85-4 Characterizing Subsurface Mafic and Ultramafic Rock Distributions and Volumes using Potential Field Data: Insights from Southeast Minnesota

Session: The Power of Hard Rocks: Driving the Energy Transition and Serving Society

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Mafic and ultramafic rocks play a crucial role in various important areas, including hydrogen generation, hydrogen simulations, and carbon mineralization, as well as providing essential minerals that support our environment and economy. We studied the subsurface distribution of mafic rocks in southeastern Minnesota, part of the Mesoproterozoic mid-continental rift system in the north-central United States. This rift zone is characterized by an abundance of subsurface mafic rocks, including basalt, diabase dikes, and gabbro sills. We analyzed publicly available aeromagnetic anomalies and petrophysical measurements using the 3D magnetic inversion technique to characterize the distribution and volumes of subsurface mafic rocks in the study area. The magnetic inversion results reveal the presence of two high-susceptibility bodies (HS-1 and HS-2). Both HS-1 and HS-2 exhibit broad and deep extensions. HS-1 geobody is located beneath the northern part of the study area, extending approximately 55 km in length and about 32 km in width. While HS-2 geobody is situated in the southern region, it has a length of around 68 km and a width of about 55 km. Both HS bodies extend from ~1 km to 5 km in depth. The estimated volume of these high-susceptibility bodies up to a depth of 2 km is approximately 5,900 km³. Although their mapped geometry and volumes are defined, the magnetic inversion solution has inherent uncertainties. To reduce ambiguity in characterizing subsurface mafic/ultramafic rocks, it is necessary to incorporate other geoscience datasets and validate the findings with borehole information. The mapped geometry and estimated volumes of mafic/ultramafic reservoirs can benefit site selection for carbon mineralization and geologic hydrogen generation.

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

doi: 10.1130/abs/2025AM-7737

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