Paroxysms at Stromboli Volcano (Italy): Source, Genesis and Dynamics
Paroxysms at Stromboli Volcano (Italy): Source, Genesis and Dynamics
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DOI：
10.3389/feart.2021.593339
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发表时间：
2021-02-24
影响因子：
2.9
通讯作者：
Pistolesi, Marco
中科院分区：
文献类型：
--
作者：
Metrich, Nicole;Bertagnini, Antonella;Pistolesi, Marco
解读剧烈爆炸活动的触发机制对于理解玄武质开口火山系统的动力学具有广泛的意义。近1300年来，斯特龙博利火山不仅以其持续的脱气活动和山顶火山口的轻微爆炸而闻名，而且还因其短暂的、剧烈的、规模不等的爆炸事件而闻名，这些事件被称为大爆炸和突发事件。在这里，我们重点关注1456年和1930年的突发事件以及2019年7月和8月在斯特龙博利发生的最近事件。我们表明，浅的现象，如侧翼崩溃，熔岩涌出通过裂缝开口，或部分排空的浅管道，只有加快挥发物丰富的岩浆上升，通过增加减压速率，而加压的地壳系统和深回填的岩浆和其富含CO2的气相触发发作中发挥了重要作用。此外，我们还提供了关于2019年大块浮石地球化学的新数据，沿着文献中的数据汇编，橄榄石晶体中的化学剖面，以及范围广泛的爆炸性喷发的物理参数。对于小的和大的阵发性，时间尺度来自橄榄石中的铁-镁扩散曲线。在这两种类型的爆炸中，结晶扩散的最后阶段表明在喷发前两到十天的岩浆快速上升速率。微量元素浓度（Nb，La和Ba）和比值（Rb/Th）表明，2019年的浮石样品位于斯特龙博利过去20年内爆发的岩浆批次区域。总的来说，岩浆地球化学与爆炸性喷发的规模或强度之间没有相关性，根据火山喷发体积的估计，爆炸性喷发的范围接近3个数量级（从大爆炸到大爆发）。相比之下，橄榄石成分是一个很好的代理喷发火山灰体积和岩浆流量。物理和化学参数之间的相关性，这是有效的喷发的整体光谱，意味着岩浆源最终控制喷发动力学。
Deciphering the triggering mechanisms of violent explosive activity is of broad interest for understanding the dynamics of basaltic open-vent volcanic systems. For nearly 1300 years Stromboli has been renowned not only for its continuous degassing activity and mild explosions at the summit craters, but also for short-lived, violent explosive events of variable scale, known as major explosions and paroxysms. Here, we focus on the 1456 and 1930 paroxysms and on the most recent events, in July and August 2019 at Stromboli. We show that shallow phenomena such as flank collapse, lava outpouring through fractures opening, or partial emptying of the shallow conduit, only speed up volatile-rich magma ascent by increasing the decompression rate, whereas pressurization of the crustal system and the deep refilling by magma and its CO2-rich gas phase play a major role in triggering paroxysms. Moreover, we present new data on the geochemistry of the 2019 bulk pumice, along with a compilation of data from the literature, chemical profiles in olivine crystals, and the physical parameters of explosive eruptions of wide ranging magnitude and intensity. For small and large paroxysms, timescales were derived from Fe-Mg diffusion profiles in olivine. In both types of explosion, the last phases of crystallization-diffusion indicate rapid magma ascent rates of two to ten days prior to eruption. Trace element concentrations (Nb, La and Ba) and ratios (Rb/Th) indicate that the 2019 pumice samples plot in the domain of magma batches erupted within the last 20 years at Stromboli. As a whole, there is no correlation between magma geochemistry and magnitude or intensity of explosive eruptions, which span a range of similar to 3 orders of magnitude (from major explosions to large paroxysms) based on estimates of erupted tephra volumes. In contrast, olivine compositions are a good proxy for erupted tephra volumes and magma flux. The correlation among physical and chemical parameters, which is valid for the overall spectrum of eruptions, implies that the magmatic source ultimately controls eruptive dynamics.