Collaborative Research: Understanding the Tectonic and Petrological Processes Controlling Iron Oxide-Apatite Mineralization in a Mesoproterozoic Collisional Orogen

合作研究：了解控制中元古代碰撞造山带氧化铁-磷灰石矿化的构造和岩石学过程

• 批准号: 2120412
• 负责人: Victor Guevara
• 金额: $ 9.86万
• 依托单位: Amherst College
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-09-01 至 2024-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2120412&HistoricalAwards=false
• 关键词: Collaborative; Research; Understanding; Tectonic; Petrological

Iron oxide-apatite (IOA) deposits in the New Jersey (NJ) Highlands were an important source of iron ore in the region for about 200 years, impacting the local economy and fueling the industrial revolution in the 18th and 19th centuries. Similar types of deposits occur globally, but there is little consensus as to how and why they form. As global demand for natural resources grows, it is increasingly important to better understand the geological processes that produce critical resources such as those found in IOA deposits. In addition to their economic and historical significance, the NJ deposits are found in rocks associated with one of Earth’s largest mountain-building events, which occurred along the eastern edge of North America approximately 1.3 to 1.0 billion years ago. This project aims to characterize the formation of IOAs using a variety of tools, leading to better understanding of IOAs worldwide. Additionally, the proposed study of IOA deposits will provide information about how massive mountain belts evolve through time. The study location and historical backdrop also opens many exciting doors for engaging the local community in regional geology and the impact of geoscience on society. This project involves organizing a 1-week seminar and a field trip on the regional geologic setting of New Jersey and the state’s historical iron industry for local K-12 teachers from underserved communities. This work also engages undergraduate students in educational and research experiences and supports two early career scientists from underrepresented identities in geoscience.The exhumed metamorphic core of Mesoproterozoic Grenville Orogeny provides a superb natural laboratory to study the enigmatic magmatic and fluid-driven processes that concentrate critical elements in orogenic systems. The widely distributed nature of over 400 Kiruna-type IOA deposits in the Grenvillian rocks of the NJ Highlands suggest that IOA genesis reflects regional-scale tectonic processes involved in the crustal evolution of the orogenic belt. These deposits are hosted by nearly every Mesoproterozoic rock type in the region, making cryptic the petrologic and tectonic mechanisms that led to their genesis and the stages of the Grenville Orogeny in which they operated. This project aims to determine whether mineralization occurred by: 1) Pre-collisional hydrothermal processes operating in a back-arc basin, 2) Magmatic processes related to the widespread intrusion of granitic to monzonitic magmas during arc accretion, or 3) Magmatic and/or metasomatic processes related to post-orogenic lithospheric delamination and extensional collapse. The key to discriminating between these hypotheses lies in integrating precise constraints on the timing of IOA deposition with the unique textural and chemical signatures of the different petrogenetic processes involved. This project evaluates five NJ IOA deposits using petrochronology. This approach involves 1) making field and petrographic observations to determine deformational and emplacement histories between IOA deposits and host rocks, 2) interpreting mineral textures and chemistries in IOA ores, and 3) using both high-spatial resolution and high-precision U-Th-Pb geochronology to determine the timing and duration of IOA mineralization and place it in the context of host rock deformation and metamorphism. The results of this work will ultimately contribute to an understanding of the tectonic mechanisms responsible for IOA genesis in collisional orogenic belts and the timescales over which they occur.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.

新泽西州 (NJ) 高地的氧化铁磷灰石 (IOA) 矿床在大约 200 年来一直是该地区的重要铁矿石来源，影响了当地经济并推动了 18 世纪和 19 世纪的工业革命。矿床在全球范围内都有出现，但随着全球对自然资源的需求不断增长，人们对它们的形成方式和原因几乎没有达成共识，更好地了解产生关键资源（例如 IOA 中发现的资源）的地质过程变得越来越重要。除了其经济和历史意义外，新泽西州矿床还发现于与地球上最大的造山事件之一相关的岩石中，该事件发生在大约 1.3 至 10 亿年前的北美东部边缘。此外，拟议的 IOA 矿床研究将提供有关大规模山地带如何随时间演变的信息，研究地点和历史背景也打开了许多令人兴奋的大门。为了让当地社区参与区域地质学以及地球科学对社会的影响，该项目包括为当地 K-12 教师组织为期 1 周的研讨会和一次关于新泽西州区域地质环境和该州历史钢铁工业的实地考察。这项工作还让本科生参与教育和研究经验，并为地球科学领域中代表性不足的两位早期职业科学家提供支持。中元古代格伦维尔造山运动挖掘出的变质核心提供了一个极好的自然实验室来研究。造山反射系统中关键元素集中的神秘岩浆和流体驱动过程，新泽西高地格伦维尔岩石中 400 多个基律纳型 IOA 矿床广泛分布的性质表明，IOA 成因涉及地壳的区域规模构造过程。这些矿床几乎存在于该地区所有的中元古代岩石类型中，使得导致其形成的岩石学和构造机制变得神秘。该项目旨在确定矿化是否通过以下方式发生：1）弧后盆地中的碰撞前热液过程，2）与花岗岩广泛侵入相关的岩浆过程。弧增生过程中的二长岩浆，或3）与造山后岩石圈分层和伸展塌陷有关的岩浆和/或交代过程。这些假设之间的区别在于将对 IOA 沉积时间的精确限制与所涉及的不同岩石成因过程的独特结构和化学特征相结合。该项目使用岩石年代学评估了新泽西州的五个 IOA 沉积物。该方法涉及 1) 进行现场和岩相观察以确定。 IOA 矿床和围岩之间的变形和侵位历史，2) 解释 IOA 矿石中的矿物结构和化学成分，3) 使用高空间分辨率和高精度U-Th-Pb 地质年代学可确定 IOA 矿化的时间和持续时间，并将其置于主岩变形和变质作用的背景下。这项工作的结果最终将有助于了解碰撞造山中 IOA 成因的构造机制。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。