Abstract

Mineralogical, geochemical, sedimentological and microbiological investigations of the evolution of supergene mineralization of mining residues at Matchless chalcopyrite–pyrite deposit (Namibia) have delineated what may be called “the minero-stratigraphy of tailings”. The encrustations of the supergene or secondary mineralization have originated from alteration of sulfides and carbonates of the primary mineralization and from chemical agents (e.g. lime, phosphate) added during processing of ore. The variation in tailings discharge and the early diagenetic alteration led to a pronounced bedding and the development of distinct layers within the tailings impoundment: (1) gypsum–carbonate (e.g. huntite), (2) gypsum–sulfate (e.g. melanterite), (3) gypsum–phosphate (e.g. brushite), (4) gypsum–chloride (e.g. halite), (5) sulfate–gypsum efflorescence (e.g. copiapite). Deposition and early diagenesis of tailings may be described as follows: During deposition of tailings, oxidation began because of relocations of the discharge point. Phyllosilicate-rich layers form local aquatards and minimize solution homogenization in the succeeding cycles of deposition. The whole impoundment is a series of paleo-oxidation zones on which the current oxidation in the vadose zone is being superimposed. Low-pH zones, even though some are now in the saturated part of the impoundment, owe their low pH to low dolomite content, reflecting variations in the input of primary minerals. Excess pyrite and Fe hydrolysis is still generating acidity and the formation of a typical “gossan-type” profile is in progress. The modern hardpans in the tailings may, during late diagenesis, eventually evolve to duricrusts analogous to those duricrusts that have largely been studied in geological series prevalently of Cenozoic age.

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call

Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.