The Dufek Intrusion Ages: Crystallization or Cooling?

杜菲克入侵时代：结晶还是冷却？

• 批准号: 1918338
• 负责人: Jill VanTongeren
• 金额: $ 30.18万
• 依托单位: Tufts University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-12-31 至 2024-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1918338&HistoricalAwards=false
• 关键词: Dufek; Intrusion; Ages; Crystallization; Cooling

Voluminous outpourings of iron-rich molten rock (magma), which can initiate from deep within the earth, occur regularly throughout geologic time. Understanding volcanic eruptions requires knowledge of the magmatic plumbing systems and magma chambers that feed eruptions. While many magma chambers are typically emplaced in the shallow subsurface of the earth, only rarely are the entirety of the solidified remnants of these chambers later exposed at the surface of the earth for study. One such magma chamber, the Dufek Intrusion, exists in Antarctica. The Dufek Intrusion is part of the Ferrar magmatic event, which was triggered by the separation or rifting of South America, Africa and Antarctic continents approximately 182 million years ago. The research objectives focus on analyzing existing samples to understand the thermal and chemical evolution of the magma in the Dufek Intrusion magma chamber and deciphering whether the exposed sections are part of the same magma chamber or represent two separate magma chambers. Results from this study may result in the research community questioning the assumption that small intrusions crystallized faster than larger layered intrusions such as the Dufek Intrusion. This project supports multiple early career researchers and provides laboratory training for undergraduate students.Preliminary high-precision U-Pb ages from zircon throughout the Dufek Intrusion show that rocks thought to represent the lowermost section of stratigraphy (the Dufek Massif) are younger than the rocks thought to represent the uppermost section (the Forrestal Range). This study tests whether the zircon ages represent a cooling profile of a single large layered intrusion, or whether the Dufek Massif and Forrestal Range are two separate smaller intrusions. Crystallization temperatures of the cumulus phases (plagioclase and clinopyroxene) and the zircons, as well as cooling rates from the cumulus phases will be obtained to test the cooling profile hypothesis. The research team will construct thermal models of emplacement and cooling to compare with the laboratory analyses. In order to test the two intrusions hypothesis, the team will analyze zircon Hf isotopic compositions and whole rock Sr, Nd, Pb isotopes from samples of the two intrusions to determine whether they are similar and therefore genetically related. Results will provide important constraints on the duration of magmatism associated with continental breakup and present a coherent picture of the construction of (possibly) one of the largest magmatic intrusions exposed on earth today.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

富含铁的熔融岩石（岩浆）的大量涌出，可以从地球深处开始，在整个地质时期定期发生。了解火山爆发需要了解岩浆管道系统和岩浆房，以养活爆发。虽然许多岩浆房通常位于地球的浅层地下，但这些岩浆房的全部固化残余物后来很少暴露在地球表面进行研究。其中一个岩浆房，Dufek侵入体，存在于南极洲。 Dufek入侵是Ferrar岩浆事件的一部分，该事件是由大约1.82亿年前南美洲，非洲和南极大陆的分离或裂谷引发的。 研究目标的重点是分析现有的样品，以了解Dufek侵入岩浆房中岩浆的热演化和化学演化，并破译暴露部分是否是同一岩浆房的一部分或代表两个独立的岩浆房。这项研究的结果可能会导致研究界质疑这样一个假设，即小型侵入体比大型层状侵入体（如Dufek侵入体）结晶得更快。该项目支持多个早期职业研究人员，并为本科生提供实验室培训。整个Dufek侵入体的锆石的初步高精度U-Pb年龄显示，被认为代表地层最低部分（Dufek地块）的岩石比被认为代表最高部分（Forrestal山脉）的岩石年轻。 这项研究测试是否锆石年龄代表一个单一的大型层状侵入体的冷却剖面，或者是否Dufek地块和福雷斯特范围是两个独立的较小的侵入体。将获得积云相（斜长石和单斜辉石）和锆石的结晶温度以及积云相的冷却速率，以检验冷却剖面假设。 研究小组将建立安放和冷却的热模型，与实验室分析进行比较。 为了检验这两个侵入体的假说，研究小组将分析两个侵入体样品中的锆石Hf同位素组成和全岩Sr、Nd、Pb同位素，以确定它们是否相似，因此在成因上是否相关。 结果将提供与大陆分裂有关的岩浆活动的持续时间的重要限制，并提出一个连贯的图片建设（可能）最大的岩浆侵入体暴露在地球上today.This奖项反映了NSF的法定使命，并已被认为是值得通过评估使用基金会的智力价值和更广泛的影响审查标准的支持。