The protracted development of the continent-ocean transition in Afar
The protracted development of the continent-ocean transition in Afar
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DOI：
10.1038/ngeo1095
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发表时间：
2011-04-01
影响因子：
18.3
通讯作者：
Keir, Derek
中科院分区：
文献类型：
--
作者：
Bastow, Ian D.;Keir, Derek
大陆裂解和向海底扩张过渡的特征是伸展断层作用、岩石圈减薄以及岩浆边缘大量的侵入和喷出岩浆作用（1-4）。在古代大陆边缘很难区分不同的伸展和岩浆作用机制，因为大陆-海洋过渡被埋在厚厚的火山岩和沉积岩层之下（5，6），而以断裂为特征的构造活动已经停止。相反，这些机制的时间是从理论模型或保存在充分发展的古代裂谷边缘的地质记录中推断出来的（1，5，7，8）。埃塞俄比亚正在进行的裂谷活动为解决这些问题提供了一个独特的机会，因为它暴露了大陆向南裂谷和海底进一步向北扩张之间的过渡。在这里，我们综合限制在埃塞俄比亚的岩浆活动和扩展的时空演化。我们表明，虽然岩浆侵入保持地壳厚度在早期阶段的大陆-海洋过渡，沉降的边缘低于海平面，大量的玄武岩流的喷发，是由后期减薄的严重侵入，削弱板块开始之前的海底扩张。因此，我们得出结论，断裂，拉伸和岩浆侵入是每个重要的，但在不同的时间在裂解。
Continental breakup and the transition to seafloor spreading is characterized by extensional faulting, thinning of the lithosphere and, at magmatic margins, voluminous intrusive and extrusive magmatism(1-4). It is difficult to discriminate between different mechanisms of extension and magmatism at ancient continental margins because the continent-ocean transition is buried beneath thick layers of volcanic and sedimentary rocks(5,6) and the tectonic activity that characterized breakup has ceased. Instead, the timing of these mechanisms is inferred from theoretical models or from the geological record preserved at the fully developed, ancient rifted margins(1,5,7,8). Ongoing rifting in Ethiopia offers a unique opportunity to address these problems because it exposes subaerially the transition between continental rifting towards the south and seafloor spreading further northward. Here we synthesize constraints on the spatial and temporal evolution of magmatism and extension in Ethiopia. We show that although intrusion of magma maintains crustal thickness during the early stages of the continent-ocean transition, subsidence of the margin below sea level, and eruption of voluminous basalt flows, is initiated by late-stage thinning of the heavily intruded, weakened plate just before the onset of seafloor spreading. We thus conclude that faulting, stretching and magma intrusion are each important, but at different times during breakup.