Vastly Different Heights of LLVPs Caused by Different Strengths of Historical Slab Push
Vastly Different Heights of LLVPs Caused by Different Strengths of Historical Slab Push
复制标题
DOI：
10.1029/2022gl099564
复制
发表时间：
2022-08
影响因子：
5.2
通讯作者：
Q. Yuan;Mingming Li
中科院分区：
文献类型：
--
作者：
Q. Yuan;Mingming Li
在非洲和太平洋的下地幔中分别观测到两个大的低速区。非洲LLVP的最大高度比太平洋LLVP的最大高度大1,000公里，但造成这种高度差异的原因尚不清楚。LLVP通常被解释为热化学堆，其形态在很大程度上受到周围地幔流的控制。地震观测表明，虽然一些俯冲板块在660- 1，200公里处发生横向偏转，但其他板块则穿透到最低地幔。在这里，通过地球动力学模拟实验，我们表明，快速下沉的停滞板的最低地幔可以导致显着的高度增加附近的热化学桩。我们的研究结果表明，非洲LLVP可能已被推动更强烈和更长的周围地幔流，以达到比太平洋LLVP更浅的深度，也许是因为特提斯板块下沉到最低的地幔。
Two large low velocity provinces (LLVPs) are observed in Earth's lower mantle, beneath Africa and the Pacific Ocean, respectively. The maximum height of the African LLVP is ∼1,000 km larger than that of the Pacific LLVP, but what causes this height difference remains unclear. LLVPs are often interpreted as thermochemical piles whose morphology is greatly controlled by the surrounding mantle flow. Seismic observations have revealed that while some subducted slabs are laterally deflected at ∼660–1,200 km, other slabs penetrate into the lowermost mantle. Here, through geodynamic modeling experiments, we show that rapid sinking of stagnant slabs to the lowermost mantle can cause significant height increases of nearby thermochemical piles. Our results suggest that the African LLVP may have been pushed more strongly and longer by surrounding mantle flows to reach a much shallower depth than the Pacific LLVP, perhaps since the Tethys slabs sank to the lowermost mantle.