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Alteration of volcanic ash glass chemistry due to lightning
Journal of Volcanology and Geothermal Research ( IF 2.4 ) Pub Date : 2021-07-14 , DOI: 10.1016/j.jvolgeores.2021.107340
T.W. Woods 1 , K. Genareau 1 , Joni Klüss 2
Affiliation  

Volcanic lightning generates high temperatures (>1500 °C) that melt volcanic ash particles, which re-solidify into lightning-induced volcanic spherules (LIVS). These LIVS have been documented within several ashfall deposits from multiple explosive volcanic eruptions. While several studies have analyzed the morphology and formation processes of LIVS, there is limited research on the chemical composition of these glassy particles. High-current (7 and 25 kA) impulse experiments were performed on very fine volcanic ash (<32 μm) produced from andesitic pyroclasts to create lightning-induced volcanic particles. The pre- and post-experimental ash was analyzed using a combination of wavelength and energy dispersive spectroscopy. The unaltered post-experimental particles, in addition to the pre-experimental samples, are characterized by angular grain shapes and euhedral mineral microlites within a glass matrix. Conversely, the 29 analyzed lightning-induced particles have a rounded morphology and are composed of chemically distinct and highly variable glass with no preserved microlites. Observed within the post-experimental particles are chemically diverse flow structures that are compositionally different than the surrounding glass, indicating mingling between molten components derived from the initial mineral and glass. Transformation of volcanic ash particles into LIVS will provide evidence of lightning during explosive eruptions and may increase the leaching rate of elements into the environment following ash deposition.



中文翻译:

闪电引起的火山灰玻璃化学变化

火山闪电产生高温 (>1500 °C),使火山灰颗粒熔化,然后重新凝固成闪电诱发的火山小球 (LIVS)。这些 LIVS 已被记录在多次爆炸性火山喷发的几个火山灰沉积物中。虽然有几项研究分析了 LIVS 的形态和形成过程,但对这些玻璃状颗粒的化学成分的研究有限。对安山质火山碎屑产生的极细火山灰 (<32 μm) 进行了高电流(7 和 25 kA)脉冲实验,以产生闪电诱发的火山颗粒。使用波长和能量色散光谱的组合分析实验前和实验后的灰分。未改变的实验后粒子,除了实验前的样品,其特征在于玻璃基质中的棱角状颗粒形状和自形矿物微晶石。相反,分析的 29 种闪电诱发粒子具有圆形形态,由化学性质不同且高度可变的玻璃组成,没有保存的微晶石。在实验后的粒子中观察到化学上不同的流动结构,其成分与周围的玻璃不同,表明源自初始矿物和玻璃的熔融成分之间存在混合。火山灰颗粒转化为 LIVS 将提供爆炸性喷发期间闪电的证据,并可能增加灰烬沉积后元素向环境中的浸出率。被分析的 29 种闪电诱发粒子具有圆形形态,由化学性质不同且高度可变的玻璃组成,没有保存的微晶石。在实验后的粒子中观察到化学上不同的流动结构,其成分与周围的玻璃不同,表明源自初始矿物和玻璃的熔融成分之间存在混合。火山灰颗粒转化为 LIVS 将提供爆炸性喷发期间闪电的证据,并可能增加灰沉积后元素向环境中的浸出率。被分析的 29 种闪电诱发粒子具有圆形形态,由化学性质不同且高度可变的玻璃组成,没有保存的微晶石。在实验后的粒子中观察到化学上不同的流动结构,其成分与周围的玻璃不同,表明源自初始矿物和玻璃的熔融成分之间存在混合。火山灰颗粒转化为 LIVS 将提供爆炸性喷发期间闪电的证据,并可能增加灰沉积后元素向环境中的浸出率。在实验后的粒子中观察到化学上不同的流动结构,其成分与周围的玻璃不同,表明源自初始矿物和玻璃的熔融成分之间存在混合。火山灰颗粒转化为 LIVS 将提供爆炸性喷发期间闪电的证据,并可能增加灰沉积后元素向环境中的浸出率。在实验后的颗粒中观察到化学上不同的流动结构,其成分与周围的玻璃不同,表明源自初始矿物和玻璃的熔融成分之间存在混合。火山灰颗粒转化为 LIVS 将提供爆炸性喷发期间闪电的证据,并可能增加灰沉积后元素向环境中的浸出率。

更新日期:2021-07-14
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