Collaborative Research: Rapid Magma Ascent Recorded in Volatile Diffusion Profiles

挥发扩散剖面中记录的快速岩浆上升是什么使一些喷发比其他喷发更具爆炸性？即使在一次特定的喷发发生之后，这个基本的问题仍然在很大程度上没有得到回答。理论将喷发的活力与岩浆的气体量和硬度联系在一起，但具有相似硬度和形成气体种类的岩浆仍然可以以多种形式喷发，有些是高度爆炸性的，有些是静止的。这个项目探索了另一个基本参数？火山喷发前岩浆在火山管道中上升的速度。岩浆上升的速度将影响喷发的体积和活力，以及气泡如何形成、生长和融合。一般来说，缓慢的岩浆上升导致更有效的气泡分离和更少的爆炸性喷发。这个项目的目的是通过从几次喷发的晶体和玻璃中提取时间尺度信息来测试岩浆上升速度的控制，这些喷发跨越了一系列外露的震级。该项目将利用利用玻璃和晶体中挥发性物质分区的新发展，获得反映喷发前几分钟到几天数量级上升的扩散时间尺度。将使用四种不同的计时器：1)通过熔体包裹体的多组分挥发扩散，2)不同大小熔体包裹体通过橄榄石的水分损失，3)橄榄石和单斜辉石中的水分带，以及4)熔体包裹体内的分带。将从记录5-25微米分辨率的化学分区的不同微束技术(纳米SIMS、FTIR、电子探针、激光烧蚀ICPMS)中获得数据。拟议的目标是埃特纳火山(2001年和3930BP)、塞罗内格罗火山(1992和1995年)和帕里库廷火山(1943和1948年)中每一座火山的两次有充分记录的喷发，这些火山的大规模喷发速度跨度很大，表征了从斯特龙博尔式到底板岩式的转变。有针对性的喷发是为了测试含水镁铁质岩浆的上升速度和喷发速度之间的关系的想法，镁铁质岩浆是最常见但最不为人所知的喷发之一。该项目将支持曼哈顿科学与数学中心的一名博士生和两名高中实习生。曼哈顿科学与数学中心是一所公立高中，主要由来自较低社会经济群体的少数族裔学生组成。

Rapid Magma Ascent Recorded in Volatile Diffusion ProfilesWhat makes some eruptions more explosive than others? This fundamental questions is still largely unanswered, even after a given eruption has occurred. Theories link eruptive vigor to the amount of gas and stiffness of the magma, but magmas that have similar stiffness and gas-forming species can still erupt in a wide range of styles, some highly explosive, some quiescent. This project explores another fundamental parameter ? the rate at which magma rises in the volcanic conduit prior to eruption. The magma ascent rate will affect eruptive volume and vigor and also how bubbles form, grow and coalesce. In general, slow magma rise leads to more efficient bubble separation and less explosive eruption. This project aims to test the control of magma rise speed by extracting timescale information from erupted crystals and glass for several eruptions that span a range of exlosive magnitudes. This project will take advantage of new developments in using the zonation of volatile species in glass and crystals to obtain diffusive timescales that reflect ascent on the order of minutes to days prior to eruption. Four different chronometers will be used: 1) multi-species volatile diffusion through melt embayments, 2) water loss through olivine from melt inclusions of different sizes, 3) water zonation in olivine and clinopyroxene, and 4) zonation inside melt inclusions. Data will be obtained that derive from different microbeam techniques (NanoSIMS, FTIR, electron probe, laser ablation ICPMS) that record chemical zonation at the resolution of 5-25 microns. The proposed targets are a pair of well-documented eruptions from each of three volcanoes: Etna (2001 and 3930BP), Cerro Negro (1992 and 1995) and Paricutin (1943 and 1948), which span the range in mass eruption rates that characterize the transition from strombolian to subplinian styles. The eruptions targeted are specifically designed to test ideas as to the relationship between ascent rate and eruption rate in hydrous mafic magmas, among the most common but least well understood eruptions. This project will support a Ph.D. student and two high school interns from the Manhattan Center for Science and Mathematics, a public high school comprised largely of minority students from lower socioeconomic groups.