Collaborative Research: Impact of crystal defects on helium diffusion in apatite crystals in (Uranium-Thorium)/Helium isotopic dating for the Earth sciences

合作研究：地球科学中（铀-钍）/氦同位素测年中晶体缺陷对磷灰石晶体中氦扩散的影响

• 批准号: 1726350
• 负责人: Peter Zeitler
• 金额: $ 14.15万
• 依托单位: Lehigh University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-07-01 至 2023-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1726350&HistoricalAwards=false
• 关键词: Collaborative; Research; Impact; crystal; defects

Understanding how the Earth's surface changes in response to mountain building and other tectonic processes requires accurate methods to determine the state and history of the crust and of sedimentary basins in which gas and oil deposits are developed. One approach involves measuring the temperature history of rocks, which allows geologists to track the rate and timing at which rocks are moved from depth to the surface. One of the most widely used of such tools is (Uranium-Thorium)/Helium isotopic dating of the mineral apatite. In apatite, the helium produced from decay of uranium and thorium will remain in a grain only at very low temperatures and in general the diffusion of helium is very sensitive to temperature, such that dates on apatite are a record of thermal history. Useful as the technique has been, in some instances isotopic dates obtained from even a single sample are scattered, even taking into account complicating factors such as grain size, radiation damage, and grain chemistry. The proposed study will test the hypothesis that the excess scatter that is sometimes seen in apatite dates originates in crystal imperfections that change helium diffusion behavior within apatite crystal grains. This project benefits society and advances desired societal outcomes by its emphasis on engaging K-12 underrepresented students in STEM (science, technology, engineering and math) earth science education through outreach efforts particularly in Bethlehem, PA, and by contributing to undergraduate and graduate student training and involvement in active research, thus contributing to a strong and globally competitive scientific workforce. The research is proving support for an early career researcher who is part of an underrepresented group in STEM as the professional level. The project is bridging the fields of geology and experimental research such that more accurate models of geologic and geochemical processes can be developed. It is also further the application of the apatite (Uranium-Thorium)/Helium dating as a robust tool in both research and commercial applications, which may have implication for resource development. Using various analytical techniques applied over different spatial scales, we will characterize a variety of apatite grains from samples known to yield dispersed apatite (Uranium-Thorium)/Helium ages. Characterization will include chemical composition by electron-probe analysis, quantification of crystal defects using etching experiments and optical microscopy, and electron-beam techniques. Diffusion experiments on natural samples using continuous ramped heating experiments will provide kinetic parameters for diffusive helium loss and characterize the temperature dependence of Helium release associated with various types of defects. To study the specific role of lattice-scale defects associated with deformation, we will deform Durango apatite single crystals to create samples with varying dislocation density. Diffusion experiments on these samples of known dislocation density will be conducted by Helium-3 ion implantation and nuclear reaction analysis. In addition, at the whole-grain level, proton-irradiated samples will be analyzed by step-heating experiments. Changes in helium diffusion kinetics will then be modeled as a combination of lattice and fast pathway diffusion to obtain a relationship between dislocation density and diffusivity. Data from deformation experiments will also be used to construct a flow law and determine a stress/dislocation-density relationship. To test these relationships, samples from four shear zones of known deformation history will be dated using an improved protocol that incorporates the new relationship between dislocation density and diffusivity.The project is a share between the Division of Earth Science's Tectonics and Petrology and Geochemistry programs.

