Volcanism in the Afar Rift sustained by decompression melting with minimal plume influence
Volcanism in the Afar Rift sustained by decompression melting with minimal plume influence
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DOI：
10.1038/ngeo1455
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发表时间：
2012-06
影响因子：
18.3
通讯作者：
C. Rychert;J. Hammond;N. Harmon;J. Kendall;D. Keir;C. Ebinger;I. Bastow;A. Ayele;M. Belachew;G. Stuart
中科院分区：
文献类型：
--
作者：
C. Rychert;J. Hammond;N. Harmon;J. Kendall;D. Keir;C. Ebinger;I. Bastow;A. Ayele;M. Belachew;G. Stuart
大陆分裂是由加热和拉伸的某种组合引起的。非洲的阿法尔裂谷系统是活跃大陆裂谷的一个例子，地幔柱可能通过热侵蚀和岩浆渗透削弱了岩石圈。然而，今天羽流影响的位置和程度仍有争议。在这里，我们使用地震S-to-P接收函数对Afar下方的地幔结构进行成像。我们在大陆裂谷侧翼下约75公里处确定了岩石圈和下层软流圈之间的过渡。然而，这个边界在裂谷本身下面是不存在的，相反，我们观察到地震速度随深度的强烈增加，大约在75公里处。我们使用地球动力学模型来表明，在没有强烈热柱的情况下，地幔的减压融化可以最好地解释这个深度的速度增加。因此，尽管裂谷下没有地幔岩石圈意味着地幔柱可能曾经活跃过，但我们得出的结论是，今天阿法尔正下方的热地幔柱的影响很小。
Continental breakup is caused by some combination of heating and stretching,. The Afar Rift system in Africa is an example of active continental rifting, where a mantle plume probably weakened the lithosphere through thermal erosion and magma infiltration. However, the location and degree of plume influence today are debated,. Here we use seismic S-to-P receiver functions to image the mantle structure beneath Afar. We identify the transition between the lithosphere and underlying asthenosphere at about 75 km depth beneath the flanks of the continental rift. However, this boundary is absent beneath the rift itself and we instead observe a strong increase in seismic velocities with depth, at about 75 km. We use geodynamic modelling to show that the velocity increase at this depth is best explained by decompression melting of the mantle in the absence of a strong thermal plume. So, although the absence of mantle lithosphere beneath the rift implies a plume may have once been active, we conclude that the influence of a thermal plume directly beneath Afar today is minimal.