On the relative importance of thermal and chemical buoyancy in regular and impact‐induced melting in a Mars‐like planet
On the relative importance of thermal and chemical buoyancy in regular and impact‐induced melting in a Mars‐like planet
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DOI：
10.1002/2016je005221
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发表时间：
2017-07
期刊：
影响因子：
--
通讯作者：
T. Ruedas;D. Breuer
中科院分区：
文献类型：
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作者：
T. Ruedas;D. Breuer
我们进行了几个系列的二维数值地幔对流模拟，以理想化的形式代表了类火星行星的热化学演化。为了研究熔融地幔成分浮力的重要性，模型成对建立，一个包含所有热和成分对浮力的贡献，另一个仅考虑热贡献。在几个模型对中，引入了单个大型撞击作为额外强烈局部异常的原因，并跟踪了它们在对流地幔框架内的演化。模型证实，地幔因定期融化而消耗所提供的额外浮力可以建立对流地幔和节流地壳生产的全球稳定分层。此外，成分浮力对于岩石圈正下方局部成分异常的稳定和保存至关重要，并为火星地幔中存在独特的、长寿的储层提供了可能的解释。然而，通过地球物理手段检测此类异常可能很困难；预计它们将通过重力测量而不是地震或热流测量来检测。结果进一步表明，如果忽略撞击引起的地幔密度异常，地壳厚度可能会被局部高估约 20 公里。
We ran several series of two‐dimensional numerical mantle convection simulations representing in idealized form the thermochemical evolution of a Mars‐like planet. In order to study the importance of compositional buoyancy of melting mantle, the models were set up in pairs of one including all thermal and compositional contributions to buoyancy and one accounting only for the thermal contributions. In several of the model pairs, single large impacts were introduced as causes of additional strong local anomalies, and their evolution in the framework of the convecting mantle was tracked. The models confirm that the additional buoyancy provided by the depletion of the mantle by regular melting can establish a global stable stratification of the convecting mantle and throttle crust production. Furthermore, the compositional buoyancy is essential in the stabilization and preservation of local compositional anomalies directly beneath the lithosphere and offers a possible explanation for the existence of distinct, long‐lived reservoirs in the Martian mantle. The detection of such anomalies by geophysical means is probably difficult, however; they are expected to be detected by gravimetry rather than by seismic or heat flow measurements. The results further suggest that the crustal thickness can be locally overestimated by up to ∼20 km if impact‐induced density anomalies in the mantle are neglected.