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。"智力优点：地幔的部分熔融和随后的熔融迁移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。原始玄武岩浆的成分理想地提供了最直接的信息，岩浆生成的深度，但他们可能会被修改的熔体岩石相互作用过程中运输到表面。为了评估原生岩浆的化学成分在地壳岩石迁移过程中可能会发生多大程度的变化，本项目将调查冰岛火山岩地壳捕虏体中以玻璃为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，因为它有一个非常厚的地壳位于大洋中脊，否则，正常的MORB样的初始原始熔体成分预计将从地幔深处上升。这项工作将涉及矿物和玻璃的主量和微量元素组成的系统研究，以及温度、压力、氧化还原条件的测定。与地壳捕虏体及其搬运岩浆有关的淬冷玻璃中的硼同位素可作为岩浆混染的独立指标。将特别注意的U-Pb地质年代学和钛地质测温的锆石，这是丰富的浅色捕虏体，其目的是确定母深成体的年龄和温度范围的形成，从而限制随之而来的熔体/岩石反应过程的时间尺度。结合岩相学方法、常规全岩分析和微分析技术，激光烧蚀电感耦合等离子体质谱（LA-ICP-MS）、电子探针微区分析（EMPA）和二次离子质谱（SIMS或离子微探针）将用于实现目标。更广泛的影响：该提案将为PI的专业发展提供基础，PI是新的NENIMF经理，也是新的NSF PI。 该项目将有助于恢复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月的一次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）。

"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).