Sulfidic Mine Wastes

Lottermoser, Bernd G.

doi:10.1007/978-3-642-12419-8_2

Cited by 52 publications

(56 citation statements)

References 262 publications

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“…Mine waste deposition at the Earth’s surface represents a massive annual production of fresh parent material for incipient soil formation whose rate is of similar magnitude to the naturally-occurring fresh rock reveal rate and the top soil loss rate ( ca . 21 Gt/yr; Wilkinson and McElroy, 2007; Lottermosser, 2010). …”

Section: Introductionmentioning

confidence: 99%

Surficial weathering of iron sulfide mine tailings under semi-arid climate

Hayes

Root

Perdrial

et al. 2014

Geochimica et Cosmochimica Acta

120

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Mine wastes introduce anthropogenic weathering profiles to the critical zone that often remain unvegetated for decades after mining cessation. As such, they are vulnerable to wind and water dispersion of particulate matter to adjacent ecosystems and residential communities. In sulfide-rich ore tailings, propagation to depth of the oxidative weathering front controls the depth-variation in speciation of major and trace elements. Despite the prevalence of surficial mine waste deposits in arid regions of the globe, few prior studies have been conducted to resolve the near-surface profile of sulfide ore tailings weathered under semi-arid climate. We investigated relations between gossan oxidative reaction-front propagation and the molecular speciation of iron and sulfur in tailings subjected to weathering under semi-arid climate at an EPA Superfund Site in semi-arid central Arizona (USA). Here we report a multi-method data set combining wet chemical and synchrotron-based X-ray diffraction (XRD) and X-ray absorption near-edge spectroscopy (XANES) methods to resolve the tight coupling of iron (Fe) and sulfur (S) geochemical changes in the top 2 m of tailings. Despite nearly invariant Fe and S concentration with depth (130–140 and 100–120 g kg−1, respectively), a sharp redox gradient and distinct morphological change was observed within the top 0.5 m, associated with a progressive oxidative alteration of ferrous sulfides to (oxyhydr)oxides and (hydroxy)sulfates. Transformation is nearly complete in surficial samples. Trends in molecular-scale alteration were co-located with a decrease in pH from 7.3 to 2.3, and shifts in Fe and S lability as measured via chemical extraction. Initial weathering products, ferrihydrite and gypsum, transform to schwertmannite, then jarosite-group minerals with an accompanying decrease in pH. Interestingly, thermodynamically stable phases such as goethite and hematite were not detected in any samples, but ferrihydrite was observed even in the lowest pH samples, indicating its metastable persistence in these semiarid tailings. The resulting sharp geochemical speciation gradients in close proximity to the tailings surface have important implications for plant colonization, as well as mobility and bioavailability of co-associated toxic metal(loid)s.

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Section: Introductionmentioning

confidence: 99%

Surficial weathering of iron sulfide mine tailings under semi-arid climate

Hayes

Root

Perdrial

et al. 2014

Geochimica et Cosmochimica Acta

120

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“…Within the critical zone, metal cycling, mineral precipitation and dissolution may be driven by inorganic processes or by organisms (Chorover et al, 2007; Gadd, 2012) and can be traced by various mineralogical and geochemical methods (Blanckenburg and Schuessler, 2014; Li et al , 2017). The oxidation zones and mine wastes are dynamic geochemical reactors where the primary minerals transform in contact with water, oxygen, CO 2 , and biological activity to a suite of secondary phases (Williams, 1990; Lottermoser, 2010). Oxidation zones deviate much from natural, pristine and uncontaminated critical zones but they provide valuable information about metal cycling in the interface between the atmosphere and bedrock.…”

Section: Introductionmentioning

confidence: 99%

Processes of metastable-mineral formation in oxidation zones and mine waste

Majzlan

2020

MinMag

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Oxidation zones and mine wastes are metal-rich, near-surface environments, natural and man-made critical zones of ore deposits, respectively. They contain a number of minerals which, despite their metastability, occur consistently and in abundance. Field studies, presented as examples in this work, show that metastable minerals form not only directly from aqueous solutions, but also from more complex precursors, such as nanoparticles, gels, X-ray amorphous solids, or clusters. Initial precipitation of metastable phases and their conversion to stable phases is described by the Ostwald's step rule. Thermodynamic data show that there is a tendency, but no rule, that structurally more complex phases are also thermodynamically more stable. The Ostwald's step rule could then state that the initial metastable phases are structurally simple and easily assembled from aqueous solutions, nanoparticles, gels, disordered solids, or clusters. The structural similarity of the precursor and the forming phase is a kinetic factor favouring the crystallisation of the new phase. Calculation of saturation indices for mine drainage solutions show that they are mostly supersaturated with respect to the stable phases and the aqueous concentrations are sufficient to precipitate metastable minerals. In our fieldwork, we often encounter gelatinous substances with copper, manganese or tungsten that slowly convert to metastable oxysalt minerals. Another possibility is the crystallisation of various metastable minerals from solid, homogeneous ‘resins’ that are X-ray amorphous. Minerals typical for near-surface environments may be stabilised by their surface energy at high specific surface areas. For example, ferrihydrite is often described as a metastable phase but can be shown to be stable with respect to nanosised hematite.

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“…Once running. the ''ARD engine'', as described by Lottermoser (2010), can continue for tens to hundreds of years. The reactions can be offset by the inherent neutralising capacity contained within many of the surrounding rocks, known as the acid neutralisation capacity (ANC).…”

Section: Introductionmentioning

confidence: 99%