Collaborative Research: The Time Scales of Magmatic Differentiation and Their Relationship to Eruptive Style

冰岛南部的Hekla火山显示出其火山活动方式与岩石学演化程度之间的显著对应关系。大多数喷发都是分区的，特别是那些以长时间休眠为标志的喷发，开始于爆炸性的硅质相，结束于镁铁质冰晶的渗出。索拉林森的开创性工作表明，赫克拉火山的分化程度与两次喷发之间的休息时间有关。该项目旨在详细研究历史喷发的带状产物，以阐明分异的机制和时间尺度。将进行实地工作，以收集每一次历史喷发的样本序列；由于喷发都是历史喷发，结晶、混合和分化的最短时间受到很好的限制。每一块岩石都将使用现代最先进的技术进行分析，但这项研究的重点是斑晶相的微量分析，斑晶相是它们结晶时的液体成分的示踪物。斑晶的主量元素和微量元素分带剖面以及熔体包裹体的分析将有助于确定斑晶的亲缘关系，以及它们在寄主岩浆中的携带时间。斑晶的氧同位素比值和熔体包裹体的水分析记录了水对岩浆演化的影响程度。最后，对斑晶进行寿命相对较短的榄系元素系列同位素分析将限制它们的年龄，即它们在岩浆管道系统中居住的时间。在更广泛的影响方面，该奖项将支持爱达荷州大学的一名博士生和六名高露洁大学本科生的研究努力。PIS设计了一项计划，为博士生提供长期与本科生合作的教学和指导经验。反过来，高露洁的学生将有机会参与广泛的实地考察，与研究科学家互动，研究独立的、专注的研究问题。研究结果还将被纳入高露洁和爱达荷大学的本科生和研究生课程，以及旨在将实践科学调查带给当地K-12学生和社区团体的外联计划。

Hekla volcano in southern Iceland displays a remarkable correspondence between its style of volcanic activity and extent of petrologic evolution. Most eruptions are zoned, especially the ones that punctuate long repose, initiating with an explosive siliceous phase and ending with effusion of mafic icelandite. The pioneering work of Thorarinsson showed that the extent of differentiation at Hekla correlates with the repose between eruptions. This project is designed to study in detail the zoned products of the historical eruptions, in order to elucidate the mechanisms and timescales of differentiation. Field work will be conducted in order to collect sequences of samples from each historical eruption; because the eruptions are all historical, the minimum time for crystallization, mixing, and differentiation is well-constrained. Each of the rocks will be analyzed using modern, state of the art techniques, but the focus of this study is microanalysis of phenocryst phases, which are tracers of the liquid compositions from which they crystallized. Major and trace element zoning profiles of phenocrysts and analyses of melt inclusions will help determine the parentage of the phenocrysts, as well as the duration they have been entrained in their host magmas. Oxygen isotopic ratios of the phenocrysts and water analyses of melt inclusions record the extent to which water influences magmatic evolution. Finally, relatively short-lived actinide-series isotopic analyses of the phenocrysts will constrain their age, the amount of time they have resided in the magmatic plumbing system. In terms of broader impacts, this award will support the research endeavors of a doctoral student at the University of Idaho and six Colgate University undergraduates. The PIs have designed a plan to provide the PhD student with teaching and mentoring experience working with the undergraduates on a protracted basis. The Colgate students, in turn, will have the opportunity to participate in extended fieldwork, interact with research scientists, work on independent, focused research questions. Results will also be incorporated into both undergraduate and graduate level courses at Colgate and the University of Idaho, as well as outreach programs designed to bring hands-on science investigation to local K-12 students and community groups.