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

详细了解大陆边缘火山下方的岩浆管道系统对于了解大陆地壳的演化和生长以及对地壳变形和矿床形成的相关影响至关重要。了解岩浆管道系统过程的时间和长度尺度有助于了解火山喷发的空间分布、类型和频率以及相关危害。尽管我们对深部陆缘岩浆作用的认识正在大大提高，但关于火山下岩浆库中大岩浆体积的尺寸甚至是否存在、岩浆体之间通过大陆地壳厚度的相互联系以及改变此类岩浆化学成分的过程的重要性和程度的争论仍在继续。这项研究的目的是通过对暴露在加利福尼亚州约塞米蒂国家公园的岩体（在深处形成的古代岩浆岩）的研究来调查这些缺失但关键的谜题。传统的块体岩石元素和同位素分析留下了太多关于地壳岩浆系统结构的基本问题，本研究的目标是通过利用岩体中单个晶体的微观地球化学分析的新方法来解决这些问题。这项研究还将为数值模拟工作提供更好的数据，并具有指导未来深成岩研究的巨大潜力。这项研究将使用结构约束、元素和同位素地球化学分析，对来自图奥勒米侵入杂岩战略选定地点的成分异质造岩和副矿物进行分析？它曾经是一个复合的中地壳弧岩浆库——以检验以下假设。 (1) 深成岩中的矿物分带和包裹体关系记录了独特的、可解读的岩浆历史。 (2)中地壳储层存在连通的岩浆糊带。 (3)从更深层次注入的岩浆与共存的糊状带之间发生富晶体岩浆的混合。 (4)晶液分离是中地壳的重要过程；因此，许多深成岩是堆积的，并不代表液体成分。测试这些假设将允许评估中地壳弧岩体的两个模型。岩脉模型预测岩浆在深地壳“热区”中获得其化学特征。并迅速上升至次火山储层，而不产生大的岩浆体。岩浆糊柱模型预测岩浆会形成垂直延伸的储层，并在许多地壳层面经历成分变化。矿物分析将能够识别不同的矿物种群，解释普遍的岩浆过程，评估同时期岩浆的存在或不存在及其尺寸，以及这些岩浆进行化学“交流”的能力。

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?.