47-2 Tracing the Origin of Manganese Oxides in Virginia’s Appalachians: Mineralogical and Geochemical Insights

Session: Minerals in Motion: Tracking Mineral Reactions Using In Situ and Synchrotron Techniques, A Celebration of the Career of Peter Heaney

Presenting Author:

Chiara Elmi

Authors:

Elmi, Chiara¹, Rosa, Sophia Michelle², Meng, Jingyao³, Smith, Michael S.⁴, Heller, Matthew J.⁵

(1) Geology & Environmental Science, James Madison University, Harrisonburg, VA, USA, (2) Geology & Environmental Science, James Madison University, Harrisonburg, VA, USA, (3) Geology and Mineral Resources, Virginia Department of Energy, Charlottesville, VA, USA, (4) Geology and Mineral Resources, Virginia Department of Energy, Charlottesville, VA, USA, (5) Geology and Mineral Resources, Virginia Department of Energy, Charlottesville, VA, USA,

Abstract:

Manganese (Mn) oxides occur widely in diverse geological settings, exhibiting over thirty structural types with varying crystallinity and Mn valence states. Their chemical composition changes with depositional conditions, and their crystal structure variability leads to non-equilibrium crystallization pathways through different metastable intermediates. Due to their variable occurrences and crystal chemistry, systematic mineralogical and chemical characterization is essential to distinguish manganese oxides accurately. Several deposits are found in the Appalachian Mountains in the eastern United States and have been mined for more than 100 years. This study analyzed six Mn-oxide samples from historic mining sites in Virginia’s Blue Ridge and Valley and Ridge geological provinces using X-ray powder diffraction (XRPD), scanning electron microscopy (SEM), and inductively coupled plasma - optical emission spectrometry (ICP-OES). The amount and speciation of Mn and trace metals were measured for accurate mineral identification. The Mn-oxides identified were primarily birnessite, hollandite, and todorokite. The other minerals identified were quartz, plagioclase, and goethite. Although the formation of manganese oxides in these deposits shares similarities, such as their association with carbonate host rocks and hydrothermal processes, the specific processes and environmental conditions that lead to manganese deposits in these geological settings vary. A comparison with literature data and chemical data from this study was carried out to shed light on the depositional environments under which the studied manganese deposits formed. The combined mineralogical and geochemical investigation revealed an affinity with Mn-oxides of sedimentary supergene and biogenic genesis. The results of this study offer an understanding of ore-forming mechanisms and in turn establish a methodological approach for characterizing critical minerals.

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

doi: 10.1130/abs/2025AM-4632

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