Paper No. 251-3
Presentation Time: 8:00 AM-5:30 PM
RARE EARTH ELEMENT (REE) ENRICHMENT IN THE BASAL CRETACEOUS TRANSGRESSIVE CLAYS IN NORTHWESTERN IOWA
CRAMER, Bradley, Department of Earth and Environmental Sciences, University of Iowa, 123 Capitol St., Iowa City, IA 52242, MEYER, Jessica, Department of Earth and Environmental Sciences, University of Iowa, 123 Capitol St., Iowa City, IA 52242; Department of Earth and Environmental Sciences, University of Iowa, 115 Trowbridge Hall, Iowa City, IA 52242, BANCROFT, Alyssa M., Iowa Geological Survey, IIHR - Hydroscience & Engineering, 300 Trowbridge Hall, Iowa City, IA 52242, TASSIER-SURINE, Stephanie, Iowa Geological Survey, IIHR - Hydroscience & Engineering, The University of Iowa, 300 Trowbridge Hall, Iowa City, IA 52242 and SMITH, Rachel, Kansas Geological Survey, University of Kansas, Lawrence, KS 66047
The ongoing search for undiscovered Rare Earth Element (REE) deposits in the United States has prompted a series of funding programs from the Department of Energy (DoE), Department of Defense (DoD), United States Geological Survey (USGS), and the National Science Foundation (NSF). As part of an ongoing project funded by the NSF Established Program to Stimulate Competitive Research (EPSCoR), the search for potential new REE resources in Iowa and Kansas has begun to yield promising results. Recently similar studies in other states have identified marine and terrestrial clays containing exceptionally enriched concentrations of REEs, that in some cases, exceed 2,000 ppm in total REE. The methodology to evaluate potential targets is nearly identical across many of these projects where initial evaluation is carried out via X-Ray Fluorescence (XRF) either using a handheld pXRF or a laboratory XRF core scanner to identify strata of interest for additional study using ICP-MS.
As part of our EPSCoR project we recently XRF core scanned a Cretaceous core from northwest Iowa and identified a nearly 40-foot interval with extremely elevated REE concentrations. The interval in this core was subjected to additional geochemical analysis via ICP-MS and can now be identified in multiple subsurface well penetrations across multiple counties. The interval of interest is the transgressive Cretaceous clay that marks the base of the Cretaceous strata preserved in Iowa that overlies either Devonian or Mississippian carbonates. This interval represents a Cretaceous soil that was well developed on this ancient bedrock surface, or an otherwise produced residual clay interval that has served to somehow scavenge REEs into the clay matrix. Stratigraphically, this interval lies within what has been referred to as the Nishnabotna Member of the Dakota Formation in Iowa and the complete regional areal extent and REE distribution are yet to be fully evaluated.
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