Strike-slip motion in the Late Mesozoic on the East Asian continental margin: Insight from 3-D numerical models with the Tan-Lu fault

It is widely accepted that the subduction system along an active continental margin has significant impacts on continental motions and deformation. The longest strike-slip fault in East Asian, the Tan-Lu Fault extends through the lithosphere and parallels the East Asian margin trench could be recognized as weak zone and left more significant geological information of plate tectonics than surrounding areas ( Collettini et al., 2019 ). Previous studies have gained some common sense about the motion of the East Eurasia continent margin from the Tan-Lu fault in the Late Mesozoic. The Tan-Lu fault experienced two phases sinistral strike-slip motion under compression with a striking-length about 150~200 km ( Zhu et al.,2005, 2009; Zhao et al.,2016 ), one stage is the Late Jurassic of the obtained age of 162~150 Ma and the other stage is the Early Cretaceous of the gained age of 143Ma~132Ma ( Zhu et al.,2005, 2010, 2018; Zhang and Dong, 2008 ). However, the formation mechanism of the large strike motion is still in doubt. Zhu et al., (2018) suggest that the Mesozoic tectonism of the Tan-Lu fault zone is dominated by paleo-Pacific plate subduction and thus can reflect its subduction history, while some others think the geodynamics of the Tan-Lu fault is controlled by the combined influences of the collision between the Tibetan blocks and Eurasia and the paleo-Pacific plate subduction ( Zhang et al., 2010 ).

 

To understand whether the paleo-Pacific subduction could have a dominant impact on the tectonic activities along the Tan-Lu fault and how does it influence the overriding plate, we perform 3-D numerical simulations of oceanic-continental subduction with a weakened fault zone simulating the Tan-Lu Fault. The results indicate that the motion and deformation of the East Asian continental plate can be strongly influenced by the interaction between the paleo-Pacific plate and East Asia, especially by the coupling degree between the subduction plate and the overriding plate. The coupling degree could significantly improve when there is micro-continent from subduction plate collide with overriding plate and the overriding plate would undergo compression. The collision between micro-continents with East Eurasia continent in Late Jurassic and Early Cretaceous has been observed ( Li et al.,2020; Charvet,2013 ). From the plate reconstructions ( Müller et al.,2016 ), in the Late Mesozoic had a northward component with an average velocity 40~50 mm/yr. In our numerical model, the generation of large sinistral strike-length could explained by strong coupling caused by collision of micro-continents with Eurasia plate.