Permian to present tectonic and geodynamic evolution of the eastern Tethys

The easternmost Tethyan tectonic system captures the breakup of eastern Gondwana and the accretionary growth of southern Eurasia, while also shaping the geodynamic evolution of Southeast Asia and northern Australia in the Mesozoic and Cenozoic. Although the tectonic evolution of these Tethyan terranes and ocean basins is obscured by a complex network of sutures and orogens, the largely north-south trend of terrane motion is generally well-documented by paleomagnetic data. By reconciling evidence for the onset of rifting, the (latitudinal) motion of these Tethyan terranes, and their eventual accretion to active margins, improved reconstructions can be made of synthetic ocean basin histories. Here we present work that improves our plate reconstructions of eastern Tethyan tectonics since the early Permian, implemented in the open-source and cross-platform GPlates ( www.gplates.org ) software and coupled to mantle flow models in CitcomS ( https://geodynamics.org/cig/software/citcoms/ ). Our results highlight two end-member mechanisms for the opening of Tethyan ocean basins. Seafloor spreading along northern Gondwana to detach South Qiangtang is driven by slab pull from north-dipping subduction along southern Eurasia from ~300-285 Ma. In contrast, the ~220 Ma drift of Lhasa from the Australian margin is driven by south-dipping subduction along northern Gondwana, with continued roll-back and back-arc opening into a full-sized ocean basin. This peculiar mechanism for Lhasa motion is supported by a continuous record of arc volcanism on the terrane, contemporaneous with northward motion toward Eurasia supported by paleomagnetic constraints. This behavior highlights that back-arc basins in the Tethyan system may have been able to evolve into large oceanic basins, whereas the same process was either impeded in the (proto) Pacific, or the record for these terrane motions are obscured or not yet explored. The improved reconstructions have first-order implications for the geodynamic evolution for this hemisphere, including the evolving mantle structure, the dynamic topography acting on the surface, and the shape of the African and Pacific LLSVPs in the lowermost mantle.