Constraining Processes & Timescales of Magma Evolution

约束流程

• 批准号: 0911182
• 负责人: Elisabeth Widom
• 金额: $ 25.75万
• 依托单位: Miami University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-09-15 至 2013-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0911182&HistoricalAwards=false
• 关键词: Constraining; Processes; & Timescales; Magma

Intellectual Merit: The processes that operate in active volcanic systems ultimately control the timescales over which magmas evolve to explosive states, as well as the nature of the resulting eruptions. Thus, linking processes and timescales of magma evolution to eruptive behavior and eruptive volume is a fundamental goal for understanding the past, present and future behavior of active volcanic systems. A multi-faceted approach is proposed to constrain magma differentiation processes and timescales via a multi-isotopic, macro- to micro-scale study of constituent phases from chemically zoned, silicic volcanic deposits in the Azores, in order to: [1] determine the relative roles of open versus closed system processes in the development of silicic magmas in ocean island settings; [2] document the nature of crustal assimilants and the history of assimilation and recharge events; [3] establish the diversity of sources and magma residence times of the "crystal cargo" and the implications for the longevity of magmatic systems; [4] constrain the timescales of magma differentiation for silicic, alkaline magmatic systems with a focus on liquid (glass) ages; and [5] assess the link between eruptive volume and pre-eruptive magma residence timescales with a focus on magmatic systems of restricted compositional and tectonic variability. The proposed approach will involve sample characterization at multiple scales using optical microscopy, cathodoluminescence and microprobe analysis of mineral phases; major and trace element and Sr-Nd-Pb isotopic analyses of whole rocks; Sr-O isotopic analyses of glass and single sanidine crystals; U-series disequilibria analyses of glass (238U-230Th-226Ra) and single sanidines (226Ra/Ba); and intra-crystal Sr isotope microsampling and Ba and Sr abundance/diffusion profiling in sanidines. A unique aspect of this project includes the direct determination of Ra and Ba partition coefficients between sanidine and trachyte melt, which is critical for magmatic differentiation timescale assessments using the 230Th-226Ra-(Ba) system.Broader Impacts: Minority Student Support & Recruiting. This project will support two Ph.D. students (including a Japanese-American female and, likely, an African-American student), as well as two to three undergraduate students. Student Training & Education: Students involved in this project will gain extensive experience in a variety of state-of-the-art analytical techniques, and at least one student will participate in fieldwork, receiving valuable training in volcanology and field geology. It is anticipated that the field work will be done in conjunction with a volcanology field workshop that will provide the opportunity for additional students to benefit from this experience. Results from this research will also be incorporated into the classroom in lecture material as well as related hands-on, inquiry-based learning activities. Mentoring Women in Science: The PI serves as a role model and mentor for women in science, and currently has a research group with 4 female Ph.D. students. The PI and her Ph.D. students have worked closely with undergraduates in the past, and it is anticipated that this research group will help attract participation of female undergraduate students. Outreach Activities: The PI and her graduate students will be involved in outreach programs through Miami University's Limper Geology Museum including providing research-based educational experiences to the community through K-12 programs and a lecture series attended by local high school students and retirees in the community. International Collaboration: The project will foster ongoing international collaboration with Azorean geologists of the Universidade dos Açores, with whom the PI has long-standing collaborations including field projects and organization of a 2009 Azores Penrose Conference. Volcanic Hazard Assessment: The results of this project will help constrain eruptive history and processes and timescales of magma evolution in several active, explosive volcanic systems, and should ultimately help facilitate evaluation of volcanic hazards in the Azores and globally

智力优势：在活火山系统中运作的过程最终控制了岩浆演化到爆炸状态的时间尺度，以及由此产生的火山爆发的性质。因此，将岩浆演化的过程和时间尺度与喷发行为和喷发量联系起来是了解活火山系统过去、现在和未来行为的基本目标。通过对亚速尔群岛化学分带的火山岩沉积物的组成相进行多同位素、宏观到微观尺度的研究，提出了一种多方面的方法来限制岩浆分异过程和时间尺度，以便：[1]确定开放与封闭系统过程在洋岛环境下岩浆发展中的相对作用;[2]记录地壳同化物的性质以及同化和补给事件的历史; [3]确定“晶体货物”的来源和岩浆停留时间的多样性以及对岩浆系统寿命的影响;[4]以液体（玻璃）年龄为重点，限制碱性岩浆系统岩浆分异的时间尺度;”[5]《明史》：“五者，其所居之地，其所居之地。喷发岩浆驻留时间尺度，重点是限制成分和构造变异的岩浆系统。所提出的方法将包括利用光学显微镜、阴极发光和矿物相的微探针分析在多个尺度上对样品进行表征;全岩的主量和微量元素以及Sr-Nd-Pb同位素分析;玻璃和透长石单晶的Sr-O同位素分析;玻璃的U系列不平衡分析。（238 U-230 Th-226 Ra）和单透长石（226 Ra/Ba）;以及透长石中的晶体内Sr同位素微量取样和Ba和Sr丰度/扩散剖面。该项目的一个独特的方面包括直接测定透长石和粗面岩熔体之间的Ra和Ba分配系数，这对于使用230 Th-226 Ra-（Ba）系统进行岩浆分异时标评估至关重要。该项目将资助两名博士。学生（包括一名日裔美国女性，可能还有一名非洲裔美国学生），以及两到三名本科生。学生培训&教育：参与该项目的学生将获得各种最先进的分析技术的丰富经验，至少有一名学生将参加实地考察，接受火山学和野外地质学方面的宝贵培训。预计实地工作将与火山学实地讲习班一起进行，这将为更多的学生提供从这一经验中受益的机会。这项研究的结果也将纳入课堂教学材料以及相关的动手，探究式学习活动。指导科学界的女性：PI是科学界女性的榜样和导师，目前有一个由4名女博士组成的研究小组。学生私家侦探和她的博士。学生们过去曾与本科生密切合作，预计该研究小组将有助于吸引女本科生的参与。外联活动：PI和她的研究生将通过迈阿密大学的Limper地质博物馆参与外展计划，包括通过K-12计划和当地高中生和社区退休人员参加的系列讲座为社区提供基于研究的教育经验。国际合作：该项目将促进与亚速尔群岛大学的亚速尔群岛地质学家正在进行的国际合作，PI与他们有着长期的合作，包括实地项目和组织2009年亚速尔群岛彭罗斯会议。火山危险性评估：该项目的结果将有助于限制几个活跃的爆炸性火山系统的喷发历史和岩浆演化的过程和时间尺度，并最终有助于促进亚速尔群岛和全球火山灾害的评估