Dannberg Juliane, Sobolev Stephan V
Helmholtz Centre Potsdam, GFZ German Research Centre for Geosciences, Telegrafenberg, 14473 Potsdam, Germany.
1] Helmholtz Centre Potsdam, GFZ German Research Centre for Geosciences, Telegrafenberg, 14473 Potsdam, Germany [2] Institute of Earth and Environmental Science, University of Potsdam, Karl-Liebknecht-Straße 24-25, 14476 Potsdam-Golm, Germany.
Nat Commun. 2015 Apr 24;6:6960. doi: 10.1038/ncomms7960.
The Earth's biggest magmatic events are believed to originate from massive melting when hot mantle plumes rising from the lowermost mantle reach the base of the lithosphere. Classical models predict large plume heads that cause kilometre-scale surface uplift, and narrow (100 km radius) plume tails that remain in the mantle after the plume head spreads below the lithosphere. However, in many cases, such uplifts and narrow plume tails are not observed. Here using numerical models, we show that the issue can be resolved if major mantle plumes contain up to 15-20% of recycled oceanic crust in a form of dense eclogite, which drastically decreases their buoyancy and makes it depth dependent. We demonstrate that, despite their low buoyancy, large enough thermochemical plumes can rise through the whole mantle causing only negligible surface uplift. Their tails are bulky (>200 km radius) and remain in the upper mantle for 100 millions of years.
地球最大的岩浆活动被认为源于大规模的熔融，即当从最下地幔上升的热地幔柱到达岩石圈底部时。经典模型预测会有巨大的地幔柱头部，导致千米级的地表隆升，以及狭窄（半径100千米）的地幔柱尾部，在地幔柱头部在岩石圈下方扩散后仍留在地幔中。然而，在许多情况下，并未观察到这种隆升和狭窄的地幔柱尾部。在此，我们使用数值模型表明，如果主要地幔柱含有高达15% - 20%以致密榴辉岩形式存在的再循环洋壳，那么这个问题就能得到解决，这会大幅降低它们的浮力并使其与深度相关。我们证明，尽管它们浮力低，但足够大的热化学地幔柱仍能穿过整个地幔，仅引起可忽略不计的地表隆升。它们的尾部体积庞大（半径>200千米），并在上地幔中留存一亿年。
