Heat‐Blanketed Convection and its Implications for the Continental Lithosphere
Heat‐Blanketed Convection and its Implications for the Continental Lithosphere
复制标题
热覆盖对流及其对大陆岩石圈的影响
DOI：
10.1029/2020jb020695
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发表时间：
2021
期刊：
影响因子：
--
通讯作者：
Deschamps F.
中科院分区：
文献类型：
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作者：
Vilella K.;Deschamps F.
地球的大陆地壳的特点是长寿命放射性同位素的强烈富集。最近的估计表明，大陆地壳贡献了地球表面释放的33%的热量，而地幔只占不到1%。这种独特的特征通过影响其热结构和热传递对下伏地幔具有深刻的意义。然而，富含产热元素的大陆地壳对下伏地幔的影响尚未得到系统的研究。在这里，我们通过考虑一个简化的对流系统进行了初步的研究，该系统由混合加热流体组成，其中所有的内部加热都集中在厚度为dHL的顶层（称为“热覆盖对流”）。我们在三维笛卡尔几何中对四种特定的设置和不同的dHL值进行了24次数值模拟。结果表明，在均匀加热情况下（dHL= 1.0），加热层的影响强烈地依赖于加热层厚度相对于热边界层厚度的比值（δTBL）。当dHL>δTBL时，加热层对对流系统的影响很小，而当dHL <δTBL时，对流系统的性质随dHL的减小而改变。特别是，表面热通量和对流活力显着增强非常薄的加热层相比，casedHL= 1.0。因此，生热元素的垂直分布可能在地幔动力学中起着关键作用。然而，对于地球来说，大陆的存在应该不会显着影响表面热通量，从而影响地球的冷却速率。
Earth's continental crust is characterized by a strong enrichment in long‐lived radioactive isotopes. Recent estimates suggest that the continental crust contributes to 33% of the heat released at the surface of the Earth, while occupying less than 1% of the mantle. This distinctive feature has profound implications for the underlying mantle by impacting its thermal structure and heat transfer. However, the effects of a continental crust enriched in heat‐producing elements on the underlying mantle have not yet been systematically investigated. Here, we conduct a preliminary investigation by considering a simplified convective system consisting in a mixed heated fluid where all the internal heating is concentrated in a top layer of thicknessdHL(referred to as “heat‐blanketed convection”). We perform 24 numerical simulations in three dimensional Cartesian geometry for four specific set‐ups and various values ofdHL. Our results suggest that the effects of the heated layer strongly depend on its thickness relative to the thickness of the thermal boundary layer (δTBL) in the homogeneous heating case (dHL= 1.0). More specifically, fordHL>δTBL, the effects induced by the heated layer are quite modest, while, fordHL<δTBL, the properties of the convective system are strongly altered asdHLdecreases. In particular, the surface heat flux and convective vigor are significantly enhanced for very thin heated layers compared to the casedHL= 1.0. The vertical distribution of heat producing elements may therefore play a key role in mantle dynamics. For Earth, the presence of continents should however not affect significantly the surface heat flux, and thus the Earth's cooling rate.