Geochemical and mineralogical investigation of cemented crusts in the tailings cover at Long Lake Gold Mine, Sudbury, Canada

Birendra Sapkota; Brent Verbuyst; Jeff Bain; Carol Ptacek; David Blowes; Tom Al

doi:10.1016/j.jhazmat.2023.131192

Geochemical and mineralogical investigation of cemented crusts in the tailings cover at Long Lake Gold Mine, Sudbury, Canada

J Hazard Mater. 2023 Jun 5:451:131192. doi: 10.1016/j.jhazmat.2023.131192. Epub 2023 Mar 11.

Authors

Birendra Sapkota¹, Brent Verbuyst², Jeff Bain², Carol Ptacek², David Blowes², Tom Al³

Affiliations

¹ University of Ottawa, Department of Earth and Environmental Sciences, 150 Louis-Pasteur Private, K1N 6N5 Ottawa, ON, Canada. Electronic address: bsapk039@uottawa.ca.
² University of Waterloo, Department of Earth and Environmental Sciences, 200 University Avenue West, N2L 3G1 Waterloo, ON, Canada.
³ University of Ottawa, Department of Earth and Environmental Sciences, 150 Louis-Pasteur Private, K1N 6N5 Ottawa, ON, Canada.

PMID: 36921421
DOI: 10.1016/j.jhazmat.2023.131192

Abstract

In mine tailings, precipitation of secondary minerals may cement the tailings material and form cemented crusts or hardpans. Hardpans typically form beneath the surface of reactive tailings. However, at the former Long Lake Gold Mine near Sudbury, Ontario, cemented crusts formed in a clean sand cover above the tailings. We applied mineralogical and geochemical techniques to investigate the formation of these cemented crusts. Representative samples were collected from the sand cover and vertical cores from the underlying tailings. Elevated concentrations of arsenic (As), iron (Fe), and sulfur (S) in the sand cover indicate the upward transport of sulfide-mineral oxidation products. The shallow porewater of the tailings is acidic (pH 4 - 6) and contains elevated concentrations of As (up to 346 mg/L), Fe (up to 1844 mg/L), and SO₄ (up to 12,000 mg/L). Mineralogical observations indicate that primary sulfide minerals in the near-surface tailings display moderate to strong oxidation, and secondary Fe-arsenate and jarosite minerals are formed both in the near-surface tailings and the sand cover. Upward migration of sulfide-mineral oxidation products leads to the formation of cemented crusts, which with continuing erosion, represent a long-term source of pollution to the surrounding environment.

Keywords: Capillarity; Hardpans; Mine tailings; Secondary minerals; Sulfide oxidation.