Theses and Dissertations

ORCID

0009-0008-2904-0416

Advisor

Gabitov, Rinat

Committee Member

Skarke, Adam

Committee Member

Kirkland, Brenda

Committee Member

Franks, Stephen

Date of Degree

8-12-2026

Original embargo terms

Immediate Worldwide Access

Document Type

Dissertation - Open Access

Major

Earth and Atmospheric Sciences

Degree Name

Doctor of Philosophy (Ph.D.)

College

College of Arts and Sciences

Department

Department of Geosciences

Abstract

Lithium‑rich brines of the Upper Jurassic Smackover Formation represent a major domestic critical‑mineral resource, with USGS estimates of 5.1–19.0 million tonnes of Li in Arkansas. Although Li enrichment occurs only in high‑TDS brines, elevated salinity alone cannot generate the observed Li concentrations; Li must be supplied through water–rock interaction with phyllosilicates. This dissertation evaluates the Triassic–Early Jurassic Eagle Mills Formation as the primary basin‑scale Li source using whole‑rock geochemistry, XRPD mineralogy, petrography, laser‑ablation ICP‑MS, and Li‑isotope analyses of produced brines. The Eagle Mills Formation is thick, made of proximal, mid, and distal fan deposits that include fluvial channel sands, floodplain fines, and organic-rich pond deposits, all dominated by clay-rich matrix and disseminated detrital micaceous minerals. Whole‑rock ICP‑MS analyses yield 82–223 ppm Li, including ~180 ppm Li at the top of the Eagle Mills in BSW No. 1 (Columbia County, Arkansas) and ~187–223 ppm Li at the base of the formation in the G.B. Royston No. 1 (Hempstead County, Arkansas). The Royston hole is interpreted to contain 7,013 ft of Eagle Mills. BSW No. 1 is paired with Eagle Mills cuttings and Smackover brine data. Its brine contains 331 mg/L Li. Laser‑ablation ICP‑MS spot analyses record 115–920 ppm Li, with elevated values restricted to mica and clay‑rich grains and matrix, whereas quartz and feldspar contain <20 ppm Li. XRPD results showing 35–55 wt% illite/mica and 10–25 wt% mixed‑layer clays, combined with the unit’s thickness and fine grain size, demonstrate that the Eagle Mills provides the phyllosilicate‑rich sediment necessary to mobilize Li. Lithium‑isotope measurements (δ⁷Li = +8‰ to +14‰) from eight Smackover brines are isotopically heavy due to preferential incorporation of ⁶Li into clays and micas, indicating significant brine interaction with phyllosilicate-rich siliciclastics consistent with Eagle Mills sourcing. New ⁸⁷Sr/⁸⁶Sr data shift Werner-Louann deposition and early brine formation into the Sinemurian-Pliensbachian, ~30 My earlier than traditional Callovian models. Outcrop study of the basal Mesozoic conglomerate in the Chihuahua basin provides a direct rift‑basin analog for the buried basal Mesozoic unconformity. Examination of Smackover equivalent shallow marine carbonates in the Malone Formation offers an analog for reservoir textures.

Sponsorship (Optional)

The Geoscience Foundation

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