Metamorphic P-T-t Evolution of Granulite in the Yishui Area: New Insights into the Tectonic Evolution of the Eastern Block, North China Craton

Abstract

The Yishui complex, located in the western Shandong area of the North China Craton, is representative of the Archean crystalline basement of the North China Craton to explore the early tectonic-thermal evolution history of the Earth. Detailed petrography, mineral chemistry, metamorphic evolution and zircon U-Pb dating are presented for felsic granulite and two-pyroxene granulite from the Yishui complex to contribute to new insights into the Neoarchean tectonic evolution of the North China Craton. Three mineral assemblages are recognized for these granulite samples, including the prograde (M1), peak (M2) and retrograde (M3) mineral assemblages. Conventional geothermobarometry and phase equilibrium modeling yield P-T conditions of 6.5–10.9 kbar/718–839°C for the peak metamorphism, which define a medium-pressure granulite-facies metamorphism occurred at middle to lower crust. Anticlockwise P-T paths with near-isobaric cooling (IBC) retrograde segments were reconstructed. Zircon LA-ICP-MS U-Pb dating suggests that the protolith of the felsic granulite was emplaced at 2541 ± 7 Ma and the subsequent medium-pressure granulite-facies metamorphism occurred at 2518–2494 Ma. A two-stage mantle plume related crustal-scale sagduction geodynamic regime is proposed in the western Shandong terrane in the Neoarchean.