Anorthite in Magmatic Systems

为了满足我们对自然资源稳定供应的日益增长的需求，需要对形成和储存这些资源的过程有越来越深入的了解。 要深入了解这些过程，就需要研究地质物质转化为可开采的地面资源的各个方面，从最初从地球内部产生的物质到资源集中在地表的最终机制的性质。该项目的重点是进一步加深我们对地球内部的基本了解，比人类可以直接进入的更深，以及在海洋中脊海底的静止火山活动期间和陆地上的猛烈火山爆发期间，地幔物质的哪一部分被带到地球表面。通过研究在这两种地质环境中发现的一种矿物，钙长石矿物，将对这些地区的地幔和岩浆向地表移动的机制有新的认识，钙长石矿物的起源仍然是个谜，不能用我们目前对地球地幔中工作的地质过程的理解来解释。这项研究利用了通过对这种矿物的合成版本进行研究而获得的一系列新观察结果，这些新观察结果表明岩浆的行为与人们普遍认为的非常不同，并且有可能极大地改变我们对岩浆如何在地幔中产生以及它们在上升时所经历的变化的看法。这项研究包括模拟地球内部条件的实验，建模和观察岩石样品中的天然钙长石晶体。这种多方面的方法对于培养下一代各级地球科学家至关重要，并将用于向大学新生介绍跨学科科学，为本科生提供研究经验，并最终提供博士学位。水平的研究机会。具体而言，拟议的工作使用实验和热力学建模方法来研究一个小的认识偏差，从经典的熔融回路拓扑结构接受为指示斜长石组成行为的火成岩，因为时间的鲍恩。这种偏离是在斜长石和斜长石-橄榄石组成空间的钙长石丰富的区域在高压下，不稳定的斜长石和抑制钙长石的斜长石从发展正常向钠富集的岩浆冷却的形式。拟议的研究将限制这种行为的成分空间的上涌地幔，这样做将提供新的见解高度钙长石斜长石晶体在洋中脊和俯冲带岩浆的起源。此外，斜长石和熔体稳定性关系的变化所决定的压力效应对这种拓扑结构意味着一个高压区域的高熔体生产和一个重要的作用，涉及铝尖晶石的围晶反应。由于这些影响都不能预测目前的模型在这些环境中的岩浆生产，这项研究有可能打开大门，各种新的研究岩浆的起源和演化的挤压和伸展板块边缘，可以整合到下一代的岩浆形成的机械模型，在地球的地幔这样的行为。

Meeting our ever increasing need for a steady supply of natural resources requires an increasingly sophisticated understanding of processes that form and store such resources. Gaining insights into these processes requires research that spans all aspects of the transformation of geologic material into exploitable ground-based resources, from what is originally brought up from the Earth's interior, to the nature of the final mechanisms of concentration of resources on the surface. This project focuses on furthering our fundamental understanding of what lies in the Earth's interior, deeper than humans can directly access, and what portion of this mantle material is brought to the Earth's surface during quiescent volcanic activity beneath the sea at mid-ocean ridges and during violent volcanic eruptions on land. New insights into the mantle in these regions and the mechanisms of moving magma to the surface will be gleaned by studying a mineral found in both of these geologic environments, the mineral anorthite, whose origin remains enigmatic and cannot be explained by our current understanding of the geologic processes at work in the Earth's mantle. This research capitalizes upon a set of new observations obtained through research on a synthetic version of the mineral that suggests very different behavior in magmas than has been broadly assumed and has the potential to dramatically change our view on how magmas are produced in the mantle and the changes they undergo as they ascend. This research involves a combination of experiments simulating conditions within the Earth, modeling, and looking at natural anorthite crystals in rock samples. This multi-faceted approach is vital for training the next generation of geoscientists at all levels and will be used to introduce college freshmen to interdisciplinary science, provide research experiences for undergraduates, and finally to provide Ph.D. level research opportunities. In specific, the proposed work uses experimental and thermodynamic modelling approaches to investigate a little-recognized deviation from the classic melting loop topology accepted as dictating plagioclase compositional behavior in igneous rocks since the time of Bowen. This deviation is in the form of a pseudo-azeotrope in the anorthite-rich region of plagioclase and plagioclase-olivine compositional space at elevated pressure that destabilizes plagioclase and inhibits anorthitic plagioclase from evolving normally towards Na-enrichment as the magma cools. The proposed research will constrain this behavior in the compositional space of upwelling mantle and by doing so will provide new insights into the origin of highly anorthitic plagioclase crystals in mid-ocean ridge and subduction zone magmas. Furthermore, the change in plagioclase and melt stability relations dictated by the pressure effect on this topology implies an elevated pressure region of high melt production and an important role for a peritectic reaction involving aluminous spinel. As neither of these implications can be predicted by current models of magma production in these environments, this research has the potential to open the door to a variety of new studies on the origin and evolution of magmas at compressional and extensional plate margins that can integrate such behavior into a next-generation mechanistic model of magma formation in the Earth's mantle.