Collaborative Research: Improving the Accuracy and Precision of Monazite and Allanite Geochronology via ID Th-Pb Ages for Reference Materials

合作研究：通过参考材料的 ID Th-Pb 年龄提高独居石和铜铜矿年代学的准确度和精度

• 批准号: 1050043
• 负责人: John Cottle
• 金额: $ 13.33万
• 依托单位: University of California-Santa Barbara
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-05-01 至 2014-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1050043&HistoricalAwards=false
• 关键词: Collaborative; Research; Improving; Accuracy; Precision

Collaborative Research: Improving the accuracy and precision ofmonazite and allanite geochronology via ID Th-Pb ages for referencematerialsThe principal limitation for obtaining high-precision, accurate standard-based 208Pb/232Th ages from monazite and allanite is the lack of appropriate, well-characterized reference materials. Because both monazite and allanite are compositionally variable and SIMS, LA-ICP-MS incur instrumental mass-dependent fractionation, it is essential to closely match standards with unknowns. This proposal seeks to determine isotope dilution (ID) Th-Pb ages for the Th-rich accessory minerals monazite and allanite. Th-Pb ages currently exist for only one reference material that is commonly used-'554'. Consequently, all standard-based geochronologic measurements require an assumption that Th-Pb and U-Pb ages are equivalent. This assumption is unnecessary and, in many cases, invalid. By obtaining high-precision ID Th-Pb ages for a suite of well-characterized, community-wide reference materials, this research will provide a means of independently calibrating Th-Pb ages for minerals that can be linked to fundamental tectonic processes.Intellectual Merito Eliminates the need to assume concordance among the three decay systems (235U, 238Uand 232Th decay chains) by providing independently verified U-Pb and Th-Pb ages.o Improves precision on age measurements for a chronometer that can be directly linkedto the metamorphic and magmatic history of a terraneo Provides well-characterized standards to the community for high-precision, standardbasedgeochronology.Broader impacts1. This proposed research seeks to address the fundamental aim of the EARTHTIME initiative: "the development of the geochronological techniques necessary to produce temporal constraints with uncertainties approaching 0.1 % of the radioisotopic ages."o A website will be developed that contains the information about the reference materials and the methods for measuring the ID TIMS and ICP-MS ages. This information will be linked to the EARTHTIME website.o An educational module will be developed that can be integrated into the EARTHTIME mission for educating students about understanding geologic time. This module will demonstrate linking pressure, temperature and time histories.2. This project supports two early career scientists-John Cottle (UCSB faculty) and Emily Peterman (Stanford Postdoctoral Fellow). In addition, Peterman is a young female scientist (Ph.D. 2009).3. This study will train undergraduates (UCSB) in laboratory investigations and provide a component of graduate research for graduate students at UCSB and Stanford.4. The results of the proposed research will impact the geochronology community at large:o Thermal Ionization Mass Spectrometryo Secondary Ionization Mass Spectrometryo Electron Probe MicroAnalysiso (Laser Ablation) Inductively Coupled Plasma Mass Spectrometry

合作研究：利用同位素Th-Pb定年标准物质提高独居石和褐帘石年代学的准确性和精密度独居石和褐帘石~（208）Pb/~（232）Th定年的主要限制因素是缺乏合适的、特征良好的标准物质。由于独居石和褐帘石都是成分可变的，并且西姆斯，LA-ICP-MS引起仪器质量依赖性分馏，因此必须将标准品与未知物紧密匹配。本文对富钍副矿物独居石和褐帘石进行了同位素稀释法Th-Pb年龄测定。目前存在的Th-Pb年龄只有一种常用的标准物质-“554”。因此，所有基于标准的地质年代学测量都需要假设Th-Pb和U-Pb年龄是相等的。这种假设是不必要的，而且在许多情况下是无效的。通过获得一套充分表征的、社区范围内的参考物质的高精度ID Th-Pb年龄，这项研究将提供一种独立校准与基本构造过程有关的矿物Th-Pb年龄的方法。智能Merito消除了假设三个衰变系统之间一致性的需要（235 U，通过提供独立验证的U-Pb和Th-Pb年龄，提高了精密计时器的年龄测量精度，可直接将其与岩石的变质和岩浆历史联系起来。向社会提供高精度、基于标准的地质年代学特征标准。这项拟议的研究旨在解决地球时间倡议的根本目标：“发展必要的地质年代学技术，以产生时间限制，不确定性接近0.1%的放射性同位素年龄。“o将建立一个网站，其中载有关于参考材料和测量ID TIMS和ICP-MS年龄的方法的信息。o将开发一个教育模块，可纳入"地球时间“使命，教育学生了解地质年代。该模块将演示连接压力、温度和时间历史。2.该项目支持两个早期的职业科学家-约翰科特尔（UCSB教师）和艾米丽彼得曼（斯坦福大学博士后研究员）。此外，彼得曼还是一位年轻的女科学家（博士）。2009年）。这项研究将训练本科生（UCSB）在实验室调查，并提供研究生研究的一个组成部分，在UCSB和斯坦福大学的研究生。拟议研究的结果将对整个地质年代学界产生影响：热电离质谱二次电离质谱电子探针显微分析（激光烧蚀）电感耦合等离子体质谱