Melting Processes and Crust-Mantle Interaction in the Cascade Arc: Constraints from U-Series, Nd, Os, Pb and Sr Isotopic Data

叶栅弧中的熔化过程和壳幔相互作用：来自 U 系列、Nd、Os、Pb 和 Sr 同位素数据的约束

• 批准号: 0948703
• 负责人: Yemane Asmerom
• 金额: $ 29.24万
• 依托单位: University of New Mexico
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-07-15 至 2013-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0948703&HistoricalAwards=false
• 关键词: Melting; Processes; Crust; Mantle; Interaction

The subduction zone system on Earth is where net material transfer from the mantle to the continental crust occurs, and where material that is created at spreading ridges is returned to the mantle. Unlike volcanism in mid-ocean ridges, where melting components are limited and melting mechanism are considerably simpler, volcanism in arcs is considerably more complex: components of melt are numerous, such as the down going slab, the mantle wedge, the overlying mantle and continental lithospheres, fluids and sediments. As a result, arc magmas exhibit rich diversity in elemental and isotopic composition over short distances. It is generally agreed that fluid addition plays an important role in melting in subduction zones, most likely by hydrating the mantle wedge and lowering the solidus temperature. The timing of fluid addition and the extent of fluid involvement in generation of magmas in certain arcs, such as the Cascade subduction zone, are not clear. The Cascade arc represents both a slow converging and warm end-member of the global arc system. It is also one of the best characterized arcs, given almost century long geophysical and geologic studies. A uranium-series based study in this arc is ideally suited to answer a number of the outstanding questions. These include, 1) the relative importance of flux melting and dynamic melting in arcs in general and the Cascades in particular, 2) the explanation for the paradox of the estimated high pre-eruptive water content (up to 8% H2O) inferred for some Cascade lavas and yet the lack of enrichment in key fluid indicating elements and isotopic ratios, 3) and the amount of crust component in Cascade lavas. The proposed study will utilize 230Th-238U, 226Ra-230Th, 231Pa-235U, Sr, Nd, Pb and Os isotopic data on young lavas and mineral separates to address the above and related questions.Although this project's aim is answering basic scientific questions, it will support the human development and infrastructural building efforts at the University of New Mexico. The project will serve as a venue for training two graduate students in analytically-based geochemistry and petrology. The lab is used not only by the PIs group but also by a variety of other groups, including students from small undergraduate colleges, such as Cornell College, Iowa, and University of Puget Sound, Washington. The University of New Mexico is a minority serving institution and the current proposal is coupled to an existing Sloan Foundation grant to the PI to support minority PhD students. The study area is a National area of concern for volcanic hazards, and results from this project may contribute towards understanding of volcanic eruption cycles.

地球上的俯冲区系统是从地幔到大陆壳的净材料转移，以及在扩散山脊时产生的材料返回地幔。 与中山脊中的火山不同，熔融组件有限且熔化机制非常简单，弧线中的火山症更为复杂：融化的组成部分很多，例如向下倾斜的平板，地幔楔，上面的地幔和大陆岩石裂，液化液，液体，液体，液体和冰块。 结果，弧岩浆在短距离内表现出丰富的元素和同位素组成。人们普遍认为，添加流体在俯冲带中熔化起着重要作用，这很可能是通过滋润地幔楔并降低固相温度的水分。 液体添加的时间和在某些弧中产生岩浆（例如级联俯冲带）中流体参与程度尚不清楚。 级联弧既代表了全球弧系统的缓慢收敛和温暖的末端成员。鉴于将近世纪的地球物理和地质研究，它也是最佳特征弧之一。 理想情况下，基于铀系列的研究非常适合回答许多杰出问题。 其中包括1）弧线中通量融化和动态融化的相对重要性，尤其是级联反应，2）对估计的高爆发前水分含量（高达8％H2O）的悖论的解释，这些悖论（高达8％H2O）对于某些级联反应而言，对于某些级联反应而言，对于某些cascade lavas而言，却缺乏指示元素和case的关键流动性的含量和3），并构成了3）。 拟议的研究将利用230th-238U，226RA-230th，231Pa-235U，SR，ND，PB，PB和OS同位素数据有关Young Lavas和矿物质的同位素数据，以解决上述问题。尽管该项目的目的是该项目的目的是回答基本的科学问题，它将支持人类的发展和基金会建立新墨西哥大学的人类发展和基金会。 该项目将作为培训两名研究生的基于分析的地球化学和岩石学的场所。 该实验室不仅由PIS组使用，还由其他各种小组使用，包括来自康奈尔学院的小学学院的学生，例如爱荷华州康奈尔大学和华盛顿普吉特大学。 新墨西哥大学是一家少数派服务机构，目前的提议与现有的斯隆基金会授予了PI，以支持少数族裔博士生。 研究区域是对火山危害的全国性地区，该项目的结果可能有助于了解火山喷发周期。