Chlorine Isotope Geochemistry of Volcanic Systems

火山系统的氯同位素地球化学

• 批准号: 0711533
• 负责人: Jaime Barnes
• 金额: $ 13.89万
• 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: 2007
• 资助国家: 美国
• 起止时间: 2007-06-01 至 2010-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0711533&HistoricalAwards=false
• 关键词: Chlorine; Isotope; Geochemistry; Volcanic; Systems

Intellectual merit. To better understand the effects of recycling of surface materials to the mantle at subduction zones, it is proposed to measure the content and isotopic composition of chlorine (Cl) in magmas and aqueous fluids from volcanoes in the Central American and Marianas volcanic arcs. Ideally, the isotopic composition (37Cl/35Cl ratios) potentially can provide critical information regarding the source of the Cl in these types of samples. Earlier work by the PIs shows that different reservoirs in subducting oceanic slabs have distinctive Cl isotopic composition, but also indicate that significant isotopic variation occurs in fumarolic gases due to isotopic fractionation associated with selective outgassing of HCl from aqueous ? thereby complicating interpretation of gas samples. It is proposed to carry out systematic studies of lavas and tephras from well-characterized active volcanoes to better constrain the Cl budget at selected sites. A laboratory study will be conducted to quantify isotopic fractionation between silicate melts and coexisting aqueous vapor, with the aim of improving interpretations of Cl data for volcanic gases. Finally, time-series studies will also be conducted on gases, and perhaps lavas, at the waxing Poas volcano in an attempt to understand how Cl systematics vary in response to increased magmatic inputs over time. Broader impacts include support for an early-career female post-doctoral scientist (Jaime Barnes) and involvement of several undergraduates in data acquisition and interpretation. Results from the proposed research project will be coupled with previous data for subduction zone lavas and ongoing work on oceanic island basalts and integrated into science classes for pre-service teachers to enhance understanding of geologic processes and geochemical recycling in the Earth''s mantle.

智力上的优点。为了更好地了解俯冲带地表物质再循环到地幔的影响，建议测量中美洲和马里亚纳火山弧火山岩浆和含水流体中氯（Cl）的含量和同位素组成。理想情况下，同位素组成（37Cl/35Cl 比率）可能可以提供有关此类样品中 Cl 来源的关键信息。 PI 的早期工作表明，俯冲海洋板片中的不同储层具有独特的 Cl 同位素组成，但也表明，由于与 HCl 从水溶液中选择性脱气相关的同位素分馏，在延胡索气体中发生了显着的同位素变化。从而使气体样品的解释变得复杂。 建议对特征明确的活火山的熔岩和火山灰进行系统研究，以更好地限制选定地点的 Cl 预算。 将进行一项实验室研究，以量化硅酸盐熔体和共存水蒸气之间的同位素分馏，目的是改进对火山气体 Cl 数据的解释。 最后，还将对逐渐增多的波阿斯火山的气体（也许还有熔岩）进行时间序列研究，试图了解氯离子系统如何随着时间的推移随着岩浆输入的增加而变化。更广泛的影响包括对职业生涯早期女性博士后科学家（Jaime Barnes）的支持以及几名本科生参与数据采集和解释。拟议研究项目的结果将与俯冲带熔岩的先前数据和正在进行的大洋岛屿玄武岩研究相结合，并纳入职前教师的科学课程，以加深对地幔地质过程和地球化学循环的了解。