Schiano P, Clocchiatti R, Ottolini L, Busà T
Laboratoire "Magmas et Volcans", Université Blaise Pascal, CNRS UMR 6524, OPGC, 5 rue Kessler, 63038 Clermont-Ferrand, France.
Nature. 2001 Aug 30;412(6850):900-4. doi: 10.1038/35091056.
Mount Etna lies near the boundary between two regions that exhibit significantly different types of volcanism. To the north, volcanism in the Aeolian island arc is thought to be related to subduction of the Ionian lithosphere. On Sicily itself, however, no chemical or seismological evidence of subduction-related volcanism exists, and so it is thought that the volcanism-including that on Mount Etna itself-stems from the upwelling of mantle material, associated with various surface tectonic processes. But the paucity of geological evidence regarding the primary composition of magma from Mount Etna means that its source characteristics remain controversial. Here we characterize the trace-element composition of a series of lavas emitted by Mount Etna over the past 500 kyr and preserved as melt inclusions inside olivine phenocrysts. We show that the compositional change in primary magmas from Mount Etna reflects a progressive transition from a predominantly mantle-plume source to one with a greater contribution from island-arc (subduction-related) basalts. We suggest that this is associated with southward migration of the Ionian slab, which is becoming juxtaposed with a mantle plume beneath Sicily. This implies that the volcanism of Mount Etna has become more calc-alkaline, and hence more explosive, during its evolution.
埃特纳火山位于两个火山活动类型显著不同的区域之间的边界附近。在其北面，伊奥利亚岛弧的火山活动被认为与爱奥尼亚岩石圈的俯冲作用有关。然而，在西西里岛本身，没有与俯冲相关的火山活动的化学或地震学证据，因此人们认为包括埃特纳火山本身的火山活动源于地幔物质的上涌，这与各种地表构造过程有关。但是，关于埃特纳火山岩浆原始成分的地质证据匮乏，这意味着其源区特征仍存在争议。在这里，我们对埃特纳火山在过去50万年中喷发的一系列熔岩的微量元素组成进行了表征，并将其作为熔体包裹体保存在橄榄石斑晶中。我们表明，埃特纳火山原始岩浆的成分变化反映了从主要为地幔柱源向岛弧（俯冲相关）玄武岩贡献更大的源的逐渐转变。我们认为这与爱奥尼亚板块向南迁移有关，该板块正与西西里岛下方的地幔柱并列。这意味着埃特纳火山的火山活动在其演化过程中变得更加钙碱性，因此更具爆炸性。
