2.1–1.85 Ga tectonic events in the Yangtze Block, South China: Petrological and geochronological evidence from the Kongling Complex and implications for the reconstruction of supercontinent Columbia

Abstract

This paper presents petrography, zircon U–Pb ages and Hf isotopic data as well as whole-rock Sm–Nd isotopic data for mafic granulites, metapelitic rocks and high-grade marble from the Kongling Complex in the Yangtze Block, South China. Petrographic observations indicate that these three types of rocks experienced high-pressure metamorphism. Their mineral assemblages and P–T conditions define a clockwise P–T path involving isothermal decompression following the peak high-pressure metamorphism, which is considered to record a continent–continent collisional event. This is systematic documentation of the tectonic evolution of the Kongling Complex from 2.1-2.0Ga deposition (constrained by youngest detrital zircon and metamorphic zircon) through ~2.0Ga collision (high-pressure metamorphism) and syn-collisional partial melting (S-type granite and migmatization of TTG gneiss) to ~1.85Ga post-collisional extension (A-type high-K granite and mafic dyke). These ages are broadly coincident with global collisional events (2.1–1.8Ga) that led to the assembly of the Palaeo-Mesoproterozoic Columbia (or Nuna) supercontinent. Therefore, this study provides strong evidence that the Yangtze Block in South China was a component of the Columbia supercontinent.