Teleseismic Tomography of the Laguna del Maule Volcanic Field in Chile
Teleseismic Tomography of the Laguna del Maule Volcanic Field in Chile
复制标题
DOI：
10.1029/2020jb019449
复制
发表时间：
2020-08
期刊：
影响因子：
--
通讯作者：
Tong Bai;C. Thurber;F. Lanza;B. Singer;N. Bennington;K. Keranen;C. Cardona
中科院分区：
文献类型：
--
作者：
Tong Bai;C. Thurber;F. Lanza;B. Singer;N. Bennington;K. Keranen;C. Cardona
由于有大量的冰后期流纹岩喷发以及持续快速的隆升，位于安第斯山脉南部的莫莱湖火山场为研究活跃的硅质岩浆系统的动力学提供了绝佳的机会。利用44个当地台站在约2.25年期间记录的137次远震的4093个P波到时，我们进行了远震层析成像，以绘制出火山场下方直至40千米深处的地壳结构图像。在海平面以下约0至12千米深度处有一个显著的低速体，其体积约为500立方千米，速度异常峰值为 - 400米/秒（约9%），与近期重力和面波层析成像研究中探测到的上地壳岩浆库位置重叠。其估计的平均P波速度约为4.6千米/秒，对应的平均熔体分数约为14%，熔体体积约为70立方千米。岩石学观测结果也与在对应于异常区域的深度上流纹岩熔体的产生和储存相符。此外，层析成像结果支持一个从约25千米深处到模型底部的MASH（熔融、同化、储存和均一化）下地壳区域，这可能反映了一个为浅部硅质岩浆库提供物质并孕育它的深部地壳岩浆源。
With substantial postglacial rhyolite eruptions and ongoing rapid uplift, the Laguna del Maule volcanic field in the southern Andes provides an exceptional opportunity to study the dynamics of an active silicic magmatic system. Using 4,093 P arrivals from 137 distant earthquakes recorded by 44 local stations over ∼2.25 years, we conduct teleseismic tomography to image the crustal structure down to 40 km below the volcanic field. A prominent low‐velocity body at depths between ∼0 and 12 km below sea level (b.s.l.), characterized by a volume of ∼500 km3 and a peak anomaly of −400 m/s (∼9%), overlaps the location of the upper‐crustal magma reservoir detected in recent gravity and surface wave tomography studies. Its estimated average P wave velocity of ∼4.6 km/s corresponds to an average melt fraction of about 14% and a melt volume of ∼70 km3. Petrologic observations are also consistent with generation and storage of rhyolitic melts at depths corresponding to the anomalous zone. Moreover, the tomographic results support a lower crust zone of MASH (melting, assimilation, storage, and homogenization) from a depth of ∼25 km to the base of the model, which likely reflects a deep crustal source of magma that contributes to and incubates the shallow silicic reservoir.