A PETROLOGICAL AND NITROGEN ISOTOPE STUDY OF CRUSTAL RECYCLING THROUGH TIME

地壳随时间循环的岩石学和氮同位素研究

• 批准号: 1144559
• 负责人: Peter Barry
• 金额: $ 8.5万
• 依托单位: Barry Peter
• 依托单位国家: 美国
• 项目类别: Fellowship Award
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-08-01 至 2014-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1144559&HistoricalAwards=false
• 关键词: PETROLOGICAL; NITROGEN; ISOTOPE; STUDY; CRUSTAL

Dr. Peter Barry has been awarded an NSF Earth Sciences Postdoctoral Fellowship to carry out a research and education plan at the University of Tennessee. His study will focus on petrology and volatile (He-N-Ne) isotope characteristics of mafic xenoliths from cratonic and ocean island settings. Subduction of oceanic crust has occurred continuously since the Archean, effectively recycling materials into the convecting mantle and enabling mass transfer between the surface, mantle, and continents. Stable (e.g., nitrogen) and noble gas (e.g., helium and neon) isotopes are powerful tracers of mantle processes, and sensitive indicators of recycling and crustal inputs. Selected xenolith samples from the Cook Islands and the Siberian Craton display strong ancillary evidence (e.g., oxygen isotope anomalies) suggesting they are derived from a recycled crustal protolith. We will target xenolith samples for He-N-Ne isotopes, which have previously been age dated using Re-Os and Pb-Pb methods and span a large (~3 billion years) age-range, to assess time-integrated mantle variations that are potentially attributed to recycling. In addition, microprobe (major elements) and LA-ICP-MS (minor and trace elements) analyses will be conducted on the sample suite. We use a combined geochemical and petrological approach, as isotopic interpretations are most meaningful when bracketed by strong petrological constraints.This study has broad impacts for the overall understanding of mantle evolution and crustal recycling throughout Earth history. A central focus will be on nitrogen and how it has been transported between Earth's reservoirs throughout geological time. Nitrogen is important because it is the principle gas (~78%) in Earth's modern-day atmosphere. However, surprisingly little is known about nitrogen characteristics of the Earth's mantle - particularly ancient recycled reservoirs. We aim to determine the nitrogen isotope characteristics of rare xenolith samples that show evidence of crustal recycling and span a large age-range. This feat will be accomplished by utilizing a newly developed nitrogen isotope extraction and purification system, recently constructed at Scripps Institution of Oceanography. Furthermore, this study will provide an excellent opportunity to engage both students and science educators, through outreach programs that introduce them to laboratory procedures and updating them on the progress of current projects and bringing cutting edge geoscience research into the classroom. Furthermore, undergraduate and graduate students at the University of Tennessee - Planetary Geosciences Institute, will be mentored and involved in this study. Findings will be presented at international science conferences as well as in seminars at the University of Tennessee.

彼得巴里博士已被授予美国国家科学基金会地球科学博士后奖学金，在田纳西大学开展研究和教育计划。他的研究将集中在岩石学和挥发性（氦-氮-氖）同位素特征的镁铁质捕虏体从大洋和岛屿设置。自太古代以来，洋壳俯冲不断发生，有效地将物质再循环到对流地幔中，并使地表、地幔和大陆之间的物质转移成为可能。稳定（例如，氮气）和稀有气体（例如，氦和氖）同位素是地幔过程的强有力的示踪剂，也是循环和地壳输入的敏感指标。来自库克群岛和西伯利亚海盆的捕虏体样本显示了强有力的辅助证据（例如，氧同位素异常），这表明它们来自于再循环的地壳原岩。我们将针对捕虏体样品的He-N-Ne同位素，这是以前使用Re-Os和Pb-Pb方法的年龄测定和跨越一个大的（约30亿年）的年龄范围，以评估时间积分地幔的变化，可能归因于再循环。此外，将对样品套件进行微探针（主要元素）和LA-ICP-MS（次要和痕量元素）分析。我们采用了地球化学和岩石学相结合的方法，因为同位素解释是最有意义的，当被强大的岩石学约束。这项研究具有广泛的影响，在整个地球历史的地幔演化和地壳循环的整体理解。一个中心焦点将是氮以及它如何在整个地质时期在地球的水库之间运输。氮很重要，因为它是地球现代大气中的主要气体（~78%）。然而，令人惊讶的是，对地球地幔的氮特征知之甚少-特别是古老的循环水库。我们的目标是确定稀有捕虏体样品的氮同位素特征，显示地壳循环的证据，并跨越一个大的年龄范围。这一壮举将通过利用斯克里普斯海洋研究所最近建造的新开发的氮同位素提取和纯化系统来完成。此外，这项研究将提供一个很好的机会，让学生和科学教育工作者参与，通过推广计划，向他们介绍实验室程序，并更新他们对当前项目的进展情况，并将尖端的地球科学研究带入课堂。此外，田纳西大学行星地球科学研究所的本科生和研究生将接受指导并参与这项研究。研究结果将在国际科学会议以及田纳西大学的研讨会上发表。