MAPPING CRITICAL MINERALS IN ARKANSAS

The Office of the State Geologist is currently mapping in the North Arkansas Lead and Zinc Region as part of the United States Geological Survey (USGS) Earth Mapping Resources Initiative (EMRI). This project will produce new two-dimensional geologic maps in an area that contains the critical mineral zinc and associated minerals in the basin brine path system (Hofstra and Kreiner, 2021).

The proposed geologic mapping of the North Arkansas Lead and Zinc District is divided into two focus areas: the Northeast District, located in Lawrence and Sharp counties and the North Central District, located in Boone, Baxter, and Marion counties. The main goal of this mapping is to constrain the Early Ordovician to Early Mississippian units that contain the mineralization and observe and describe the dolomitization of the surrounding rocks. In addition to the mapping, 200 samples will be collected and sent to the USGS for geochemical analysis. So far, the OSG has produced one geologic map compilation of the northeast district (DGM-AR-LZD-NE-001) and will have a second compilation of the north-central district completed by July 2025.

The OSG began mapping for EMRI in 2019. The first EMRI mapping project was focused on the Batesville Manganese District with an emphasis on the Cason Formation. The Cason Formation was historically a producer of phosphate and manganese and is now known to be enriched in Rare Earth Elements. During the project, the OSG produced two, 1:24,000-scale compilations of the Batesville Manganese District and the surrounding area: West Part (DGM-AR-BMD-W-001) and East Part (DGM-AR-BMD-E-002). The OSG collected 100 samples from the area that were sent to the USGS for geochemical analysis.