We model the magnetic signature of rift‐related volcanism to understand the distribution and volume of magmatic activity that occurred during the breakup of Pangaea and early Atlantic opening at the Eastern North American Margin (ENAM). Along‐strike variations in the amplitude and character of the prominent East Coast Magnetic Anomaly (ECMA) suggest that the emplacement of the volcanic layers producing this anomaly similarly varied along the margin. We use three‐dimensional magnetic forward modeling constrained by seismic interpretations to identify along‐margin variations in volcanic thickness and width that can explain the observed amplitude and character of the ECMA. Our model results suggest that the ECMA is produced by a combination of both first‐order (~600–1,000 km) and second‐order (~50–100 km) magmatic segmentation. The first‐order magmatic segmentation could have resulted from preexisting variations in crustal thickness and rheology developed during the tectonic amalgamation of Pangaea. The second‐order magmatic segmentation developed during continental breakup and likely influenced the segmentation and transform fault spacing of the initial, and modern, Mid‐Atlantic Ridge. These variations in magmatism show how extension and thermal weakening was distributed at the ENAM during continental breakup and how this breakup magmatism was related to both previous and subsequent Wilson cycle stages.

中文翻译：

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北美东部边缘断裂火山活动的沿边缘差异

我们对与裂谷有关的火山岩的磁性特征进行建模，以了解在北美东部边缘（ENAM）的Pangea破裂和早期大西洋开放期间发生的岩浆活动的分布和数量。沿罢工的东海岸磁异常（ECMA）振幅和特征的变化表明，产生这种异常的火山层的位置沿边缘也有类似的变化。我们使用受地震解释约束的三维磁正向建模来确定火山厚度和宽度沿边界的变化，这些变化可以解释观测到的ECMA的振幅和特征。我们的模型结果表明，ECMA是由一阶（〜600–1,000 km）和二阶（〜50–100 km）岩浆分割共同产生的。一阶岩浆分割可能是由Pangaea构造合并过程中地壳厚度和流变学的预先存在的变化引起的。二阶岩浆分割在大陆破裂期间发展，并可能影响了初始和现代中大西洋海岭的分割和转换断层间距。岩浆作用的这些变化说明了大陆破裂过程中ENAM的伸展和热弱化是如何分布的，以及这种破裂岩浆作用是如何与先前和随后的威尔逊循环阶段相关的。二阶岩浆分割在大陆破裂期间发展，并可能影响了初始和现代中大西洋海岭的分割和转换断层间距。岩浆作用的这些变化说明了大陆破裂过程中ENAM的伸展和热弱化是如何分布的，以及这种破裂岩浆作用是如何与先前和随后的威尔逊循环阶段相关的。二阶岩浆分割在大陆破裂期间发展，并且可能影响了初始和现代中大西洋海岭的分割和转换断层间距。岩浆作用的这些变化说明了大陆破裂过程中ENAM的伸展和热弱化是如何分布的，以及这种破裂岩浆作用是如何与先前和随后的威尔逊循环阶段相关的。