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。“智力优点：渐新世纳瓦霍火山区的硅质岩墙中心是科罗拉多高原地质历史和演化的重要组成部分。虽然以前的研究主要集中在与NVF相关的岩浆的生成和演化，但对一些基本问题知之甚少。关于NVF岩石的地幔-岩浆成因和演化的最深入的假说（Nowell，1993; Carlson和Nowell，2001）认为，硅不饱和的岩浆是由富含碳酸盐的金云母-石榴石橄榄岩的0.5%至1%熔融产生的，而更多的“硅饱和”岩浆（矿物的来源）是由水-岩石圈地幔的较高程度熔融产生的。这个模型是建立在这样的想法，软流圈熔体注入到岩石圈地幔近端CO2和远端H2O交代。洞察到原始地幔岩浆的组成和成因，并了解所涉及的挥发性物质，目前还没有充分的限制，以充分测试这个模型。NVF岩石中原生硅酸盐熔体包裹体和矿物相的化学和挥发分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，岩石学和地球化学数据的大块岩石样品相结合的信息，从显微分析技术（电子和离子探针，激光消融ICP-MS）的原生硅酸盐熔融包裹体和矿物相将被用来重建母源组合物和洞察岩浆挥发过程。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用于评估初级熔体成分的变化。对熔体包裹体和分带矿物相（例如， 金云母和磷灰石）将允许洞察岩浆过程中挥发物的参与和演化（例如，交代作用、脱气作用）。这项研究的综合数据将允许对NVF岩浆活动的现有假设进行强有力的测试，并将结果传播到更广泛的地质界，将提供更多的岩浆过程知识。这对于理解科罗拉多高原上的区域新生代岩浆事件以及该岩浆脉动与其他同期区域地质事件的联系非常重要。更广泛的影响：在本科阶段的火成岩学在历史上发挥了重要作用，在地质学学生的教育，作为一个桥梁，其他关键课程，并为学生提供机会，发展重要的技能，在调查，观察，和分析该项目的主要影响超出了基础研究，是支持刘易斯堡学院本科生的教育和成功的科学事业，通过在基于岩石学的研究项目中教授他们基本的知识和技能。这将促进科学思维习惯，让学生成为发现、创造性发展和检验想法的“积极分子”。它还将使学生在科学过程和知识构建中产生主人翁感。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。PI将努力招聘代表性不足的群体（少数民族和妇女）。PI还将获得专业的进步和洞察力，这将被纳入刘易斯堡学院的本科研究和课程。

"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.