法国巴黎地球物理研究所 Vlastlic, I.及其研究小组报道岩浆源小规模交代驱动的弧火山活动。这一研究成果于2023年3月27日发表在国际顶尖学术期刊《自然—地球科学》上。
研究人员展示了厄瓜多尔通古拉瓦火山，在1999-2016年喷发序列中的喷发活动与岩浆源的小规模交代之间的联系。根据高分辨率的火山灰Pb和Sr同位素组成的时间序列，研究人员确定了在喷发序列中，岩浆产生的平均速率随源交代的程度呈对数变化，该序列由于交代源在最后周期内枯竭而结束。这种联系表明地幔交代作用在短时间和空间尺度上，控制着岩浆的产生，并最终控制着通古拉瓦火山的喷发活动。对于玄武盾状火山来说，交代作用对其单次喷发的影响已经得到众学者的认可，但研究发现，这也是安山质弧状火山产生持久喷发的一种合理机制。
据悉，弧火山活动起源于下降板块释放的流体，通过降低固相线温度使地幔楔熔化。地幔的交代作用-由流体引起的成分变化-在火山弧的岩浆生产中具有重要作用。然而，一般认为单个弧火山的幕式喷发主要受地壳岩浆的演化和补给的控制，与地幔过程没有建立联系。
附：英文原文
Title: Arc volcano activity driven by small-scale metasomatism of the magma source
Author: Vlastlic, I., Sainlot, N., Samaniego, P., Bernard, B., Nauret, F., Hidalgo, S., Auclair, D., Gannoun, A.
Issue&Volume: 2023-03-27
Abstract: Arc volcanism arises from the release of fluids from the descending slab, which enables melting in the mantle wedge by lowering the solidus temperature. Metasomatism—compositional alteration by fluids—of the mantle is known to have an important role in magma production in volcanic arcs over long spatial and temporal scales. However, the episodic eruption of individual arc volcanoes is generally thought to be regulated primarily by the evolution and recharge of crustal magma reservoirs, with no established link to mantle processes. Here we show a link between eruptive activity in the 1999–2016 eruption sequence of Tungurahua volcano in Ecuador and small-scale metasomatism of the magma source. From high-resolution time series of the Pb and Sr isotopic composition of ashes, we determine that during the eruption sequence, the average rate of magma production varies logarithmically with the degree of source metasomatism, and that the sequence ended because of the exhaustion of the metasomatized source during its final weeks. Such an association points to mantle metasomatism over short spatial and temporal scales regulating magma production and ultimately eruptive activity of Tungurahua volcano. The influence of metasomatism on individual eruptions has been recognized for basaltic shield volcanoes, but our findings suggest that it is also a plausible mechanism to produce long-lasting eruptions at andesitic arc volcanoes.
DOI: 10.1038/s41561-023-01143-0
Source: https://www.nature.com/articles/s41561-023-01143-0