Anomalous mantle transition zone beneath the Yellowstone hotspot track
Anomalous mantle transition zone beneath the Yellowstone hotspot track
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DOI：
10.1038/s41561-018-0126-4
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发表时间：
2018-06
影响因子：
18.3
通讯作者：
Ying Zhou
中科院分区：
文献类型：
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作者：
Ying Zhou
黄石和蛇河平原火山的起源一直备受争议。地幔热柱模型成功地解释了年龄递进的火山轨迹，但地震成像中缺乏深部的热柱结构。在这里，我将衍射层析成像应用于在美国阵列台站记录的接收函数，以绘制地幔过渡带不连续的高分辨率地形。这些图像显示了一系列异常，这些异常密切跟随地表热点轨迹，并与俯冲法拉隆板块中的地震波速间隙密切相关。这一观察结果与羽流模型相矛盾，后者要求地幔中段的异常被限制在今天黄石火山口正下方的狭窄区域内。我提出了对黄石火山作用的另一种解释。大约1600万年前，一段从地幔俯冲扩张中心断裂的年轻板块首先穿透了俄勒冈州和爱达荷州下方660 公里的不连续面，并拉倒了更老的停滞不前的板块。板片撕裂沿着原有的断裂带发生，并向东北方向传播。这种反转的极性俯冲产生了来自下地幔的被动上涌，通过富含水的地幔过渡带上升，产生了熔融和年龄递进的火山作用。
The origin of the Yellowstone and Snake River Plain volcanism has been strongly debated. The mantle plume model successfully explains the age-progressive volcanic track, but a deep plume structure has been absent in seismic imaging. Here I apply diffractional tomography to receiver functions recorded at USArray stations to map high-resolution topography of mantle transition-zone discontinuities. The images reveal a trail of anomalies that closely follow the surface hotspot track and correlate well with a seismic wave-speed gap in the subducting Farallon slab. This observation contradicts the plume model, which requires anomalies in the mid mantle to be confined in a narrow region directly beneath the present-day Yellowstone caldera. I propose an alternative interpretation of the Yellowstone volcanism. About 16 million years ago, a section of young slab that had broken off from a subducted spreading centre in the mantle first penetrated the 660 km discontinuity beneath Oregon and Idaho, and pulled down older stagnant slab. Slab tearing occurred along pre-existing fracture zones and propagated northeastward. This reversed-polarity subduction generated passive upwellings from the lower mantle, which ascended through a water-rich mantle transition zone to produce melting and age-progressive volcanism.