Collaborative Research: "Double-Double Dating" of Detrital Monazite and Detrital Zircon: Quantifying Sediment Recycling in Tectonic Studies

合作研究：碎屑独居石和碎屑锆石的“双双测年”：量化构造研究中的沉积物循环

• 批准号: 1624716
• 负责人: Scott Samson
• 金额: $ 19.93万
• 依托单位: Syracuse University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-08-01 至 2021-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1624716&HistoricalAwards=false
• 关键词: Collaborative; Research; Double; Dating; Detrital; Collaborative; Research; Double; Dating; Detrital

Many geoscientists have suggested that it is likely that sedimentary rocks are "recycled", i.e. sediment is first eroded from pre-existing sedimentary rocks, gets placed back into the hydrologic cycle, and then is once again deposited into a basin to become a new sedimentary rock. Although this is an important suggestion, there are limited data that quantify to what degree this process occurs. This research will test a new approach, using a novel and relatively inexpensive method utilizing chemical analysis and dating of uranium and thorium isotopes in order to provide this needed quantitative data. If these new methods are successful, they can be used by a wide variety of scientists to develop a much better understanding of the history of a sedimentary basin - information critical not only to academic scientists but to those in both the petroleum and economic minerals industry as well. In addition to the scientific goals of the research, the project train undergraduate and graduate students in an important STEM (science, technology, engineering and mathematics) discipline, thus contributing to the education of the next generation of scientists. In addition, it will provide outreach to high schools for pathways for high school students to go into the earth sciences in both central New York and Kentucky, and will also facilitate the development of teaching modules for teachers and students based on the results of the research. Results of the research will be disseminated as peer-reviewed publications and as presentations at professional society meetings. Analytical data will be made available through publicly accessible online databases.Consideration of sediment recycling in tectonic studies is critical for accurate assessment of tectonic reconstructions such as terrane movement and collisional histories. Preliminary research indicates that some detrital monazite grains exhibit textural evidence of having formed diagenetically in an older clastic sequence (i.e. detrital diagenetic monazite) and therefore must be recycled. The principal investigators suggest that the detrital diagenetic grains are readily distinguishable, based on textures and ages, from detrital monazite derived from crystalline rocks in the source terranes. This project will test the effectiveness of this rapid approach for detecting recycling compared to the much more expensive and labor intensive method of "double dating" detrital zircon (i.e. Uranium-Lead geochronology combined with (Uranium-Thorium)/Helium thermochronology of the same crystal). The principal investigators will perform textural analysis, using backscatter electron imaging of monazite crystals, to characterize grains identified as diagenetic detrital monazite versus detrital metamorphic/igneous monazite. These grains will then be dated using Thorium-Lead geochronologic techniques followed by (Uranium-Thorium-Samarium)/Helium dating to quantitatively establish if our rapid, qualitative approach is valid. The researchers will also determine the Neodymium isotopic composition of the dated single monazite grains to determine if this is a new and useful approach to expand sedimentary provenance information. The isotopic methods will be applied to Neoproterozoic and Paleozoic sedimentary strata from the eastern United States.

许多地球科学家都认为，沉积岩可能是“回收的”，即首先从既有的沉积岩石中侵蚀沉积物，将其放回水文循环中，然后再次沉积到盆地中，成为新的沉积岩。尽管这是一个重要的建议，但有限的数据量化了此过程在多大程度上发生。这项研究将使用一种新型且相对廉价的方法来测试一种新方法，该方法利用化学分析和对铀和th ro的同位素进行测试，以提供此必需的定量数据。如果这些新方法是成功的，那么它们可以被各种科学家使用，以更好地了解沉积盆地的历史 - 信息不仅对学术科学家，而且对石油和经济矿物业行业的人都至关重要。除了研究的科学目标外，该项目还以重要的茎（科学，技术，工程和数学）学科培训本科生和研究生，从而为下一代科学家的教育做出了贡献。此外，它将为高中学生提供高中途径，让高中学生进入纽约中部和肯塔基州的地球科学，还将根据研究结果促进教师和学生教学模块的发展。该研究的结果将作为经同行评审的出版物和专业社会会议的演讲传播。分析数据将通过公开访问的在线数据库提供。构造研究中的沉积物回收利用对于准确评估地层运动和碰撞历史等构造重建至关重要。 初步研究表明，某些碎屑独居石的晶粒表现出具有较旧的碎屑序列形成的质地证据（即，有碎裂的成岩性独居石），因此必须回收。主要研究人员认为，根据质地和年龄，与源自源地板中的晶岩的碎屑独居石相比，很容易区分碎裂成岩颗粒。与“双重约会”碎屑锆石的更昂贵和劳动密集型方法相比，该项目将测试这种快速方法检测回收的有效性（即，铀铅的地球人数与（铀thorium-thorium）/同一晶体的氦气热量学结合在一起）。 主要研究人员将使用独居石晶体的反向散射电子成像进行质地分析，以表征被鉴定为成岩碎屑碎裂的颗粒与碎屑变质/火成岩/火成岩的谷物。然后，这些晶粒将使用thor-Lead地质技术技术，然后是（铀氨基铵）/氦气的日期，以定量确定我们的快速定性方法是否有效。 研究人员还将确定过时的单个独居石晶粒的新近同位素组成，以确定这是否是扩展沉积物出处信息的新方法。同位素方法将应用于美国东部的新元古代和古生代沉积层。