Secondary Phases From the Alteration of a Pile of Zinc-Smelting Slag as Indicators of Environmental Conditions: An Example From Swietochlowice, Upper Silesia, Poland

Abstract

Slags produced by the pyrometallurgical treatment of Zn ore, deposited at the dump in Świętochłowice, in Upper Silesia, southern Poland, are dominated by synthetic analogues of olivine, melilite, pyroxene, feldspars, willemite, zincite and spinel, occurring in various assemblages. Secondary phases either formed at high-temperature or due to weathering are both common at the pile. They include efflorescences of gypsum, epsomite, hexahydrite and bianchite, encrustations of gypsum, anglesite and cerussite, and accumulations of jarosite, goethite and hematite. Two groups are identified: the first one, where sulfates are dominant, is ubiquitous; the second one, of local importance, has originated under conditions varying significantly from one place to another. The weathered phases originate during episodic outflow of water from the pile after rainfall. These mineralogical data and leaching experiments show that, among the primary phases, zincite is most readily weathered, followed by willemite, melilite and the spinel-group phases.sOMMaIre Les scories issues de la pyrométallurgie du zinc déposées sur les haldes de Świętochłowice, en Haute Silésie, Pologne, comportent diverses paragenèses de minéraux primaires dominées par des analogues synthétiques de l'olivine, la mélilite, la willémite, la zincite, de pyroxènes, de feldspaths et de spinelles. Les phases secondaires, qui comprennent à la fois des phases de haute température et des phases issues de l'altération supergène, sont abondantes sur tout le site. On y reconnaît des efflorescences de gypse, d'epsomite, d'hexahydrite et de bianchite, des encroûtements de gypse, d'anglésite et de cérussite, et des accumulations de jarosite, de goethite et d'hématite. Ces phases s'organisent en deux groupes, l'un ubiquiste où dominent les sulfates, et l'autre plus local, témoignant des conditions particulières qui peuvent varier selon leurs positions sur le site. Les phases issues de l'altération supergène se forment lors des écoulements qui suivent les épisodes pluvieux. Ces données minéralogiques et les expériences de lixiviation effectuées montrent que parmi les phases primaires, la zincite est le minéral le plus altérable, suivi par la willemite, la mélilite et les spinelles.

Understanding Heterogeneity of a Slag-Derived Weathered Material: The Role of Automated SEM-EDS Analyses

“…Finally, despite some inconsistencies, the generic phase classification based on MLA (as primary, secondary and detrital) is consistent with phase composition and classification described in previous studies [20,21]. Furthermore, the application of diagrams designed in this study (for example Figure 8) allowed the quick spotting of the grains, which were wrongly assigned to the phase generic group as it is discussed below.…”

“…Hematite was recognized as secondary phase typical for the Świętochłowice heap [19,20]. Hematite dominates in the heavy mineral fraction in all three horizons, but it has different grain size distribution in horizon B (middle size grains are the most abundant, Figure 6a) compared to that in horizons A and C (more uniform distribution between different grain sizes, Figure 6a).…”

“…Slag heaps are potential sites of extensive weathering and metal release [1,5,10,19] and they are usually comprised of numerous phases with various grain sizes, compositions, weathering potentials and composed of high abundances of potentially toxic elements [5]. Even in a single heap, phase composition of slags [21,27] and proportions of primary and secondary phases [19,20] may vary strongly. Additionally, the relationship between primary and secondary phases may be disturbed by hydrothermal crystallization from hot fluids remaining in the slag heap shortly after the slag deposition [22,28].…”

“…In this paper, such a technique was applied to delineate the material sources contributing to a complex weathering profile in theŚwiętochłowice slag heap and see if the conclusions are consistent with those based on bulk and leachate chemistry [19]. The heap was previously extensively studied and is well characterized in terms of phase composition [19][20][21][22] and, therefore, is a perfect testing site to apply SEM-automated analyses. This paper also proposes some general features of automated SEM datasets based on heavy mineral fractions that can be used for analyses of similarly complex material, in particular, to classify and estimate the proportions between primary, secondary and detrital phases in weathered zones formed on slag heaps.…”

Mine Wastes

“…2.9) (Bril et al 2008;Ettler et al 2009;Lottermoser 2005;Navarro et al 2008a). Evaporation of the seepage waters emanating from slag dumps may cause the precipitation of mobilized elements and compounds and leads to their temporary fixation in secondary soluble sulfate and arsenate minerals ( Fig.…”