Cryptic evolved melts beneath monotonous basaltic shield volcanoes in the Galápagos Archipelago
Cryptic evolved melts beneath monotonous basaltic shield volcanoes in the Galápagos Archipelago
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加拉帕戈斯群岛单调的玄武岩盾状火山下的神秘演化熔体
DOI：
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发表时间：
2020
影响因子：
16.6
通讯作者：
J. Maclennan
中科院分区：
文献类型：
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作者：
M. Stock;D. Geist;D. Neave;M. Gleeson;B. Bernard;K. Howard;I. Buisman;J. Maclennan
许多火山喷发的岩浆成分均匀，时间跨度从几十年到几千年不等。这种单调的活动被认为反映了它们的岩浆系统中高度的化学均匀性，导致了可预测的喷发行为。我们结合联合收割机的岩石学分析喷发的晶体与新的热力学模型，在加拉帕戈斯群岛（沃尔夫和费尔南迪纳）单调的盾状火山下的岩浆系统中的熔体的多样性。与均匀的玄武岩岩浆在长时间尺度的表面喷发相比，我们发现，次火山系统包含极端的异质性，熔体延伸到流纹岩成分。演化的熔体丰度低，大量玄武岩从地壳深处冲刷出来，覆盖了它们的化学特征。这一过程只会维持单调的活动，而进入地壳的熔体量很高，如果地壳熔体流量减少，就有可能过渡到更大的活动。在这项研究中，作者表明，单调的玄武质火山可以在其次火山系统中容纳一系列熔体，延伸到流纹岩成分。这项研究意味着，在很长一段时间内产生单调玄武岩熔岩的火山在未来可能会转变为更具爆炸性的、富含二氧化硅的喷发。
Many volcanoes erupt compositionally homogeneous magmas over timescales ranging from decades to millennia. This monotonous activity is thought to reflect a high degree of chemical homogeneity in their magmatic systems, leading to predictable eruptive behaviour. We combine petrological analyses of erupted crystals with new thermodynamic models to characterise the diversity of melts in magmatic systems beneath monotonous shield volcanoes in the Galápagos Archipelago (Wolf and Fernandina). In contrast with the uniform basaltic magmas erupted at the surface over long timescales, we find that the sub-volcanic systems contain extreme heterogeneity, with melts extending to rhyolitic compositions. Evolved melts are in low abundance and large volumes of basalt flushing through the crust from depth overprint their chemical signatures. This process will only maintain monotonous activity while the volume of melt entering the crust is high, raising the possibility of transitions to more silicic activity given a decrease in the crustal melt flux. In this study the authors show that monotonous basaltic volcanoes can host a range of melts in their sub-volcanic systems, extending to rhyolitic compositions. The study implies that volcanoes which have produced monotonous basaltic lavas on long timescales could transition to more explosive, silica-rich eruptions in the future.
影响因子：
18.3
作者：
M. Stock;M. Humphreys;V. Smith;R. Isaia;D. Pyle
通讯作者：
M. Stock;M. Humphreys;V. Smith;R. Isaia;D. Pyle