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

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.