In December 2018, an unusually large intra- and extra-caldera eruption took place at Ambrym volcano (Vanuatu). The eruption drained the volcano’s five active lava lakes and terminated, at least momentarily, the surface activity that had been ongoing for decades to hundreds of years, sustaining the largest recorded persistent degassing on the planet. Here, we investigate the mechanisms and dynamics of this major eruption. We use major elements and volatiles in olivine and clinopyroxene-hosted melt inclusions, embayments, crystals and matrix glasses together with clinopyroxene geobarometry as well as olivine and clinopyroxene geothermometry and diffusion modelling in crystals and embayments to reconstruct the chronology and timing of the subsurface processes that accompanied the eruption. We find that the eruption began with the meeting, mingling and limited chemical mixing of mostly two magma bodies occupying similar vertical but different horizontal locations in the crust, one corresponding to the main plumbing system at Ambrym that fed the lava lakes and the other corresponding to an older, previously cutoff and more chemically evolved branch of the plumbing system. Within the primitive magma, two texturally distinct components—one microlite rich and one microlite poor—can further be identified. The 2018 eruption hence provides a detailed image of Ambrym’s complex plumbing system. Our diffusion timescales and geobarometric estimates coincide closely with geophysical observations. They point to a reconnection of the evolved magmatic branch with the main system occurring less than 10 h prior to the intra-caldera eruption and a period of 2 days for the subsequent > 30-km lateral magma transport along a deeper dike prior to submarine eruption just off the SE coast of the island with the more primitive magma reaching first followed by mingled magma containing both compositions. Magma ascent rates are estimated at 95 ± 24 m/s in the last ~ 2.5 km of ascent during the intra-caldera eruption and at 80 ± 6 m/s in the last ~ 4 km of ascent during the submarine eruption. Comparison with other lava lake draining eruptions reveals striking similarities both in terms of precursory activity, with lake level rising prior to the eruption in all cases, and in terms of plumbing system organization with the presence of peripheral magma pockets, isolated from the main magmatic system but that can be mobilized and erupted when met by dikes propagating laterally from the main system.

2018年12月，安布林火山（瓦努阿图）发生了异常大的火山口内和火山口外喷发。火山喷发耗尽了火山的五个活跃的熔岩湖，并至少暂时终止了已经进行了数十年至数百年的地表活动，维持了地球上最大的持续性脱气。在这里，我们调查这种主要喷发的机制和动力学。我们使用橄榄石和斜柏石中的熔体包裹体，浮体，晶体和基质玻璃中的主要元素和挥发物，以及斜柏石地压法，橄榄石和斜柏石地热法以及晶体和浮体中的扩散模型来重构地下过程的时间顺序和时间，伴随着喷发。我们发现喷发始于会议，混合和有限的化学混合，主要是两个地壳在地壳中具有相似的垂直但水平位置不同，一个对应于Ambrym的主要管道系统，为熔岩湖供水，另一个对应于较旧的，先前已被切断且化学演化程度更高的分支在原始岩浆中，可以进一步识别出两个在质地上截然不同的组成部分-一个微矿富集和一个微矿贫集-。因此，2018年的火山喷发提供了Ambrym复杂管道系统的详细图像，我们的扩散时间尺度和地压估算值与地球物理观测结果非常吻合。他们指出，演化的岩浆分支与主系统的重新连接发生在火山口内喷发前不到10小时，随后的2天为 在岛屿东南沿海海底喷发之前，沿着更深的堤坝进行30公里的横向岩浆运输，首先是较原始的岩浆，然后是包含这两种成分的混合岩浆。在火山口内爆发的最后一个〜2.5 km内，岩浆上升速率估计为95±24 m / s，而在水下爆发的最后一个〜4 km内，岩浆上升速率为80±6 m / s。与其他熔岩湖排水爆发的比较表明，无论是在前兆活动方面，还是在所有情况下都在喷发之前，湖水位都升高了；在管道系统的组织方面，存在着与主要岩浆系统隔离的外围岩浆囊，这两者具有惊人的相似性。但是当遇到从主系统横向传播的堤防时，它可以被动员和爆发。