Lithium Distribution in Proterozoic Sedimentary Rocks of the Southern Urals

Lithium is currently a critically important resource for high-tech industries. However, data on the Li content in the sedimentary rocks of the Southern Urals have not been provided. The limited understanding of lithium geochemistry in the Proterozoic sedimentary rocks dictates the need for detailed geochemical studies.

The objective of this study was to determine the lithium distribution in the Proterozoic sedimentary rocks on the western slope of the Southern Urals and analyze the potential causes of enrichment.

Inductively coupled plasma atomic emission spectrometry (ICP-AES) was used to analyze sandstones, shales, and carbonate rocks.

Two stratigraphic intervals of lithium enrichment were identified in the Proterozoic sedimentary rocks on the western slope of the Southern Urals: the Suran and Avzyan Mesoproterozoic formations. The maximum enrichment of this alkali element occurred in carbonate rocks, where Li concentrations reached 125–268 ppm, exceeding the Clarke value by 5–12 times on average. In the Avzyan Formation, lithium showed a strong positive correlation with chlorite content. In the Suran Formation, lithium was highly correlated with fluorine (r = 0.97) and rubidium (r = 0.93), indicating its association with F-bearing phlogopite. The highest lithium concentrations, reaching industrially significant levels of up to 0.1 wt.% Li₂O, were confirmed within the fluorite ore halo of the Suran deposit. Cryolithionite was the dominant lithium-bearing mineral, accounting for 0.1–7 wt.% of the bulk composition.

The lithium enrichment in the sedimentary rocks of the Suran and Avzyan Mesoproterozoic formations resulted from sedimentation under near-evaporitic conditions, as well as the subsequent influence of postmagmatic fluids during epigenesis caused by the intrusion of gabbrodolerite dikes. These findings are significant for both regional metallogeny and the broader pursuit of lithium resources, highlighting the substantial potential of sedimentary rocks.

The sedimentary rocks of the Suran and Avzyan formations on the western slope of the Southern Urals have the potential to host economically significant lithium concentrations. Of particular interest are the host rocks of the Suran Formation in the vicinity of the Suran fluorite deposit.