studied mozo-granites have a crystallization age of ∼2.8 Ga. Geochemically, they exhibit high heavy rare earth element (HREE) contents and elevated K/Na ratios, typical of potassic granites derived from a shallow crust source. By integrating zircon Hf-O isotopes with thermodynamic modelling, we propose that these potassic granites were products of partial melting of an isotopically juvenile tonalitic crust. Furthermore, Bayesian change-point analysis detected a step increase in K/Na ratios at ∼2.7 Ga, which we interpret as the final stage of crustal maturation for the Yangtze Block. The intracrustal melting of TTG crust during the late Mesoarchean to Neoarchean contributed significantly to stabilization of the Archean continental crust during that period.