Controls on Asymmetric Continental Crustal Thinning to Symmetric Mantle Exhumation at Magma‐Poor Rifted Margins: Processes Constrained by the West Iberia‐Newfoundland Conjugate Margins

作者：Yuan Wang, Zhonglan Liu, W. Roger Buck, Xuanlong Shan, Dian‐Ju Wang, Weimin Li · 发表于：Journal of Geophysical Research Solid Earth · 年份：2025 · DOI：10.1029/2025jb032184 · 被引用次数：3 · 研究领域：Geological and Geochemical Analysis、Geological and Geophysical Studies Worldwide、High-pressure geophysics and materials

Abstract Observations indicate that the Iberia‐Newfoundland conjugate margins, a typical example of magma‐poor rifted margins, exhibit a transition from asymmetric continental crustal thinning to symmetric exhumation of the mantle. In this study we use 2‐D thermo‐mechanical models of continental rifting to seafloor spreading to try to elucidate the cause of this transition. Our numerical model integrates grain‐size dependent viscous rheology in the mantle and accounts for hydrothermal cooling along shear zones. Our findings reveal that besides the well‐accepted role of strain‐weakening, two other factors affect asymmetric continental thinning: crustal density, which directly affects horizontal crustal buoyancy; and lower crustal rheology, which primarily influences the evolution of lithospheric strength. Furthermore, the results indicate that the extension rate is the primary parameter governing fault spacing during mantle exhumation. Hydrothermal cooling efficiency along the shear zone increases the strength of the faults, thereby leading to a reduction in the mantle fault offset. Only when the ratio of energy available for deformation that is diverted into reducing the grain size is moderate will the grain size along the shear zone be significantly smaller than that in the surrounding area, thereby producing significant viscous strain weakening and large fault offsets. Our reference model successfully replicates the structural characteristics of the Iberia‐Newfoundland conj...