283 Critical Mineral Resources and Recovery in the Americas: Emerging Methods in Exploration and Sustainable Extraction, Part II

This session explores the role of critical minerals in technology and the low-carbon economy, focusing on geological discoveries, sustainable extraction methods, and recycling to support secure, environmentally responsible mineral supply chains in the Americas.

Wednesday, 22 October 2025
1:30 PM - 5:30 PM
HBGCC, 217A

The Genesis of the Bourbon Iron Ore Deposit in Southeast Missouri, USA

Paper number: 283-5
Program: Technical Sessions
Time: 2:40 PM – 2:55 PM

Authors

Abstract

Three main types of iron ore deposits exist in the Mesoproterozoic Eastern Granite-Rhyolite province in southeast Missouri, USA, i.e., Iron Oxide Apatite (IOA), Iron Oxide Copper Gold (IOCG), and low temperature hydrothermal iron ore deposits. Although there are no current iron ore mining activities in Missouri, there is renewed interest in these deposits because of their potential to contain economically significant amounts of ‘critical minerals’, especially Ni, Co, and rare earth elements. Most iron ore deposits in Missouri are thought to have been emplaced at the same time ~1.44 Ga ago and thus are hypothesized to be genetically related. However, little is known about the magmatic-hydrothermal plumbing system that might have formed them. Understanding this plumbing system will help to identify areas that are most likely to contain undiscovered, critical mineral-rich, iron ore deposits.

To develop such a ‘Mineral Systems Concept’ for iron ore exploration in Missouri, it is pivotal to understand how individual deposits in the region formed and what possibly connects them. For this purpose, this project investigates the subsurface Bourbon iron ore deposit. The deposit was identified as a potential prospect in the 1930s through magnetic and gravity remote sensing surveys along with a handful of other smaller potential prospects in the area. Although the Bourbon deposit has been drilled for exploration in the past, it has not been mined and its genesis remains to be fully understood. Drill core samples show that the Bourbon deposit consists of a 100 to 200-m-thick massive magnetite ore body with minor secondary hematite underneath ~600 m of rhyolitic overburden. A comparison of bulk rock data for Bourbon magnetite ore to magnetite ore from the nearby Kratz Spring (IOA) and Shephard Mountain (low temperature hydrothermal) deposits shows that the bulk rock chemistry of the Bourbon mineralization is notably similar to the magmatic hydrothermal IOA mineralization at Kratz Spring. An IOA origin for Bourbon is also consistent with its deep emplacement level and presence of brecciated intervals. Future work will investigate possible genetic links between the Bourbon deposit and other IOA systems in the region and interpret the findings within the framework of the geodynamic evolution of the St. Francois Mountain terrane to guide mineral exploration.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6

doi: 10.1130/abs/2025AM-412790

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