U-Th zircon dating reveals a correlation between eruptive styles and repose periods at the Nisyros-Yali volcanic area, Greece
U-Th zircon dating reveals a correlation between eruptive styles and repose periods at the Nisyros-Yali volcanic area, Greece
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U-Th 锆石测年揭示了希腊尼西罗斯-亚利火山区喷发风格与休止期之间的相关性
DOI：
10.1016/j.chemgeo.2020.119830
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发表时间：
2020
期刊：
影响因子：
3.9
通讯作者：
Ellis, Ben
中科院分区：
文献类型：
--
作者：
Popa, Răzvan-Gabriel;Guillong, Marcel;Bachmann, Olivier;Szymanowski, Dawid;Ellis, Ben
富含水的硅质岩浆能够喷发并爆发，这种喷发方式的急剧变化被称为喷发-爆炸转变，对管理火山灾害具有重要意义。一些火山在同一喷发事件中表现出从喷涌到爆炸的转变，而另一些火山则在不同的喷发之间表现出这种行为。在后一种情况下，岩浆室过程导致岩浆中的物理化学变化，这可能有利于喷发或爆炸性。这就是来自南爱琴海的尼西罗斯-雅利火山中心的情况。在最近的活动阶段(超过120Ky)，火山区产生了八次流纹岩喷发和爆炸事件(五次在尼西罗斯岛，三次在雅利岛)，包括两次形成火山口的喷发。喷流沉积和爆炸沉积之间的水含量、温度和喷发前水饱和度的变化表明，这两种喷发方式之间存在潜在的时间相关性。我们通过对锆石晶体进行USingle Bond Th不平衡测年来研究这种时间依赖性。我们对所调查单元的喷发年龄估计范围为尼西罗斯118.7 Ma±610 ka至19.9 Ma±21.5 ka，雅利为40 Ma±65.2 ka至22.7 Ma±81.6 ka。雅利火山是在尼西罗斯上发生两次破火山口事件后发育起来的，分别发生在63.1±47.7亿和58.4万±62.7万年。雅利标志着向一个几何上更复杂的系统的转变，在那里，上地壳的硅质泥浆至少有两个可喷发的岩浆室(一个在雅利下面，一个在尼西罗斯下面)。这两座火山的喷发风格似乎都与休息期的长短有关。喷发事件发生在较长的火山静止期之后，而爆炸性事件发生在~5-10Ky的较短休止期之后，根据喷发年龄的不确定性，可以延长到尼西罗斯的<；18Ky和雅利的<；12Ky。这一观察结果是由岩浆室中挥发分的物理状态解释的，较长的休止期有利于挥发分的积累。这可能会导致水在储存压力下过饱和，这被证明有利于沸腾。根据这种解释，尼西罗斯火山和雅利火山目前都处于喷发的时间窗口，这使得下一次喷发很可能是非爆炸性的。
Water-rich silicic magmas are capable of erupting effusively and explosively, and this drastic change in eruptive styles, termed effusive-explosive transition, has important implications in managing volcanic hazards. Some volcanoes exhibit effusive-explosive transitions during the same eruptive event, while others show this behavior between different eruptions. In the latter case, magma chamber processes induce physical-chemical changes in the magma, which can favor either effusivity or explosivity. This is the case for the Nisyros-Yali volcanic center, from the South Aegean Sea. In the recent stages of activity (past 120 ky), the volcanic area generated eight rhyolitic effusive and explosive events (five on the island of Nisyros and three on the island of Yali), including two caldera-forming eruptions. Changes of water content, temperature and pre-eruptive water-saturation between effusive and explosive deposits point to a potential time-dependency between the two eruptive styles. We investigate this time-dependency by applying Usingle bondTh disequilibrium dating to zircon crystals. Our eruptive age estimates of the investigated units range from 118.7 ± 10 ka to 19.9 ± 1.5 ka for Nisyros, and from 40 ± 5.2 ka to 22.7 ± 1.6 ka for Yali. Yali volcano has developed after the two caldera-forming events on Nisyros, which occurred at 63.1 ± 4.7 ka and 58.4 ± 2.7 ka. Yali marks the transition to a more geometrically complex system, where the upper-crustal silicic mush hosts at least two eruptible magma chambers (one under Yali, and one under Nisyros). The eruptive styles at both volcanoes seem to be correlated with the length of the repose periods. Effusive events occur after longer periods of volcanic quiescence, while explosive events are generated after shorter periods of repose of ~5–10 ky, which can be extended based on eruption age uncertainty to <18 ky for Nisyros and <12 ky for Yali. This observation is explained by the physical state of the volatiles in the magma chamber, with longer repose periods favoring volatile build-up. This can lead to water-supersaturation at storage pressures which was shown to favor effusivity. Based on this interpretation, both Nisyros and Yali volcanoes are presently in the effusive time window, which makes it probable for the next eruptions to be non-explosive.
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DOI：
--
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DOI：
--
发表时间：
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作者：
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