Working Paper Article Version 1 This version is not peer-reviewed

Characterization of Weathering Processes of the Giant Copper Deposit of Tizert (Igherm Inlier, Anti-Atlas, Morocco)

Version 1 : Received: 3 July 2020 / Approved: 5 July 2020 / Online: 5 July 2020 (12:18:38 CEST)

A peer-reviewed article of this Preprint also exists.

Poot, J.; Verhaert, M.; Dekoninck, A.; Oummouch, A.; El Basbas, A.; Maacha, L.; Yans, J. Characterization of Weathering Processes of the Giant Copper Deposit of Tizert (Igherm Inlier, Anti-Atlas, Morocco). Minerals 2020, 10, 620. Poot, J.; Verhaert, M.; Dekoninck, A.; Oummouch, A.; El Basbas, A.; Maacha, L.; Yans, J. Characterization of Weathering Processes of the Giant Copper Deposit of Tizert (Igherm Inlier, Anti-Atlas, Morocco). Minerals 2020, 10, 620.

Journal reference: Minerals 2020, 10, 620
DOI: 10.3390/min10070620

Abstract

The giant Tizert copper deposit is considered as the largest copper resource in the western Anti-Atlas (Morocco). The site is characterized by Cu mineralization carried by malachite, chalcocite, covellite, bornite and chalcopyrite; azurite is not observed. The host rocks are mainly limestones (Formation of Tamjout Dolomite) and sandstones/siltstones (Basal Series) of the Ediacaran/Cambrian transition. The supergene enrichment is most likely related to episodes of uplift/doming (last event since 30 Ma), which triggered the exhumation of primary/hypogene mineralization (chalcopyrite, pyrite, galena, chalcocite I and bornite I), generating their oxidation and the precipitation of secondary/supergene sulfides, carbonates and Fe-oxyhydroxides. The Tizert supergene deposit mainly consists in i) a residual patchwork of laterite rich in Fe-oxyhydroxides, ii) a saprolite rich in malachite, or « green oxide zone » where primary structures such as stratification are preserved, and iii) a cementation zone containing secondary sulfides (covellite, chalcocite II and bornite II). The abundance of Cu carbonates results from the rapid neutralization of acidic meteoric fluids, due to oxidation of primary sulfides, by carbonate host rocks. Chlorite is also involved in the neutralization processes in the sandstones/siltstones of the Basal Series, in which supergene clays such as kaolinite and smectites subsequently precipitated. At Tizert, as it can be highlighted in other supergene Cu-deposits around the world, azurite is absent due to low pCO2 and relatively high pH conditions. In addition to copper, Ag enrichment is also observed in weathered rocks; Fe-oxyhydroxides contain high Zn, As, and Pb contents. However, these secondary enrichments are quite low compared to Cu in the whole Tizert site, therefore considered as relatively homogeneous.

Subject Areas

Tizert deposit; copper; weathering; supergene; western Anti-Atlas; Morocco; malachite; azurite; Tamjout Dolomite; Lower Limestone; Basal Series

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