Seminar Details

Seminar Lab Date: February 9, 2026

Seminar Lab Subject: *Hematite Ore Formation in the Lake Vermilion-Soudan Underground Mine State Park, Northeastern Minnesota (V)

Seminar Lab Presenter: Zsuzsanna Allerton, Ph.D. Candidate, University of Minnesota

Seminar Lab Location:

*** NOTE: THIS LECTURE HAS BEEN CHANGED FROM IN-PERSON TO ONLINE ***

Virtual lecture 7:00 PM CT.

This lecture is now available on the Geological Society of Minnesota YouTube channel: 

https://www.youtube.com/watch?v=q5uHQyfD8kM&pp=ygUSWnN1enNhbm5hIEFsbGVydG9u

Seminar Lab Detail:

Summary: The Soudan iron mine in northeastern Minnesota’s Vermilion Range—now preserved as part of Lake Vermilion-Soudan Underground Mine State Park—operated from 1882 until 1962. It was the state’s oldest and deepest iron mine, extracting millions of tons of exceptionally high-grade massive hematite ore (>65 wt% Fe) hosted within Neoarchean (~2.7 Ga) banded iron formations (BIFs). These ore bodies, initially discovered during gold prospecting, supported premium steel production before competition from Mesabi Range taconite led to closure. The hematite ore formed through hydrothermal processes that dissolved silicates and concentrated iron oxides in the ancient sedimentary deposit. Recent research employing U-Pb and (U-Th)/He radiometric dating of hematite provides the first direct ages for the high-grade ore at Soudan. These studies reveal a previously unrecognized Paleoproterozoic mineralization event (~1.8–1.6 Ga), challenging earlier assumptions of Neoarchean origins. The data further suggest a thermal overprint from the Mesoproterozoic Midcontinent Rift System (~1.1 Ga). This new geochronological evidence refines models of iron ore genesis in the Lake Superior region, linking hematite ore upgrading in BIFs to Proterozoic tectonic events.

Biography: Zsu Allerton was born in Hungary and moved to the United States in 2017. Before pursuing geology, she worked as a social worker, scuba diving instructor and guide, and underwater and land photographer and photography instructor.

Her doctoral research specialized in the thermal and hydrothermal evolution of Archean iron formations and Proterozoic mineralization in northeastern Minnesota, with a dissertation focused on hematite ore genesis in the Soudan iron mine, hydrothermal alteration, and the thermal imprint of the Midcontinent Rift System on the Superior Province.

Current research interests include the geology of iron deposits, geochronology, mineral and meteorite characterization, and public geoscience outreach. She is involved in ongoing projects at Lake Vermilion–Soudan Underground Mine State Park.