Identifying Crustal and Mantle Processes in the Central Trans-Mexican Volcanic Belt

识别跨墨西哥火山带中部的地壳和地幔过程

• 批准号: 1019798
• 负责人: Elisabeth Widom
• 金额: $ 27.75万
• 依托单位: Miami University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-09-15 至 2015-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1019798&HistoricalAwards=false
• 关键词: Identifying; Crustal; Mantle; Processes; Central

Intellectual Merit: Subduction zones are the sites of much of the Earth's active explosivevolcanism and associated hazards, and also important sites of mass exchange between the crust and mantle, and fundamental agents in the growth of the continental crust and evolution of the crust-mantle system through time. Much attention has been focused on explosive silicicstratovolcanoes, yet less studied mafic monogenetic cones are very common and can be highly destructive. In addition, their mafic composition makes them ideal for study of mantle processes in subduction settings. We propose to do a detailed multi-isotopic study of the historic Jorullo and Parícutin monogenetic volcanic centers in the central Trans-Mexican Volcanic Belt. Jorullo and Parícutin volcanoes are ideal for a paired case study because: they both produced well documented historic eruptions; detailed field studies have been done so samples selected for geochemical analysis can be placed in stratigraphic context; they both exhibit a temporal compositional trend of increasing SiO2 with time that is common in mafic monogenetic eruptions but the origin of which is poorly understood; they represent possible endmembers in inferred extents of crustal interaction, with lesser contamination of Jorullo lavas and very extensive contamination of Parícutin lavas; existing local upper and lower crustal xenoliths will allow rigorous investigation of the role of lithospheric assimilation; and their close geographic proximity enables a comparison of potential variability of mantle and crustal processes in different volcanic centers in a relatively fixed tectonic/geologic setting. Sr-Nd-Pb-Hf-Os isotopic compositions will be measured on whole-rock lavas, tephra, and crustal xenoliths, O and Os isotopes on olivine-oxide-matrix separates, and Sr isotopes in single melt-inclusion-bearing olivines. These data should uniquely constrain the relative roles of lower and upper crustal assimilation and the potential addition of slab-derived components to the mantle wedge including hydrous slab-fluid and sediment-melt. This study will have important implications regarding the establishment of magma reservoirs in mafic monogenetic volcanic systems and the cause of temporal-compositional variations in eruptive products, and will provide insights into the nature and heterogeneities of slab-derived fluids/melts over small spatial scales within a mantle wedge.Broader Impacts: Student Training & Education: Students involved in this project will gain extensive experience in several state-of-the-art analytical techniques, and at least one student will participate in fieldwork, receiving training in field volcanology. It is anticipated that the field work will be done in conjunction with a volcanology field workshop, providing the opportunity for additional students to benefit. Results from this research will also be incorporated into the classroom in lecture material and related hands-on, inquiry-based learning activities. Mentoring Women in Science: Widom serves as a role model/mentor for women in science, and currently has a research group with 4 female Ph.D. students. Widom and her students have worked closely with undergraduates in the past, and it is anticipated that the female-dominated research group will help attract participation of female undergraduate students. Outreach Activities: This project will be closely linked to the recent von Humboldt Foundation grant to Siebe and Schmincke, in which results of field mapping and volcanological studies, and our new geochemical data, will be integrated with the establishment of Jorullo as a new UNESCO GeoPark. In addition, Widom and her students will be involved in outreach programs through Miami U, including serving as consultants with Miami's Limper Geology Museum and providing research-based educational experiences to the community through the museum's K-12 programs as well as lab tours/demonstrations to local retirees and community college students. Volcanic Hazard Assessment: The results of this project will help constrain pre-eruptive processes in two historic volcanoes in a highly active volcanic region in which any future eruption will have a major impact on the local population and major urban centers including Morelia and likely Mexico City. International Collaboration: This project will foster ongoing international collaborations with Mexican geologists Siebe and Schaaf, as well as German volcanologist Schmincke.This award is co-funded by the Office of International Science and Engineering (OISE).

智力价值：俯冲带是地球上许多活跃的爆发演化和相关灾害的所在地，也是地壳和地幔之间进行质量交换的重要场所，是大陆地壳生长和壳幔系统随时间演变的基本动因。爆发性硅质层火山一直是人们关注的焦点，但对镁铁质单生锥体的研究较少，这种现象非常常见，具有很强的破坏性。此外，它们的镁铁质成分使其成为研究俯冲环境中地幔过程的理想工具。我们建议对横贯墨西哥火山带中部的历史悠久的Jorullo和Parícutin单生火山中心进行详细的多同位素研究。Jorullo火山和Parícutin火山都是成对研究的理想案例，因为：它们都产生了有充分记录的历史喷发；已经进行了详细的实地研究，以便选择进行地球化学分析的样品可以放在地层背景下；它们都显示出随着时间增加二氧化硅的时间组成趋势，这在镁铁质单源喷发中很常见，但其来源尚不清楚；它们在推断的地壳相互作用程度上代表了可能的端元，Jorullo熔岩的污染较少，Parícutin熔岩的污染非常广泛；现有的上地壳和下地壳捕捉体将允许对岩石圈同化作用进行严格调查；而且它们在地理上的接近使人们能够在相对固定的构造/地质环境中比较不同火山中心的地幔和地壳过程的潜在变异性。将在全岩熔岩、特弗拉和地壳包体上测量锶-钕-铅-氟-铯同位素组成，在橄榄石-氧化物-基质分离物上测量氧和Os同位素，在单个熔体包裹体橄榄石中测量锶同位素。这些数据应唯一地限制下地壳同化和上地壳同化的相对作用，以及可能向地幔楔体增加板片衍生成分，包括含水板片-流体和沉积物-熔融。这项研究将对镁铁质单一成因火山系统中岩浆储集层的建立和喷发产物的时间成分变化的原因具有重要意义，并将提供对地幔楔体内小空间尺度上板岩衍生流体/熔体的性质和非均质性的见解。广泛影响：学生培训和教育：参与该项目的学生将在几种最先进的分析技术方面获得丰富的经验，至少有一名学生将参加野外工作，接受现场火山学培训。预计实地工作将结合火山学实地讲习班进行，为更多的学生提供受益的机会。这项研究的结果还将纳入课堂讲授材料和相关的动手、探究性学习活动。指导科学领域的女性：Widom是科学领域女性的榜样/导师，目前有一个由4名女性博士生组成的研究小组。Widom和她的学生过去曾与本科生密切合作，预计以女性为主的研究小组将有助于吸引女性本科生的参与。宣传活动：该项目将与冯·洪堡基金会最近向Siebe和Schmincke提供的赠款密切相关，其中实地测绘和火山研究的结果以及我们新的地球化学数据将与建立Jorullo作为新的教科文组织地质公园相结合。此外，Widom和她的学生将通过迈阿密大学参与外展项目，包括担任迈阿密林珀地质博物馆的顾问，通过博物馆的K-12项目向社区提供基于研究的教育体验，以及为当地退休人员和社区大学学生提供实验室参观/演示。火山灾害评估：该项目的结果将有助于限制高度活跃火山地区两座历史悠久的火山的喷发前过程，未来的任何喷发都将对当地人口和主要城市中心(包括莫雷利亚和可能的墨西哥城)产生重大影响。国际合作：该项目将促进与墨西哥地质学家Siebe和Schaaf以及德国火山学家Schmincke正在进行的国际合作。该奖项由国际科学与工程办公室(OISE)共同资助。