了解地球的表面如何响应山区建筑和其他构造过程需要准确的方法来确定开发天然气和石油沉积物的地壳和沉积盆地的状态和历史。一种方法涉及测量岩石的温度历史，这使地质学家可以跟踪岩石从深度向表面移动的速度和时机。这种工具中使用最广泛的工具之一是矿物磷灰石的（铀）/氦同位素约会。在磷灰石中，由于铀和th的衰减而产生的氦气只能在非常低的温度下保留在晶粒中，而且通常，氦的扩散对温度非常敏感，因此，在磷灰石上的日期是热史的记录。与该技术相同，在某些情况下，即使是单个样品也散布了同位素日期，甚至考虑到复杂因素，例如晶粒尺寸，辐射损伤和谷物化学。拟议的研究将检验以下假设：磷灰石日期中有时会看到的过量散射起源于晶体缺陷，这些散射改变了磷灰石晶体晶粒内的氦扩散行为。该项目通过强调使K-12不足的学生参与STEM（科学，技术，工程和数学）地球科学教育，尤其是在Bethlehem，PA，PA，以及为在本科生和研究生培训中做出贡献，从而使社会科学的努力促进STEM（科学，技术，工程和数学）地球科学教育，从而使社会成果受益。这项研究证明了对早期职业研究人员的支持，他是STEM中代表性不足的一部分的一部分。该项目正在弥合地质和实验研究领域，以便可以开发出更准确的地质和地球化学过程模型。这也进一步应用了磷灰石（铀硫）/氦气的应用，作为研究和商业应用中的强大工具，这可能对资源开发产生影响。使用在不同的空间尺度上应用的各种分析技术，我们将表征来自已知产生分散的磷灰石（铀 - 硫代）/氦气的各种磷灰石晶粒。表征将包括通过电子探针分析的化学组成，使用蚀刻实验和光学显微镜对晶体缺陷的定量以及电子梁技术。使用连续坡道加热实验对天然样品进行扩散实验将为扩散氦损失提供动力学参数，并表征与各种缺陷相关的氦释放的温度依赖性。为了研究与变形相关的晶格规模缺陷的特定作用，我们将变形Durango磷灰石单晶以创建脱位密度不同的样品。这些已知脱位密度样品的扩散实验将通过氦-3离子植入和核反应分析进行。此外，在整个颗粒水平上，将通过逐步加热实验来分析质子辐照的样品。 然后，氦扩散动力学的变化将建模为晶格和快速途径扩散的组合，以获得位错密度和扩散率之间的关系。变形实验的数据还将用于构建流量定律并确定应力/错密度关系。为了测试这些关系，将使用改进的方案进行改进的方案，该方案结合了位错密度和扩散率之间的新关系。该项目是地球科学构造学与岩石学和地球化学计划之间的份额。

项目成果

Characterization of helium release from apatite by continuous ramped heating

通过连续斜坡加热表征磷灰石释放的氦气

• DOI: 10.1016/j.chemgeo.2017.11.019
• 发表时间: 2018
• 期刊: Chemical geology
• 影响因子: 3.9
• 作者: Idleman, Bruce D;Zeitler, Peter K;McDannell, Kalin T
• 通讯作者: McDannell, Kalin T

Noble Gases Deliver Cool Dates from Hot Rocks

稀有气体从热岩中提供冷枣

• DOI: 10.2138/gselements.16.5.303
• 发表时间: 2020
• 期刊: Elements
• 影响因子: 4.5
• 作者: Gautheron, Cécile;Zeitler, Peter K.
• 通讯作者: Zeitler, Peter K.

Screening apatites for (U-Th)/He thermochronometry via continuous ramped heating: He age components and implications for age dispersion

通过连续斜坡加热筛选磷灰石 (U-Th)/He 热测时法：He 年龄成分及其对年龄分散的影响

• DOI: 10.1016/j.gca.2017.11.031
• 发表时间: 2018
• 期刊: Geochimica et Cosmochimica Acta
• 影响因子: 5
• 作者: McDannell, Kalin T.;Zeitler, Peter K.;Janes, Darwin G.;Idleman, Bruce D.;Fayon, Annia K.
• 通讯作者: Fayon, Annia K.

Helium diffusion systematics inferred from continuous ramped heating analysis of Transantarctic Mountains apatites showing age overdispersion

通过对横贯南极山脉磷灰石的连续斜坡加热分析推断出的氦扩散系统学显示年龄过度分散

• DOI: 10.1016/j.gca.2021.07.015
• 发表时间: 2021
• 期刊: Geochimica et Cosmochimica Acta
• 影响因子: 5
• 作者: Guo, Hongcheng;Zeitler, Peter K.;Idleman, Bruce D.;Fayon, Annia K.;Fitzgerald, Paul G.;McDannell, Kalin T.
• 通讯作者: McDannell, Kalin T.