Collaborative Research: Elucidating Physical Processes in Upper Crustal Magma Systems - Evidence from Miocene Intrusive and Extrusive Sequences in Southern Nevada

合作研究：阐明上地壳岩浆系统的物理过程——来自内华达州南部中新世侵入和喷出层序的证据

• 批准号: 0409876
• 负责人: Calvin Miller
• 金额: $ 19.07万
• 依托单位: Vanderbilt University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-07-01 至 2009-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0409876&HistoricalAwards=false
• 关键词: Collaborative; Research; Elucidating; Physical; Processes

Physical transport processes determine the ways in which magmas traverse the upper crust, how they are modified, where they are deposited, whether and how they erupt, and what their final products will be. This project will investigate the physical mechanisms that transport and distribute magmatic materials using a superb natural laboratory: the Colorado River region south of Las Vegas, where relatively young (~15 million years old) magmatic systems are spectacularly exposed through a combination of steep tilting during rift-related faulting, high relief, and sparse vegetation. Numerous plutons, extensive dike swarms, and thick volcanic sequences document a relatively brief but highly productive episode of magma influx. A key part of the project will be devoted to understanding the plutons (large bodies of intrusive rock, solidified beneath the surface) and what they say about the nature and history of magma chambers (temporary melt-rich zones at depth that solidify to form plutons and may expel magma to erupt at the surface). Plutons, the magma chambers that formed them, dikes that fed the chambers, and dikes that fed volcanic eruptions at the surface all must have dynamic histories, but the physical processes that move crystals, melts, and fragments of solid or near-solid rocks within these systems are not well understood. General distributions of volcanic and intrusive rocks in the study area and details of their internal structure suggest fluid dynamic models that are analogous to fluid and particle transport in surface environments - notably sedimentation and mass wasting processes.The project will address this fundamental, general issue:How do physical transport processes in the upper crust determine the eventual distribution and physical and compositional characteristics of the products of a magma system?To evaluate this broad problem, the focus will be on the following more specific questions:(1) How do depositional processes dictate the construction and ultimate architecture of plutons?(2) How do external factors (recharging, roof collapse, eruption, tectonism) influence internal physical processes within magma chambers?(3) How much, and why, do melt fraction and volume vary over the lifetime of a pluton (~magma chamber)? (4) What determines whether deep-level magmas transit the upper crust unmodified or are modified during residence in magma chambers?; Do magma chambers serve as effective filters, selectively inhibiting further ascent of certain magmas or magmatic materials? (5) What determines whether magma pools to form plutons, remains restricted to dikes, or erupts?Field studies of key areas will characterize critical structures and map patterns that provide evidence for mechanical transport and deposition processes and provide samples for further analysis. These samples will be used for detailed radiometric dating and microanalysis of tracer elements and isotopes in minerals. Complementary lab experiments on liquid + particle analogs of magma will evaluate plausible fluid dynamic processes in the magma systems. Together, the sample geochemistry and geochronology and lab experiments will test field-based magma transport hypotheses.This project will provide ideal research training and constitute the basis for theses for 7 Master's and 12 undergraduate students. The students will present and publish their results and gain experience in combining careful field observation with advanced analytical work, in collaborative research, and in integrating their local efforts into a global framework. This work prepares them not only for further research in petrology, geochemistry, and tectonics, but also for a broad range of Earth science problem solving and teaching. Based on past experience a large proportion of these students will be female and participation by minority students is likely. The study will stimulate exchange of ideas between the PI's and their students and several informal collaborators who will add their own perspectives and expertise and in some cases analytical methodologies. These collaborations, formal and informal field trips, and presentations to specialist and general audiences as well as published work will disseminate developing ideas, foster discussion in a variety of forums, and showcase this spectacular example of magmatic processes. Much of the research will take place in Lake Mead National Recreation area, which will provide an excellent venue for presentation of new ideas to the public. The project will also contribute to a new cooperative program at Vanderbilt involving geology and environmental engineering.Although principally a basic science project, the results of this work will contribute to understanding of eruptive processes and thus will bear upon volcanic hazards.

