Tectonics of the Grenville orogen and micropetrology in metamorphic rocks

变质岩石学中一个长期存在的问题是无法明确地将变质岩的P-T估计（由地质温压法确定）与变质作用的时间（由地质年代学确定）联系起来。问题的出现是因为通常用于地热测压的矿物（例如，主要硅酸盐相如石榴石、辉石、斜长石）与通常用于地质年代学的那些不同（例如，锆石、独居石、钛铁矿、金红石），并且因为在传统的测年方法中，岩石被压碎，从而破坏了矿物种类之间的空间关系和它们内部的任何分区。在过去几年中，新的分析方法在解决这一问题方面取得了重大进展。其中包括：（i）成像地质年代学中使用的单个矿物相对于变质组构的各种成分和地质温压法中使用的矿物的位置，（ii）成像和地质温压法和地质年代学中使用的矿物的分区模式的相关性，从而证明同期生长或溶解，以及（iii）通过EPMA、LA ICPMS、或离子微探针，其减少或消除压碎岩石的需要，从而保留重要的空间信息。我们建议使用和发展这些方法的应用程序前寒武纪（格伦维尔，奴隶）和古生代（阿巴拉契亚）造山带。将这种研究获得的数据与区域结构信息相结合，可以深入了解变质过程，并允许对造山地壳的构造演化进行强有力的重建。

A long-standing problem in metamorphic petrology has been the inability to unequivocally link the P-T estimates of metamorphic rocks (determined by geothermobarometry) to the timing of the metamorphism (determined by geochronology). The problem arises because the minerals generally used for geothermobarometry (e.g., major silicate phases such as garnet, pyroxene, plagioclase) are not the same as those typically used for geochronology (e.g., zircon, monazite, titanite, rutile), and because in conventional dating methods the rock is crushed, thereby destroying the spatial relationships between mineral species and any zoning within them. In the last few years, new analytical approaches have yielded significant advances towards the resolution of this problem. These include: (i) imaging the locations of individual minerals used in geochronology with respect to the various components of the metamorphic fabric and the minerals used in geothermobarometry, (ii) imaging and correlation of zoning patterns of minerals used in geothermobarometry and geochronology, thereby demonstrating contemporaneous growth or dissolution, and (iii) in situ microprobe methods of geochronology by EPMA, LA ICPMS, or ion microprobe that reduce or eliminate the need to crush the rock, thereby retaining important spatial information. We propose to use and develop these methods for application to Precambrian (Grenville, Slave) and Paleozoic (Appalachian) orogens. Coupling the data obtained from studies of this kind with regional structural information provides insight into metamorphic processes, as well as permitting robust reconstructions of the tectonic evolution of the orogenic crust.