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

新泽西州高地的氧化铁-磷灰石(IOA)矿床在约200年的时间里一直是该地区重要的铁矿石来源，影响了当地经济，并推动了18世纪和19世纪的工业革命。全球都有类似类型的存款，但对于它们是如何以及为什么形成的，人们几乎没有达成共识。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的地质过程变得越来越重要，例如在IOA矿藏中发现的资源。除了它们的经济和历史意义外，新泽西州的矿床还存在于与地球上最大的造山事件之一有关的岩石中，该事件发生在大约13亿至10亿年前的北美东部边缘。该项目的目的是利用各种工具描述IOAS的形成特点，从而使全世界更好地了解IOAS。此外，拟议中的IOA沉积研究将提供有关大型山脉带如何随时间演化的信息。研究地点和历史背景也为当地社区参与区域地质学和地球科学对社会的影响打开了许多令人兴奋的大门。该项目包括为来自缺乏服务的社区的当地K-12教师组织一个为期一周的研讨会和一次关于新泽西州区域地质背景和该州历史上的铁矿石工业的实地考察。这项工作还吸引了本科生参与教育和研究经验，并支持两名来自地球科学中未被充分代表的身份的早期职业科学家。中元古代格伦维尔造山带的出土变质核为研究造山系统中聚集关键元素的神秘岩浆和流体驱动过程提供了一个极好的天然实验室。新泽西州高地格勒维利安岩石中400多个基律纳型IOA矿床的广泛分布表明，IOA的成因反映了造山带地壳演化所涉及的区域尺度的构造过程。这些矿床赋存于该地区几乎每一种中元古代岩石类型中，导致它们的成因和格伦维尔造山运动阶段的岩石学和构造机制令人费解。该项目旨在确定成矿作用是否通过：1)弧后盆地中的碰撞前热液作用，2)与弧后增生期间花岗岩-二长岩岩浆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坍塌有关的岩浆和/或交代过程。区分这些假说的关键在于将对IOA沉积时间的精确限制与所涉及的不同岩石形成过程的独特结构和化学特征结合起来。该项目利用岩石年代学对5个新泽西州IOA矿床进行了评价。这种方法包括：1)进行野外和岩石学观测，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)利用高空间分辨率和高精度U-Th-Pb年代学来确定IOA成矿的时间和持续时间，并将其置于围岩变形和变质的背景中。这项工作的结果最终将有助于理解碰撞造山带中IOA形成的构造机制和它们发生的时间尺度。这一奖项反映了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。

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.