A rift‐scale view at strain partitioning during multiphase rifting: Insights from the Hailar Basin, northeast Asia

Abstract

AbstractThe spatial strain variations while continental lithospheric extension progresses and leads to either a failed rift basin or a fully rifted passive margins have been extensively studied. However, determining the spatial kinematics of rift basins throughout their entire temporal evolution at rift scale is often difficult due to the sparsity of spatial data coverage; this limits our current understanding of rift evolution and our ability to ascertain the controlling factors on basin development. This study uses extensive high‐quality 2D and 3D seismic reflection data and borehole data from the Hailar Basin (northeast Asia) to investigate the spatial strain variations that occurred during multiphase rifting at both high resolution and rift scale. By coupling fault evolution and depocenter analysis, we demonstrate that the Hailar Basin experienced complex strain partitioning with a progressively eastward migration of strain and eventual strain localization onto rift axis. This strain localization occurred in the area that had been dominated by syn‐rift sagging. We propose that the observed eastward strain migration has been driven by the multiphase rollback of the Paleo‐Pacific slab. Contrastingly, during the final rift phase, crustal rheology played the dominant role in rift development, while the influence of geodynamic processes significantly decreased, resulting in the cessation of the eastward rift migration and the ultimate strain localization. This pattern of strain migration and localization is likely to be applicable to other multiphase rifts where the main controlling factors varied through time.