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Rifted margins in the central South Atlantic portray spatial variability in terms of preserved width and thickness, which relates to complex rift‐related fault activities. However, there is still a lack of systematic and quantitative explanations for the causes of the variations that are observed along the paired rifts. To elucidate this issue, 2D viscous‐plastic thermomechanical numerical models are applied to capture the behavior of deformation, in which we investigate the effects of extensional rate, crustal strength and thickness on crust‐mantle coupling, and timing of transition from rifting to breakup. Our numerical experiments demonstrate that crust‐mantle decoupling accounts for crustal hyperextension, and that incorporating moderate‐intensity rheology into lower crust may yield insights into the hyper‐extended crust and asymmetric architecture observed in the central South Atlantic. The results also suggest that undulations in lithospheric basement cause asymmetric mantle upwelling. The lower crust of fold belts takes priority to be thermally weakened over craton and induces rift migration simultaneously. A new mechanism for the formation of failed rift is described, where the mechanical decoupling derived from thermally weakened lower crust gives access to dual rift migration. These results reinforce the interpretation on how crustal rheology shapes margins architectures and highlight the first‐order effects of crust‐mantle coupling. [ABSTRACT FROM AUTHOR]

There is a controversy regarding the amalgamation of Xing'an and Songnen Blocks along the Hegenshan‐Heihe Suture (HHS) in the eastern Central Asian Orogenic Belt (CAOB). To solve this problem, we performed detailed study on the granites from the Zhangdaqi area, adjacent to the north of the HHS in the northern part of the Great Xing'an Range, NE China. Geochemically, the granites in the study area are metaluminous‐weak peraluminous and high‐K calc‐alkaline series. Trace elements of the granites show that LREEs are relatively enriched, while HREEs are relatively deficient and obvious REE fractionation. The granites are characterized by obvious negative Eu anomalies, meanwhile, they are relatively enriched in Rb, K, Th and depleted in Ba, Nb, Sr, P, Ti. All the geochemical features suggest that the granites in the Zhangdaqi area are aluminum A‐type granites. The zircon LA‐ICP‐MS U‐Pb ages of these granites are 294–298 Ma, indicating that they formed in the Early Permian. These granites also have positive εHf (t) values (8.4–14.2) and a relatively young two‐stage model age between 449 Ma and 977 Ma, implying that the magma was derived from the re‐melting of the Early Paleozoic‐Neoproterozoic juvenile crust. Combined with geochemical characteristics (Nb/Ta ratios of 9.0–22.2, and Zr/Hf ratios of 52.3–152.0), we believe that the magmatic source area is a mixture of partial melting of the lower crust and depleted mantle. A‐type granites and bimodal volcanic rocks along the Hegenshan‐Heihe Suture formed during the Late Carboniferous‐Early Permian, indicating that the HHS between Xing'an and Songnen Blocks closed in the late Early‐Carboniferous. Subsequently, the Zhangdaqi area was in a post‐orogenic extensional environment from Late Carboniferous to Early Permian and resulted in the formation of the A‐type granites. [ABSTRACT FROM AUTHOR]