Collaborative Research: Halogen Behavior In the Pluton-to-Volcanic Arc System

合作研究：岩体-火山弧系统中的卤素行为

• 批准号: 2400028
• 负责人: Emily Cooperdock
• 金额: $ 29.16万
• 依托单位: Brown University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-10-01 至 2025-07-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2400028&HistoricalAwards=false
• 关键词: Collaborative; Research; Halogen; Behavior; Pluton

Halogen elements (fluorine, chlorine, bromine, and iodine) are abundant, highly reactive elements in the atmosphere, oceans, and lithosphere. Halogens within Earth’s crust can affect magmatic properties and carry elements to form economic mineral deposits. Within volcanic arc systems, halogen elements are carried to depth by subducting crust and can travel within melts through the overriding crust and out at volcanoes. Estimates of halogen inputs at subduction zones and outputs through volcanic gases show a deficit that suggest a portion of halogens are trapped deep within the Earth. There are multiple possible reservoirs to host halogens that are not well characterized because they are too difficult to access and sample. One example is the magmatic system under volcanoes where concentrations of halogens in subsurface magma chambers and erupted volcanic rocks are not well known. This team will measure the full halogen suite in intrusive plutonic rocks and extrusive volcanic rocks from the same ancient arc system now exposed in the Sierra Nevada, California. This will allow them to address key open questions including: whether halogens are enriched in the plutonic magma chamber or erupted volcanic rock; where halogens are hosted within the rocks; and what impact halogens have on magmatic processes and mineral deposits at volcanic arcs. Through this research, the principal investigators and graduate students will design an undergraduate mineralogy and petrology class with accessibility, equity, and inclusion principles and engage in undergraduate students in research and safe, inclusive field experiences. A subset of the samples used for this study come from an historic collection. These samples will be digitized using 3D technology and created into an educational resource hosted on the Virtual Microscope public website.Halogen movement and reservoirs within the deep Earth are highly uncertain due to the lack of data from key reservoirs, namely, the fore-arc, deeply subducted slab residues, subcontinental mantle, and – the focus of this study – continental crust. Given halogen incompatibility in the mantle and affinity towards more evolved melts, continental crust is a potentially important reservoir; however, bulk rock compositions of plutonic and volcanic arc rocks are relegated to a handful of studies. This research will characterize the full halogen (Fl, Cl, Br, I) composition and behavior within an arc magmatic system by analyzing a suite of spatially-related plutonic and volcanic rocks that share similar chemical composition and age from the Sierra Nevada Arc. Specifically, this team will measure bulk rock halogen (Cl, F, Br, I) concentrations, in-situ mineral concentrations (F, Cl), and O and H-isotopes on a suite of geochemically well-characterized samples. This sample suite will be used to 1) determine whether halogens are concentrated in the plutonic or volcanic section within a single arc system, 2) identify where halogens are hosted (i.e., in minerals or other sites), and 3) assess the role of halogens in magmatic processes during the formation of continental crust. In order to interpret the role of processes, such as assimilation and hydrothermal alteration, on halogen behavior, they also propose to analyze a complimentary suite that includes lower crustal xenoliths, host wall rocks (e.g., schists, marbles), hydrothermally altered rocks and associated veins, and more mafic lithologies (e.g., gabbros) to strengthen our interpretations. The dataset will significantly contribute to what is known of bulk rock halogen compositions for continental arc crust, and be used with major element, trace element, and isotopic compositions to evaluate the impact of primary magmatic processes (e.g., crustal assimilation, fractional crystallization) on the halogen record and interpret overall halogen systematics through the arc magmatic system.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

卤素元素（氟、氯、溴和碘）是大气、海洋和岩石圈中丰富的高活性元素。地壳中的卤素可以影响岩浆性质，并携带元素在火山弧系统中形成经济矿床。元素通过俯冲地壳被带到深处，并且可以在熔体中穿过上覆地壳并从火山中流出。 俯冲带的卤素输入和通过火山的输出的估计。火山气体显示出缺陷，表明一部分卤素被困在地球深处，但由于难以获取和取样，有多种可能的卤素储层。其中一个例子是火山下的岩浆系统。地下岩浆房和喷发火山岩中的卤素浓度尚不清楚，该团队将测量侵入性深成岩和喷出岩中的全部卤素。来自加利福尼亚州内华达山脉的同一古老弧系统的火山岩这将使他们能够解决关键的悬而未决的问题，包括：卤素是否在深成岩浆室或喷发的火山岩中富集；以及卤素对火山弧岩浆过程和矿藏的影响通过这项研究，主要研究人员和研究生将设计一个易于理解的本科矿物学和岩石学课程，公平和包容性原则，并让本科生参与研究和安全、包容性的现场体验。本研究使用的样本子集来自历史收藏，这些样本将使用 3D 技术进行数字化，并创建为托管的教育资源。虚拟显微镜公共网站。由于缺乏关键储层（即弧前、深俯冲残留物、次大陆地幔）的数据，地球深处的卤素运动和储层高度不确定，并且 - 本研究的重点– 大陆地壳。考虑到地幔中的卤素不相容性以及对更演化的熔体的亲和力，大陆地壳是一个潜在的重要储层；然而，深成岩和火山弧岩的块体岩石成分仅限于少数研究。通过分析一系列空间相关的深成岩和火山岩，这些岩石具有相似的化学成分和年龄，从而确定弧岩浆系统中的卤素（Fl、Cl、Br、I）成分和行为。具体来说，该团队将测量一组地球化学特征良好的样品中的大块岩石卤素（Cl、F、Br、I）浓度、原位矿物浓度（F、Cl）以及 O 和 H 同位素。该样本套件将用于 1) 确定卤素是否集中在单个弧系统内的深成岩或火山部分，2) 确定卤素的存在位置（即在矿物或火山岩中）。其他地点），3）评估卤素在大陆地壳形成过程中岩浆过程中的作用，为了解释同化和热液蚀变等过程对卤素行为的作用，他们还建议分析一套互补的套件。其中包括下地壳捕虏体、围岩（例如片岩、大理石）、热液蚀变岩和相关矿脉，以及更多镁铁质岩性（例如，辉长岩）以加强我们的解释。该数据集将极大地有助于了解大陆弧地壳的大块岩石卤素成分，并与主量元素、微量元素和同位素成分一起使用，以评估初级岩浆过程的影响（例如，地壳同化、分异结晶）对卤素记录并通过弧岩浆系统解释整体卤素系统。该奖项是 NSF 的法定使命，并通过评估被认为值得支持利用基金会的智力优势和更广泛的影响审查标准。