Inversion of polyphase calcite-twin data for deviatoric stress tensors: 2. Application to the Huangling Dome, northern South China

Abstract

The north-trending Huangling Dome, located on the northern margin of the reactivated Yangtze Platform, provides an appropriate place to understand the complexity of intraplate deformation of the South China continent since the Early Mesozoic. In this study, palaeostress analysis using calcite twins was carried out to address the deformation mechanism of the dome, poorly understood at present. Ten limestone samples and three marble samples were collected from the platform cover on the eastern and western flanks and the core basement, measured under the universal stage, and inverted for stress analysis using our recently proposed method. All the stress estimates for the samples were classified into two layer-parallel shortening (LPS) subsets and two non-LPS subsets. They represent NW–SE compression, NE–SW compression, N–S compression, and N–S or E–W extension, respectively, in correspondence to principal tectonic events since the Early Mesozoic. They do not verify existing explanations about the genesis of the dome, for example, extrusion-induced E–W compression and differential uplift-related E–W extension. A new formation model was therefore proposed: under the nearly N–S compression, the dome initiates as an E–W trending brachy anticline and, owing to basement inheritance and variation of regional shortening, gains the current configuration.