Evaluating Mantle and Crustal Processes in Off-axis Volcanism on Iceland

评估冰岛离轴火山活动中的地幔和地壳过程

• 批准号: 1550415
• 负责人: David Peate
• 金额: $ 25.05万
• 依托单位: University of Iowa
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-08-01 至 2021-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1550415&HistoricalAwards=false
• 关键词: Evaluating; Mantle; Crustal; Processes; Off

Most volcanoes in Iceland are concentrated in a NE-SW rift that traverses the center of the island. This rift marks where two tectonic plates are drifting apart, which causes the underlying mantle rocks to rise and melt, forming magma that creates volcanic eruptions at the surface. However, the reasons are less clear why some volcanoes are found in the Snaefellsnes Peninsula in the western part of Iceland (including Snaefellsjökull - made famous in Jules Verne's novel as the place where travellers could 'Journey to the Center of the Earth'). This project aims to understand why and how the mantle melts in this region by analysing the chemical composition of the lavas. From the size distribution and chemical composition of crystals of specific minerals in lavas, it is possible to determine how and where the crystals were formed, thereby revealing details of what was happening at depth beneath each volcano prior to lavas eruption. College-level teaching resources will be developed based on these samples that integrate chemical data sets with field photographs and a web-based digital virtual microscope, and made available to other educators. Public outreach activities will be coordinated through the University of Iowa Museum of Natural History, with the creation of a "Discovery Trunk" on Volcanoes for local schools to use, and participation in the Museum's public lecture series.More attention has been given to melt generation and storage in the Iceland rift zones because of their dominance on melt production, but the reasons for melt generation at large (~100km+) distances from the rifts, like at Snaefellsnes, remain uncertain. This project will be the first in-depth study of primitive lavas in this off-axis zone that focuses on how melts are generated and transported to the surface, to investigate the underlying cause of melting and how details of melt aggregation and transport through thick lithosphere contrasts with the extensional setting and thinner lithosphere of the rift zones. Crystallization depths will be estimated from glass analyses (using ol-cpx-plag saturation) and clinopyroxene thermobarometry, and melt diversity will be characterized with olivine-hosted melt inclusions and clinopyroxene compositions. Radiogenic isotopes and U-series disequilibria will be used to provide insights into the compositional heterogeneity and melting behavior of mantle sources and the process of melt extraction, and additional constraints on the details of melting will come from REE inversion models. The potential of high-precision minor element analyses of olivines to show involvement of non-peridotite sources for off-axis magmas will also be evaluated. The project will provide training in research methods and data acquisition/interpretation for a Ph.D. student, and research experiences for undergraduates. Results will be disseminated through journal articles and conference presentations.

冰岛的大多数火山都集中在穿越岛中心的NE-SW裂谷中。这个裂痕标记了两个构造板正在分开起草，从而导致下面的地幔岩石升起和融化，形成岩浆，在地面形成火山喷发。但是，原因不太清楚为什么在冰岛西部的Snaefellsnes半岛中发现了一些火山（包括Snaefellsjökull-在Jules Verne的小说中闻名，因为旅行者可以“前往地球中心”的地方）。该项目旨在通过分析熔岩的化学成分来了解该区域中的地幔为什么以及如何融化。从熔岩中特定矿物质的晶体的尺寸分布和化学组成，可以确定形成晶体的形成方式和地点，从而揭示了熔岩喷发前每个火山下方的深度处发生的情况。将根据这些样本将化学数据集与现场照片和基于Web的数字虚拟显微镜整合，并提供给其他教育工作者的样本。公共宣传活动将通过爱荷华大学自然历史博物馆进行协调，并在火山上创建了一个“发现树干”，并参与了博物馆的公开讲座系列。更多地关注了冰岛的融化生成和存储，因为它们在梅尔特生产上具有占主导地位的原因，但依靠梅尔特的生产占主导地位，但在大型融资中脱颖而出（〜100k）（〜100k+），〜〜〜〜〜〜）〜〜〜〜〜）〜〜〜〜〜） Snaefellsnes，仍然不确定。该项目将是该离轴区域中原始熔岩的首次深入研究，该研究的重点是如何产生熔体并运输到表面，以研究熔化的根本原因，以及熔体聚集的细节以及如何通过厚岩石圈通过厚实的岩石圈对比与延伸式构建和较薄的岩石层的薄质层。结晶深度将根据玻璃分析（使用OL-CPX-Plag饱和度）和斜盘热量计估计，并以橄榄石托管的熔体夹杂物和斜氧烯组成来表征熔体多样性。放射异位素和U系列的二动作用将用于提供有关地幔源的组成异质性和熔融行为以及熔体提取过程的见解，以及熔化细节的其他约束将来自REE反演模型。还将评估橄榄石的高精度次要元素分析的潜力，以表明非童岩源岩质的参与。该项目将提供有关博士学位的研究方法和数据获取/解释的培训。学生和本科生的研究经验。结果将通过期刊文章和会议演讲来传播。