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.

地球上的行星壳主要是由玄武岩岩浆结晶而成的岩石。这些岩浆是由地幔部分熔融形成的，它们在地球表面喷发，在那里它们产生了壮观的火山特征，包括多山的大洋中脊、一连串的热点火山，以及可能引发灾难性生物圈崩溃的大量溢流玄武岩。大多数玄武岩岩浆不会喷发，而是在地壳浅层到深层的储集层中停滞和结晶，例如层状侵入体，保存着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岩浆形成行星壳的时间尺度和过程。这将通过对选定的层状侵入体进行地质年代学和地球化学调查来实现。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。 理解层状侵入体和地壳演化之间的关系的关键是(1)岩浆在地壳中积累的持续时间和速率，(2)单个侵入体的热历史，以及(3)地幔来源的组成，所有这些对层状侵入体的约束都很差。我将为单独的侵入开发综合的时间-温度-组成框架，作为对比地质记录的基准。我将研究一系列古老的(太古代)到年轻的(新生代)侵入岩，包括那些已经建立了岩浆室结晶基本原理的侵入岩(Skairgaard，Stillwater)和加拿大的侵入岩，它们提供了测试当前和新兴的岩浆储集层物理状态范式的机会(Fox River，Polaris)。我还将研究使用非传统稳定同位素作为一种新的地球化学工具来跟踪层状侵入体中的矿物控制过程，这将对它们的结晶条件和序列产生新的见解。 层状侵入体包含世界级的铬、铂族元素和钒的矿床，这些金属对整个社会都是至关重要的。这项研究的结果将对加拿大和世界其他地方侵入岩浆矿床的成因产生直接的影响。这项工作的最终目标是为岩浆作用和冷却的时间尺度和路径提供新的科学约束，这些过程和冷却产生了层状侵入体中存在的引人注目的岩石。这一成果将被用来挑战岩浆演化和地壳在时间和空间中发展的基本概念。