Assessing silicate melt behaviour with granite microstructure

用花岗岩微观结构评估硅酸盐熔融行为

• 批准号: RGPIN-2019-04248
• 负责人: Dyck, Brendan
• 金额: $ 1.82万
• 依托单位: Simon Fraser University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=714736
• 关键词: Assessing; silicate; melt; behaviour; granite

The upward flow and crystallization of magma (molten rock) are two of the most important processes in the formation and evolution of Earth's crust. These processes are particularly important within the continental crust, where the majority of magmas are granitic in composition. Understanding the evolution of granitic magma is critical because (a) granite is a principal carrier of many economic minerals, including gold, copper, tin, tungsten and uranium, and (b) the genesis and emplacement of granitic magma has had a significant bearing on continental evolution from the Precambrian to the present day. Little is known about the details of granitic magma migration and crystallization because we have not yet developed a set of rigorous methods to measure and evaluate these processes. As such, we are currently unable to describe, in any given body of granite, how the crystal and liquid parts of the magma behaved, and how the rate of cooling affected crystal growth and grain dimensions. This gap in knowledge severely limits our understanding of the most fundamental physical, chemical, spatial and temporal conditions of granite formation and, in turn, the evolution of the continental crust. In the proposed program of research, I will investigate the internal behaviour of granitic magma by applying recent advances in the analysis and interpretation of rock microstructures. These investigations will be made on samples collected during new field work planned for Canada and South Africa. An immediate result of my research program will be a new set of methods to (1) identify the mobility of crystals and liquid during granite crystallization, and (2) quantify the crystallization rate of granitic intrusions. These methods will be used to parameterize the evolution of granitic magma and ultimately improve our understanding of large continental magmatic systems. The proposed research will consist of two interrelated themes: I. the internal behaviour of high-silica granites (>70 wt.% SiO2); and II. the thermal evolution of granitic intrusions. We will use crystallographic orientation relationships of the mineral quartz to determine if crystals were mobile during crystallization and if crystalmelt segregation occurred. The results will allow us to evaluate the influence of intrusion composition and dimensions on the physical evolution of granitic bodies. To address gaps in our understanding of cooling behaviour of granitic magma, we will develop and calibrate a new crystallization rate speedometer, based on the morphology of the mineral plagioclase and the chemical composition of the granite. Given the nearly ubiquitous occurrence of plagioclase in granitic rocks, this method will be applicable to the study of magma dynamics and thermal histories of magmatic complexes worldwide. The results of my research will also provide a new platform for the understanding of granite-related mineral deposits.

岩浆（熔融岩）的上升流动和结晶作用是地壳形成和演化过程中最重要的两个过程。这些过程在大陆地壳中特别重要，因为大陆地壳中大多数岩浆的成分都是花岗岩。了解花岗质岩浆的演化是至关重要的，因为（a）花岗岩是许多经济矿物的主要载体，包括金、铜、锡、钨和铀，（B）花岗质岩浆的成因和侵位对从前寒武纪到今天的大陆演化有着重要的影响。 关于花岗质岩浆迁移和结晶的细节知之甚少，因为我们还没有开发出一套严格的方法来测量和评估这些过程。因此，我们目前无法描述，在任何给定的花岗岩体中，岩浆的晶体和液体部分如何表现，以及冷却速度如何影响晶体生长和晶粒尺寸。这种知识上的差距严重限制了我们对花岗岩形成的最基本的物理、化学、空间和时间条件的了解，从而也限制了我们对大陆地壳演变的了解。在建议的研究计划中，我将通过应用岩石显微结构分析和解释的最新进展来研究花岗岩岩浆的内部行为。这些调查将对计划在加拿大和南非开展的新的实地工作期间收集的样本进行。我的研究计划的直接结果将是一套新的方法，以（1）确定花岗岩结晶过程中晶体和液体的流动性，（2）量化花岗岩侵入体的结晶速率。这些方法将用于参数化花岗岩岩浆的演化，并最终提高我们对大型大陆岩浆系统的认识。 拟议的研究将包括两个相互关联的主题：一。高硅花岗岩（>70重量%）的内部特性SiO2）;和II.花岗岩体的热演化我们将使用矿物石英的晶体学取向关系来确定晶体在结晶过程中是否是移动的以及是否发生晶体熔体偏析。结果将使我们能够评估侵入体的组成和尺寸对花岗岩体的物理演化的影响。为了解决我们对花岗岩岩浆冷却行为的理解存在的差距，我们将根据矿物斜长石的形态和花岗岩的化学成分开发和校准一种新的结晶速率速度计。鉴于斜长石在花岗质岩石中几乎无处不在，这种方法将适用于全球范围内的岩浆动力学和岩浆杂岩热历史的研究。研究成果也将为认识花岗岩类矿床提供新的平台。