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首页> 外文期刊>Journal of Volcanology and Geothermal Research2012V243-244NOCT,15 >Eruption of magmatic foams on the Moon: Formation in the waning stages of dike emplacement events as an explanation of 'irregular mare patches'
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Eruption of magmatic foams on the Moon: Formation in the waning stages of dike emplacement events as an explanation of 'irregular mare patches'

机译：月球上岩浆泡沫的喷发：堤防事件逐渐减弱的阶段形成，以解释“不规则的母马斑块”

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摘要

Volcanic eruptions on the Moon take place in conditions of low gravity and negligible atmospheric pressure, very different from those on Earth. These differences lead to characteristic lunar versions of hawaiian and strombolian explosive activity, and to the production of unusual eruption products neither predicted nor observed on Earth in the terminal stages of eruptions. These include the unusual mounds and rough (hummocky, blocky) floors of some small-shield summit pit crater floors, elongate depressions and mare flows (similar to those named "irregular mare patches", IMPs, by Braden et al., 2014). We examine the ascent and eruption of magma in the waning stages of the eruptive process in small-shield summit pit crater floors and show that many IMP characteristics can be plausibly explained by basaltic magma behavior as the rise rate of the ascending magma slows to zero, volatiles exsolve in the dike and lava lake to form a very vesicular foam, and the dike begins to close. Stresses in the very vesicular and porous lava lake crust produce fractures through which the foam extrudes at a rate determined by its non-Newtonian rheology. Waning-stage extrusion of viscous magmatic foams to the surface produces convex mounds whose physical properties inhibit typical impact crater formation and regolith development, creating an artificially young crater retention age. This mechanism for the production and extrusion of very vesicular magmatic foams is also applicable to waning-stage dike closure associated with pit craters atop dikes, and fissure eruptions in the lunar maria, providing an explanation for many irregular mare patches. This mechanism implies that IMPs and associated mare structures (small shields, pit craters and fissure flows) formed synchronously billions of years ago, in contrast to very young ages (less than similar to 100 million years) proposed for IMPs by some workers. (c) 2017 Elsevier B.V. All rights reserved.
机译：月球上的火山喷发是在低重力和大气压可忽略的条件下发生的，与地球上的情况大不相同。这些差异导致夏威夷和斯特林堡爆发活动具有特征性的月球形式，并导致在喷发末期未曾在地球上预测或观察到的异常喷发产物的产生。其中包括一些小盾构山顶坑坑底的不寻常的土丘和粗糙的（丘陵状，块状）底，拉长的凹陷和母马流（类似于Braden等人，2014年的IMPs，称为“不规则的母马斑块”）。我们研究了小型盾构山顶坑火山口底板喷发过程逐渐减弱阶段的岩浆上升和喷发，并显示出随着上升岩浆的上升速率减慢至零，许多IMP特征可以用玄武岩浆行为合理地解释，挥发物在堤坝和熔岩湖中溶解，形成非常呈囊泡状的泡沫，堤坝开始关闭。极具泡孔性和多孔性的熔岩湖地壳中的应力会产生裂缝，泡沫以非牛顿流变学所确定的速率挤出。粘性岩浆泡沫向表面的逐步挤压会产生凸丘，其物理性质会抑制典型的撞击坑形成和重生砾岩，从而形成人为的年轻坑保留期。这种用于生产和挤出极易泡状岩浆泡沫的机制也适用于与堤坝顶上的坑坑相关的减弱阶段的堤坝封闭，以及月球玛丽亚中的裂缝喷发，这为许多不规则的母马斑块提供了解释。这种机制意味着，IMP和相关的母马结构（小的盾牌，坑坑和裂隙流）是数十亿年前同步形成的，这与某些工人为IMP提出的非常年轻的年龄（不到1亿年）形成了鲜明的对比。 （c）2017 Elsevier B.V.保留所有权利。

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