194-5 Towards Detrital Hematite U-Pb geochronology

Session: Broad Applications of Thermochronology to Understanding Geologic Rates and Processes Through the Sedimentary Record (Posters)

Poster Booth No.: 184

Presenting Author:

Anthony Fuentes

Authors:

Fuentes, Anthony J¹, Courtney-Davies, Liam², Flowers, Rebecca Marie³, Wieser, Penny Elaine⁴, Gleeson, Matthew⁵, Zhang, Yiming⁶, Swanson-Hysell, Nicholas⁷

Abstract:

Hematite is one of the most common iron oxides in sedimentary units on Earth and Mars and has been leveraged to parse the paleoredox state of ancient terrestrial hydrologic systems. It is also a critical magnetic remanence holder over geologic time due to its thermal and chemical stability, making it central to many paleomagnetic records. These paleomagnetic records in turn underpin paleogeographic, tectonic, and temporal interpretations from sedimentary sequences. An outstanding challenge in paleomagnetism is whether coarse-grained hematite (specularite) in sedimentary rocks is detrital and therefore records a primary remanence, or if it formed authigenically during diagenesis and holds a secondary magnetization. In the absence of conclusive paleomagnetic field tests it can be challenging to determine if hematite is detrital and holds a primary magnetization. In this work, we extend in-situ hematite U-Pb dating to individual hematite crystals from coarse-grained sandstones in the Mesoproterozoic Freda Formation to assess the utility of dating sedimentary-hosted hematite to understand its provenance. The dated hematite from the Freda yields pre-depositional ages consistent with the robust paleomagnetic and chronostratigraphic constraints for this unit. Additionally, we identify several populations of hematite that crystallized post-deposition, demonstrating the ability of single-grain isochrons to delineate pre- and post-depositional hematite growth. While further method development remains, these results greatly extend the application of hematite as a non-traditional geochronometer and open new avenues of research into ancient fluid flow events preserved in terrestrial and planetary materials containing hematite. 

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-5376

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