The Ferrar Magmatic Mush Column System, Dry Valleys, Antarctica

南极洲干谷的费拉尔岩浆柱系统

• 批准号: 9814332
• 负责人: Bruce Marsh
• 金额: $ 42.49万
• 依托单位: Johns Hopkins University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-04-15 至 2004-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9814332&HistoricalAwards=false
• 关键词: Ferrar; Magmatic; Mush; Column; System

This award, provided by the Antarctic Geology and Geophysics Program of the Office of Polar Programs, supports research on magma crystallization processes through studies of sills of the Ferrar Group in Antarctica.Earth's basic structure came about through processes involving the crystallization of magma or molten rock. The operation of these processes over billions of years has produced a wide diversity of rock types that have in turn given rise to the basic surface features of Earth, namely, continents and ocean basins. Yet the very details of these physical and chemical processes remain largely undiscovered. Although present day volcanism exemplifies this overall process of differentiation through the variety of lava erupted, it is not clear how this dramatic end result relates to the prolonged and detailed processes at depth responsible for this result. Solidified bodies of magma (called plutons), once deeply buried and now exposed through erosion, also furnish evidence, but most often the context of these plutons within the magmatic-volcanic system is not clear. The aim of the present research is to make a significant contribution to solving this fundamental problem by studying a group of magmatic rocks in Antarctica that uniquely display these magmatic processes. They expose the relationship of plutonism to volcanism and may be an important key to understanding planetary magmatism.The emerging global paradigm of a stack of magmatic sheets or sills connected below to a deep-seated magmatic source and above to a volcanic center is exemplified by the Ferrar magmatic system of the Dry Valleys, Antarctica (Ferrar-DV). The world's major magmatic systems (i.e., at ocean ridges, Kilauea, Mt. Etna, Stillwater, and Rum, among many others) tend also to exhibit this style of system, but only the Ferrar-DV clearly reveals the critical physical and chemical connections between the deep, mush-dominated system and the near-surface. pre-eruptive sill system. At the deepest level, for example, an extensive mush-filled, ultramafic sill forms a small (400 m) layered intrusion with many features common to the largest layered intrusions of similar composition such as Dufek and Stillwater. Moving up-section, the progressive loss of large crystals of orthopyroxene (opx), which largely form the mush, and smaller plagioclase leads to differentiated tholeiitic sills. Formerly extensive coeval and chemically contiguous lavas (Kirkpatrick Basalt) complete this remarkably complete, exceptionally exposed, and extensive (~10,000 cubic-km) magmatic system.Previous work in tracing the opx mush tongue over an area of ~3,000 sq.-km has revealed the thunderhead-like filling pattern of a stack of sills interconnected in the fashion of the limbs and trunk of a fir tree. The opx tongue records an episodic sequence of sill emplacement coupled with pulsative filling of the individual sills themselves. The apparent emplacement rhythm of the Ferrar-DV system is akin to both plutonic and volcanic systems. Moreover, although layering is pervasive within, and confined to, the opx-rich tongue, at one locale (the Dais) the layers are particularly well formed on many scales (mm to m) and show scour and fill, ripples and other forms of sorting. The relatively small size and high crustal level of the magma body at the Dais allowed rapid quenching, uniquely preserving textures commonly lost to annealing in large magma systems.This project seeks to ascertain the full physical and chemical nature of the Ferrar-DV magmatic system. The major goals are to delineate fully its vertical and horizontal extent; to understand the dynamics of its establishment; to understand the mechanics of formation of the Dais layered intrusion; to produce a map of Ferrar rocks throughout the Dry Valleys; and to produce a 3-D model of the opx tongue and feeder system. Overall, the project will attempt to elucidate a rarely seen transition between plutonic and volcanic systems, which may well have implications fundamental to planetary magmatism in the b

该奖项由极地项目办公室南极地质和地球物理项目提供，通过对南极洲费拉尔群基岩的研究，支持对岩浆结晶过程的研究。地球的基本结构是通过涉及岩浆或熔岩结晶的过程形成的。这些过程数十亿年的运行产生了各种各样的岩石类型，进而形成了地球的基本表面特征，即大陆和海洋盆地。然而，这些物理和化学过程的细节在很大程度上仍未被发现。尽管当今的火山活动通过喷发的各种熔岩体现了这种整体分化过程，但尚不清楚这种戏剧性的最终结果与导致这一结果的深层长期而详细的过程有何关系。岩浆凝固体（称为岩体）曾经被深埋，现在通过侵蚀暴露出来，也提供了证据，但大多数情况下，这些岩体在岩浆-火山系统中的背景尚不清楚。本研究的目的是通过研究南极洲一组独特地展示这些岩浆过程的岩浆岩，为解决这一基本问题做出重大贡献。它们揭示了岩体作用与火山作用的关系，可能是理解行星岩浆作用的重要关键。新兴的全球范式是一堆岩浆片或岩床在下方连接到深层岩浆源，上方连接到火山中心，南极洲干谷的费拉尔岩浆系统（Ferrar-DV）就是例证。世界上主要的岩浆系统（即海脊、基拉韦厄、埃特纳火山、斯蒂尔沃特和朗姆等）也往往表现出这种类型的系统，但只有费拉尔-DV清楚地揭示了深部、糊状为主的系统与近地表之间的关键物理和化学联系。喷发前窗台系统。例如，在最深处，一个广泛的、充满糊状的超镁铁质基岩形成了一个小型（400 m）层状侵入体，其许多特征与类似成分的最大层状侵入体（例如 Dufek 和 Stillwater）所共有。向上移动剖面，主要形成糊状的斜方辉石 (opx) 大晶体的逐渐损失，以及较小的斜长石导致分化的拉斑岩基岩。以前广泛的同时代和化学上连续的熔岩（柯克帕特里克玄武岩）完成了这个非常完整、异常暴露和广泛（约 10,000 立方公里）的岩浆系统。之前在约 3,000 平方公里的区域内追踪 opx 糊舌的工作揭示了一堆以四肢和树干的方式相互连接的雷雨云状填充图案。 一棵枞树。 opx 舌头记录了窗台安放的情景序列以及各个窗台本身的脉动填充。 Ferrar-DV 系统的表观侵位节律类似于深成系统和火山系统。此外，虽然分层在富含opx的舌头内普遍存在，并且仅限于富含opx的舌头，但在一个区域（Dais），分层在许多尺度（毫米到米）上形成得特别好，并显示出冲刷和填充、波纹和其他形式的排序。 Dais 岩浆体的尺寸相对较小且地壳高度较高，因此能够快速淬火，独特地保存了大型岩浆系统中通常因退火而丢失的纹理。该项目旨在确定 Ferrar-DV 岩浆系统的完整物理和化学性质。主要目标是充分描绘其垂直和水平范围；了解其成立动态；了解Dais层状侵入体的形成机制；绘制整个干谷费拉尔岩石的地图；并制作 opx 舌头和供料器系统的 3D 模型。总体而言，该项目将试图阐明火成岩系统和火山系统之间罕见的转变，这很可能对地球上的行星岩浆活动产生根本影响。