Mafic magmatism in layered intrusions through time and space

时空层状侵入中的镁铁质岩浆作用

• 批准号: RGPIN-2018-04664
• 负责人: Scoates, James
• 金额: $ 3.13万
• 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: 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=712608
• 关键词: Mafic; magmatism; layered; intrusions; through

Terrestrial planetary crusts are dominated by rocks crystallized from basaltic magma. These magmas form by partial melting of the mantle and they erupt at the Earth's surface where they produce spectacular volcanic features, including the mountainous mid-ocean ridges, linear chains of hotspot volcanoes, and vast outpourings of flood basalts that may be triggers for catastrophic biosphere collapse. Most basaltic magmas do not erupt and instead they stall and crystallize in shallow to deep crustal reservoirs such as layered intrusions that preserve stunning rock records of the processes by which magma evolves. The overall goal of my proposed research program is to evaluate the timescales and processes by which basaltic magmas form planetary crusts. This will be accomplished through investigation of the geochronology and geochemistry of select layered intrusions. The research will take advantage of analytical developments, especially trace element and isotopic micro-analysis, and utilize state-of-the-art instrumentation at the Pacific Centre for Isotopic and Geochemical Research. Key to understanding the relationships between layered intrusions and crustal evolution is (1) the duration and rate at which magmas accumulate in the crust, (2) the thermal history of individual intrusions, and (3) the composition of the mantle source, all of which remain poorly constrained for layered intrusions. I will develop integrated time-temperature-composition frameworks for individual intrusions that will serve as benchmarks for comparison across the geological record. I will study a range of ancient (Archean) to young (Cenozoic) intrusions, including those where the basic principles of crystallization in magma chambers have been established (Skaergaard, Stillwater) and Canadian intrusions that provide opportunities to test current and emerging paradigms on the physical state of magma reservoirs (Fox River, Polaris). I will also investigate the use of non-traditional stable isotopes as a new geochemical tool for tracking mineral-controlled processes in layered intrusions that will yield novel insights into their crystallization conditions and sequences. Layered intrusions contain world-class deposits of chromium, platinum group elements, and vanadium, metals that are vital to society in general. The results of this research will have direct implications for the origin of magmatic ore deposits in intrusions in Canada and elsewhere in the world. The ultimate goal of this work is to provide new scientific constraints on the timescales and pathways of magmatic processes and cooling that produce the striking rocks present in layered intrusions. The results will be used to challenge basic concepts of magma evolution and development of the Earth's crust through time and space.

陆地地壳主要由玄武岩浆结晶而成的岩石构成。这些岩浆是由地幔的部分熔融形成的，它们在地球表面喷发，在那里它们产生壮观的火山特征，包括多山的洋中脊，热点火山的线性链，以及可能引发灾难性生物圈崩溃的洪水玄武岩的大量涌出。大多数玄武岩浆不会喷发，而是在浅到深的地壳储层中停滞和结晶，例如层状侵入体，保留了岩浆演化过程的惊人岩石记录。我提出的研究计划的总体目标是评估玄武岩浆形成行星地壳的时间尺度和过程。这将通过调查选定的分层侵入体的地质年代学和地球化学来实现。这项研究将利用分析方面的发展，特别是微量元素和同位素微量分析，并利用太平洋同位素和地球化学研究中心最先进的仪器。 理解层状侵入体与地壳演化之间关系的关键是（1）岩浆在地壳中积聚的持续时间和速率，（2）单个侵入体的热历史，以及（3）地幔源的组成，所有这些对于层状侵入体仍然没有很好的约束。我将为各个侵入体开发综合的时间-温度-组成框架，作为比较地质记录的基准。我将研究一系列古老（太古代）年轻（新生代）的侵入体，包括那些在岩浆房结晶的基本原则已经建立（Skaergaard，静水）和加拿大的侵入体，提供机会来测试当前和新兴的范例上的物理状态的岩浆水库（福克斯河，北极星）。我还将研究使用非传统的稳定同位素作为一种新的地球化学工具，用于跟踪层状侵入体中的矿物控制过程，这将产生对结晶条件和序列的新见解。 层状侵入体含有世界级的铬、铂族元素和钒等对社会至关重要的金属矿床。这项研究的结果将对加拿大和世界其他地方侵入岩中岩浆矿床的起源产生直接影响。这项工作的最终目标是提供新的科学约束的时间尺度和路径的岩浆过程和冷却，产生了引人注目的岩石存在于层状侵入体。研究结果将用于挑战岩浆演化和地壳时空发展的基本概念。