The two convective systems that dominate Earth's internal dynamics meet at the boundary between the rocky mantle and metallic liquid core. Energy transfer between processes driving plate tectonics and the geodynamo is controlled by thermal conduction in the lowermost mantle (D″). We use atomic scale simulations to determine the thermal conductivity of MgSiO3 perovskite and post-perovskite under D″ conditions and probe how these two convective systems interact. We show that the thermal conductivity of post-perovskite (∼12 W/mK) is 50% larger than that of perovskite under the same conditions (∼8.5 W/mK) and is anisotropic, with conductivity along the a-axis being 40% higher than conductivity along the c-axis. This enhances the high heat flux into cold regions of D″ where post-perovskite is stable, strengthening the feedback between convection in the core and mantle. Reminiscent of the situation in the lithosphere, there is potential for deformation induced texturing associated with mantle convection to modify how the mantle is heated from below. We test this by coupling our atomic scale results to models of texture in D″ and suggest that anisotropic thermal conductivity may help to stabilise the roots of mantle plumes over their protracted lifetime.
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机译:支配地球内部动力学的两个对流系统在岩石地幔与金属液核之间的边界处相遇。驱动板块构造与大地动力学的过程之间的能量转移受最下层地幔(D'')中的热传导控制。我们使用原子尺度模拟确定在D''条件下MgSiO3钙钛矿和钙钛矿后的热导率,并探讨这两个对流系统如何相互作用。我们表明,在相同条件下(〜8.5 W / mK),钙钛矿后的热导率(〜12 W / mK)比钙钛矿大50%,并且是各向异性的,沿a轴的热导率为40%高于沿c轴的电导率。这增加了进入钙钛矿后钙钛矿稳定区D”的寒冷区域的高热通量,从而增强了岩心和地幔对流之间的反馈。让人联想到岩石圈的情况,与地幔对流相关的变形诱发纹理化的潜力,可能会改变地幔从下方加热的方式。我们通过将原子尺度结果与D''中的纹理模型耦合来进行测试,并表明各向异性的热导率可能有助于稳定地幔柱的根部。
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