Cryomagma ascent on Europa
Cryomagma ascent on Europa
复制标题
欧罗巴上的冰岩浆上升
DOI：
10.1016/j.icarus.2019.07.003
复制
发表时间：
2018
期刊：
影响因子：
3.2
通讯作者：
F. Schmidt
中科院分区：
文献类型：
--
作者：
E. Lesage;H. Massol;F. Schmidt
木卫二的表面呈现出与低陨石坑密度相关的形态特征，可能被解释为是最近的冰火山活动的结果。特别是，覆盖部分表面的光滑沉积物的形态，以及它们与周围地形的关系，表明它们是由液体挤压造成的。此外，最近的文献表明，与液体有关的特征，如双脊、微脊和混沌的就位可能是由于地表下存在液体储存。我们模拟上升的液态水通过裂缝或管道状管道从地下水库欧罗巴的表面，并计算喷发的时间尺度和喷发过程中挤出的总体积，作为水库体积和深度的函数。我们还估计了触发火山爆发所需的地下水库的冻结时间。我们的模型是针对纯液态水和Kargel（1991）概述的盐水混合物推导的：81 wt% H2O + 16 wt% MgSO 4 + 3 wt% Na 2SO 4。结合木卫二的盐杂质成分数据，讨论了MgSO 4和Na 2SO 4对低温岩浆冻结时间尺度和上升的影响。对于可能的储集层体积和深度分别为106 m3 ≤V≤ 1010 m3和1 km ≤H≤ 10 km的范围，总喷出的冰熔岩体积为103 - 108 m3，喷发持续时间从几分钟到几十小时不等。低温岩浆库的冻结时间尺度随低温岩浆成分和冰壳温度梯度的不同而变化：纯水低温岩浆的冻结时间从几天到一千年不等，盐水低温岩浆的冻结时间从几个月到104年不等。
Europa's surface exhibits morphological features which, associated with a low crater density, might be interpreted to have formed as a result of recent cryovolcanic activity. In particular, the morphology of smooth deposits covering parts of the surface, and their relationship to the surrounding terrains, suggest that they result from liquid extrusions. Furthermore, recent literature suggests that the emplacement of liquid-related features, such as double ridges, lenticulae and chaos could result from the presence of liquid reservoirs beneath the surface. We model the ascent of liquid water through a fracture or a pipe-like conduit from a subsurface reservoir to Europa's surface and calculate the eruption time-scale and the total volume extruded during the eruption, as a function of the reservoir volume and depth. We also estimate the freezing time of a subsurface reservoir necessary to trigger an eruption. Our model is derived for pure liquid water and for a briny mixture outlined by Kargel (1991): 81 wt% H2O + 16 wt% MgSO4+ 3 wt% Na2SO4. Considering compositional data for salt impurities for Europa, we discuss the effect of MgSO4and Na2SO4on the cryomagma freezing time-scale and ascent. For plausible reservoir volumes and depths in the range of 106m3≤V≤1010m3and 1 km ≤H≤ 10 km respectively, the total extruded cryolava volume ranges from 103m3to 108m3and the duration of the eruptions varies from few minutes to few tens of hours. The freezing time-scale of the cryomagma reservoirs varies with cryomagma composition and the temperature gradient in the ice shell: from a few days to a thousand years for pure water cryomagma, and from a few months to a 104years for briny cryomagma.