Finite strain, kinematic vorticity, rheological behavior and thermochronology of the Diancang Shan complex: Insights into channel flow of the southeastern Tibetan plateau

Abstract

This study investigates the crustal flow within the southeastern orogenic belt of the Tibetan Plateau, with a focus on the Diancang Shan (DCS) complex. As an A-type gneiss dome, the DCS complex offers valuable insights into the deformation and evolution of intra-continental orogenic belts and the flow of deep crustal material. We have identified three main stages of deformation within the DCS complex since the Cenozoic. The initial stage (D1), spanning 41–30 Ma, was characterized by high-temperature pure shear deformation, which developed penetrative foliations, symmetric folds, and structural lenses. The subsequent major stage (D2), which shaped the overall architecture of the DCS complex from approximately 27–21 Ma, was primarily influenced by strike-slip stress regimes, resulting in shear fabrics with a top-to-the SE orientation in the releasing bend. The final stage (D3), initiated around 13 Ma, was marked by retrograde metamorphism at lower temperatures. Kinematic vorticity calculations indicate that the D1 stage was dominated by pure shear, while the D2 stage was primarily influenced by simple shear. The deformation temperature for the major deformation stage (D2) is estimated to range between 450 and 550 °C. During this stage, strain rates lie between 10−13–10−16 s−1 at 450 °C and 10−12–10−14 s−1 at 550 °C, indicating relatively low strain rates within the DCS complex. Our findings suggest that the formation of the DCS dome can be attributed to the ductile extrusion of channel flow, driven by the gravitational collapse of the Tibetan Plateau. Partial melting of the thickened middle and lower crust may have provided the channels and material sources. Furthermore, shear strain analysis (0.15–0.49) indicates that pure shear played a more significant role, contributing ∼ 65 % to the formation of the DCS dome.