100 Snowballs, Unconformities, BIFs and Beyond: Navigating the Neoproterozoic Rock and Climate Records Using Geochronology
The Neoproterozoic comprised periods of upheaval in Earth’s climate which changed the course of life and resulted in unique geologic features and formations. We welcome contributions applying geochronometers to investigate the timing of events and processes which shaped the Neoproterozoic.
Monday, 20 October 2025
8:00 AM - 12:00 PM
HBGCC, 304C
A Billion Years of Hematite Ore Development in the Lake Superior Region
Paper number: 100-10
Program: Technical Sessions
Time: 10:40 AM – 10:55 AM
Authors
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Anthony Fuentes Presenting AuthorDepartment of Earth and Planetary Science, University of California Berkeley, Berkeley, CA
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Liam Courtney-DaviesDepartment of Geological Sciences, University of Colorado Boulder, Boulder, CO
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Rebecca FlowersDepartment of Geological Sciences, University of Colorado Boulder, Boulder, CO
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Yiming ZhangInstitute for Rock Magnetism, Department of Earth and Environmental Sciences, University of Minnesota, Minneapolis, MN
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Nicholas Swanson-HysellInstitute for Rock Magnetism, Department of Earth and Environmental Sciences, University of Minnesota, Minneapolis, MN
Abstract
Iron formation (IF)-hosted hematite deposits are the primary source of high-grade iron and are found globally. The mechanism(s) by which iron becomes more concentrated in these deposits remains contentious in many instances. Geochronology can provide an efficient means to test ore formation hypotheses by evaluating the temporal association of iron oxide crystallization with independently dated geologic events, however most of the existing age constraints on ore mineralization come from accessory minerals. The recent development of direct hematite U-Pb dating via LA-ICPMS has resulted in significant re-evaluations of the formation timelines of the world’s largest iron ore deposits, showing greater nuance than age information obtained from accessory phases alone. In this work, we paired in-situ hematite U-Pb and paleomagnetism to evaluate the enrichment pathway of Paleoproterozoic iron formation in Northern Michigan to an economic hematite ore deposit. Our geochronologic and paleomagnetic results demonstrate that growth of hematite in these units was far more protracted than previously interpreted, with hematite crystallization spanning the Proterozoic. Most notably, we have identified a previously unrecognized period of ore genesis from ca 580 to 460 Ma that is supported by both the U-Pb and paleomagnetic data. Our results indicate that the study locality would have been located at tropical latitudes at this time during an especially warm non-glacial interval and positioned in the shallow subsurface. These constraints implicate warm, downward propagated meteoric fluids as a mechanism for the enrichment of this deposit rather than Paleoproterozoic tectonism as had previously been argued. These results highlight how paleomagnetism and hematite U-Pb geochronology can yield complementary insights into hematite mineralization throughout Earth history. This integrated approach opens new research directions for evaluating valuable information from hematite-bearing units.
Geological Society of America Abstracts with Programs. Vol. 57, No. 6
doi: 10.1130/abs/2025AM-414115
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