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石的P-T估计（由地温计确定）与变质作用的时间（由地质年代学确定）联系起来。出现这个问题是因为通常用于地温测量的矿物（例如，主要的硅酸盐相，如石榴石、辉石、斜长石）与通常用于地质年代学的矿物（例如，锆石、独一石、钛矿、金红石）不同，而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。这些包括:(i)对地质年代学中使用的单个矿物的位置进行成像，与变质构造的各种组成部分和用于地温压测量的矿物进行对比，（ii）对地温压测量和地质年代学中使用的矿物的分带模式进行成像和对比，从而证明同期生长或溶解，（iii）通过EPMA、LA ICPMS或离子微探针进行地质年代学的原位微探针方法，减少或消除对岩石粉碎的需要。从而保留重要的空间信息。我们建议将这些方法应用于前寒武纪（Grenville, Slave）和古生代（Appalachian）造山带。将从这类研究中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，并允许对造山带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.