The 660-km seismic discontinuity, which is a significant structure in the Earth's mantle, is generally interpreted as the post-spinel transition, as indicated by the decomposition of ringwoodite to bridgmanite + ferropericlase. All precise high-pressure and high-temperature experiments nevertheless report 0.5-2 GPa lower transition pressures than those expected at the discontinuity depth (i.e. 23.4 GPa). These results are inconsistent with the post-spinel transition hypothesis and, therefore, do not support widely accepted models of mantle composition such as the pyrolite and CI chondrite models. Here, we present new experimental data showing post-spinel transition pressures in complete agreement with the 660-km discontinuity depth obtained by high-resolution in situ X-ray diffraction in a large-volume high-pressure apparatus with a tightly controlled sample pressure. These data affirm the applicability of the prevailing mantle models. We infer that the apparently lower pressures reported by previous studies are experimental artefacts due to the pressure drop upon heating. The present results indicate the necessity of reinvestigating the position of mantle mineral phase boundaries previously obtained by in situ X-ray diffraction in high-pressure-temperature apparatuses.

中文翻译：

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脊柱后过渡带与660公里地震不连续性完全一致。

660 km的地震不连续性是地球地幔中的重要结构，通常被解释为脊柱后过渡，这由林伍德石分解为水辉石+铁硅藻土表示。然而，所有精确的高压和高温实验都报告，其过渡压力比在不连续深度处预期的过渡压力（即23.4 GPa）低0.5-2 GPa。这些结果与脊柱后过渡假说不一致，因此，不支持被广泛接受的地幔组成模型，如黄铁矿和CI球粒陨石模型。这里，我们提供了新的实验数据，表明在严格控制样品压力的情况下，通过大体积高压设备中的高分辨率原位X射线衍射获得的660公里不连续深度与脊柱后过渡压力完全一致。这些数据证实了现行地幔模型的适用性。我们推断，先前研究报告的明显较低的压力是由于加热时的压降导致的实验伪像。目前的结果表明有必要重新研究先前在高压设备中通过原位X射线衍射获得的地幔矿物相边界的位置。我们推断，先前研究报告的明显较低的压力是由于加热时的压降导致的实验伪像。目前的结果表明有必要重新研究先前在高压设备中通过原位X射线衍射获得的地幔矿物相边界的位置。我们推断，先前研究报告的明显较低的压力是由于加热时的压降导致的实验伪像。目前的结果表明有必要重新研究先前在高压设备中通过原位X射线衍射获得的地幔矿物相边界的位置。