Rift segmentation caused by reactivation of multiple basement structure systems: Evidence from the Hailar-Tamtsag Rift, northeast Asia

Since the influence of structural inheritance on rift geometry has been widely documented, it is easy to assume that rift segmentation, a prominent feature of rift geometry, may have been also influenced by structural heterogeneity. However, limited studies using high-quality seismic data have considered how basement reactivation is accommodated at individual fault scale and then how this results in rift segmentation at sub-basin scale. Using extensive high-quality 3D seismic data and 76 borehole data, we investigate the characteristics of rift architecture, rift-related fault systems, basement structures and rift evolution in the Hailar-Tamtsag Rift, northeast Asia. We identify three distinct rift segments which are defined by three rift-related fault systems and accompanied by three underlying basement structure systems. We recognize three phases of basement reactivation and three types (including five styles) of interactions between basement structures and rift-related faults. Our study shows that rift segmentation has been caused by reactivation of multiple basement structure systems which not only influence the orientation of rift segments and type of rift architecture, but also control the location, strike, dip and style of the major rift-related faults. Rift segmentation was completely achieved through multiple phases of basement reactivation, while the main structural framework of segmentation was established through 'extensive reactivation' during the second phase extension. Our study examines how multiple basement structure systems control rift segmentation at both individual fault and sub-basin scales, which can significantly improve our understanding of relationship between structural inheritance and rift segmentation. The pre-rift 3D geometries of multiple basement structure systems (a) and their influence on rift segmentation (b).image