Multiple-frequency tomography of the upper mantle beneath the African/Iberian collision zone
Multiple-frequency tomography of the upper mantle beneath the African/Iberian collision zone
复制标题
非洲/伊比利亚碰撞带下方上地幔的多频断层扫描
DOI：
10.1093/gji/ggu214
复制
发表时间：
--
影响因子：
2.8
通讯作者：
Thomas
中科院分区：
文献类型：
--
作者：
Bonnin;Villasenor;Gallart;Thomas
新生代期间，地中海西部地区的地球动力学特征是中生代海洋岩石圈俯冲的复杂历史。这些过程的最后阶段被认为导致了卡拉布里亚和直布罗陀弧的发展，其形成仍在争论中。在这项研究中，我们利用阿尔博兰海地区现有的密集宽带站网络，开发了非洲/伊比利亚碰撞带下方上地幔的高分辨率3D层析速度模型，该模型将更好地约束该区域过去的动态。该模型基于 2008 年至 2012 年期间在 279 个台站记录的 13200 个远震到达时间，使用新技术在以 0.03 至 1.0 Hz 为中心的不同频段测量互相关延迟，并首次使用多频率断层扫描进行解释。我们的模型显示，在阿尔博兰海下方，至少在 650 公里深度处观察到了强烈的（4%）快速垂直倾斜异常现象。这种异常的拱形形状及其深度范围与岩石圈板片一致，因此有利于利古里亚洋板片在新生代因回滚而向西消耗的假说。除了上地幔深处的这种快速异常之外，摩洛哥和西班牙南部下方的岩石圈和软流圈也广泛存在高强度的慢速异常。这些异常现象在地表与里夫造山带和阿特拉斯造山带的位置以及新生代火山场相关。因此，我们证实了摩洛哥地下存在异常（热？）上地幔，但没有明确迹象表明加那利羽流向东部横向扩展。
During the Cenozoic, the geodynamics of the western Mediterranean domain has been characterized by a complex history of subduction of Mesozoic oceanic lithosphere. The final stage of these processes is proposed to have led to the development of the Calabria and Gibraltar arcs, whose formation is still under debate. In this study, we take advantage of the dense broad-band station networks now available in the Alborán Sea region, to develop a high-resolution 3-D tomographicPvelocity model of the upper mantle beneath the African/Iberian collision zone that will better constraint the past dynamics of this zone. The model is based on 13200 teleseismic arrival times recorded between 2008 and 2012 at 279 stations for which cross-correlation delays are measured with a new technique in different frequency bands centred between 0.03 and 1.0 Hz, and for the first time interpreted using multiple frequency tomography. Our model shows, beneath the Alborán Sea, a strong (4 per cent) fast vertically dipping anomaly observed to at least 650 km depth. The arched shape of this anomaly, and its extent at depth, are coherent with a lithospheric slab, thus favouring the hypothesis of a westward consumption of the Ligurian ocean slab by roll-back during Cenozoic. In addition to this fast anomaly in the deep upper mantle, high intensity slow anomalies are widespread in the lithosphere and asthenosphere beneath Morocco and southern Spain. These anomalies are correlated at the surface with the position of the Rif and Atlas orogens and with Cenozoic volcanic fields. We thus confirm the presence, beneath Morocco, of an anomalous (hot?) upper mantle, but without clear indication for a lateral spreading of the Canary plume to the east.