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首页> 外文期刊>Journal of Volcanology and Geothermal Research >New approaches to inferences for steep-sided domes on Venus
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New approaches to inferences for steep-sided domes on Venus

机译：金星上陡峭的圆顶推论的新方法

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New mathematical approaches for the relaxation and emplacement of viscous lava domes are presented and applied to steep-sided domes on Venus. A similarity solution approach is applied to the governing equation for fluid flow in a cylindrical geometry for two distinct scenarios. In the first scenario, dome relaxation is explored assuming a constant volume of fluid (i.e. lava) has been rapidly emplaced onto the surface. Cooling of lava is represented by a time-variable viscosity and singularities inherent in previous models for dome relaxation have been eliminated. At the onset of relaxation, bulk dynamic viscosities lie in the range between 10(10)-10(16) Pa s, consistent with basaltic-andesite to rhyolitic compositions. Plausible relaxation times range from 5 to 5000 years, depending on initial lava viscosity. The first scenario, however, is only valid during the final stages of dome relaxation and does not consider the time taken for lava to be extruded onto the surface. In the second scenario, emplacement and growth of a steep-sided dome is considered when the volume of lava on the surface increases over time (i.e. time-variable volume approach). The volumetric flowrate may depend on an arbitrary power of the dome thickness, thus embracing Newtonian as well as other rheologies for describing terrestrial and planetary mass flows. The approach can be used to distinguish between basic flowrate models for fluid emplacement. The formalism results in radial expansion of a dome proportional to t(1/2), consistent with the diffusive nature of the governing equation. The flow at the front is shown to thicken as the front advances for a constant rate of lava supply. Emplacement times are intimately correlated with the bulk rheology. Comparison of the theoretical profiles with the shape of a typical dome on Venus indicates that a Newtonian bulk rheology is most appropriate, consistent with prior studies. However, results here suggest a bulk dynamic viscosity of 10(12)-10(13) Pa s and emplacement times of approximately 2-16 years. Both scenarios investigated give emplacement times significantly less than prior estimates and compositions consistent with basaltic andesite. (C) 2016 Elsevier B.V. All rights reserved.
机译：提出了放松和安置粘性熔岩穹顶的新数学方法，并将其应用于金星上陡峭的穹顶。将相似性解决方案方法应用于两种不同情况下圆柱几何形状中流体流动的控制方程。在第一种情况下，假设已经将恒定体积的流体（即熔岩）迅速放置到表面上，则探索了圆顶松弛。熔岩的冷却是由随时间变化的粘度来表示的，以前的圆顶松弛模型固有的奇异性已经消除。松弛开始时，体积动态粘度在10（10）-10（16）Pa s之间，与玄武质-安山岩至流纹岩组成一致。可能的松弛时间范围为5至5000年，具体取决于初始熔岩粘度。但是，第一种情况仅在穹顶松弛的最后阶段才有效，并且没有考虑将熔岩挤出到地面上所花费的时间。在第二种情况下，当表面上熔岩的体积随时间增加（即随时间变化的体积方法）时，考虑陡峭的圆顶的位置和生长。体积流率可取决于圆顶厚度的任意幂，因此包含牛顿流以及用于描述地面和行星质量流的其他流变学。该方法可用于区分基本的流量模型以进行流体注入。形式主义导致圆顶的径向膨胀与t（1/2）成比例，这与控制方程的扩散性质一致。如图所示，随着熔岩供给量的恒定增加，随着熔岩流的增加，熔岩流的厚度增加。进位时间与整体流变学密切相关。理论轮廓与金星上典型圆顶形状的比较表明，牛顿体流变学是最合适的，与先前的研究一致。但是，这里的结果表明，整体动态粘度为10（12）-10（13）Pa s，放置时间约为2-16年。所研究的两种情况下的安置时间均显着少于先前的估计，并且组成与玄武岩安山岩一致。 （C）2016 Elsevier B.V.保留所有权利。

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