US-Italy Collaboration: Determination of Boron Isotope Ratios in Subducted Sediments

美国-意大利合作：俯冲沉积物中硼同位素比率的测定

• 批准号: 1324971
• 负责人: Maureen Feineman
• 金额: $ 3.05万
• 依托单位: Pennsylvania State Univ University Park
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-08-15 至 2015-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1324971&HistoricalAwards=false
• 关键词: US; Italy; Collaboration; Determination; Boron

Subduction zones are the primary site of crustal recycling into the Earth¡¯s mantle, with important implications for mantle and continental crustal evolution throughout Earth history. Subducted sediments contribute volatiles including H2O and CO2, trace elements, and unique isotopic signatures to the formation of arc magmas. By assessing the co-variation of boron concentrations and isotope ratios in progressively dehydrated marine clays, the proposed study will constrain 1) the initial variability in the composition of marine clay inputs to the trench within a well-constrained segment of a single subduction zone; 2) the evolution of sediment composition through progressive dehydration prior to entering the sub-arc region; and 3) the composition of fluids that are ultimately expelled back to the ocean, or carried deeper and released into the forearc mantle. The proposed catalytic investigation makes use of a novel sample set collected from the Nankai Trough and Shikoku Island in Southwest Japan, which effectively samples a continuous transect along the surface of the subducted slab from the trench to the inner forearc, and for which peak paleo-temperatures are extraordinarily well-constrained by previous studies. The sample set consists of twenty subducted, underplated, and exhumed shales and mudstones from the Tertiary and Cretaceous Shimanto Belts, (peak paleo-temperatures ~100-285¢ªC). This unique suite of samples provides an opportunity to constrain the geochemical effects of diagenesis and metamorphism during the first few tens of kilometers of subduction.Understanding elemental cycling through subduction zones is critical for understanding the complex interactions and exchanges between the Earth¡¯s atmosphere, hydrosphere, and geosphere. For example, carbon dioxide levels in the atmosphere influence carbonate solubility in the oceans, and subduction of precipitated carbonate sediments is an important long-term sink for atmospheric carbon. In addition, significant amounts of ocean water are subducted into the deep Earth at subduction zones, which over geologic time may lead to the accumulation of a significant reservoir of hydrogen in the Earth¡¯s deep mantle. Boron and lithium are light elements with distinct isotopic signatures that allow us to track the recycling of surface materials such as water and sediments into the depths of the Earth. This catalyzing research project, supported by the CNIC program, will establish a close collaboration between US and Italian geoscientists, and gives early-career student researchers the valuable experience of being trained in the internationally recognized isotope geochemistry laboratory at the Consiglio Nazionale delle Ricerche (CNR) in Pisa.

俯冲带是地壳回收到地球地幔的主要部位，对整个地球历史的地幔和连续的地壳进化具有重要意义。俯冲的沉积物贡献了挥发物，包括H2O和CO2，微量元素以及独特的同位素特征，以形成弧岩浆。通过评估逐渐脱水的海洋粘土中硼浓度和同位素比的共同变化，拟议的研究将限制海洋粘土输入的组成的初始变异性在单个俯冲区域的良好约束段内的沟槽中； 2）在进入亚弧形区域之前，通过进行性脱水的沉积物组成的演变； 3）流体的组成最终被探索回海洋，或更深地释放到前牙壁架中。提出的催化投资利用了从日本西南部的南卡槽和Shikoku Island收集的新样品集，该样品有效地沿着从沟槽到内饰的俯冲平板表面进行了连续的样品，为此，峰值古植物是先前的研究非常良好的。样品集由二十个俯冲，被低估和挖掘的阴影和泥石组成，以及三级和白垩纪光环带（峰值古植物峰值〜100-285¢ªC）。这套独特的样品套件提供了一个机会，可以在前几十公里的俯冲公里内限制成岩作用和变质的地球化学作用。理解通过俯冲带的元素循环的理解对于理解复杂的相互作用至关重要，这对于理解复杂的相互作用至关重要，例如地球上的碳水化合物在大气层中的重要性繁殖型碳水化合物，并影响了碳酸盐的繁殖量，并且是碳酸盐的繁殖量，并且是碳酸盐的碳水化合物。下沉的大气碳。此外，在俯冲区域，大量的海水被俯冲到深地球上，在地质时间内，这可能会导致在地球中积累大量的氢储层。硼和锂是具有独特的同位素特征的光元素，这些元素具有独特的同位素特征，使我们能够追踪水和沉积物等地面材料的复杂物，例如地球深处。在CNIC计划的支持下，这个催化研究项目将建立我们和意大利地球科学家之间的密切合作，并为早期职业学生研究人员提供在PISA的Consiglio Nazionale Delle Richerche（CNR）的国际认可的同位素地球化学实验室中接受培训的宝贵经验。