Martin Števko

Soluble secondary minerals of antimony in Pezinok and Kremnica (Slovakia) and the question of mobility or immobility of antimony in mine waters

Environmental context Antimony enters the environment from tailings and mines but there are widely divergent statements about its mobility in the environment. This work addresses the question of mobility of Sb by a combination of mineralogical and geochemical studies. Abstract This work characterises two occurrences with an abundance of the supergene Sb minerals brandholzite [Mg[Sb(OH)6]2·6H2O], klebelsbergite [Sb4O4(OH)2(SO4)] and peretaite [CaSb4O4(OH)2(SO4)2·2H2O]. Brandholzite forms from near-neutral waters, where stibnite (Sb2S3) decomposes in the presence of abundant carbonates. The SbIII sulfates form from acidic waters, where stibnite decomposes in the presence of marcasite or pyrite (FeS2). These initial supergene minerals form rapidly (brandholzite within weeks) and supply Sb into local waters. Calculation of saturation indices from underground water (present study) and many waters discharged from Sb mines (data from the literature) show that brandholzite (and related soluble Sb minerals) are undersaturated. Hence, if they do exist, they should dissolve. Insoluble Sb phases, such as tripuhyite (FeSbO4) are grossly supersaturated, but do not form (or form very slowly). Hence, we conclude that the mobility of antimony observed in geochemical studies is due to the solubility of the initial supergene minerals. The immobility of antimony stated in mineralogical studies is due to the slow but persistent formation of insoluble tripuhyite. When the kinetics of formation of these minerals are taken into account, the widely divergent statements about mobility or immobility of antimony in the environment can be reconciled.

Mineralogical controls on antimony and arsenic mobility during tetrahedrite-tennantite weathering at historic mine sites Špania Dolina-Piesky and Ľubietová-Svätodušná, Slovakia

Abstract The legacy of copper (Cu) mining at Špania Dolina-Piesky and Ľubietová-Svätodušná (central Slovakia) is waste rock and soil, surface waters, and groundwaters contaminated with antimony (Sb), arsenic (As), Cu, and other metals. Copper ore is hosted in chalcopyrite (CuFeS2) and sulfosalt solid-solution tetrahedrite-tennantite {Cu6[Cu4(Fe,Zn)2]Sb4S13–Cu6[Cu4(Fe,Zn)2]As4S13} that show widespread oxidation characteristic by olive-green color secondary minerals. Tetrahedrite-tennantite can be a significant source of As and Sb contamination. Synchrotron-based μ-XRD, μ-XRF, and μ-XANES combined with electron microprobe analyses have been used to determine the mineralogy, chemical composition, element distribution, and Sb speciation in tetrahedrite-tennantite oxidation products in waste rock. Our results show that the mobility of Sb is limited by the formation of oxidation products such as tripuhyite and roméite group mineral containing 36.54 wt% Sb for samples where the primary mineral chemical composition is close to tetrahedrite end-member. Antimony K-edge μ-XANES spectra of these oxidation products indicate that the predominant Sb oxidation state is 5+. Arsenic and Cu are also hosted by amorphous phases containing 6.23 wt% Sb on average and these are intergrown with tripuhyite and roméite. Antimony in this environment is not very mobile, meaning it is not easily released from solid phases to water, especially compared to As, Cu, and S. For samples where the primary sulfosalt is close to tennantite composition, the oxidation products associated with tennantite relicts contain 2.43 wt% Sb and are amorphous. The variable solubility of the secondary minerals that have been identified is expected to influence mobility of Sb and As in near-surface environment.