Computation of phase equilibria by linear programming: A tool for geodynamic modeling and its application to subduction zone decarbonation
Computation of phase equilibria by linear programming: A tool for geodynamic modeling and its application to subduction zone decarbonation
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DOI：
10.1016/j.epsl.2005.04.033
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发表时间：
2005-07-30
影响因子：
5.3
通讯作者：
Connolly, JAD
中科院分区：
文献类型：
--
作者：
Connolly, JAD
构造相图截面的算法，制定了非常适合于地球动力学问题，其中有必要评估相变对岩石性质或流体的演化和迁移的影响。该算法的基础是由一系列离散组成的溶液相的连续组成变化的表示。作为这种近似的结果，经典的非线性自由能最小化问题是平凡地解决线性规划。然后，使用二分法将相位关系映射为感兴趣变量的函数以定位相位边界。用这种方法处理了长英质和镁铁质硅酸盐熔体的等熵和等温相关系。为了证明更复杂的问题，涉及传质的易处理性，渗透驱动脱碳在俯冲带的模型进行了评估。从早期的封闭系统模型得出的结论是，开放系统模型表明，碳酸盐很可能持续在俯冲洋壳超过亚弧深度，即使海洋地幔的上部广泛水合。然而，与更简单的板脱挥发分模型相比，开放系统模型表明板流体生产是异质的和短暂的。计算的地震速度剖面图以及热力学约束表明，在典型的地热条件下，俯冲地幔的蛇纹化不可能延伸到> 25 km的深度，蛇纹化地幔的平均含水量< 2 wt.%。(c)2005 Elsevier B.V.保留所有权利。
An algorithm for the construction of phase diagram sections is formulated that is well suited for geodynamic problems in which it is necessary to assess the influence of phase transitions on rock properties or the evolution and migration of fluids. The basis of the algorithm is the representation of the continuous compositional variations of solution phases by series of discrete compositions. As a consequence of this approximation the classical non-linear free energy minimization problem is trivially solved by linear programming. Phase relations are then mapped as a function of the variables of interest using bisection to locate phase boundaries. Treatment of isentropic and isothermal phase relations involving felsic and mafic silicate melts by this method is illustrated. To demonstrate the tractability of more complex problems involving mass transfer, a model for infiltration driven-decarbonation in subduction zones is evaluated. As concluded from earlier closed system models, the open-system model indicates that carbonates are likely to persist in the subducted oceanic crust beyond sub-arc depths even if the upper section of the oceanic mantle is extensively hydrated. However, in contrast to more simplistic models of slab devolatilization, the open-system model suggests slab fluid production is heterogeneous and ephemeral. Computed seismic velocity profiles, together with thermodynamic constraints, imply that for typical geothermal conditions serpentinization of the subducted mantle is unlikely to extend to > 25 km depth and that the average water-content of the serpentinized mantle is < 2 wt.%. (c) 2005 Elsevier B.V. All rights reserved.