Can nanolites enhance eruption explosivity?
Can nanolites enhance eruption explosivity?
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DOI：
10.1130/g47317.1
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发表时间：
2020-10-01
期刊：
影响因子：
5.8
通讯作者：
Dingwell, Donald B.
中科院分区：
文献类型：
--
作者：
Caceres, Francisco;Wadsworth, Fabian B.;Dingwell, Donald B.
脱气动力学在控制火山喷发时岩浆的爆炸性方面起着至关重要的作用。岩浆水的脱气通常包括气泡成核和生长，这推动了岩浆的上升。悬浮在岩浆中的晶体可能影响气泡的成核和生长。微米至厘米大小的晶体可引起非均相气泡成核，并促进气泡聚并。纳米级结晶相，即所谓的“纳米岩”，是喷发岩浆中的一种未被充分报道的现象，可能对硅质火山的喷发方式起主要控制作用。然而，纳米石对脱气过程的影响仍未得到充分研究。为了测试纳米石对气泡成核和生长动力学的影响，我们采用实验方法记录了纳米石如何增加气泡数密度并影响脱气含纳米石硅岩浆的生长动力学。然后，我们检查了来自爆炸喷发的天然火山岩的这些值的汇编，从而推断出一些非常高的自然发生的气泡数密度可能与岩浆纳米岩的存在有关。最后，利用岩浆上升数值模型，我们表明，在合理的硅质火山爆发起始条件下，与纳米岩相关的气泡数密度的增加可以推动火山爆发，否则火山喷发将是喷涌的，从而达到爆发行为所需的条件。
Degassing dynamics play a crucial role in controlling the explosivity of magma at erupting volcanoes. Degassing of magmatic water typically involves bubble nucleation and growth, which drive magma ascent. Crystals suspended in magma may influence both nucleation and growth of bubbles. Micronto centimeter-sized crystals can cause heterogeneous bubble nucleation and facilitate bubble coalescence. Nanometer-scale crystalline phases, so-called "nanolites", are an underreported phenomenon in erupting magma and could exert a primary control on the eruptive style of silicic volcanoes. Yet the influence of nanolites on degassing processes remains wholly uninvestigated. In order to test the influence of nanolites on bubble nucleation and growth dynamics, we use an experimental approach to document how nanolites can increase the bubble number density and affect growth kinetics in a degassing nanolite-bearing silicic magma. We then examine a compilation of these values from natural volcanic rocks from explosive eruptions leading to the inference that some very high naturally occurring bubble number densities could be associated with the presence of magmatic nanolites. Finally, using a numerical magma ascent model, we show that for reasonable starting conditions for silicic eruptions, an increase in the resulting bubble number density associated with nanolites could push an eruption that would otherwise be effusive into the conditions required for explosive behavior.