COLLABORATIVE RESEARCH: Thermochronologic Closure Temperature in Regional Metamorphic Settings: An Empirical Study

小行星9303839 对岩石学和地质年代学数据进行严格的反演，以估计古造山带的去顶率等参数，需要精确估计各种构造层次的压力-温度和时间-温度路径。 Tt路径的不确定性主要源于同位素温度计时器关闭时放射性子体核素丢失的温度的不确定性。 对于给定的矿物-同位素系统，可导致可变闭合温度的因素包括：1）组成差异; 2）与渗透流体相互作用的程度;和3）由于反应或变形历史，放射成因子体的有效扩散维度的差异。 这些因素或变形历史的相对重要性。 对于大多数常用的温度计，这些因素在控制闭合行为方面的相对重要性还没有得到很好的理解。 本项目旨在通过对康尼马拉地区或爱尔兰的U-Pb和K-Ar（40 Ar/39 Ar）衰变方案的温度计时器进行系统的经验研究来改善这种情况。 选择康内马拉进行这项研究，因为它提供了一个无与伦比的机会，种族的各种岩性，含有许多热年代学的重要矿物，连续从石榴石级到第二硅线石级。 我们打算探索矿物年龄的变化作为组成，显微结构，粒度和变质等级的函数。 这项工作的一个重要组成部分将是耦合的热年代学与详细的稳定同位素的工作，努力评估流体的热年代学系统的放射性同位素演化的意义。 该研究将提高我们对这些系统的地球化学行为的理解，并为造山环境中时间-温度路径的构建和解释中常用的假设的可靠性提供重要的见解。

9303839 Chamberlain Rigorous inversion of petrologic and geochronologic data to estimate parameters such as unroofing rate in ancient orogenic belts requires precise estimates of pressure-temperature and time-temperature paths for a variety of structural levels. Uncertainties in Tt paths largely stem from uncertainties in the temperatures at which isotopic themochronometers become closed with respect to loss of radiogenic daughter nuclides. Factors that can result in variable closure temperatures for a given mineral- isotopic system include: 1) compositional differences; 2) the extent of interaction with infiltrating fluids; and 3) differences in the effective diffusion dimension for the radiogenic daughter due to reaction or deformational history. The relative importance of these factors or deformational history. The relative importance of these factors in governing closure behavior is not well understood for most commonly used thermochronometers. This project is intended to improve this situation through a systematic empirical study of thermochronometers based on the U-Pb and K-Ar (40Ar/39Ar) decay schemes in the Connemara region or Ireland. Connemara was chosen for this study because it provides an unparalleled opportunity to race a variety of lithologies, containing many thermochronometrically important minerals, continuously from garnet grade to second sillimanite grade. We intend to explore variations in mineral ages as a function of composition, microstructure, grain size, and metamorphic grade. An important component of this work will be the coupling of thermochronology with detailed stable isotopic work in an effort to evaluate the significance of fluids in the radiogenic isotopic evolution of thermochronologic systems. The research will improve our understanding of the geochemical behavior of these systems, as well as provide important insights into the reliability of assumptions commonly used in the construction and interpretatio n of time- temperature paths in orogenic settings.