Collaborative Research:Processing Magma and Constructing Plutons in the Upper Crust:Insights on Magma Chambers from Top-to-Bottom Views of Plutons and Associated Volcanic Sequences

了解岩浆在从源头到最终岩石安息地的过程中是如何被处理的，对于了解地壳演化、岩浆上升和侵位的机制及其与构造和喷发过程的关系至关重要。上地壳岩浆室中的储存一直是，而且仍然是这次旅程的大多数观点的中心。然而，关于岩浆室的概念、在其中发生的过程，以及它与最终建成的深成岩的关系，近年来都得到了强烈的重新评估。许多普遍持有的观点(例如，岩浆房在其大部分的“寿命”中大多是贫乏晶体的岩浆体)受到了质疑。我们建议调查内华达州埃尔多拉多山脉和高地山脉异常暴露的深成岩和可能相当的火山序列的演化，并检验有关岩浆进入岩浆室、驻留在岩浆室和从岩浆室中提取时的机械和化学处理的假说。现有的数据包括一般制图和相当大的40Ar/39Ar年龄数据集，以及全岩元素和同位素分析，为这项研究提供了可靠的初步基础。我们将增加现有的数据库，但我们的主要重点将是最新的传统方法和新方法的结合(非常详细的内部深成岩结构制图；使用成分成像的详细岩石学以强调分带、反应结构和副矿物特征；晶体粒度分布分析；长石的原位铅和锶同位素分析；锆石的离子探针测年)。这一方法将阐明这些岩浆室的演化，包括它们的充填和补充；对流、质量损耗、屋顶坍塌和喷发等内部和外部过程的破坏和重新排列；以及最终的岩体构造。它还将使我们能够通过比较输入岩浆、输出岩浆(喷发的岩浆)和留存的物质(钚)来评估岩浆室的过滤效果，并限制喷发触发和喷发方式的控制。

MillerEAR-0107119Understanding how magma is processed on its journey from source to final rocky resting place is vital for understanding crustal evolution, the mechanics of magma ascent and emplacement and their relation to tectonics, and eruptive processes. Storage in upper crustal magma chambers has been, and still is, central to most views of this journey. However, concepts of the magma chamber, the processes that occur within it, and its relationship to plutons that are ultimately constructed have been intensely reevaluated in recent years. Many widely held views (e.g. that magma chambers are mostly crystal-poor bodies of magma throughout most of their "lifespan") have been called into question. We propose to investigate the evolution of exceptionally exposed plutons and probable equivalent volcanic sequences in the Eldorado Mountains and Highland Range, Nevada, and to test hypotheses about the mechanical and chemical processing of magma as it enters, resides in, and is extracted from magma chambers.Existing data that include general mapping and a sizable data set of 40Ar/39Ar ages and whole-rock elemental and isotopic analyses provide a sound initial basis for this study. We will add to the existing data base, but our main emphasis will be on a combination of updated traditional and new methods (very detailed mapping of internal pluton structures; detailed petrography using compositional imaging to emphasize zoning, reaction textures, and accessory mineral features; crystal size distribution analysis; in situ Pb and Sr isotope analysis of feldspars; ion probe dating of zircon). This methodology will clarify the evolution of these magma chambers, including their filling and replenishment; disruption and rearrangement by internal and external processes such as convection, mass wasting, roof collapse, and eruption; and, ultimately, pluton construction. It will also permit us to evaluate the filtering effect of magma chambers by comparing input magmas, outputs (erupted magmas), and retained materials (plutons), and to constrain eruptive triggers and controls of eruptive styles.