Bilateral Subduction Model Explaining Abnormal Rapid Joining of Indian and Asian Plates Confirmed

The Tethys Ocean’s closure and the Tibetan plateau’s subsequent formation is one of the important tectonic events in Earth’s history. How the Indian peninsula drifted to the north at a remarkable speed and merged with Asia; continues as a fundamental problem in analysing global changes in tectonic, climate and ecosystems.

The double subduction of the Tethys Ocean appears to be a guiding model for interpreting this anomalous fusion rate. However, no solid evidence has previously been identified to support this model, neither from the Himalayas nor neighbouring regions.

Recently, Chinese Academy of Sciences (CAS) Institute of Geology and Geophysics (IGG) doctoral student Yang Shun, under the supervision of Professor He Yumei and Jiang Mingming, with colleagues, revealed necessary seismic evidence that will confirm the bilateral subduction model. This evidence, the team put forward in the journal Science Advances, was the slab remains they detected in the upper mantle.[1]

The study was conducted in the eastern Myanmar region of the Indo-Asian collision system. This was because Myanmar was less affected by the continent-continent collision. Therefore, it was an ideal place to look for the remains of a double subduction plate. But until recently, no seismic observations or structural imaging of the Earth’s interior have been made here.

Working on Earth’s interior at IGG/CAS, the team deployed a seismic array to Myanmar in 2016 with the China-Myanmar Geophysical Survey (CMGSMO) of the Myanmar Orogeny. Using data from this innovative seismic array, the researchers could study the structure of the upper mantle in Myanmar in high resolution. With seismic tomography and waveform modelling, the researchers detected, for the first time, two parallel subduction plates standing in a calm state in the upper mantle of the Tethys tectonic regime.

Finally, the researchers compared the plate image obtained with the time-space distribution of subduction-related magmatism and ophiolites in Myanmar. They concluded that their findings confirmed bilateral immersion.

Another geodynamic numerical modelling effort soon followed, explaining why the slab remained in the upper mantle without ever being broken off and buried deep. The study solidified the double-sided subduction model of the Tethys ocean with satisfactory multidisciplinary geological findings.

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