Thermal Structure of the Forearc in Subduction Zones: A Comparison of Methodologies
Thermal Structure of the Forearc in Subduction Zones: A Comparison of Methodologies
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DOI：
10.1029/2019gc008334
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发表时间：
2019-07
期刊：
影响因子：
3.7
通讯作者：
P. V. Keken;I. Wada;N. Sime;G. Abers
中科院分区：
文献类型：
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作者：
P. V. Keken;I. Wada;N. Sime;G. Abers
Molnar和England （1990, https://doi.org/10.1029/JB095iB04p04833）采用半解析方法引入了近似于俯冲带弧前区域热结构的方程。与高分辨率有限元模型的详细比较表明，原始方程提供了可靠的预测，并且可以通过理论推导后的一些修改来改进。更新后的近似方程被证明是相当准确的直浸板，它是由热流从其底部和剪切加热在其顶部。上覆板块地壳放射性成因加热的近似精度较低，但这种加热方式的总体影响较小。结果表明，随着热参数的减小和板倾角变异性的增大，原有的近似方程和更新后的近似方程越来越不准确。结果还表明，在脆性-韧性转变之后，近似方程不能准确地外推。最近的一篇论文（Kohn et al., 2018, https://doi.org/10.1073/pnas.1809962115）得出的结论认为，适度的剪切加热可以解释从挖掘出的变质岩记录中过去俯冲的热条件，但由于在应用Molnar和England （1990, https://doi.org/10.1029/JB095iB04p04833）的脆性-韧性过渡之后的方程时存在一些复合误差，该结论无效。如果考虑到改进的近似方程的局限性，强烈建议使用改进的近似方程。对于倾角可变和/或热参数低的俯冲带，建议采用有限元建模。
Molnar and England (1990, https://doi.org/10.1029/JB095iB04p04833) introduced equations using a semianalytical approach that approximate the thermal structure of the forearc regions in subduction zones. A detailed new comparison with high‐resolution finite element models shows that the original equations provide robust predictions and can be improved by a few modifications that follow from the theoretical derivation. The updated approximate equations are shown to be quite accurate for a straight‐dipping slab that is warmed by heat flowing from its base and by shear heating at its top. The approximation of radiogenic heating in the crust of the overriding plate is less accurate but the overall effect of this heating mode is small. It is shown that the previous and updated approximate equations become increasingly inaccurate with decreasing thermal parameter and increasing variability of slab dip. It is also shown that the approximate equations cannot be extrapolated accurately past the brittle‐ductile transition. Conclusions in a recent paper (Kohn et al., 2018, https://doi.org/10.1073/pnas.1809962115) that modest amount of shear heating can explain the thermal conditions of past subduction from the exhumed metamorphic rock record are invalid due to a number of compounding errors in the application of the Molnar and England (1990, https://doi.org/10.1029/JB095iB04p04833) equations past the brittle‐ductile transition. The use of the improved approximate equations is highly recommended provided their limitations are taken into account. For subduction zones with variable dip and/or low thermal parameter finite element modeling is recommended.