Weathering-induced Sb isotope fractionation during leaching of stibnite and formation of secondary Sb minerals

Autor(en)
Andreas B. Kaufmann, Marina Lazarov, Ingo Horn, Martin Števko, Tamara Đorđević, Stefan Kiefer, Stefan Weyer, Juraj Majzlan
Abstrakt

In this work, we investigated the extent of antimony (Sb) isotopic fractionation during weathering of stibnite at supergene conditions. Antimony isotope data have been obtained from secondary Sb minerals collected from Pezinok, Dobšiná (both Slovakia) and Allchar (North Macedonia) deposits and mine tailings. The Sb isotope compositions of sulfides and secondary Sb minerals formed on the primary stibnite [Sb

2S

3] or in mine tailings grains were compared with each other. Furthermore, we experimentally investigated Sb isotope fractionation during stibnite leaching with different acids. Our study reveals a large isotopic range for δ

123Sb (from −0.50 to +0.69 ‰) for secondary Sb minerals. They are either isotopically indistinguishable or isotopically lighter than the primary stibnite. Isotopically indistinguishable weathering products likely formed by quantitative Sb transfer from stibnite to the secondary minerals, such as brandholzite [Mg(H

2O)

6[Sb(OH)

6]

2] from Pezinok. Isotopic fractionation towards lighter δ

123Sb was observed for adsorption of Sb onto iron oxides. Distinctly isotopically lighter δ

123Sb was observed in secondary Sb minerals tripuhyite [FeSbO

4], chapmanite [Fe

3+

2Sb

3+(Si

2O

5)O

3(OH)], hydroxyferroromeite [Fe

2Sb

2O

6(OH)], and stibiconite [Sb

3O

6OH] that either replace stibnite or formed in mine tailings from the pore solutions. These secondary minerals were likely generated by partial precipitation of Sb from aqueous solutions produced by dissolution of stibnite. In the leaching experiments with HCl and oxalic acid, Sb was leached without significant isotope effects during the first 2–3 days, followed by a drop of the dissolved Sb concentration associated with Sb isotope fractionation towards high δ

123Sb in the leachate (by up to 0.5 ‰) after 4–7 days. We interpret these observations to be related to the precipitation of secondary Sb oxides with low δ

123Sb, resulting in an isotopically heavy dissolved Sb pool. These findings are in agreement with previous results of isotopically heavy groundwater and mine drainage water with δ

123Sb > +0.36 ‰ that may suggest that the ‘truly’ dissolved (operationally defined as <0.45 μm) Sb fraction in general may be isotopically heavy.

Organisation(en)
Institut für Mineralogie und Kristallographie
Externe Organisation(en)
Friedrich-Schiller-Universität Jena, Gottfried Wilhelm Leibniz Universität Hannover, Národní muzeum, Technische Universität Wien, Univerzita Komenského v Bratislave
Journal
Chemical Geology
Band
662
Seiten
122253–122266
Anzahl der Seiten
14
ISSN
0009-2541
DOI
https://doi.org/10.1016/j.chemgeo.2024.122253
Publikationsdatum
09-2024
Peer-reviewed
Ja
ÖFOS 2012
105116 Mineralogie, 105113 Kristallographie
Schlagwörter
ASJC Scopus Sachgebiete
Geochemistry and Petrology, Geology
Link zum Portal
https://ucrisportal.univie.ac.at/de/publications/e5202f51-ebd8-4faa-9654-ca5d421ec9e8