A top-down control on upper crustal inheritance on the southeastern Tibetan Plateau

Mantle tectonics, such as asthenospheric upwelling, usually controls subsequent fluid formation and migration from deep to shallow levels in the lower lithosphere and promotes rock failure and deformation, especially in southeastern Tibetan Plateau. Some models have proposed that lithospheric shearing and lower-crustal flow have controlled the crustal deformation in the Cenozoic. However, crustal rotation models show less possibility of a channel flow and relate the crustal deformation to the remote effect of India-Asia collision. Based on the concept whereby the fluid migration location defines the structural inheritance, we aim to relate crustal processes to mantle tectonics using fluids revealed by a new dense magnetotelluric (MT) array across the Ailao Shan-Red River belt with high quality, investigating above hypotheses. The 3D resistivity model of the study area reveals notable variations in the electrical property throughout the lithosphere. The lithosphere is interpreted to have been divided into two horizontal systems by a fluid diffusion layer at the bottom of upper crust, indicating a transition zone. In the lower lithosphere, two prominent near-vertical conductive regions are revealed and determined as consistent with the Dian-Qiong (DQ) suture and Song Da (SD) belt. These resistivity lows, which have spread at the bottom of upper crust, are inferred due to partial melting of deep lithosphere and reworking of the paleo sutures (DQ and SD) in the Late Cenozoic, because surface potassic magmatism in our study region was enabled by partial melting in the lower lithosphere. Therefore, fluid migration is considered to generate a transition zone featured by low-viscosity conductivity, which is inferred feeding by aqueous and melt fluids originating from the two channels and diffusing at depths from 15-20 km. Rather than the channel flow, this fluid migration process sensitively reflected in our model relates the mantle tectonics to crustal rotation by providing rheological conditions. We, hence, propose an inherited structure model featured by vertical mantle tectonic and upper-crustal translation-rotation that may occur before the major strike-slip event. The lithospheric transition zone could have provided convenience to induce the entirely upper crustal translation-rotation. The upper crust may move southwards and rotate clockwise, with respect to the lower part of the lithosphere, which is consistent with the surface geological and petrological observations to the north of our study region. Moreover, this transition-rotation process may have occurred within the time interval between potassic magmatism and strike-slip of the RRF (34-31 Ma), constrained by the geochronology results and duration estimation of shear zone by electrical model and energy equation. This translation-rotation process is inherited from the underlying mantle processes and may further be remotely affected by the upper crustal movement of the Tibetan Plateau, conforming with the mechanism interpretation of crustal rotation observed to the north of our study region. Furthermore, the crustal translation-rotation may also control the inherited strike-slip event in our study region.