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

新泽西（NJ）高地的氧化铁-磷灰石（IOA）矿床是该地区约200年来重要的铁矿石来源，影响了当地经济并推动了18世纪和19世纪的工业革命。类似类型的矿床在全球范围内都有，但对于它们如何形成以及为什么形成，几乎没有共识。随着全球对自然资源需求的增长，更好地了解产生关键资源（如IOA矿床中发现的资源）的地质过程变得越来越重要。除了其经济和历史意义外，新泽西州的矿床还发现于与地球上最大的造山活动之一有关的岩石中，该活动发生在沿着北美东部边缘约13亿至10亿年前。该项目旨在利用各种工具描述国际组织协定的形成，从而更好地了解世界各地的国际组织协定。此外，对IOA矿床的拟议研究将提供有关大规模山脉带如何随时间演变的信息。研究地点和历史背景也为当地社区参与区域地质和地球科学对社会的影响打开了许多令人兴奋的大门。该项目包括为来自服务不足社区的当地K-12教师组织为期1周的研讨会和新泽西区域地质环境和该州历史上的钢铁工业实地考察。这项工作也从事本科生的教育和研究经验，并支持两个早期的职业科学家从代表性不足的身份在geoscience.The中元古界格伦维尔造山带的挖出变质核提供了一个极好的天然实验室，研究神秘的岩浆和流体驱动的过程，集中在造山系统的关键要素。广泛分布的性质超过400基律纳型IOA矿床的格伦维尔岩的新泽西州高地表明，IOA成因反映了区域规模的地壳演化的造山带的构造过程。这些矿床几乎由该地区的每一种中元古代岩石类型所承载，使得导致其成因的岩石学和构造机制以及它们所处的格伦维尔造山运动阶段变得神秘。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）与弧增生期间花岗岩到二长岩岩浆的广泛侵入有关的岩浆过程，或3）与造山后岩石圈拆沉和伸展塌陷有关的岩浆和/或交代过程。区分这些假说的关键在于将IOA沉积时间的精确限制与所涉及的不同成岩过程的独特纹理和化学特征相结合。该项目使用岩石年代学评估了五个NJ IOA矿床。这种方法包括1）进行野外和岩相学观察，以确定IOA矿床和寄主岩石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，以及3）使用高空间分辨率和高精度U-Th-Pb地质年代学来确定IOA矿化的时间和持续时间，并将其置于寄主岩石变形和变质的背景下。这项工作的结果将最终有助于了解负责IOA成因碰撞造山带的构造机制和它们发生的时间尺度。这个奖项反映了NSF的法定使命，并已被认为是值得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的支持。

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.