A continuous 55-million-year record of transient mantle plume activity beneath Iceland
A continuous 55-million-year record of transient mantle plume activity beneath Iceland
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DOI：
10.1038/ngeo2281
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发表时间：
2014-12
影响因子：
18.3
通讯作者：
R. Parnell‐Turner;N. White;T. Henstock;B. Murton;J. Maclennan;S. Jones
中科院分区：
文献类型：
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作者：
R. Parnell‐Turner;N. White;T. Henstock;B. Murton;J. Maclennan;S. Jones
在北大西洋，一个洋中脊将冰岛地幔柱一分为二，并提供了一个了解其时间演化的窗口。在冰岛南部观测到的厚洋壳的V形脊被认为记录了羽流内的上升流脉冲。特别是，过剩地壳被认为是在地幔热不稳定性触发的热孤立波准周期生成过程中形成的。在这里，我们使用地震反射数据显示，V形脊已经形成在过去的5500万年-提供了最长的记录，其烟羽周期性的。我们发现的证据，轻微的，但系统的，不对称的地壳形成，由于迁移的洋中脊相对于底层羽。我们还发现了周期性的变化：从5500万年到3500万年前，V形脊每隔300万年左右形成一次，反映了羽流温度约5-10 °C的小幅波动。从3500万年前开始，周期性变为约800万年，反映了25-30 °C的地幔温度变化。我们认为，这种周期性的变化可能是由扰动热状态的地幔柱源，无论是在地幔过渡带或核幔边界。
In the North Atlantic Ocean, a mid-ocean ridge bisects the Icelandic mantle plume, and provides a window into its temporal evolution,,. V-shaped ridges of thick oceanic crust observed south of Iceland are thought to record pulses of upwelling within the plume,,,. Specifically, excess crust is thought to form during the quasi-periodic generation of hot solitary waves triggered by thermal instabilities in the mantle. Here we use seismic reflection data to show that V-shaped ridges have formed over the past 55 million years—providing the longest record of plume periodicity of its kind. We find evidence for minor, but systematic, asymmetric formation of crust, due to migration of the mid-ocean ridge with respect to the underlying plume. We also find changes in periodicity: from 55 to 35 million years ago, the V-shaped ridges form every 3 million years or so and reflect small fluctuations in plume temperature of about 5–10 °C. From 35 million years ago, the periodicity changes to about 8 million years and reflects changes in mantle temperature of 25–30 °C. We suggest that this change in periodicity is probably caused by perturbations in the thermal state at the plume source, either at the mantle-transition zone or core–mantle boundary.