Collaborative Research: Testing the Existence of Magma Mush Zones and Potential Processes of Magma Differentiation in the Mid-crust with In situ Mineral Geochemistry

合作研究：用原位矿物地球化学测试中地壳中岩浆糊状带的存在和岩浆分异的潜在过程

• 批准号: 1550935
• 负责人: Valbone Memeti
• 金额: $ 18.66万
• 依托单位: CSU Fullerton Auxiliary Services Corporation
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-03-01 至 2020-02-29
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1550935&HistoricalAwards=false
• 关键词: Collaborative; Research; Testing; Existence; Magma

Detailed knowledge of magma plumbing systems beneath continent-margin volcanoes is crucial for understanding the evolution and growth of continental crust and the associated effects on crustal deformation and ore deposit formation. Understanding the time and length scales of processes in the magma plumbing system sheds light on the spatial distribution, type and frequency of volcanic eruptions and associated hazards. Although our understanding of continent-margin magmatism at depth is vastly improving, debate continues as to the dimensions, and even existence, of large magma volumes in sub-volcanic magma reservoirs, the interconnectivity between magma bodies through the thickness of the continental crust, and the importance and extent of processes that modify the chemistry of such magmas. The aim of this study is to investigate these missing, but critical pieces of the puzzle through study of plutons - ancient magmatic rocks formed at depth - as exposed in Yosemite National Park, California. Traditional bulk-rock element and isotope analyses have left too many fundamental questions about the architecture of crustal magmatic systems, resolution of which is a goal of this study through a new approach of utilizing micro-scale geochemical analysis of individual crystals in plutons. This research will also provide better data for numerical modeling efforts and has great potential to guide future studies of plutonic rocks.This study will use texturally-constrained, element and isotope geochemical analysis of compositionally heterogeneous rock-forming and accessory minerals from strategically selected sites of the Tuolumne Intrusive Complex ? which was once a composite, mid-crustal arc magma reservoir - to test the following hypotheses. (1) Mineral zoning and inclusion relationships in plutonic rocks record distinct, decipherable magmatic histories. (2) Interconnected magma mush zones exist in mid-crustal reservoirs. (3) Mixing of crystal-rich magmas occurs between magmas injected from deeper levels and coexisting mush zones. (4) Crystal-liquid separation is an important process in the middle crust; consequently, many plutonic rocks are cumulate and do not represent liquid compositions. Testing these hypotheses will allow assessment of two models for mid-crustal arc plutons. A dike model predicts that magmas attain their chemical signatures in deep-crustal ?hot zones? and rise rapidly to sub-volcanic reservoirs without producing large magma bodies. A magma mush column model predicts that magmas form vertically-extensive reservoirs and undergo compositional modification at many crustal levels. Mineral analysis will allow identification of distinct mineral populations, interpretation of prevalent magmatic processes, assessment of the presence or absence of coeval magmas and their dimensions, and the ability of such magmas to chemically ?communicate?.

大陆上岩石火山下的岩浆管道系统的详细知识对于理解大陆地壳的演化和生长以及对地壳变形和矿石沉积形成的影响至关重要。了解岩浆管道系统中过程的时间和长度尺度阐明了火山喷发和相关危害的空间分布，类型和频率。尽管我们对深度岩石岩浆的理解正在大大改善，但辩论仍在继续辩论，甚至在亚伏洛加尼克岩浆储层中的巨大岩浆量的尺寸，甚至存在，岩浆体之间的互连性通过大陆甲壳的厚度以及对化学化学的重要性和过程的层次进行了互连。这项研究的目的是通过在加利福尼亚州优胜美地国家公园暴露的岩石研究来调查这些缺失但关键的难题 - 古老的岩浆岩石。传统的散装岩石元素和同位素分析对地壳岩浆系统的结构留下了太多的基本问题，通过采用新方法利用微尺度的地球化学分析，对岩层的岩浆系统的结构进行了解决。这项研究还将为数值建模工作提供更好的数据，并具有指导未来岩石岩的未来研究的巨大潜力。本研究将对来自Tuolumne Intrusive Complects的战略性选择地点的构图岩石形成和辅助矿物的组成岩体形成和附属矿物进行质感约束，元素和同位素地球化学分析？它曾经是一个复合物中弧形岩浆储层，用于检验以下假设。 （1）冥王星岩石中的矿物分区和包容关系记录了不同的，可解密的岩浆历史。 （2）互连的岩浆糊状区域存在于中壳中部储层中。 （3）富含晶体的岩浆的混合发生在从更深层次的岩浆和共存的糊状区域中注入的岩浆之间。 （4）晶体液体分离是中壳中的重要过程；因此，许多岩石岩是累积的，不代表液体成分。测试这些假设将允许评估两种模型的中壳弧形岩体。堤防模型预测，岩浆在深层热区中获得了他们的化学特征？并迅速上升到亚伏岩储层，而不会产生大型岩浆体。岩浆糊状柱模型预测，岩浆会形成垂直扩展的储层，并在许多地壳水平上进行组成修饰。矿物分析将允许鉴定不同的矿物质人群，普遍的岩浆过程的解释，评估存在或不存在的同时岩浆及其尺寸以及此类岩浆在化学上的能力吗？