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ID Th-Pb年龄作为参考材料，提高独居石和尿囊石年代学的准确性和精确度从独居石和尿晶石获得高精度、准确的基于标准的208Pb/232Th年龄的主要限制是缺乏适当的、表征良好的参考物质。由于独居石和尿囊石的组成都是可变的，而且SIMS、LA-ICPMS会引起仪器质量相关的分馏，因此必须将标准与未知数紧密匹配。这项建议寻求确定富Th副矿物独居石和尿囊石的同位素稀释(ID)Th-Pb年龄。目前只有一种常用的参考物质--‘554’的Th-Pb年龄存在。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年龄相等。这一假设是不必要的，而且在许多情况下是无效的。通过获得一套表征良好的、社区范围的参考材料的高精度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的Th-Pb年龄的方法。Intelligence Merito通过提供独立验证的U-Pb和Th-Pb年龄，消除了假设三个衰变系统(235U、238U和232Th衰变链)之间的一致性的需要。o提高了计时器的年龄测量精度，可以直接与地体的变质和岩浆历史联系起来，为社区提供了高精度的标准地质年代学。Broader Broader Impact 1。这项拟议的研究旨在解决EARTHTIME倡议的基本目标：“开发必要的地质年代学技术，以产生时间约束，其不确定度接近放射性同位素年龄的0.1%。”o将开发一个网站，其中载有有关参考材料以及测量ID TIMS和电感耦合等离子体质谱年龄的方法的信息。这些信息将被链接到EARTHTIME网站。o将开发一个教育模块，可以整合到EARTHTIME任务中，教育学生了解地质时间。本模块将演示连接压力、温度和时间历史。该项目支持两位早期职业科学家--John Cottle(UCSB教师)和Emily Peterman(斯坦福博士后研究员)。此外，彼得曼是一位年轻的女科学家(2009年博士)。这项研究将对本科生(UCSB)进行实验室调查方面的培训，并为UCSB和斯坦福的研究生提供研究生研究的组成部分。拟议的研究结果将影响整个地质年代学领域：O热电离质谱学二次电离质谱学电子探针微分析(激光烧蚀)电感耦合等离子体质谱

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