New laboratory constraints on the water content of the mantle

我们早就知道，名义上无水的地幔矿物，如可以采取大量的水进入他们（如3%的wadsleyite和ringwoodite）。我们还知道，水对这些矿物的物理和化学性质有着巨大的影响，使相关系改变数百开尔文，并导致粘度、电导率和空位数量级的变化。这创造了一个关于地幔中含水量及其对地幔动力学影响的推测流派（例如，“中地幔水过滤器”; Bercovici和Karato 2003：“过渡区的九个海洋”; Smyth等人1994：“过渡区没有水”;绿色在al 2010）。然而，我们没有确切的了解的水含量的地幔深约100公里，这些文件将保持推测，直到我们把严格的限制水含量的地幔深处。我们可以这样做，结合地球物理反演的电导率的地磁响应函数与实验室测量的含水量对电导率的影响。这就是目前的项目将使用尖端设计师金刚石砧细胞电导率测量与同时红外测量水含量。这些新的数据将用于直接反演含水量的地磁响应函数的蒙特卡罗模拟。

We have long known that the nominally anhydrous mantle minerals, such as can take substantial amounts of water into them (eg 3% for wadsleyite and ringwoodite). We also know that water has a drastic effect on the physical and chemical properties of these minerals, changing phase relations by hundreds of Kelvin and causing order-of-magnitude variations in viscosity, electrical conductivity and vacancy populations. This has created a whole genre of speculation about the water content in the mantle and its effects on mantle dynamics (eg; 'The mid-mantle water filter'; Bercovici and Karato 2003: 'Nine oceans of water in the transition zone'; Smyth et al 1994: 'No water in the transition zone'; Green at al 2010). We have, however, no firm understanding of the water content of the mantle deeper than about 100 km and these papers will remain speculative until we place firm constraints on the water content of the deep mantle. We can do this by combining geophysical inversions for electrical conductivity of the geomagnetic response function with laboratory measurements of the effect of water content on electrical conductivity. This is what the current project will do using cutting-edge designer-diamond anvil cell conductivity measurements with simultaneous infra-red measurements of water content. These new data will be used in Monte Carlo simulations of the geomagnetic response function which invert directly for water content.