Engaging Undergraduate Students in Petrologic Research to Test Hypotheses on the Genesis and Evolution of Mantle Magmas of the Navajo Volcanic Field

“该奖项是根据2009年美国复苏和再投资法案(公法111-5)资助的。”学术价值：渐新世纳瓦霍火山田(NVF)的岩浆中心是科罗拉多高原地质历史和演化的重要组成部分。尽管以前的研究主要集中在与NVF相关的岩浆的产生和演化上，但一些基本问题却知之甚少。关于NVF岩的地幔岩浆成因和演化的最深入的假说(Nowell，1993；Carlson和Nowell，2001)认为，硅质不饱和岩浆是由富含碳酸盐的金云母-石榴石橄榄岩熔融0.5%-1%产生的，而更多的硅质饱和岩浆(Minette的来源)是由水化-岩石圈地幔较高的熔融程度产生的。该模型是建立在软流圈熔体被注入岩石圈地幔产生近端二氧化碳和远端水的交代作用的基础上的。对原始地幔岩浆的成分和成因的洞察，以及对所涉及的挥发性物种的理解，目前还不足以充分检验这一模型。NVF岩中原生硅酸盐熔体包裹体和矿物相的化学和挥发性特征有助于了解母地幔熔体的组成和形成条件。在这项拟议的研究中，将利用块状岩石样品的岩石学和地球化学数据，结合对原生硅酸盐熔体包裹体和矿物相的微观分析技术(电子和离子微探针，以及激光烧蚀电感耦合等离子体质谱)获得的信息，重建母源成分并深入了解岩浆挥发过程。来自熔体包裹体和早期形成的橄榄石(±辉石)的主要和微量元素数据将有助于评估原始熔体成分的变化。对熔体包裹体和带状矿物相(例如金云母和磷灰石)中挥发性物质(C、H、Cl、F)的浓度和变化的限制将有助于深入了解挥发物在岩浆过程(例如交代作用、脱气作用)中的参与和演化。这项研究的综合数据将允许对现有的NVF岩浆作用假设进行强有力的测试，结果传播到更广泛的地质界将使人们对岩浆过程有更多的了解。这对于了解科罗拉多高原新生代区域岩浆事件，以及这一岩浆脉动与其他同时代区域地质事件的联系具有重要意义。广泛影响：本科生水平的火成岩石学在地质学学生的教育中历来发挥着重要作用，是通往其他关键课程的桥梁，并为学生提供了发展重要的探究、观察和分析技能的机会。除了基础研究之外，该项目的主要影响是通过在岩石学研究项目的背景下向他们传授基本知识和技能，支持刘易斯堡学院本科生的教育和成功的科学职业生涯。这将促进学生的科学思维习惯，使他们成为发现、创造性开发和测试想法的“积极代理人”。它还将使学生对科学过程和知识建构有一种主人翁意识。PI和刘易斯堡学院的学生将与亚利桑那州和美国地质调查局的几位知名研究科学家合作，获得新的技能和知识。国际和平协会将努力招募代表性不足的群体(少数民族和妇女)。PI还将获得专业发展和洞察力，这些将整合到刘易斯堡学院的本科生研究和课程中。

"This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5)."Intellectual Merit: Diatreme-dike centers in the Oligocene Navajo volcanic field (NVF) arean important part of the geologic history and evolution of the Colorado Plateau. Although previous studies have focused on the generation and evolution of magmas associated with the NVF, some fundamental issues are poorly understood. The most in-depth hypothesis (Nowell, 1993; Carlson and Nowell, 2001) on mantle-magma genesis and evolution for NVF rocks argues that silica-undersaturated magmas were created by 0.5% to 1% melting of a carbonate-rich phlogopite-garnet peridotite whereas more "silica-saturated" magmas (source of minette) were generated by higher degrees of melting of hydrous-lithospheric mantle. This model is founded on the idea that asthenospheric melts were injected into the lithospheric mantle creating proximal CO2 and distal H2O metasomatism. Insight into the composition and genesis of primary mantle magmas, and an understanding of the volatile species involved, currently are not adequately constrained to fully test this model. Chemical and volatile signatures of primary silicate-melt inclusions and mineral phases in NVF rocks can contribute to an understanding of compositions and formation conditions of parent mantle melts. In this proposed research, petrologic and geochemical data on bulk-rock samples combined with information gained from micro-analytical techniques (electron and ion microprobe, and laser-ablation ICP-MS) on primary silicate-melt inclusions and mineral phases will be employed to reconstruct parental source compositions and gain insight into magmatic-volatile processes. Major and trace element data from melt inclusions and early-formed olivine (± pyroxene) will serve to assess variations in primary melt compositions. Constraints on the concentration and variation of volatile species (C, H, Cl, F) in melt inclusions and zoned-mineral phases (e.g., phlogopite and apatite) will allow insight into the involvement and evolution of volatiles in magmatic processes (e.g., metasomatism, degassing). The combined data from this research will permit a robust test of existing hypotheses on NVF magmatism, and dissemination of the results into the broader geologic community will give greater knowledge of magmatic processes. This is important in understanding regional Cenozoic magmatic events on the Colorado Plateau, and perhaps the connection of this magmatic pulse with other contemporaneous regional geologic events.Broader Impacts: Igneous petrology at the undergraduate level has historically played an important role in the education of geology students, serving as a bridge to other key courses, and offering students opportunities to develop important skills in inquiry, observation, and analysis. A prime impact of this project beyond the basic research is to support the education and successful scientific careers of undergraduate students at Fort Lewis College by teaching them basic knowledge and skills in context of a petrologic-based research project. This will promote scientific habits of mind by engaging students as "active agents" in discovery, and the creative development and testing of ideas. It will also give students a sense of ownership in the scientific process and knowledge construction. The PI and students from Fort Lewis College will acquire new skills and knowledge in collaboration with several well-established research scientists at Arizona and the U.S. Geological Survey. An effort will be made by the PI to recruit under-represented groups (ethnic minorities and women). The PI will also gain professional advancement and insight that will be integrated into undergraduate research and curriculum at Fort Lewis College.