Thermochronological Studies of High-Grade Metamorphism: The Grenville Terrane

石榴石是许多中、高档地体中常见的变质矿物。该项目将探索U， Pb， Nd和Sm在石榴石中足够不动的可能性，如果可以观察到石榴石从核心到边缘的年龄进展，则可以将其等同于活跃的渐进变质作用期间的生长。如果成功，则可以将石榴石生长年龄信息与地热测量相结合，以跟踪变质作用期间的温度变化率。该项目将评估U、Pb、Nd和Sm在富含钙和铁的石榴石中扩散的阻断温度，并将检查两个研究得很好的高变质区域的带状石榴石——安大略和纽约的Grenville以及马尼托巴省的太古代Pikwitonei区域。结果，如果成功，将提供一种方法来确定高温变质作用的升温速率，这是一个在造山研究中相当重要的参数，但目前还不能测量或令人满意地估计。

Garnet is a common metamorphic mineral in many medium and high-grade terranes. This project will explore the possibility that U, Pb, Nd and Sm are sufficiently immobile in garnet that if an age progression from core to rim of garnets can be observed, it may be equated to growth during active prograde metamorphism. If successful, garnet growth age information can be combined with geothermometry to follow the rate of temperature change during metamorphism. The project will evaluate the blocking temperatures for the diffusion of U, Pb, Nd and Sm in calcic and iron-rich garnets, and will examine zoned garnets from two well- studied areas of high grade metamorphism - the Grenville of Ontario and New York and the Archean Pikwitonei Domain of Manitoba. Results, if successful will provide a method to determine heating rates in high temperature metamorphism, a parameter that has considerable importance in orogenic studies but can not be measured or satisfactorily estimated at present.