The closure of the Neo-Tethyan Ocean and the subsequent formation of the Tibetan Plateau is one of the most significant tectonic events to have ever occurred on Earth. How the Indian subcontinent drifted northward anomaly fast and collided with Asia is an essential problem in solving global changes in tectonics, climate and ecosystems.
The double subduction of the Neo-Tethyan Ocean is a leading model in interpreting this anomalous convergent speed. However, no compelling evidence of this found along the entire Himalaya and adjacent regions has ever been reported.
Recently, YANG Shun, a PhD candidate at IGGCAS, under the supervision of Profs. HE Yumei and JIANG Mingming, along with their team of collaborators, reported a crucial seismic evidence of slab remnants in the present upper mantle, which serves to strongly support the double subduction model.
This work was published in Science Advances.
The Myanmar region occupies the eastern end of the Indian-Asian collisional system. It is an ideal place to probe the possible slab remnants of double subduction, due to the minimal reworking of continental collision there. However, it is still a blank area for seismic observation and structural imaging of the Earth's interior. Since 2016, the research group of structure of the Earth's interior from IGGCAS has deployed the pioneering seismic arrays associated with the China-Myanmar Geophysical Survey in the Myanmar Orogen (CMGSMO) in Myanmar.
The upper mantle structures beneath Myanmar with high resolution were investigated based on the data from novel seismic arrays. Next, by compiling seismic tomography and waveform modeling, the researchers revealed two subparallel subducted slabs preserved in the present upper mantle beneath the Neo-Tethyan tectonic regime for the first time.
Comparing with the time-space distribution of subduction-related magmatism and ophiolite in Myanmar, the results implied double subduction of the Neo-Tethyan Ocean. Further geodynamic numerical modeling revealed why the slab remnants were preserved intactly in the upper mantle without breaking off and sinking into the deep.
This work provides a convincing evidence chain of multidiscipline in geoscience to consolidate the double subduction model of the Neo-Tethyan Ocean.
The study was performed in collaboration with the Myanmar Geoscience Society, Yangon University, and Dagon University.
The work was supported through the Major Research Project on Tethys Geodynamic System by the National Science Foundation of China, International Partnership Programme of the Chinese Academy of Sciences, and Key Research Program of the Institute of Geology and Geophysics, CAS.
Contact:
JIANG Mingming
Institute of Geology and Geophysics, Chinese Academy of Sciences
Phone: 86-10-82998056
E-mail: jiangmm@mail.iggcas.ac.cn
HE Yumei
Institute of Geology and Geophysics, Chinese Academy of Sciences
E-mail: ymhe@mail.iggcas.ac.cn
