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

了解岩浆从源头到最终的岩石静止地是如何被处理的，对于理解地壳演化、岩浆上升和就位的机制以及它们与构造和喷发过程的关系至关重要。上地壳岩浆房的储存一直是，而且仍然是大多数关于这段旅程的观点的核心。然而，近年来，岩浆房的概念、岩浆房内部发生的过程以及岩浆房与最终形成的岩体的关系都得到了激烈的重新评估。许多被广泛接受的观点（例如，岩浆房在其“生命周期”的大部分时间里主要是岩浆的结晶性差的岩浆体）已经受到质疑。我们建议研究内华达州埃尔多拉多山脉和高地山脉异常暴露的岩体和可能等效的火山序列的演化，并测试岩浆进入、居住和从岩浆房中提取时的机械和化学过程的假设。现有数据包括一般制图和40Ar/39Ar年龄的大量数据集以及全岩元素和同位素分析，为本研究提供了良好的初步基础。我们将对现有的数据库进行补充，但我们的主要重点将放在更新的传统方法和新方法的结合上（非常详细的岩体内部结构作图；使用成分成像来强调分带、反应结构和辅助矿物特征的详细岩石学；晶体尺寸分布分析；长石的原位Pb和Sr同位素分析；锆石的离子探针定年）。这种方法将阐明这些岩浆库的演化，包括它们的填充和补充；内部和外部过程（如对流、物质消耗、顶板坍塌和喷发）造成的破坏和重新排列；最后，是岩体的形成。它还将使我们能够通过比较输入岩浆、输出岩浆（喷发岩浆）和保留物质（岩体）来评估岩浆房的过滤效果，并约束喷发触发因素和喷发样式的控制。

MillerEAR-0107094Understanding 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.