New insights into the initiation and venting of the Bronze-Age eruption of Santorini (Greece), from component analysis
New insights into the initiation and venting of the Bronze-Age eruption of Santorini (Greece), from component analysis
复制标题
DOI：
10.1007/s00445-014-0794-x
复制
发表时间：
2014-02-01
影响因子：
3.5
通讯作者：
Druitt, T. H.
中科院分区：
文献类型：
--
作者：
Druitt, T. H.
公元前17世纪末圣托里尼岛的米诺斯火山喷发释放出30-60公里(3)的岩浆，火山口塌陷加深并扩大了现有的22 ka火山口。对喷发产物中的幼年成分、同源成分和偶然成分的研究为五个喷发阶段的喷口发育以及引发喷发的过程提供了新的限制。喷发从平分火山场的 NE-SW 断层线上的喷口开始，分为亚普林尼阶（0 相）和普林尼阶（1 相）阶段。在第一阶段，岩浆破碎水平从地表下降到次火山基底和岩浆侵入体的水平。破碎水平再次变浅，喷口向北迁移（在第二阶段）进入被淹没的 22 ka 破火山口。然后喷发变成强烈的岩浆喷发，并喷出低温熔结岩，其中含有丰富的 22 ka 后、前米诺斯火山口内熔岩碎片（第 3 阶段）。第四阶段从地下喷口排出炽热的流态化火山碎屑流，并在火山周围构建了三个主要的熔结岩扇（西北、东部和南部）。第一阶段 4 流从火山田北半部的一个或多个通风口排出，并在西北扇的大部分地区沉积了富含岩块的火凝灰岩和滞后角砾岩。这些岩流中大约十分之一的岩屑是地下火山基底。随后，新的地下喷口打开，可能横跨火山场的大部分区域，更细粒的火凝灰岩被排出，形成 E 和 S 扇。如果在喷发过程中发生了主要的破火山口塌陷，那么它可能发生在第 4 阶段。在喷发过程中释放出三种幼年成分——体积占主导地位的流纹英安岩浮石和两种安山岩成分：富含微斑晶的安山岩浮石和淬火安山岩包体。富含微斑晶的浮石与共喷发的角闪长闪长岩结核形成了结构、矿物学、化学和热学的连续体，它们一起被解释为在喷发过程中碎裂和排出的小型、不同结晶侵入体的内容物，主要是在第 0 和 1 阶段。富含微斑晶的浮石、角闪长岩、安山岩包体和前米诺斯火山口内安山岩熔岩的碎片共同形成了一组化学上独特的富Ba、贫Zr安山岩，这在圣托里尼岛自530ka以来的产物中是独一无二的。一旦米诺斯岩浆库因补给产生的加压而准备好喷发，流英安岩就会利用先前存在的安山岩-闪长岩侵入体提供的薄弱面向上移动，并拖动侵入体中一些富含晶体的内容物。
The late-seventeenth century BC Minoan eruption of Santorini discharged 30-60 km(3) of magma, and caldera collapse deepened and widened the existing 22 ka caldera. A study of juvenile, cognate, and accidental components in the eruption products provides new constraints on vent development during the five eruptive phases, and on the processes that initiated the eruption. The eruption began with subplinian (phase 0) and plinian (phase 1) phases from a vent on a NE-SW fault line that bisects the volcanic field. During phase 1, the magma fragmentation level dropped from the surface to the level of subvolcanic basement and magmatic intrusions. The fragmentation level shallowed again, and the vent migrated northwards (during phase 2) into the flooded 22 ka caldera. The eruption then became strongly phreatomagmatic and discharged low-temperature ignimbrite containing abundant fragments of post-22 ka, pre-Minoan intracaldera lavas (phase 3). Phase 4 discharged hot, fluidized pyroclastic flows from subaerial vents and constructed three main ignimbrite fans (northwestern, eastern, and southern) around the volcano. The first phase-4 flows were discharged from a vent, or vents, in the northern half of the volcanic field, and laid down lithic-block-rich ignimbrite and lag breccias across much of the NW fan. About a tenth of the lithic debris in these flows was subvolcanic basement. New subaerial vents then opened up, probably across much of the volcanic field, and finer-grained ignimbrite was discharged to form the E and S fans. If major caldera collapse took place during the eruption, it probably occurred during phase 4. Three juvenile components were discharged during the eruption-a volumetrically dominant rhyodacitic pumice and two andesitic components: microphenocryst-rich andesitic pumices and quenched andesitic enclaves. The microphenocryst-rich pumices form a textural, mineralogical, chemical, and thermal continuum with co-erupted hornblende diorite nodules, and together they are interpreted as the contents of a small, variably crystallized intrusion that was fragmented and discharged during the eruption, mostly during phases 0 and 1. The microphenocryst-rich pumices, hornblende diorite, andesitic enclaves, and fragments of pre-Minoan intracaldera andesitic lava together form a chemically distinct suite of Ba-rich, Zr-poor andesites that is unique in the products of Santorini since 530 ka. Once the Minoan magma reservoir was primed for eruption by recharge-generated pressurization, the rhyodacite moved upwards by exploiting the plane of weakness offered by the preexisting andesite-diorite intrusion, dragging some of the crystal-rich contents of the intrusion with it.