Quantification of the Intrusive Magma Fluxes during Magma Chamber Growth at Soufriere Hills Volcano (Montserrat, Lesser Antilles)
Quantification of the Intrusive Magma Fluxes during Magma Chamber Growth at Soufriere Hills Volcano (Montserrat, Lesser Antilles)
复制标题
DOI：
10.1093/petrology/egt075
复制
发表时间：
2014-03-01
影响因子：
3.9
通讯作者：
Kiddley, E. J.
中科院分区：
文献类型：
--
作者：
Annen, C.;Paulatto, M.;Kiddley, E. J.
地壳中的岩浆流控制着岩浆房的热活性和机械稳定性。我们估计产生负的地震速度异常观察下面的苏弗里埃山火山，蒙特塞拉特所需的岩浆通量。安山岩床的增生的岩浆体的增长进行了数值模拟和由此产生的温度和熔体分数被用来计算合成异常的地震波速度，这是过滤，可与层析实验获得的速度异常。岩石学表明，在它被重新加热，重新流动和喷发之前，岩浆房中的岩浆温度约为850摄氏度。我们进行了模拟，假设对流很低，热传递主要是通过传导进行的，以及假设对流足够强烈，可以迅速将岩浆房冷却到850摄氏度的模拟。在这两种情况下，过去350年的岩浆房增长导致层析成像异常太强，除非岩浆以不太可能的低熔融分数（< 0中心点5）侵位。根据侵位岩浆的温度和熔融分数，在半径为2-5 km的岩床中，获得了模拟和观测到的速度异常之间的良好拟合。由于侵入体尺寸和侵位持续时间之间的权衡，体积岩浆通量被限制在7 x 10（-4）和5 x 10（-3）km（3）a（-1）。这种速度异常可以用含有高熔体分数岩浆或大量晶体和熔体的岩浆房来再现。模拟岩浆房中的岩浆年龄范围远大于喷发安山岩的晶体停留时间。这表明，喷发水龙头最近聚集的岩浆和速度异常的小口袋主要是由于非喷发糊状物。
Magma fluxes in the crust control the thermal viability and mechanical stability of magma chambers. We estimated the magma fluxes required to generate the negative seismic velocity anomaly observed below Soufriere Hills volcano, Montserrat. Growth of a magma body by accretion of andesitic sills was simulated numerically and the resulting temperatures and melt fractions were used to calculate a synthetic anomaly of seismic wave velocity, which was filtered to be comparable with the velocity anomaly obtained from a tomographic experiment. Petrology indicates that before it was reheated, remobilized and erupted, the temperature of the magma residing in the chamber was about 850 degrees C. We ran simulations where convection is assumed to be low and heat transfer is mostly by conduction and simulations where convection is assumed to be vigorous enough to rapidly cool the magma chamber to 850 degrees C. In both cases, magma chamber growth over the last 350 years results in tomography anomalies that are too strong, unless the magma was emplaced at an unlikely low melt fraction (< 0 center dot 5). Good fits between the modelled and the observed velocity anomaly were obtained with sills 2-5 km in radius emplaced over 6000-150 000 years, depending on the temperature and melt fraction of the emplaced magma. Because of a trade-off between intrusion dimensions and emplacement durations, the volumetric magma fluxes are restricted to 7 x 10(-4) and 5 x 10(-3) km(3) a(-1). The velocity anomaly can be reproduced with a chamber containing high melt-fraction magma or with a mush of crystals and melt. The range of magma ages in the modelled magma chamber is much wider than the crystal residence time of the erupted andesite. This suggests that the eruption taps small pockets of recently assembled magma and that the velocity anomaly is mostly due to a non-eruptible mush.