Deep intrusions, lateral magma transport and related uplift at ocean island volcanoes
Deep intrusions, lateral magma transport and related uplift at ocean island volcanoes
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DOI：
10.1016/j.epsl.2015.09.031
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发表时间：
2015-12-01
影响因子：
5.3
通讯作者：
Stix, John
中科院分区：
文献类型：
--
作者：
Kluegel, Andreas;Longpre, Marc-Antoine;Stix, John
海洋板内火山是由喷发物质的堆积以及同时期或离散的岩浆侵入形成的。火山大厦内的岩脉和其他侵入体研究得相对较好，但火山深处的侵入过程仍然难以捉摸。虽然有地质证据表明，深部岩浆侵入通过隆升促进了火山的生长，但这一点很少得到实时监测的证实。本文利用加那利群岛耶罗岛的地球物理和岩石学数据，证明了来自地幔的侵入和海洋地壳内岩浆的亚水平运输导致了内源性岛屿的快速生长。与2011-2012年海底喷发相关的地震活动和地面变形揭示了深亚水平侵入片（基），这导致了岛屿规模的数十厘米的隆起。火山爆发前的侵入物在较低的海洋地壳内横向移动了15-20公里，为随后喷发的岩浆从地幔上升到地表打开了通道。在2012年至2014年的6次喷发后，下地壳和上地幔的进一步侵入使岩浆横向迁移了20公里，岩浆聚集量超过了喷发前阶段。2011-2012年耶罗火山喷发的地球气压数据与大西洋其他板块内火山的数据进行了比较，发现了类似的双峰压力分布，这表明喷发阶段通常伴随着深部岩浆侵入和横向岩浆输送。这些过程为海洋地壳增加了大量物质，引起隆起，因此对火山岛的生长和演化具有根本的重要意义。我们认为，这种下洋壳岩浆聚集带的发育始于火山演化早期，是地幔储层系统规模和复杂性增加的结果，也可能是岩石圈应力增加造成的。(C) 2015 Elsevier B.V.版权所有
Oceanic intraplate volcanoes grow by accumulation of erupted material as well as by coeval or discrete magmatic intrusions. Dykes and other intrusive bodies within volcanic edifices are comparatively well studied, but intrusive processes deep beneath the volcanoes remain elusive. Although there is geological evidence for deep magmatic intrusions contributing to volcano growth through uplift, this has rarely been demonstrated by real-time monitoring. Here we use geophysical and petrological data from El Hierro, Canary Islands, to show that intrusions from the mantle and subhorizontal transport of magma within the oceanic crust result in rapid endogenous island growth. Seismicity and ground deformation associated with a submarine eruption in 2011-2012 reveal deep subhorizontal intrusive sheets (sills), which have caused island-scale uplift of tens of centimetres. The pre-eruptive intrusions migrated 15-20 km laterally within the lower oceanic crust, opening pathways that were subsequently used by the erupted magmas to ascend from the mantle to the surface. During six post-eruptive episodes between 2012 and 2014, further sill intrusions into the lower crust and upper mantle have caused magma to migrate up to 20 km laterally, resulting in magma accumulation exceeding that of the pre-eruptive phase. A comparison of geobarometric data for the 2011-2012 El Hierro eruption with data for other Atlantic intraplate volcanoes shows similar bimodal pressure distributions, suggesting that eruptive phases are commonly accompanied by deep intrusions of sills and lateral magma transport. These processes add significant material to the oceanic crust, cause uplift, and are thus fundamentally important for the growth and evolution of volcanic islands. We suggest that the development of such a magma accumulation zone in the lower oceanic crust begins early during volcano evolution, and is a consequence of increasing size and complexity of the mantle reservoir system, and potentially the lithospheric stresses imposed by increasing edifice load. (C) 2015 Elsevier B.V. All rights reserved.