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

冰岛的大多数火山都集中在横跨岛屿中心的东北-西南裂谷中。这个裂隙标志着两个构造板块漂移的地方，这导致下面的地幔岩石上升和融化，形成岩浆，在地表产生火山喷发。然而，为什么在冰岛西部的斯奈菲尔斯内斯半岛发现了一些火山(包括斯奈菲尔斯约科尔火山--在儒勒·凡尔纳的小说中，斯奈菲尔斯约科尔因游客可以在那里旅行到地球中心而闻名)，原因尚不清楚。该项目旨在通过分析熔岩的化学成分来了解该地区地幔融化的原因和方式。根据熔岩中特定矿物晶体的大小分布和化学成分，可以确定晶体是如何以及在哪里形成的，从而揭示了熔岩喷发前每座火山下方深处发生的细节。将在这些样本的基础上开发大学一级的教学资源，将化学数据集与现场照片和基于网络的数字虚拟显微镜相结合，并向其他教育工作者提供。公众推广活动将通过爱荷华大学自然历史博物馆进行协调，为当地学校创建一个关于火山的“发现箱”，并参加博物馆的公开讲座系列。冰岛裂谷地带的熔体产生和储存受到了更多的关注，因为它们在熔体产生方面占据主导地位，但在距离裂谷很远(约100公里以上)的地方，如Snaefellses，熔体产生的原因仍不确定。该项目将首次深入研究这一离轴区的原始熔岩，重点研究熔体是如何产生和运往地表的，以调查熔融的根本原因，以及熔体聚集和穿过厚岩石圈的细节如何与裂谷带的伸展环境和较薄的岩石圈形成对比。结晶深度将通过玻璃分析(使用ol-cpx-Plag饱和度)和单斜辉石温度压力计来估计，熔体多样性将以橄榄石为宿主的熔体包裹体和单斜辉石成分来表征。放射性同位素和U系列不平衡将用于深入了解地幔来源的成分不均一性和熔融行为以及熔体提取过程，对熔融细节的额外限制将来自REE反转模型。还将对橄榄石进行高精度微量元素分析以显示离轴岩浆的非橄榄岩来源的潜力进行评估。该项目将为博士生提供研究方法和数据获取/解释方面的培训，并为本科生提供研究经验。结果将通过期刊文章和会议演示文稿传播。

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.