The deformation and compaction of partial molten zones
The deformation and compaction of partial molten zones
复制标题
部分熔融区的变形和压实
DOI：
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发表时间：
1985
期刊：
影响因子：
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通讯作者：
N. Ribe
中科院分区：
文献类型：
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作者：
N. Ribe
摘要熔体从部分熔融的源区域的分离需要未熔融的残余物（“基体”）的相应变形。使用简单的一维模型，其中的变形只包括体积压缩或“收缩”的熔体偏析过程中的基质变形的作用进行检查。在模型I中，上升地幔物质的体积分数&在深度z = 0处经历压力释放熔融（局部熔融）。基质的压实发生在边界层中，边界层的厚度（折合压实长度δ）与基质粘度的平方根成比例。在地球的地幔，6，- 10-100米，表明压实不可能是重要的大距离。模型I1考察了在h级深度范围内发生熔化的情况（分布熔化）。在极限k Q S中，除了在z = 0附近厚度为- k的“熔化层”中，解与局部熔化的情况相同。在更现实的限制h > 6时，压实对与熔体偏析相关的力的平衡的贡献可以忽略不计。这一结果对更一般的二维流动情况也是有效的。因此，压实作用在地幔中的重要性可以忽略不计，其结果是熔体偏析可以用达西定律精确描述。
Summary. The segregation of melt from a partially molten source region requires a corresponding deformation of the unmelted residue (‘matrix’). The role of matrix deformation during melt segregation is examined using simple one-dimensional models, for which the deformation consists only of bulk compression or ‘compaction’. In model I, a volume fraction & of ascending mantle material undergoes pressure-release melting at a depth z = 0 (localized melting). Compaction of the matrix occurs in a boundary layer whose thickness (reduced compaction length 6,) is proportional to the square root of the matrix viscosity. In the Earth’s mantle, 6, - 10-100 m, indicating that compaction cannot be important over large distances. Model I1 examines the case in which melting occurs over a depth range of order h (distributed melting). In the limit k Q S,, the solution is the same as for the case of localized melting, except in a ‘melting layer’ of thickness - k near z = 0. In the more realistic limit h > 6,, compaction makes a negligible contribution to the balance of forces associated with melt segregation. This result is also valid for the more general case of two-dimensional flow. Compaction is therefore likely to be of negligible importance in the Earth’s mantle, with the consequence that melt segregation can be accurately described by Darcy’s law.