Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
Science. 2011 May 27;332(6033):1068-71. doi: 10.1126/science.1202731.
The Hawaiian hotspot is often attributed to hot material rising from depth in the mantle, but efforts to detect a thermal plume seismically have been inconclusive. To investigate pertinent thermal anomalies, we imaged with inverse scattering of SS waves the depths to seismic discontinuities below the Central Pacific, which we explain with olivine and garnet transitions in a pyrolitic mantle. The presence of an 800- to 2000-kilometer-wide thermal anomaly (ΔT(max) ~300 to 400 kelvin) deep in the transition zone west of Hawaii suggests that hot material does not rise from the lower mantle through a narrow vertical plume but accumulates near the base of the transition zone before being entrained in flow toward Hawaii and, perhaps, other islands. This implies that geochemical trends in Hawaiian lavas cannot constrain lower mantle domains directly.
夏威夷热点通常归因于地幔深处上升的热物质，但地震探测热羽流的努力尚未得出明确结论。为了研究相关的热异常，我们利用 SS 波的逆散射对中太平洋下方地震不连续面的深度进行成像，我们用在热液地幔中橄榄石和石榴石的转变来解释这些不连续面。在夏威夷以西的转换带深处存在一个 800 至 2000 公里宽的热异常（ΔT(max)~300 至 400 开尔文），这表明热物质并非从下地幔通过狭窄的垂直羽流上升，而是在过渡带底部附近积聚，然后在流向夏威夷和其他岛屿的流动中被卷入。这意味着夏威夷熔岩的地球化学趋势不能直接约束下地幔域。
