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: University of British Columbia
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2021
• 资助国家: 加拿大
• 起止时间: 2021-01-01 至 2022-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=737512
• 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 crystal-melt 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（熔融岩石）的向上流和结晶是地壳形成和进化中最重要的两个过程。这些过程在大陆地壳中尤为重要，因为大多数岩浆在组成中都是花岗岩。了解花岗岩岩浆的演变至关重要，因为（a）花岗岩是许多经济矿物的主要载体，包括黄金，铜，锡，钨，钨和铀，以及（b）花岗岩岩浆的起源和增强对从前寒武纪到现在的大陆进化具有重要意义。关于花岗岩岩浆迁移和结晶的细节知之甚少，因为我们尚未开发出一组严格的方法来测量和评估这些过程。因此，我们目前无法在任何给定的花岗岩体中描述岩浆的晶体和液体部分的表现以及冷却速率如何影响晶体生长和谷物尺寸。知识的这一差距严重限制了我们对花岗岩形成最基本的物理，化学，空间和时间条件的理解，进而又是大陆地壳的演变。在拟议的研究计划中，我将通过在岩石微观结构的分析和解释中应用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计划的新现场工作期间收集的样品进行。我的研究计划的直接结果将是（1）在花岗岩结晶过程中确定晶体和液体的迁移率的新方法，以及（2）量化花岗岩侵入的结晶速率。这些方法将用于参数化花岗岩岩浆的演变，并最终提高我们对大型大陆岩浆系统的理解。拟议的研究将由两个相互关联的主题组成：I。高硅花岗岩的内部行为（> 70 wt。％sio2）；和II。花岗岩侵入的热演化。我们将使用矿物石英的晶体学取向关系来确定在结晶过程中晶体是否流动，以及是否发生了晶体熔体隔离。结果将使我们能够评估入侵组成和维度对花岗岩身体物理进化的影响。为了解决我们对花岗岩岩浆冷却行为的理解的差距，我们将根据矿物斜长石的形态和花岗岩的化学成分来开发和校准新的结晶速度速度表。鉴于花岗岩岩石中斜长石的几乎普遍存在，该方法将适用于全球岩浆动力学和岩浆复合物的热历史的研究。我的研究结果还将为了解与花岗岩相关的矿物质矿床提供新的平台。