The force that drives continental drift has been one of the most challenging subjects of the plate tectonics theory in the last decades. The Proto-Tethys evolution exemplifies a scenario of drifting of continental plates during closure of the Proto-Tethys Ocean. The Pan-Cathaysian blocks in the Southeast Asian tectonic realm (SATR) derived from break-up of the Rodinia supercontinent witnessed the entire process of the Proto-Tethys evolution. The blocks and suture zones between them offer crucial information on the dynamics of continental drifting linked to shallow mantle convection and deep mantle flow.

Break-up of the Pan-Cathaysian blocks from the Rodinia and opening of the Proto-Tethys Ocean, e.g., the Changning-Menglian (CM) Ocean and the Tam Ky-Phuoc Son-Po Ko (TPP) Ocean, is evidenced by the volcano-sedimentary records in the SATR and their source affinities. Subsequent convergent tectonics occurred during the subduction of the Proto-Tethys CM oceanic plate beneath the northern margin of the Gondwana and of the oceanic plate of the TPP subsidiary ocean beneath the Truong Son and Kontum blocks. Occurrence of tectonic mélanges, e.g., the Lancang mélange, and extensive arc (continental or intra-oceanic) magmatic rocks attests the switch from passive to active plate margins, forming advancing subduction zones (Andean-type) along both the distal and proximal margins of the CM Ocean, and within the TPP Ocean. Jinshajiang-Ailao Shan-Song Ma (JAS) rifting proceeded and Dapingzhang back-arc rifting occurred during or subsequent to the transition from advancing to retreating subduction along the southern margin of the Indochina block. Closing of the CM and TPP oceans in the SATR by suturing of the oceans and collision of the continental blocks occurred in the late early Paleozoic, which is evidenced by, e.g., existence of high-pressure rocks along the CM suture and post-collisional magmatic rocks along the TPP suture zone.

The Proto-Tethys evolution in the SATR narrates a scenario of supercontinent break-up and assembly through continental drifting. Progressive Gondwana-centered convergent drifting of the Pan-Cathaysian blocks induced progressive closure of the Proto-Tethys main and subsidiary oceans, and rifting and closing of the rift basin and back-arc basin. Advancing subduction-ridge spreading-retreating subduction systems (ARRs) or subduction-spreading-subduction systems (SSSs) were formed and transported toward the Gondwana during the convergent drifting of the continental blocks. It is suggested that coupled shallow- and deep mantle flow, i.e., stratified mantle convection, is the major driving mechanism of the Gondwana-centered convergence of the Pan-Cathaysian blocks. In the model, the shallow-mantle convections directly control the subduction geometries and plate kinematics, while the deep-mantle convection is responsible for the drifting of the continental blocks, formation and migration of the SSSs and ARRs.

Article link: https://www.sciencedirect.com/science/article/pii/S0012825221003305