Tectonic evolution of core zones of orogenic belts (Canadian Cordillera and Grenville Province)

为了建立和检验碰撞造山带形成的模型，必须了解内部带地壳垂直剖面的构造演化、压力（P）-温度（T）历史以及变形和变质作用的相对和绝对时间。这样的一个部分是暴露在南BC的科迪勒拉，在那里的结构历史，时间和P-T条件的最后阶段的造山活动是很好的理解。在建造的早期阶段，对P-T历史进行年龄限制存在困难，因为容易定年的矿物不包含直接的P-T信息。第一个目标是建立一种新的技术，使用Sm-Nd同位素来确定石榴石的晶内畴，这种矿物的化学成分和纹理的变化可以记录其生长和变形历史期间的环境P-T条件。因此，可以直接测定不同时期形成的P-T条件和构造的年代，这是一种最有力的工具，适用于广泛的地质研究。第二个目标是将这项技术与其他领域的岩石学和地质年代学研究相结合，应用于科迪勒拉和安大略格伦维尔的早期变形和P-T条件的直接日期丢失。结果将提供一个测试模型的中地壳过程和建设和崩溃的山区带，与应用解释古代地质遗迹在加拿大地盾和完善模型的资源勘探。第三，由矿物化学成分确定岩石P-T条件的方法是以热力学原理为基础的，没有考虑变形的影响。变形和变质过程之间的相互作用将通过对岩石进行详细研究来评估，在岩石中，我们可以跟踪变质作用的差异，作为微观结构变化的函数。这一研究结果对认识变形岩石中P-T结果的意义具有重要意义。本科生和研究生的研究涉及项目设计，实地考察，分析技术和构造合成的各个方面是拟议的研究计划的一个组成部分。

In order to formulate and test models for the formation of collisional mountain belts, it is essential to know the structural evolution, pressure (P) - temperature (T) history, and relative and absolute timing of deformation and metamorphism throughout a vertical crustal section in the internal zone. Such a section is exposed in the Cordillera of southern BC where the structural history, timing and P-T conditions of the last stages of mountain building events are well understood. Difficulties arise in placing age constraints on the P-T history during the early stages of construction, because minerals that are readily dated do not contain direct P-T information. The first goal is to set up a new technique that uses Sm-Nd isotopes to date intracrystalline domains of garnet, a mineral whose variations in chemical composition and textures may record the ambient P-T conditions during its growth and deformation history. Thus P-T conditions and structures that formed at different stages may be dated directly, a most powerful tool with applications to a wide spectrum of geological studies. The second goal is to apply this technique, in conjunction with other field, petrology and geochronology studies, to the Cordillera and Ontario Grenville where direct dates on early-stage deformation and P-T conditions are missing. Results will provide a test of models about mid-crustal processes and the construction and collapse of mountain belts, with applications to interpreting ancient geologic terranes in the Canadian Shield and refining models for resource exploration. Thirdly, methods used to determine P-T conditions of rocks from chemical compositions of minerals are based on thermodynamic principles, and do not account for the effects of deformation. The interplay between deformation and metamorphic processes will be evaluated by carrying out detailed studies in rocks where we can track differences in metamorphism as a function of variation in microstructures. The results of this study will have broad reaching implications for significance of P-T results in deformed rocks. Undergraduate and Graduate Student research involving all aspects of project design, fieldwork, analytical techniques and tectonic synthesis is an integral part of the proposed research program.