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).

智力优势：俯冲带是地球大部分活跃的爆炸演化和相关灾害的发生地，也是壳幔物质交换的重要场所，是大陆地壳生长和壳幔系统演化的基本动因。许多注意力都集中在爆发硅质层火山，但较少研究镁铁质单成锥是非常常见的，可以是高度破坏性的。此外，它们的镁铁质成分使它们成为研究俯冲环境中地幔过程的理想材料。我们建议做一个详细的多同位素研究的历史Jorullo和Parícutin单成因火山中心在中部跨墨西哥火山带。Jorullo火山和Parícutin火山是进行成对案例研究的理想选择，因为：它们都产生了有据可查的历史喷发;已进行了详细的实地研究，以便选择用于地球化学分析的样品置于地层环境中;它们都表现出SiO2随时间增加的时间成分趋势，这在镁铁质单成因喷发中很常见，但其起源却知之甚少;在推断的地壳相互作用范围内，它们代表了可能的端元，Jorullo熔岩的污染较小，Parícutin熔岩的污染非常广泛;现有的当地上地壳和下地壳捕虏体将允许对岩石圈同化作用进行严格的调查;它们在地理上的接近使得能够在相对固定的构造/地质背景下比较不同火山中心的地幔和地壳过程的潜在变化性。将测量全岩熔岩、火山灰和地壳捕虏体的Sr-Nd-Pb-Hf-Os同位素组成，橄榄岩-氧化物-基质分离物的O和Os同位素，以及含熔融包裹体的单一橄榄岩的Sr同位素。这些数据应独特地约束下地壳和上地壳同化的相对作用，以及可能增加的板衍生组件的地幔楔，包括含水板流体和沉积物熔体。这项研究将对在基性单成因火山系统中建立岩浆库以及喷发产物的时间成分变化的原因产生重要影响，并将提供对地幔楔内小空间尺度上板片衍生流体/熔体的性质和非均匀性的见解。更广泛的影响：学生培训&教育：参与该项目的学生将获得几种最先进的分析技术的丰富经验，至少有一名学生将参加野外工作，接受野外火山学培训。预计实地工作将与火山学实地讲习班一起进行，为更多的学生提供受益的机会。这项研究的结果也将纳入课堂教学材料和相关的动手，探究式学习活动。指导科学界的女性：Widom是科学界女性的榜样/导师，目前有一个由4名女博士组成的研究小组。学生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本科生的参与。外联活动：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，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Jorullo作为新的教科文组织地质公园的建立相结合。此外，Widom和她的学生将通过迈阿密U参与外展计划，包括担任迈阿密的Limper地质博物馆的顾问，并通过博物馆的K-12计划以及实验室图尔斯/演示向当地退休人员和社区大学生提供基于研究的教育经验。火山危险性评估：该项目的结果将有助于限制高度活跃的火山地区的两个历史火山的喷发前过程，其中任何未来的喷发都将对当地人口和主要城市中心（包括莫雷利亚和墨西哥城）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的持续国际合作。该奖项由国际科学与工程办公室（OISE）共同资助。