Nature and origin of natural Zn clay minerals from the Bou Arhous Zn ore deposit: Evidence from electron microscopy (SEM-TEM) and stable isotope compositions (H and O)

Buatier, Martine; Choulet, Flavien; Petit, Sabine; Chassagnon, R.; Vennemann, Torsten

doi:10.1016/j.clay.2016.07.004

Cited by 13 publications

(11 citation statements)

References 34 publications

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“…According to the crystallographic and chemical features of fraipontite observed in this study, the 14 Å periodicity detected with the HRTEM survey (Fig. 5f and 7c) has to be considered to be related to local double layer stacking sequence of fraipontite, which is due to the intergrowth of different polytypes, as it was already observed for the 2H1 polytype of cronstedtite case, a trioctahedral 1:1 clay belonging to the kaolinite-serpentine group (Kogure et al 2002), and for several fraipontite occurrences studied elsewhere (Buatier et al 2016).…”

Section: Zn-clays Identificationsupporting

confidence: 70%

“…Furthermore, the dissolution of aluminosilicates from siliciclastic rocks during the ore-formation process can result in the formation of various clay minerals, which may behave as effective sinks for valuable metals as Zn and Cu (Boni and Mondillo 2015 and references therein). Consequently, the occurrence of Zn-clays, either as subordinate phases (e.g., La Calamine, Belgium; Bou Arhous, Marocco; Bongarà, Perù; Coppola et al 2008;Choulet et al 2016;Balassone et al 2020) or as prevailing ore minerals (e.g., Accha-Yanque, Peru; Skorpion, Namibia; Borg et al 2003;Mondillo et al 2015;Balassone et al 2017), has been documented in several research Moroccan High Atlas (Buatier et al 2016;Choulet et al 2016) and in the Bongarà (Perù) mining districts (Arfè et al 2017;Balassone et al 2021). In both cases its formation was explained by a direct precipitation process from hydrothermal to supergene metals-rich solutions;…”

Section: Introductionmentioning

confidence: 99%

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Zn-clays in the Kihabe and Nxuu prospects (Aha Hills, Botswana): A XRD and TEM study

Putzolu

Abad

Balassone

et al. 2023

American Mineralogist

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Zinc clays are commonly found in oxidized Zn deposits and, even though they rarely represent the main target of the ore exploitation, they can be used as a proxy to restore the genetic conditions during ore-forming processes. This work sheds light on the micro-to nano-mineralogy and on the genesis of Zn-clays in the Kihabe and Nxuu prospects (located in the Aha Hills district, Northern Botswana), through an integrated XRD and TEM study of the mineralized facies occurring in the mineralized system. The Kihabe and Nxuu ores are hosted in a Neoproterozoic metamorphozed quartzwacke unconformably covered by the recent sedimentary rocks, also containing calcretes, of the Kalahari Group. In the analyzed samples, four distinct mineralogical facies have been recognized: i. vanadatecalcrete facies, poor of Zn-clays; ii. low Zn-clay facies, characterized mostly by clays showing low Zn concentrations; iii. Zn-clay facies, containing proper Zn clay minerals; iv. sulfide facies, devoid of Znclays. In all the facies detrital dioctahedral mica (muscovite and illite) is interstratified with smectite in the form of random (R0) to short-range ordered (R1) I/S, which locally shows significant Zn concentrations. In the sulfide facies kaolinite overgrowing onto mica packets has been detected. The low Zn-clay facies is dominated by Zn-bearing beidellite, with minor kaolinite and fraipontite. The Znclay facies consists mostly of a random (R0) interstratified clay between a 7-Å phase corresponding to fraipontite, and a 2:1 swelling clay component identifiable with the dioctahedral smectite, with minor sauconite.

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Section: Zn-clays Identificationsupporting

confidence: 70%

Section: Introductionmentioning

confidence: 99%

Zn-clays in the Kihabe and Nxuu prospects (Aha Hills, Botswana): A XRD and TEM study

Putzolu

Abad

Balassone

et al. 2023

American Mineralogist

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“…5c) correspond to the white clayey material that encompasses the willemite ore (Fig. 2d); they were described in detail by Buatier et al (2016) and Choulet et al (2016). Radial-fibrous willemite aggregates seem to postdate early cerussite (Cer I, often associated with Gn I) and predate late cerussite infilling (Cer III, without galena) (Figs.…”

Section: Host Rock and Ore Characterizationmentioning

confidence: 91%

“…The limestone has developed a 120-m thick karst that extends over 18,000 m 2 (Fig. 1b); sinkholes and tunnels are filled with detrital and residual clays (Buatier et al 2016;Choulet et al 2016). The mineralization consists of a network of interconnected vertical veins that meet the karst cavities (Fig.…”