物理输运过程决定了岩浆穿过上地壳的方式、它们如何被改变、它们沉积在哪里、它们是否喷发以及如何喷发，以及它们的最终产物是什么。 本项目将利用一个极好的天然实验室来研究岩浆物质的运输和分布的物理机制：拉斯维加斯以南的科罗拉多河地区，在那里，相对年轻（约1500万年）的岩浆系统通过裂谷相关断层作用期间的陡峭倾斜、高起伏和稀疏植被的组合而异常暴露。 大量的深成岩体、广泛的岩墙群和厚的火山序列记录了一个相对短暂但高产的岩浆流入期。 该项目的一个关键部分将致力于了解岩体（在地表下凝固的侵入岩的大型岩体）以及它们对岩浆房（在深处凝固形成岩体并可能排出岩浆在地表喷发的临时熔融富集区）的性质和历史的看法。 冥王星、形成它们的岩浆房、为岩浆房提供食物的岩脉以及为地表火山喷发提供食物的岩脉都必须有动态历史，但移动晶体、熔体和固体或近固体岩石碎片的物理过程在这些系统中还没有得到很好的理解。 火山岩和侵入岩在研究区的一般分布和详细的内部结构表明，流体动力学模型，类似于流体和颗粒在地表环境中的运输-特别是沉积和质量wasting processes.The项目将解决这个基本的，一般的问题：如何在上地壳的物理运输过程中确定最终的分布和物理和成分特征的产品的岩浆系统？为了评估这个广泛的问题，重点将放在以下更具体的问题：（1）沉积过程如何决定的建设和最终架构的岩体？(2)外部因素（补给、顶板塌陷、喷发、构造作用）如何影响岩浆房内部的物理过程？(3)在一个岩体（~岩浆房）的整个生命周期中，熔体分数和体积变化有多大，为什么变化？(4)是什么决定了深层岩浆是未经修改地穿过上地壳，还是在岩浆房中停留期间发生了变化？岩浆房是否起到有效的过滤作用，有选择地抑制某些岩浆或岩浆物质的进一步上升？(5)是什么决定了岩浆池是形成深圳湾，仍然局限于岩脉，还是喷发？对关键地区的实地研究将确定关键结构的特征，绘制模式图，为机械搬运和沉积过程提供证据，并为进一步分析提供样本。 这些样品将用于矿物中示踪元素和同位素的详细放射性测年和微量分析。 对岩浆的液体+颗粒类似物的补充实验室实验将评估岩浆系统中合理的流体动力学过程。 样品地球化学、地质年代学和实验室实验将共同检验基于野外的岩浆运移假设。该项目将提供理想的研究培训，并构成7名硕士和12名本科生论文的基础。 学生们将展示并发表他们的成果，并在将仔细的实地观察与先进的分析工作相结合，合作研究以及将当地的努力融入全球框架方面获得经验。 这项工作不仅为他们在岩石学，地球化学和构造学方面的进一步研究做好了准备，而且还为广泛的地球科学问题解决和教学做好了准备。 根据以往的经验，这些学生中有很大一部分是女生，少数民族学生也有可能参加。 这项研究将促进PI及其学生和几个非正式合作者之间的思想交流，这些合作者将增加自己的观点和专业知识，并在某些情况下增加分析方法。 这些合作，正式和非正式的实地考察，并介绍给专家和一般观众以及出版的工作将传播发展的想法，促进在各种论坛的讨论，并展示岩浆过程的这个壮观的例子。 大部分研究将在米德湖国家娱乐区进行，这将为向公众介绍新想法提供一个很好的场所。 该项目还将有助于范德比尔特一项涉及地质学和环境工程的新合作方案。虽然主要是一项基础科学项目，但这项工作的结果将有助于了解喷发过程，从而对火山灾害产生影响。