Pal�o-bact�ries et min�ralisations plombo-zincif�res du Bled Zelfane (tunisie centrale)

Miocene karsts and associated Fe–Zn-rich minerals in Aïn Khamouda (Central Tunisia)

“…Some fractures and moldic cavities are filled with secondary mm-wide minerals that are identified (using XRD) as: (1) Such Zn minerals correspond to the ''calamine" ore mentioned by Jurkovic (1968), Fuchs (1973) and Amouri (1977) and mined in Aïn Khamouda in the early 20th century. Amouri et al (1978) also mention the presence of tiny (5-50 lm) euhedral galena microcrystals associated with calamine (altered microcrystals) and within white clay (well-preserved microcrystals). The authors refer to this galena as to the result of a biogeochemical precipitation.…”

“…Sulphide minerals (pyrite, Fe-Zn sulphide, galena) found within the karst infilling (galena in calamine and white clay; pyrite and FeZn sulphide in leached Beglia sand) are late in the system (mostly void filling). Galena in calamine and white clay results from biogeochemical reduction in overall oxidizing conditions (Fuchs, 1973;Amouri et al, 1978), while pyrite and Fe-Zn sulphide in Beglia sand could result either from similar biogeochemical processes or from other late geochemical reprecipitation. These sulphides in turn are oxidized in jarosite (whose K + derives from the Beglia sand), which occasionally predates quartz overgrowth on detrital grains, suggesting that the (occasional) cementation of sand into sandstone is also a late feature in the studied system.…”

“…In his extensive survey of Pb-Zn deposits in Tunisia, Sainfeld (1952) refers to Aïn Khamouda as to ''mineralized decalcification caves", but did not pay much more attention to this economically uninteresting ore deposit. In the last 50 years, several mineralogical studies have been dedicated firstly to the Pb-Zn minerals and secondly to the clay minerals, among which halloysite (Sainfeld, 1952;Jurkovic, 1968;Fuchs, 1973;Amouri, 1977;Amouri et al, 1978). Amri (1981) mentioned the presence of halloysite in Aïn Khamouda in his survey of clay minerals in Tunisia.…”

Complementarite des rayons X et de la microscopie electronique pour la determination des diverses phases d'une argile zincifere

“…nH20 et goethite a-FeOOH), d'h6mimorphite (Zn4Si2OT(OH)2. H20 ) et de smithsonite (ZnCO3); (ii) une phase blanche argileuse halloysitique, objet de cette &ude, contenant parfois quelques microcristaux de gal6ne (Amouri et al, 1978) et localis6e le plus souvent au mur et dans la pattie centrale des grottes; (iii) une phase d&ritique miocene constituant la partie sup~rieure du remplissage des cavernes.…”