Thermal expansivity, heat capacity and bulk modulus of the mantle
Thermal expansivity, heat capacity and bulk modulus of the mantle
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DOI：
10.1093/gji/ggab394
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发表时间：
2021-10-25
影响因子：
2.8
通讯作者：
Lithgow-Bertelloni, Carolina
中科院分区：
文献类型：
--
作者：
Stixrude, Lars;Lithgow-Bertelloni, Carolina
我们推导出精确的表达式的热膨胀系数，热容和体积模量与任意大数目的组件和阶段，包括相变和化学交换的影响的组合。我们说明结果在简单的两个组件，两相系统，包括镁铁橄榄石，wadsleyite和钙镁单斜辉石，斜方辉石和地幔组成的多组分模型的地幔岩的形式。对于后者，我们展示了整个地幔压力-温度制度的热膨胀率和热容量的结果为40 GPa，或1000公里的深度。从热膨胀系数，我们推导出一个新的表达式的相浮力参数，是有效的任意大量的相和组分，并定义在压力-温度空间中的每一点。结果显示，在地幔的相浮力参数的大小的幅度大于那些相变，最常见的地幔对流模拟的幅度。这些地区包括wadsleyite石榴石和铁方镁石过渡，这是遇到沿着热等熵线（如2000 K的潜在温度）的过渡区，和铁方镁石和stishovite bridgmanite过渡，这是遇到沿着冷等熵线（如1000 K的潜在温度）在浅下地幔。我们还显示了体积模量沿着一个典型的地幔等熵，并将其与布伦不均匀性参数。所有结果计算与我们的代码HeFESTo，更新和改进，我们讨论，包括实施的热膨胀率，热容和体积模量的精确表达式，泛化，以允许非理想的解决方案参数的压力依赖性和改进的数值方案，最大限度地减少吉布斯自由能。最后，我们提出了一个新的全球反演的参数更新，以纳入最近的实验和第一原理理论的结果，以及一个新的阶段（最终阶段），和新的物种：钠majorge和NaAlO 2端成员的铁方镁石的结果。
We derive exact expressions for the thermal expansivity, heat capacity and bulk modulus for assemblages with arbitrarily large numbers of components and phases, including the influence of phase transformations and chemical exchange. We illustrate results in simple two-component, two-phase systems, including Mg-Fe olivine-wadsleyite and Ca-Mg clinopyroxene-orthopyroxene and for a multicompontent model of mantle composition in the form of pyrolite. For the latter we show results for the thermal expansivity and heat capacity over the entire mantle pressure-temperature regime to 40 GPa, or a depth of 1000 km. From the thermal expansivity, we derive a new expression for the phase buoyancy parameter that is valid for arbitrarily large numbers of phases and components and which is defined at every point in pressure-temperature space. Results reveal regions of the mantle where the magnitude of the phase buoyancy parameter is larger in magnitude than for those phase transitions that are most commonly included in mantle convection simulations. These regions include the wadsleyite to garnet and ferropericlase transition, which is encountered along hot isentropes (e.g. 2000 K potential temperature) in the transition zone, and the ferropericlase and stishovite to bridgmanite transition, which is encountered along cold isentropes (e.g. 1000 K potential temperature) in the shallow lower mantle. We also show the bulk modulus along a typical mantle isentrope and relate it to the Bullen inhomogeneity parameter. All results are computed with our code HeFESTo, updates and improvements to which we discuss, including the implementation of the exact expressions for the thermal expansivity, heat capacity and bulk modulus, generalization to allow for pressure dependence of non-ideal solution parameters and an improved numerical scheme for minimizing the Gibbs free energy. Finally, we present the results of a new global inversion of parameters updated to incorporate more recent results from experiment and first principles theory, as well as a new phase (nal phase), and new species: Na-majorite and the NaAlO2 end-member of ferropericlase.