The presence of water in minerals generally alters their physical properties. Ringwoodite is the most abundant phase in the lowermost mantle transition zone and can host up to 1.5–2 wt% water. We studied high‐pressure lattice thermal conductivity of dry and hydrous ringwoodite by combining diamond‐anvil cell experiments with ultrafast optics. The incorporation of 1.73 wt% water substantially reduces the ringwoodite thermal conductivity by more than 40% at mantle transition zone pressures. We further parameterized the ringwoodite thermal conductivity as a function of pressure and water content to explore the large‐scale consequences of a reduced thermal conductivity on a slab's thermal evolution. Using a simple 1‐D heat diffusion model, we showed that the presence of hydrous ringwoodite in the slab significantly delays decomposition of dense hydrous magnesium silicates, enabling them to reach the lower mantle. Our results impact the potential route and balance of water cycle in the lower mantle.

中文翻译：

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水对菱铁矿晶格热导率的影响及其对下降平板热演化的影响

矿物质中水的存在通常会改变其物理性质。在最下层的地幔过渡带中，林伍德石是最丰富的相，可以容纳高达1.5–2 wt％的水。我们通过结合金刚石-砧室实验和超快光学技术研究了干燥和含水林木的高压晶格热导率。在地幔过渡区压力下，掺入1.73 wt％的水会使林伍德石的导热系数大大降低40％以上。我们进一步将林木热导率参数化为压力和水含量的函数，以探索降低热导率对平板热演化的大规模后果。使用简单的一维热扩散模型，我们发现，平板中含水林木矿的存在显着延迟了致密含水硅酸镁的分解，使它们能够到达下地幔。我们的结果影响下地幔的潜在途径和水循环的平衡。