Mountain building, mantle convection, and supercontinents: revisited
Mountain building, mantle convection, and supercontinents: revisited
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造山运动、地幔对流和超大陆：再探讨
DOI：
10.1016/j.epsl.2021.116905
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发表时间：
2021-06
影响因子：
5.3
通讯作者：
C. Faccenna;T. Becker;A. Holt;J. Brun
中科院分区：
文献类型：
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作者：
C. Faccenna;T. Becker;A. Holt;J. Brun
造山运动是活动边缘地壳增厚的结果，并且在理解相关运动学方面已经取得了很大进展。然而，造山运动的最终原因仍然存在争议，特别是对于地壳极端增厚的情况。受到 Holmes (1931) 开创性工作的启发，我们探索了造山运动风格与地幔动力学之间的联系。我们区分两种类型的造山运动，一种与单侧的、主要是上地幔俯冲有关的造山运动，即“板拉造山运动”，另一种与更对称的、整个地幔对流细胞有关的造山运动，称为“地幔造山运动”或“板吸造山运动”。只有后者才会导致地壳极度增厚。我们认为地幔造山运动是由板片侵入下地幔以及与之相关的对流长度尺度的变化而产生的。这一建议得到了数值动力模型的支持，该模型表明上板块压缩与板片侵入下地幔有关。板块可以进一步触发从核心-地幔边界上升的浮力羽流，从而增强整个地幔对流单元，并随之而来的上板块压缩。我们探索地质记录来测试这种模型的有效性。目前，压缩弧后区域通常与俯冲到下地幔深处的板块有关。纳斯卡和特提斯板块与相关的安第斯山脉和青藏-喜马拉雅造山运动的时间演化同样表明，玻利维亚和青藏高原下方的地壳极端增厚发生在板块渗透到下地幔期间。第三纪的这一地壳增厚事件与盘古大陆组装事件相似，其中冈瓦尼德增生造山运动与瓦里斯-阿巴拉契亚造山运动和乌拉尔造山运动同时发生。我们认为，这种晚古生代大规模挤压同样与过渡带的瞬时板片积水到下地幔俯冲的变化有关。如果我们的模型是正确的，大陆岩石圈造山运动的地质记录可以用来解释与时间相关的地幔对流，并且幕式下地幔俯冲可能与超大陆旋回存在因果关系。
Orogeny results from crustal thickening at active margins, and much progress has been made on understanding the associated kinematics. However, the ultimate cause of orogeny is still debated, especially for the case of extreme crustal thickening. Inspired by the seminal work of Holmes (1931), we explore the connections between the style of orogeny and mantle dynamics. We distinguish between two types of orogeny, those that are associated with one-sided, mainly upper mantle subduction, “slab-pull orogeny”, and those related to more symmetric, whole mantle convection cells, referred to as “mantle”, or “slab-suction orogeny”. Only the latter leads to extreme crustal thickening. We propose that mantle orogeny is generated by the penetration of slabs into the lower mantle and the associated change in the length scales of convection. This suggestion is supported by numerical dynamic models which show that upper plate compression is associated with slab penetration into the lower mantle. Slabs can further trigger a buoyant, plume upwelling from the core-mantle boundary which enhances this whole mantle convection cell, and with it upper plate compression. We explore the geological record to test the validity of such a model. For the present-day, compressional backarc regions are commonly associated with slabs that subduct to the deep lower mantle. The temporal evolution of the Nazca and Tethyan slabs with the associated Andean Cordillera and the Tibetan-Himalayan orogenies likewise suggests that extreme crustal thickening below the Bolivia and Tibetan plateau occurred during slab penetration into the lower mantle. This episode of crustal thickening in the Tertiary bears similarity with Pangea assembly events, where the Gondwanide accretionary orogen occurred at the same time of the Variscan-Appalachian and Ural orogeny. We propose that this Late Paleozoic large-scale compression is likewise related to a change from transient slab ponding in the transition zone to lower mantle subduction. If our model is correct, the geological record of orogeny in continental lithosphere can be used to decipher time-dependent mantle convection, and episodic lower mantle subduction may be causally related to the supercontinental cycle.