Rheological controls on slab delamination

俯冲的大洋岩石圈表现出一系列复杂的行为，包括侵入下地幔、在过渡带停滞、在660公里地震不连续处或略低于660公里的地震间断处积水，以及这些末端成员之间的中间行为。在更细的尺度上，MORB组分被认为是从板片核心机械解耦，在下地幔产生地震散射体，并在核-地幔边界和过渡带底部产生富含OIB物质的潜在储藏库。板块及其不同组成部分的确切行为将取决于它们相对于彼此和周围地幔的密度和强度。虽然地幔中各种岩石和矿物的密度是众所周知的，但我们对它们的强度的了解非常有限；地球动力学模拟显示了取决于这些性质的一系列板岩行为。我们将测量组成板块的主要岩石(大洋中脊玄武岩和亏损橄榄岩)在俯冲板块压力和温度范围到~1000公里深度下的相对强度。这将使我们能够评估沿板坯地热的两种成分的哪种相组合显示了主要的流变学对比，从而更好地了解板坯变形和分层的过程。

Subducted oceanic lithosphere displays a range of complex behaviours including penetration into the lower mantle, stagnation in the transition zone and ponding at, or just below, the 660 km seismic discontinuity, and intermediate behaviour between these end-members. At a finer scale, the MORB component is thought to mechanically decouple from the slab core to produce seismic scatterers in the lower mantle and potential reservoirs for enriched OIB material at the core-mantle boundary and the base of the transition zone. The exact behaviour of the slab and its different components will depend on their densities and strengths relative to each other and the surrounding mantle. While the densities of the various rocks and minerals in the mantle are well known our knowledge of their strengths is very poor; geodynamical simulations show a range of slab behaviours dependent on these properties. We will measure the relative strength of the main rocks which comprise the slab (mid-ocean-ridge basalt and depleted peridotite) under the range of pressure and temperature conditions of the subducting slab to ~1000 km depth. This will allow us to assess which phase assemblages of the two compositions along the slab geotherm show the main rheological contrasts and hence better understand the processes of slab deformation and delamination.