Collaborative Research: Characterizing Iron Deposits in Puerto Rico to Elucidate Metal Transport and Magnetite Mineralization Processes in Skarn Systems

矿床是我们社会的金属来源，它的特征提供了有关其形成过程的关键信息。铁是一种金属，对发达国家的基础设施至关重要，对那些正在发展的国家至关重要，因为它是钢铁的主要成分。铁对于风力涡轮机和电动汽车等更可持续的基础设施的生产也至关重要。因此，更好地了解铁矿是如何以及在哪里形成的，有助于提高社会进步的安全性。该项目将描述波多黎各的三个铁矿床，那里的矿床基本上尚未研究。由于这些沉积物在数千万年后相对不变，因此它们将提供有关其形成过程的见解，这些过程通常由于广泛的变质作用和/或侵蚀而丢失。这项工作将为来自阿拉巴马州奥本大学（AU）和波多黎各大学（RUM）的至少10名本科生和4名研究生提供实地和研究机会，为期三年。这两所大学的学生将每月联合起来，并在每年的波多黎各实地考察季和非洲大学的分析研讨会上亲自联合起来，培养一个名为AURUM的多元化实验室小组。AURUM的建立和发展将在不同的早期职业科学家之间培养长期的关系，为未来的合作和地球科学中代表性不足的人的成功奠定基础。在未来，这项研究将有助于告知与这些资源相关的当地管理决策。本研究的科学目标是：1)详细表征波多黎各的铁夕卡岩矿床；2)追踪金属运输、流体流动事件与岩浆活动的时间和关系。矿床是地质过程和环境的极好记录，但对该岛大多数矿床的详细研究从未发表过。特别是，Tibes、Keystone和Island Queen铁矿早在几十年前就被勘探并短暂开采。然而，这些潜在的经济储量一直没有被调查。这些地点提供了一个独特的机会来研究相对未受干扰的铁矽卡岩例子，因为它们没有经历过广泛的沉积后变质作用。研究目标将通过实地测绘、微观观测、磁铁矿微量元素和稳定同位素（铁、铁、氧、O）地球化学、石榴石地球化学和地质年代学在每个地点实现。该项目将进一步发展利用磁铁矿中的铁同位素比率和配对铁-氧同位素作为夕卡岩表征工具，通过在这三个未吸积的夕卡岩系统中战略性地生成数据。扩展现有的铁-氧同位素数据库是建立铁-氧同位素系统的关键一步，它将成为矽卡岩研究和含磁铁矿矿床研究的有效工具。与已测绘矿体相关的石榴石年代学将为成矿提供有效的日期，而整个夕卡岩的石榴石年代学将限制夕卡岩形成流体事件的持续时间。石榴石地球化学与地质年代学相结合，将允许在成矿与非成矿事件之间进行时间和化学区分。考虑到对波多黎各矿床的研究相对缺乏，以及有机会详细研究未增生的铁矽卡岩系统，新的数据将为了解铁矿床的位置和形成方式做出重大贡献。该项目由岩石与地球化学计划和促进竞争性研究的既定计划（EPSCoR）共同资助。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Characterizing ore deposits, the sources of metal for our society, provides key information about the processes related to their formation. Iron is a metal that is vital for the infrastructure of developed countries and essential for those that are developing as it is the primary component of steel. Iron is also critical for the production of a more sustainable infrastructure that includes technologies such as wind turbines and electric cars. Therefore, an improved understanding of how and where iron ore deposits form works toward increased security for societal progress. This project will characterize three iron ore deposits in Puerto Rico, where ore deposits have remained largely unstudied. As these deposits are relatively unchanged after tens of millions of years, they will provide insight into the processes involved in their formation, which are generally lost due to extensive metamorphism and/or erosion. This work will provide field and research opportunities for at least ten undergraduate and four graduate students from Auburn University (AU) in Alabama and the University of Puerto Rico, Mayagüez (RUM) over three years. Students from these two universities will unite virtually on a monthly basis and in person for annual field seasons in Puerto Rico and analytical workshops at AU, fostering a diverse lab group called AURUM. Establishing and growing AURUM will cultivate long-lasting relationships between diverse early career scientists, setting the foundation for future collaborations and success of persons underrepresented in Geoscience. In the future, this research will help inform local management decisions related to these resources. The scientific goals of this study are: 1) to characterize in detail the iron skarn deposits of Puerto Rico; 2) to track the timing and relationship between metal transport, fluid flow events, and magmatic activity. Ore deposits are excellent records of geologic processes and environments, yet detailed studies of most deposits on this island have never been published. In particular, the Tibes, Keystone, and Island Queen iron skarns were prospected and briefly mined decades ago. However, these potentially economic deposits have not been investigated since. These sites present a unique opportunity to study relatively undisturbed iron skarn examples because they have not experienced extensive post-depositional metamorphism. The research goals will be achieved through field mapping, microscopic observations, magnetite trace element and stable isotope (iron, Fe; oxygen, O) geochemistry, and garnet geochemistry and geochronology at each site. This project will further develop the use of Fe isotope ratios and paired Fe-O isotopes in magnetite as tools in skarn characterization by strategically generating data in these three unaccreted skarn systems. Expanding the existing Fe-O database is a critical step in establishing Fe-O isotope systematics as an effective tool in skarn research and magnetite-bearing deposits in general. Geochronology of garnets associated with the mapped ore bodies will provide an effective date for ore formation, while the geochronology of garnets throughout the skarn will constrain the duration of skarn-forming fluid events. Garnet geochemistry coupled with geochronology will allow for temporal and chemical discrimination between ore-forming versus non-ore-forming events. Considering the relative lack of research on the ore deposits of Puerto Rico and the opportunity to study in detail unaccreted iron skarn systems, the new data will contribute significantly to foundational knowledge on where and how iron ore deposits form.This project is jointly funded by the Petrology & Geochemistry Program and the Established Program to Stimulate Competitive Research (EPSCoR).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.