Evidence for focused magmatic accretion at segment centers from lateral dike injections captured beneath the Red Sea rift in Afar
Evidence for focused magmatic accretion at segment centers from lateral dike injections captured beneath the Red Sea rift in Afar
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DOI：
10.1130/g25147a.1
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发表时间：
2009-01-01
期刊：
影响因子：
5.8
通讯作者：
Bennati, Laura
中科院分区：
文献类型：
--
作者：
Keir, Derek;Hamling, Ian J.;Bennati, Laura
大陆破裂是通过在离散、狭窄的裂谷段内重复发生机械拉伸和岩脉注入而发生的。然而，岩墙侵入的时间和长度尺度，以及大陆和海洋裂谷内的熔融源区，很少受到限制。我们使用卫星雷达、全球定位系统和地震数据集，对阿法尔红海裂谷目前活跃的 60 公里长的达巴胡段变形的空间和时间变化进行了测量，这些数据在 2006 年 6 月和 7 月捕获了两个类似 10 公里长、类似 1-2 米宽的堤坝侵入物的就位。我们的观察表明，大部分应变是由 沿裂谷轴横向传播约 4-5 小时时间尺度的岩脉，源自裂谷段中心下方中下地壳或上地幔的储层。阿法尔正在进行的裂谷事件期间的新侵入表明，从裂谷段中心下方的岩浆库注入侧向岩墙是在大陆裂解的最后阶段形成和维持规则的沿轴裂谷分段的关键组成部分。我们的观察还提供了证据，表明在缓慢扩张的洋中脊中观察到的分段中心的集中岩浆增生发生在海底扩张开始之前。
Continental breakup occurs through repeated episodes of mechanical stretching and dike injection within discrete, narrow rift segments. However, the time and length scales of the dike intrusions, along with the source regions of melt within continental and oceanic rifts, are poorly constrained. We present measurements of spatial and temporal variability in deformation from the currently active 60-km-long Dabbahu segment of the Red Sea rift in Afar, using satellite radar, global positioning system, and seismicity data sets, that capture emplacement of two similar to 10-km-long, similar to 1-2-m-wide dike intrusions in June and July 2006. Our observations show that the majority of strain is accommodated by dikes that propagate laterally over similar to 4-5 h time scales along the rift axis and are sourced from a reservoir in the middle to lower crust, or upper mantle, beneath the center of the rift segment. New intrusions during the ongoing rifting episode in Afar show that the injection of lateral dikes fed from magma reservoirs beneath rift segment centers is a key component in creating and maintaining regular along-axis rift segmentation during the final stages of continental breakup. Our observations also provide evidence that the focused magmatic accretion at segment centers observed in slow-spreading mid-ocean ridges occurs prior to the onset of seafloor spreading.