Melt inclusion record of the conditions of ascent, degassing, and extrusion of volatile‐rich alkali basalt during the powerful 2002 flank eruption of Mount Etna (Italy)
Melt inclusion record of the conditions of ascent, degassing, and extrusion of volatile‐rich alkali basalt during the powerful 2002 flank eruption of Mount Etna (Italy)
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2002 年埃特纳火山（意大利）强烈侧翼喷发期间富含挥发分的碱性玄武岩的上升、脱气和挤出条件的熔体包裹体记录
DOI：
10.1029/2005jb003934
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发表时间：
2006
影响因子：
--
通讯作者：
A. Sobolev
中科院分区：
文献类型：
--
作者：
N. Spilliaert;P. Allard;N. Métrich;A. Sobolev
[1] 埃特纳火山于 2001 年 7 月 8 月和 2002 年 10 月至 2003 年 1 月期间成功发生了两次不同寻常的高爆炸性侧翼喷发，增加了改变岩浆条件的可能性。在这里，我们从其南翼喷口爆炸产物中橄榄石熔体包裹体的成分和挥发性（H2O、CO2、S、Cl）含量来破译第二次喷发的起源和机制。我们的研究结果表明，喷发开始时强大的熔岩喷泉和灰柱是由一批原始的、富含挥发物（≥4wt%）玄武岩岩浆的封闭系统上升所维持的，这些玄武岩岩浆从海平面以下≥10公里的深度（bsl）上升，并突然通过2001年向东扩展而保持张开的裂缝挤出。这种岩浆是 240 年来最原始的岩浆，可能代表了自 20 世纪 70 年代初以来埃特纳火山熔岩演化的富含碱的母体最终成员。其中很少有在喷发开始时直接被挤出的，但它的输入可能在喷发前几周给浅层管道系统加压。后者随后通过大量相同但演化程度稍高的岩浆的挤压和脱气而供给，这些岩浆在 6-4 km bsl 处积水，这与地震数据一致，并且在硫解出的初始深度（~3 km bsl）之上缺乏喷发前 SO2 积累。我们发现，在积水时，岩浆被更深层次的富含二氧化碳的气相冲刷和脱水，这一过程可能通常会影响埃特纳火山和其他碱性玄武岩火山的管道系统。
[1] Two unusual, highly explosive flank eruptions succeeded on Mount Etna in July August 2001 and in October 2002 to January 2003, raising the possibility of changing magmatic conditions. Here we decipher the origin and mechanisms of the second eruption from the composition and volatile (H2O, CO2, S, Cl) content of olivine-hosted melt inclusions in explosive products from its south flank vents. Our results demonstrate that powerful lava fountains and ash columns at the eruption onset were sustained by closed system ascent of a batch of primitive, volatile-rich (≥4 wt %) basaltic magma that rose from ≥10 km depth below sea level (bsl) and suddenly extruded through 2001 fractures maintained opened by eastward flank spreading. This magma, the most primitive for 240 years, probably represents the alkali-rich parental end-member responsible for Etna lavas' evolution since the early 1970s. Few of it was directly extruded at the eruption onset, but its input likely pressurized the shallow plumbing system several weeks before the eruption. This latter was subsequently fed by the extrusion and degassing of larger amounts of the same, but slightly more evolved, magma that were ponding at 6–4 km bsl, in agreement with seismic data and with the lack of preeruptive SO2 accumulation above the initial depth of sulphur exsolution (∼3 km bsl). We find that while ponding, this magma was flushed and dehydrated by a CO2-rich gas phase of deeper derivation, a process that may commonly affect the plumbing system of Etna and other alkali basaltic volcanoes.