Decadal to monthly timescales of magma transfer and reservoir growth at a caldera volcano
Decadal to monthly timescales of magma transfer and reservoir growth at a caldera volcano
复制标题
DOI：
10.1038/nature10706
复制
发表时间：
2012-02-02
期刊：
影响因子：
64.8
通讯作者：
Scaillet, B.
中科院分区：
文献类型：
--
作者：
Druitt, T. H.;Costa, F.;Scaillet, B.
形成破火山口的火山喷发是一种频率低、影响大的事件，能够在数小时到数天的时间尺度上喷发出数万至数千立方公里的岩浆，在当地和全球范围内造成毁灭性影响(1)。由于在其漫长的积累阶段没有监测到这种喷发，因此对其前兆现象没有很好的了解。在美国黄石火山和意大利Campi Flegrei火山等火山口最近的动荡事件中获得的地球物理信号很难解释，而且对大喷发的必要条件也知之甚少（2,3）。在这里，我们利用希腊圣托里尼火山“米诺斯”火山口形成喷发的化学带晶体，对爆发前的岩浆过程及其时间尺度进行了研究(4)，该火山爆发发生在公元前1600年晚期。结果提供了对大型硅系统如何快速地从静止状态过渡到喷发边缘的见解（5,6）。尽管喷发的岩浆体积很大（40-60立方千米），而且米诺斯火山喷发与上一次大喷发之间有1.8万年的孕育期，但米诺斯火山岩浆中的大多数晶体记录的过程发生在喷发前不到100年的时间里。在火山喷发前的一个世纪里，大量的硅质岩浆（和一些基性岩浆）对岩浆库进行了补充，在火山喷发的最后几个月里，不同硅质岩浆批次之间的混合仍在发生。大型硅质岩浆储层的最终组合可能发生在地质上与之前的休止期相比非常短的时间尺度上，主要的生长阶段紧接在喷发之前。这些观察结果对监测长期休眠但潜在活跃的火山口系统具有重要意义。
Caldera-forming volcanic eruptions are low-frequency, high-impact events capable of discharging tens to thousands of cubic kilometres of magma explosively on timescales of hours to days, with devastating effects on local and global scales(1). Because no such eruption has been monitored during its long build-up phase, the precursor phenomena are not well understood. Geophysical signals obtained during recent episodes of unrest at calderas such as Yellowstone, USA, and Campi Flegrei, Italy, are difficult to interpret, and the conditions necessary for large eruptions are poorly constrained(2,3). Here we present a study of pre-eruptive magmatic processes and their timescales using chemically zoned crystals from the 'Minoan' caldera-forming eruption of Santorini volcano, Greece(4), which occurred in the late 1600s BC. The results provide insights into how rapidly large silicic systems may pass from a quiescent state to one on the edge of eruption(5,6). Despite the large volume of erupted magma(4) (40-60 cubic kilometres), and the 18,000-year gestation period between the Minoan eruption and the previous major eruption, most crystals in the Minoan magma record processes that occurred less than about 100 years before the eruption. Recharge of the magma reservoir by large volumes of silicic magma (and some mafic magma) occurred during the century before eruption, and mixing between different silicic magma batches was still taking place during the final months. Final assembly of large silicic magma reservoirs may occur on timescales that are geologically very short by comparison with the preceding repose period, with major growth phases immediately before eruption. These observations have implications for the monitoring of long-dormant, but potentially active, caldera systems.