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

合作研究：岩体到火山弧系统中的卤素行为

• 批准号: 2211242
• 负责人: Jaime Barnes
• 金额: $ 14.96万
• 依托单位: University of Texas at Austin
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-08-15 至 2025-07-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2211242&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、海洋和岩石圈中含量丰富的高活性元素。地壳中的卤素可以影响岩浆的性质，并携带元素形成经济矿藏。在火山弧系统中，卤素元素被俯冲地壳带到深处，并可以在熔体中穿过覆盖地壳并在火山中传播。对俯冲带卤素输入和火山气体输出的估计显示，一部分卤素被困在地球深处。存在多种可能的储存器来容纳卤素，这些卤素没有被很好地表征，因为它们太难接近和采样。一个例子是火山下的岩浆系统，其中地下岩浆房和喷发的火山岩中的卤素浓度并不为人所知。该小组将测量侵入深成岩和喷出火山岩中的全部卤素套件，这些岩石来自同一个古老的岛弧系统，现在暴露在加州的内华达州山脉。这将使他们能够解决关键的开放问题，包括：卤素是否在深成岩浆房或喷发的火山岩中富集;卤素在岩石中的位置;以及卤素对火山弧的岩浆过程和矿床有什么影响。通过这项研究，主要研究人员和研究生将设计一个本科矿物学和岩石学课程，具有可访问性，公平性和包容性原则，并让本科生参与研究和安全，包容性的实地经验。本研究使用的样本子集来自历史采集。这些样本将使用3D技术进行数字化，并创建成虚拟显微镜公共网站上托管的教育资源。由于缺乏关键储层的数据，地球深部的卤素运动和储层非常不确定，这些关键储层包括弧前、深俯冲板片残留物、陆下地幔和本研究的重点-大陆地壳。鉴于地幔中的卤素不相容性和对更进化的熔体的亲和力，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大块岩石成分被归入少数研究。这项研究将通过分析一套空间相关的深成岩和火山岩，具有相似的化学成分和年龄从塞拉内华达州弧内的弧岩浆系统的特征的全卤素（氟，氯，溴，我）的组成和行为。具体而言，该团队将测量大量岩石卤素（Cl，F，Br，I）浓度，原位矿物浓度（F，Cl）以及一套地球化学特征良好的样品上的O和H同位素。该样品组将用于1）确定卤素是否集中在单个弧系统内的深成或火山部分，2）确定卤素的托管位置（即，在矿物或其他地点），和3）评估卤素在大陆地壳形成期间的岩浆过程中的作用。为了解释同化和热液蚀变等过程对卤素行为的作用，他们还建议分析一个补充套件，其中包括下地壳捕虏体、寄主围岩（例如，片岩、大理石）、热液蚀变岩和相关矿脉，以及更多镁铁质岩石（例如，辉长岩），以加强我们的解释。该数据集将大大有助于了解大陆弧地壳的大块岩石卤素成分，并与主要元素，微量元素和同位素成分一起用于评估原始岩浆过程的影响（例如，该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。