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.

要了解地球表面如何因造山运动和其他构造过程而发生变化，就需要有准确的方法来确定地壳的状态和历史，以及开发天然气和石油矿床的沉积盆地的状态和历史。一种方法是测量岩石的温度历史，这使地质学家能够跟踪岩石从深度移动到表面的速度和时间。最广泛使用的工具之一是矿物磷灰石的（铀-钍）/氦同位素测年。在磷灰石中，铀和钍衰变产生的氦只会在非常低的温度下保留在颗粒中，一般来说，氦的扩散对温度非常敏感，因此磷灰石上的日期是热历史的记录。尽管这项技术很有用，但在某些情况下，即使考虑到诸如颗粒大小、辐射损伤和颗粒化学等复杂因素，从单个样品中获得的同位素日期也是分散的。拟议的研究将测试的假设，即有时在磷灰石日期中看到的过量散射起源于晶体缺陷，改变磷灰石晶粒内的氦扩散行为。该项目有利于社会，并通过其重点从事K-12代表性不足的学生在干（科学，技术，工程和数学）地球科学教育通过推广工作，特别是在伯利恒，PA，并通过促进本科生和研究生的培训和参与积极的研究，从而促进了一个强大的和全球竞争力的科学劳动力的社会成果。这项研究为一位早期职业研究人员提供了支持，他是STEM专业水平代表性不足的群体的一部分。该项目是地质学和实验研究领域的桥梁，以便能够开发更准确的地质和地球化学过程模型。磷灰石（铀-钍）/氦定年法作为一种强有力的工具在研究和商业应用中的应用也是进一步的，这可能对资源开发产生影响。使用各种分析技术应用于不同的空间尺度，我们将表征各种磷灰石颗粒的样品已知产生分散的磷灰石（铀钍）/氦年龄。表征将包括通过电子探针分析的化学成分，使用蚀刻实验和光学显微镜以及电子束技术对晶体缺陷进行量化。使用连续斜坡加热实验对天然样品进行的扩散实验将提供扩散氦损失的动力学参数，并表征与各种类型的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尺度缺陷的具体作用，我们将使杜兰戈磷灰石单晶变形以产生具有不同位错密度的样品。用氦-3离子注入和核反应分析对这些已知位错密度的样品进行扩散实验。此外，在全谷物水平上，质子辐照样品将通过逐步加热实验进行分析。 氦扩散动力学的变化将被建模为晶格和快速通道扩散的组合，以获得位错密度和扩散率之间的关系。从变形实验的数据也将被用来构建一个流动定律，并确定应力/位错密度的关系。为了测试这些关系，从已知的变形历史的四个剪切带的样品将使用改进的协议，结合位错密度和diffusives.The项目之间的新关系是地球科学的构造学和岩石学和地球化学计划的分工的份额。

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.