Locating magma reservoirs using InSAR and petrology before and during the 2011-2012 Cordon Caulle silicic eruption
Locating magma reservoirs using InSAR and petrology before and during the 2011-2012 Cordon Caulle silicic eruption
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DOI：
10.1016/j.epsl.2014.03.046
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发表时间：
2014-06-01
影响因子：
5.3
通讯作者：
Herrin, Jason
中科院分区：
文献类型：
--
作者：
Jay, Jennifer;Costa, Fidel;Herrin, Jason
我们结合联合收割机岩石学和干涉合成孔径雷达观测，探讨在2011-2012年喷发之前和期间，在智利南部的Cordon Caulle火山变形的起源。喷发的流纹英安岩是晶体贫乏，并储存在约900摄氏度与约。4重量%的H（2）0和220 ppm的CO2的熔体中，对应于约6-7公里的存储深度。除了先前记录的2007-2008年变形事件外，我们还发现了三次喷发前变形事件：第一次发生在2008年至2009年，覆盖范围约为400 km（2），最大抬升18.5 cm，第二次发生在2010年2月至3月，覆盖范围约为20 km（2），最大抬升10 cm，第三次发生在2011年3月至5月，覆盖面积约为40 km（2），最大隆起为6 cm。2008-2009年变形幕的建模表明，源深度约为5-9公里，与岩石学确定的岩浆储存深度一致。从2007年到2009年，模拟的震源体积变化的总和比观测到的喷发体积小约12倍。我们对岩浆可压缩性的计算表明，储层中一定有大量的预先存在的岩浆，以解释这种差异。共喷发沉降显示了三个不同的岩浆源的证据，并在三个来源中的两个被认为是爆发前的通货膨胀。模拟变形源位于2011-2012年喷发喷口2-10公里处，与以前历史喷发（1921- 22，1960）的喷口和邻近的普耶韦火山一致。这意味着存在一个相互连接的岩浆管道系统，可以进行压力传递，覆盖面积至少为20平方公里。因此，Cordon Caulle的变形和地球化学特征类似于一个大型的火山口系统。一个镁铁质晶体凝块的存在表明玄武质熔体的存在，但我们发现，镁铁质岩浆到达水库至少几百年前喷发。因此，如果喷发前的变形是由浅储层的补充引起的，则新的岩浆与先前存在的岩浆相似，并且/或者两者之间没有相互作用。我们发现，喷发前的变形可以发生在脉冲和达到高峰年前喷发，因此缺乏变形并不一定意味着喷发是不是迫在眉睫。(C)2014 Elsevier B. V.保留所有权利，
We combine petrological and InSAR observations to probe the origin of deformation of Cordon Caulle volcano in Southern Chile before and during the 2011-2012 eruption. The erupted rhyodacite is crystal-poor and was stored at about 900 degrees C with ca. 4 wt% H(2)0 and 220 ppm CO2 in the melt, corresponding to a storage depth of about 6-7 km. In addition to a previously documented 2007-2008 deformation episode, we find three pre-eruptive deformation episodes: the first between 2008 and 2009 that covers similar to 400 km(2) with a maximum uplift of 18.5 cm, the second between February and March 2010 that covers similar to 20 km(2) with a maximum uplift of 10 cm, and the third between March and May 2011 that covers similar to 40 km(2) with a maximum uplift of 6 cm. Modeling of the 2008-2009 deformation episode suggests source depths of about 5-9 km, consistent with the petrologically determined magma storage depth. The sum of modeled source volume changes from 2007 to 2009 is about 12 times smaller than the observed erupted volume. Our calculation of magma compressibility shows that there must have been a significant volume of pre-existing magma in the reservoir to account for this difference. Co-eruptive subsidence shows evidence for three distinct magma sources, and pre-eruptive inflation is seen at two of the three sources. Modeled deformation sources are located 2-10 km from the 2011-2012 eruptive vent and coincide with the vents from previous historical eruptions (1921-22,1960) and with the neighboring Puyehue volcano. This implies the existence of an interconnected magma plumbing system that allows for pressure transfer and which covers an area of at least 20 km2. Thus, the deformation and geochemical characteristics of Cordon Caulle resemble those of a large silicic caldera system. The presence of a mafic crystal clot demonstrates the existence of basaltic melts in the silicic reservoir, but we find that the mafic magmas reached the reservoir at least several hundred years before eruption. Therefore, if the pre-eruptive deformation was caused by replenishment to a shallow reservoir, the new magma was silicic and similar to the pre-existing magma, and/or there was no interaction between the two. We find that pre-eruptive deformation can occur in pulses and reach its peak years before eruption, and thus lack of deformation does not necessarily imply that eruption is not imminent. (C) 2014 Elsevier B.V. All rights reserved,