Variability of ash deposits at Piton de la Fournaise (La Reunion Island): insights into fragmentation processes at basaltic shield volcanoes
Variability of ash deposits at Piton de la Fournaise (La Reunion Island): insights into fragmentation processes at basaltic shield volcanoes
复制标题
Piton de la Fournaise（留尼汪岛）火山灰沉积物的变化：深入了解玄武岩盾状火山的破碎过程
作者：
S. Thivet;L. Gurioli;A. Di Muro;J. Eychenne;P. Besson;J. Nedelec
人们普遍认为，玄武岩盾状火山的主要喷发岩浆是由喷涌活动引起的。在Piton de La Fournaise（法国La r<s:1> union岛），火山喷发活动主要发生在无人居住的Enclos fouquaur火山口内，一般不会对居民构成任何危险。然而，历史观察、最近的监测数据和对麻风矿床的实地工作表明，一些喷发产生了不寻常的和意想不到的爆炸阶段。从这座火山历史上和最近的主要火山喷发中采集的全面样本使我们能够进行系统的成分、颗粒大小、化学和形态分析，以表征这些爆炸性玄武岩喷发的喷发动力学。这种综合方法揭示了所研究的麻药的高度可变特征，反映了不同的破碎效率和多种相关机制。在夏威夷喷泉或温和的斯特龙堡喷发期间释放的不同强度的幼岩浆的初级韧性和部分脆性破碎被认为是最常见的破碎机制，特别是在2014-2018年以喷流为主的喷发序列期间。与此同时，我们区分了更有效的短期破碎事件，这些事件与(i)同步喷发结晶增强的塞子加压和脆性破碎，（ii）岩浆/水相互作用，（iii）罕见的潜水爆炸，以及（iv）火山口崩塌期间产生细灰的次级破碎有关。我们的结论是，结构、地球化学和形态分析使识别和表征喷发过程的可变性成为可能，而颗粒大小和火山灰颗粒的成分可能是量化破碎效率和性质的最重要参数。
It is commonly accepted that effusive activity emplaces the main emitted magmatic volume in basaltic shield volcanoes. At Piton de La Fournaise (La Réunion Island, France), eruptive activity occurs mostly within the non-populated Enclos Fouqué caldera and generally does not pose any risk to the population. However, historical observations, recent monitoring data, and field work on tephra deposits suggest that some eruptions have produced unusual and unexpected explosive phases. A comprehensive sampling of tephra from major historical and recent eruptions on this volcano allowed us to perform systematic componentry, grain size, and chemical and morphological analyses in order to characterize the eruptive dynamics involved in these explosive basaltic eruptions. This integrative approach reveals highly variable characteristics of the studied tephra reflecting different fragmentation efficiencies and multiple associated mechanisms. Primary ductile and partially brittle fragmentation of various intensity of juvenile magma emitted during Hawaiian fountaining or mild Strombolian explosions were identified as the most common fragmentation mechanisms, in particular during the 2014–2018 dominantly effusive eruptive sequence. In parallel, we distinguished more efficient short-lived fragmentation events related to (i) plug pressurization and brittle fragmentation enhanced by syn-eruptive crystallization, (ii) magma/water interactions, (iii) rare phreatic explosions, and (iv) secondary fragmentation producing fine ash during caldera collapse. We conclude that textural, geochemical, and morphological analyses make it possible to identify and characterize the variability in eruptive processes, with the grain size, and the componentry of the ash particles being probably the most important parameters to quantify both the efficiency and the nature of the fragmentation.
影响因子：
18.3
作者：
Arzilli, Fabio;La Spina, Giuseppe;Lee, Peter D.
通讯作者：
Lee, Peter D.
影响因子：
5.8
作者：
Applegarth, L. Jane;Tuffen, Hugh;Cashman, Katharine V.
通讯作者：
Cashman, Katharine V.