Palaeoproterozoic metamorphic evolution and geochronology of the Wugang block, southeastern terminal of the Trans-North China Orogen

Abstract

Amphibolites of the Wugang block in the Taihua metamorphic complex, which is located in the southeastern terminal of the Palaeoproterozoic Trans-North China Orogen (TNCO), preserve three generations of metamorphic mineral assemblages, i.e., the prograde (M1), peak (M2) and retrograde (M3) assemblages, forming during the Palaeoproterozoic tectono-metamorphic event. These amphibolites record metamorphic P–T conditions of 4.8–6.7kbar/720–750°C (M1), 9.0–10.6kbar/710–780°C (M2) and 7.1–8.5kbar/700–780°C (M3), which define clockwise P–T paths involving isothermal decompression (ITD). The metamorphic peak reached upper amphibolite facies, and high resolution in situ SIMS U–Pb dating of metamorphic zircons suggests that the peak metamorphism took place at 1.96–1.92Ga in the Wugang block. The present new data suggest that the Wugang block was also involved in the continental collision between the Eastern and Western Blocks of the North China Craton (NCC) in the Palaeoproterozoic. Combining metamorphic and geochronological data concerning the TNCO obtained by previous scholars, it may be anticipated that the middle and southern sections of the TNCO were involved in a long-lived continental collision, and the collision event can be possibly traced back to as early as ∼1.96Ga and lasted to as late as ∼1.80Ga.