Modification of Primary Magma Composition Through Reaction With Lower Crust: Insights from Icelandic Glass Bearing Crustal Xenoliths

“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：地幔的部分融化和随后的熔体输送有助于形成新的海洋和大陆地壳，影响低温表面过程，并对大气化学产生重大影响。原始玄武岩岩浆的成分理想地提供了有关深部岩浆生成的最直接信息，但它们可能会在运往地表的过程中受到熔岩相互作用的影响。为了评估原生岩浆在通过地壳岩石迁移过程中的化学成分可能发生多大程度的变化，该项目将研究冰岛火山地壳包体中的玻璃所代表的地壳部分熔体的成分。冰岛为拟议的研究提供了一个理想的环境，因为它有一个异常厚的地壳位于大洋中脊，否则，正常的类似MORB的原始熔体成分预计会从地幔深处上升。这项工作将包括系统地研究矿物和玻璃的主元素和微量元素组成，并确定温度、压力和氧化还原条件。与地壳包体及其输送的岩浆有关的淬火玻璃中的硼同位素将被用作岩浆混染的独立指标。将特别注意锆石的U-Pb年代学和钛地质测温法，这些锆石中有丰富的白色包体；目的是确定母质深成体的年龄及其形成的温度范围，从而限制随后的熔体/岩石反应过程的时间尺度。为了实现目标，将结合岩相学方法、传统的全岩分析和微观分析技术，如激光烧蚀电感耦合等离子体质谱(LA-ICP-MS)、电子探针显微分析(EMPA)和二次离子质谱仪(SIMS或离子微探针)。广泛影响：该提案将为PI作为新的NENIMF经理和新的NSF PI的专业发展提供基础。该项目将有助于重振科学界对使用世界卫生组织离子探测器设施的兴趣，该设施在2002年10月的一场火灾中遭到严重破坏。最后，该项目将促进伍兹霍尔海洋研究所(A.Gurenko)和南冰岛自然中心(Ingvar A.Sigurdsson)之间的国际合作。

"This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5)."Intellectual Merit: Partial melting in the Earth's mantle and subsequent melt transport contribute to the formation of a new oceanic and continental crust, affect low-temperature surface processes and have significant impact on chemistry of the atmosphere. Compositions of primitive basaltic magmas ideally provide the most direct information about magma generation at depth, but they may be modified by melt-rock interaction during transport to the surface. To evaluate how extensively chemical compositions of primary magmas may be modified during migration through crustal rocks, this project will investigate compositions of crustal partial melts as represented by glasses in crustal xenoliths from Icelandic volcanics. Iceland provides an ideal setting for the proposed study because it has an anomalously thick crust situated on a mid-ocean ridge where, otherwise, normal MORB-like initial primitive melt compositions are expected to rise from mantle depths. This work will involve systematic study of major and trace element compositions of minerals and glasses and determination of temperature, pressure, redox conditions. Boron isotopes in quenched glasses associated with crustal xenoliths and their transporting magmas will be used as an independent proxy for magma contamination. Special attention will be given to U-Pb geochronology and Ti-geothermometry of zircons, which are abundant in leucocratic xenoliths; the aim is to determine the age of parent plutonic bodies and temperature range of their formation, thereby constraining time scales of the consequent melt/rock reaction processes. A combination of petrographic methods, conventional whole rock analytical and microanalytical techniques i.e., Laser Ablation Inductively-Coupled Plasma Mass Spectrometry (LA-ICP-MS), Electron Probe Microanalysis (EMPA) and Secondary Ion Mass Spectrometry (SIMS or Ion Microprobe) will be used to achieve the goals.Broader Impacts: The proposal will provide a basis for professional development of the PI who is a new NENIMF manager and also a new NSF PI. The project will help revitalize interest of the scientific community in using the WHOI ion probe facility, which was seriously damaged in a fire in October 2002. Finally, the project will foster international collaboration between Woods Hole Oceanographic Institution (A. Gurenko) and South Iceland Nature Center (Ingvar A. Sigurdsson).