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首页> 外文期刊>Journal of Volcanology and Geothermal Research2012V243-244NOCT,15 >Role of large flank-collapse events on magma evolution of volcanoes. Insights from the Lesser Antilles Arc
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Role of large flank-collapse events on magma evolution of volcanoes. Insights from the Lesser Antilles Arc

机译：大型侧倾崩塌事件在火山岩浆演化中的作用。小安的列斯群岛的见解

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摘要

Flank-collapse events are now recognized as common processes of destruction of volcanoes. They may occur several times on a volcanic edifice pulling out varying volumes of material from km~3 to thousands of km~3. In the Lesser Antilles Arc, a large number of flank-collapse events were identified. Here, we show that some of the largest events are correlated to significant variations in erupted magma compositions and eruptive styles. On Montagne Pelee (Martinique), magma production rate has been sustained during several thousand years following a 32 ka old flank-collapse event. Basic and dense magmas were emitted through open-vent eruptions that generated abundant scoria flows while significantly more acidic magmas were produced before the flank collapse. The rapid building of a new cone increased the load on magma bodies at depth and the density threshold. Magma production rate decreased and composition of the erupted products changed to more acidic compared to the preceding period of activity. These low density magma generated plinian and dome-forming eruptions up to the Present. In contrast at Soufriere Volcanic Centre of St. Lucia and at Pitons du Carbet in Martinique, the flank-collapses have an opposite effect: in both cases, the acidic magmas erupted immediately after the flank-collapses. These magmas are highly porphyritic (up to 60% phenocrysts) and much more viscous than the magmas erupted before the flank-collapses. They have been generally emplaced as voluminous and uptight lava domes (called "the Pitons"). Such magmas could not ascent without a significant decrease of the threshold effect produced by the volcanic edifice loading before the flank-collapse.
机译：侧面崩塌事件现在被认为是破坏火山的常见过程。它们可能会在火山大厦上发生几次，从而拉出从km〜3到数千km〜3的各种物质。在小安的列斯群岛，发现了许多侧翼塌陷事件。在这里，我们表明一些最大的事件与喷出的岩浆成分和喷发样式的重大变化有关。在Montagne Pelee（马提尼克岛），发生了32 ka的侧面崩塌事件之后，岩浆生产率一直维持了几千年。基本的和密集的岩浆通过开孔喷发而产生，产生大量的矿渣流，而在侧翼塌陷之前产生了更多的酸性岩浆。快速建造新的圆锥体增加了岩浆体在深度和密度阈值上的负荷。与前一个活动时期相比，岩浆生产率降低，喷发产物的组成变为酸性。直到现在，这些低密度岩浆都产生了lin利系和形成圆顶的喷发。与之相反，在圣卢西亚的Soufriere火山中心和马提尼克岛的Pitons du Carbet，侧面崩塌具有相反的作用：在两种情况下，酸性岩浆在侧面崩塌后立即爆发。这些岩浆具有高度的斑状（最多有60％的表晶），并且比侧面崩塌之前喷出的岩浆粘稠得多。通常将它们安置成巨大且密实的熔岩穹顶（称为“岩钉”）。如果没有大幅降低侧面崩塌之前火山建筑物荷载产生的阈值效应，这种岩浆将无法上升。

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