金星地壳高原的岩石圈结构
Lithospheric Structure of Venusian Crustal Plateaus
摘要：
地壳高原是以构造化地形为特征的金星高地。通常的解释是，它们的地形是均衡支撑的，它们代表了一个灭绝的构造体系的化石。利用重力和地形，我们进行了全面调查的岩石圈结构的六个地壳高原。我们计算了每个区域的导纳（重力与地形波长相关的比率），并将其与建模导纳进行比较。三种补偿方案进行了测试：艾里等值线，表面加载弯曲模型，弯曲模型与表面和地下负载。我们的研究结果表明，大多数高原的地形是由地壳增厚的支持，并增加了地幔的支持组件是没有必要在调查的波长。弹性厚度被限制在35公里以下，最佳拟合平均值为15公里，证实这些区域符合均衡状态。高原的平均地壳厚度为15 - 34 km，如果它们处于艾里等厚线上，这意味着金星的全球平均地壳厚度约为20 km。Phoebe Regio是我们分析中唯一的例外，因为只有当包括浮力层时，才能获得与其他高原相容的地壳厚度。根据弹性厚度计算的热流估计表明，与当前全球平均值相比，在较高的热流条件下形成的高原可能导致局部熔化。现今的热流预测表明榴辉岩化可能发生在地壳最厚的地方。
英文摘要：
Crustal plateaus are Venusian highlands characterized by tectonized terrains. It is commonly interpreted that their topography is isostatically supported and that they represent fossils of an extinct tectonic regime. Using gravity and topography we perform a comprehensive investigation of the lithospheric structure of six crustal plateaus. We computed the admittance (gravity to topography wavelength-dependent ratio) for each region and compared them to modeled admittances. Three compensation scenarios were tested: Airy isostasy, a surface-loading flexural model, and a flexural model with surface and subsurface loads. Our results show that the topography of most plateaus is supported by crustal thickening and that the addition of a mantle support component is not necessary at the investigated wavelengths. The elastic thickness was constrained to be less than 35 km with a best-fitting average of 15 km, confirming that these regions are consistent with an isostatic regime. The average crustal thickness of the plateaus ranges from 15 to 34 km, and if they are in Airy isostasy, this implies that the global average crustal thickness of Venus is about 20 km. Phoebe Regio is the sole exception of our analysis in that crustal thicknesses that are compatible with the other plateaus are obtained only when a buoyant layer is included. Heat flow estimations computed from the elastic thickness indicate that the plateaus formed under higher heat flow conditions compared to the current global average and could have caused localized melting. Present-day heat flow predictions suggest that eclogitization could occur where the crust is thickest.
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