Section: The Bou Arhous Depositmentioning

confidence: 99%

Characterization and origin of low-T willemite (Zn2SiO4) mineralization: the case of the Bou Arhous deposit (High Atlas, Morocco)

et al. 2016

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International audienceWillemite (Zn2SiO4) usually reported in hypogene non-sulfide deposits is described as the main ore mineral in the carbonate-hosted Bou Arhous zinc deposit. This deposit is located in the High Atlas intracontinental range that formed during the Tertiary. Based on a set of microscopic observations, it was possible to establish that willemite replaces primary sphalerite. On the basis of cathodoluminescence imaging, three successive generations of willemite are distinguished, with evidence of dissolution–reprecipitation processes. Willemite is also variably enriched in Ge (up to 1000 ppm), while Ge contents lower than 100 ppm are reported in the primary sulfide minerals. Depending on the willemite generation, this substitution was positively or negatively correlated to the Zn-Pb substitution. According to the nature of zoning (sector versus oscillatory), the incorporation of Ge was either controlled by crystallographic factors or by the nature of the mineralizing fluids. Willemite is associated with other oxidation-related mineral species, like cerussite (PbCO3) but is not in isotopic equilibrium and therefore not considered to be cogenetic. Oxygen isotope compositions support the formation of willemite at temperatures below 130 °C, from mixed meteoric and deeper, hydrothermal fluids. The formation of the High Atlas Belt during the Tertiary has contributed to the exhumation of the sulfide minerals and the development of vertical conduits for percolation of meteoric water and ascending hydrothermal fluids. In addition to a local contribution of silicate minerals of the host limestone, hydrothermal fluids probably transported Si and Ge that are incorporated in willemite

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“…They could therefore have enabled the Tasdremt metal association (Mn, Ba and Pb). Similarly, MVT and other base-metal deposits are widespread in Jurassic rocks in the Atlas belt (i.e., Choulet et al 2014;Bouabdellah and Sangster 2016;Buatier et al 2016;Verhaert et al 2017Verhaert et al , 2018 and could act as a potential source of metals, leading to the enrichment, up to several percents in Pb, in Tasdremt (Tables 1 and 2). The enrichment in other metals (Cu, Mo, As, V, and Zn; Fig.…”

Section: Metal(s) Source(s)mentioning

confidence: 99%

Multistage genesis of the late Cretaceous manganese karst-hosted Tasdremt deposit (High Atlas, Morocco)

et al. 2020

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The eastern part of the Souss Basin (Morocco) contains several Mn deposits in the Tasdremt district. Three Mn orebodies occur within the Cenomanian-Turonian dolostones and the Senonian (Coniacian to Maastrichtian) detrital series, the main orebody being located at the boundary between them. The Mn ores consist of coronadite group minerals, mostly coronadite and hollandite, in a karstified dolostone. New field observations, petrographic analyses, and geochemical data define the Tasdremt deposits as a karst-hosted accumulation (11-60 wt.% Mn), particularly enriched in Ba (1.5-8.2 wt.%) and Pb (1.0-5.0 wt.%) with poor contaminations in Al, Fe, and P. This study shows that the ore-forming process is similar to that occurring in the Imini C3 level, located~100 km to the northeast. Such similarities with the high-grade pyrolusite-bearing ore suggest that the Tasdremt deposit is a lateral equivalent of the Imini deposits. However, the scarcity of pyrolusite in Tasdremt results in lower Mn grades, the Tasdremt ores being considered an aborted/ incomplete system in comparison with the Imini deposits. 40 Ar/ 39 Ar geochronology of K-bearing Mn oxides yields late Cretaceous ages, defining three phases at~91.5 Ma,~77.5-82 Ma, and~65-67 Ma. Although the source of metals remains hypothetical, mineralizing fluids were carried by O 2-free groundwater that mixed with O 2-rich shallow meteoric waters at the Tasdremt depositional site. The dissolution of the host dolostones and the karst environment have provided suitable conditions for the precipitation of Mn oxides, causing the coeval increase of pH and Eh, respectively. The Early Atlasic deformation during the Late Cretaceous is associated with mineralization events and was responsible for creation of low stand reliefs from Tasdremt to Imini. This period enabled karstification and mineralization. Connecting the Tasdremt deposits to other African Mn deposits is difficult since the latter consist of laterite resting above Paleoproterozoic Mn protores, and consequently formed under different conditions from karst-hosted deposits. It is likely that other Mn occurrences formed along the Atlas belt in similar settings.

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Nature and origin of natural Zn clay minerals from the Bou Arhous Zn ore deposit: Evidence from electron microscopy (SEM-TEM) and stable isotope compositions (H and O)

Cited by 13 publications

References 34 publications

Zn-clays in the Kihabe and Nxuu prospects (Aha Hills, Botswana): A XRD and TEM study

Zn-clays in the Kihabe and Nxuu prospects (Aha Hills, Botswana): A XRD and TEM study

Characterization and origin of low-T willemite (Zn2SiO4) mineralization: the case of the Bou Arhous deposit (High Atlas, Morocco)

Multistage genesis of the late Cretaceous manganese karst-hosted Tasdremt deposit (High Atlas, Morocco)

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