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

表征矿藏是我们社会的金属来源，提供了与其形成相关的过程的关键信息。铁是一种金属，对发达国家的基础设施至关重要，对发展中国家也是必不可少的，因为它是钢铁的主要成分。铁对于生产更可持续的基础设施也至关重要，这些基础设施包括风力涡轮机和电动汽车等技术。因此，更好地理解铁矿石是如何形成的，在哪里形成，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的特点，这些铁矿在很大程度上仍未得到研究。由于这些矿床在数千万年后相对没有变化，它们将提供对其形成过程的洞察，这些过程通常因广泛的变质作用和/或侵蚀而丧失。这项工作将为阿拉巴马州奥本大学(AU)和波多黎各大学马亚格斯分校(朗姆酒)的至少10名本科生和4名研究生提供为期三年的实地考察和研究机会。来自这两所大学的学生将在波多黎各的年度田野季节和AU的分析研讨会上每月和亲自联合起来，培养一个名为Aurum的多样化实验室小组。建立和发展Aurum将在不同的早期职业科学家之间培养长期的关系，为未来的合作和在地球科学中代表性不足的人的成功奠定基础。在未来，这项研究将有助于为与这些资源相关的当地管理决策提供信息。这项研究的科学目标是：1)详细描述波多黎各的矽卡岩铁矿床；2)追踪金属运移、流体流动事件和岩浆活动之间的时间和关系。矿床是地质过程和环境的极好记录，但对岛上大多数矿床的详细研究从未发表过。尤其是泰伯斯岛、Keystone和岛后铁夕卡岩，几十年前就被勘探和短暂开采。然而，自那以来，这些潜在的经济存款一直没有受到调查。这些遗址为研究相对未受干扰的铁夕卡岩提供了一个独特的机会，因为它们没有经历广泛的沉积后变质作用。研究目标将通过野外填图、显微镜观察、磁铁矿微量元素和稳定同位素(铁、铁、氧、氧)地球化学、石榴石地球化学和年代学来实现。该项目将进一步发展利用磁铁矿中的铁同位素比率和成对的铁-氧同位素作为描述夕卡岩特征的工具，战略性地生成这三个未凝聚的夕卡岩系统的数据。扩展现有的Fe-O数据库是建立Fe-O同位素系统学作为夕卡岩研究和总体上含磁铁矿的有效工具的关键一步。与测绘矿体有关的石榴石年代学将提供成矿的有效日期，而整个夕卡岩中石榴石的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，将允许在时间和化学上区分成矿和非成矿事件。考虑到对波多黎各矿藏的研究相对缺乏，以及有机会详细研究未凝结的夕卡岩系统，新的数据将大大有助于了解铁矿石矿藏在哪里以及如何形成的基础知识。该项目由岩石学与地球化学计划和既定的激励竞争研究计划(EPSCoR)联合资助。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.