Phase relations of carbonated basalts have been investigated at 13–20 GPa and 1200–1600°C, to model the decarbonation process of stagnant slab in the mantle transition zone (MTZ). Two synthetic mixes with CO₂ contents of 2.5 wt% (PC‐a) and 5.0 wt% (PC‐b) were used as the starting materials. The estimated solidus was ~1350°C at the top of the MTZ (~13–15 GPa), which declined to ~1250°C for pressures of above ~15–16 GPa for both mixes. The average slab geotherms are lower than the obtained solidus, creating a carbonate‐bearing stagnant slab, followed by decarbonation of stagnant slab with increased residence time. Dehydration of stagnant oceanic lithosphere could induce decarbonation of the upper oceanic crust for temperatures below the solidus of carbonated basalts. The resulting carbonate melt is highly reactive with the ambient mantle, producing a carbonated domain in the MTZ or at the top of the 410‐km seismic discontinuity. A portion of carbonate melt could ascend to shallow depth because of low density and low viscosity and bring oceanic crust signatures into the source of some volcanoes after complex interactions with the surrounding mantle. On the example of Eastern Asia, decarbonation of stagnant slab is inferred to be a possible prerequisite for the formation of the big mantle wedge and triggered the intraplate volcanoes of Eastern Asia.

中文翻译：

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地幔过渡带停滞板脱碳

已经研究了在13-20 GPa和1200-1600°C的碳酸玄武岩的相关系，以模拟地幔过渡带（MTZ）中停滞板的脱碳过程。两种含CO _2的合成混合物分别以2.5 wt％（PC-a）和5.0 wt％（PC-b）的含量作为起始原料。在MTZ的顶部（〜13–15 GPa），估计的固相线为〜1350°C，对于两种混合物而言，当压力高于〜15-16 GPa时，固相线均降至〜1250°C。板坯的平均地热低于获得的固相线，从而生成了一个含碳酸盐的停滞板，随后使停滞板脱碳并增加了停留时间。在温度低于碳酸玄武岩固相线的温度下，停滞的海洋岩石圈的脱水可能导致上层洋壳脱碳。所产生的碳酸盐熔体与周围地幔具有高反应性，在MTZ或410 km地震不连续性的顶部产生了一个碳酸盐化畴。由于低密度和低粘度，一部分碳酸盐熔体可能会上升到浅层深度，并在与周围地幔发生复杂相互作用之后将洋壳签名带入某些火山的源头。以东亚为例，认为停滞板块的脱碳是形成大地幔楔并触发东亚板内火山的可能先决条件。