Diffusion, Closure Temperatures and Accessory Mineral Petrogenesis in a High-Temperature Aureole: Refining the Integration of P-T and t

暴露在大陆碰撞带（造山带）的岩石中的矿物组合通常保存了它们各自进入地壳深处时所经历的高温和高压的重要信息。了解这些带的地壳动力学需要对温度(T)、压力(P)和年龄(T)进行整合，从而推导出造山带不同部分的P-T- T路径。然而，P-T- T路径不容易定义，因为P、T和T的独立估计是基于同位素和化学分布的，这些分布依赖于在不同温度下停止的反应或扩散。这可能导致压力估计没有相应的温度估计，反之亦然，从而排除了实际P-T路径上实际点的定义。对变质作用时间的估计是基于在不太了解的反应中形成的矿物，并且可能在与P或T估计不一致的温度下重新设定。改进的P-T- T路径需要对控制元素和同位素分布的一阶过程进行精细校准，这些元素和同位素分布用于定义矿物系统中的P、T和T。我们将研究高温（+1000摄氏度）的Nain深成岩复合体（拉布拉多，加拿大）周围矿物的元素和同位素变化，在那里压力恒定，温度系统变化。这项工作将有助于校准元素扩散和相关矿物反应作为温度，矿物学和质地关系的函数。反过来，这将有助于我们构建更精确的P-T-t路径，从而完善我们对碰撞造山带地壳动力学的理解。

Connelly/CarlsonEAR-0087564Mineral assemblages in rocks exposed in continental collisional belts (orogens) commonly preserve important information about the high temperatures and pressures they experienced on their respective excursions into the deep crust. Understanding crustal dynamics of these belts requires integration of temperature (T) and pressure (P) and ages (t) to derive P-T-t paths for different parts of an orogen. However, P-T-t paths are not easily defined since independent estimates of P, T and t are based on isotopic and chemical distributions that are dependent on reactions or diffusion that stop at different temperatures. This may leave pressure estimates without corresponding temperature estimates and vice versa, thus precluding definition of real points on the actual P-T path. Estimates of the timing of metamorphism are based on minerals that form in poorly understood reactions and may be reset at temperatures that do not coincide with either P or T estimates. Improved P-T-t paths require refined calibrations of the first-order processes that control elemental and isotopic distributions that are used to define, P, T and t in mineral systems. We will examine elemental and isotopic variations in minerals around a high-temperature (+1000 degrees C) igneous complex of the Nain Plutonic Complex (Labrador, Canada), where pressures were constant and temperatures varied systematically. This work will facilitate calibration of elemental diffusion and relevant mineral reactions as a function of temperature, mineralogy and textural relationships. In turn, this will contribute to our ability to construct more accurate P-T-t paths and thus refine our understanding of the crustal dynamics in collisional orogens.