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

造山带核心区（加拿大科迪勒拉和格伦维尔省）构造演化

• 批准号: 105982-2012
• 负责人: Carr, Sharon
• 金额: $ 1.97万
• 依托单位: Carleton University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2013
• 资助国家: 加拿大
• 起止时间: 2013-01-01 至 2014-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=522031
• 关键词: Tectonic; evolution; core; zones; orogenic

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.

为了建立和检验碰撞山带的形成模式，有必要了解构造演化、压力(P)-温度(T)历史以及整个地壳内部垂直剖面的变形和变质作用的相对和绝对时间。这样的一个剖面暴露在公元前南部的科迪勒拉，在那里人们很好地了解了造山事件最后阶段的构造历史、时间和P-T条件。在建造的早期阶段对P-T历史施加年龄限制会出现困难，因为很容易确定年代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区域，这种矿物的化学成分和结构的变化可能记录其生长和变形历史期间的环境P-T条件。因此，可以直接确定不同阶段形成的P-T条件和结构的年代，这是一种最强大的工具，可应用于广泛的地质研究。第二个目标是将这项技术与其他野外、岩石学和地质年代学研究结合起来，应用于科迪勒拉和安大略省格伦维尔，那里缺少早期变形和P-T条件的直接日期。研究结果将检验有关中地壳过程和山带建造和崩塌的模型，并应用于解释加拿大地盾的古代地质地体和完善资源勘探模型。第三，根据矿物的化学成分确定岩石的P-T条件的方法是基于热力学原理的，没有考虑变形的影响。将通过对岩石进行详细研究来评估变形和变质过程之间的相互作用，在岩石中我们可以追踪作为微结构变化函数的变质作用的差异。这项研究的结果将对变形岩石的P-T结果的意义产生广泛的影响。本科生和研究生的研究涉及项目设计、实地工作、分析技术和构造综合的方方面面，是拟议研究计划的组成部分。