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C-O Stable Isotopes Geochemistry of Tunisian Nonsulfide Zinc Deposits: A First Look

By: Garnit, H.1; Boni, M.2; Buongiovanni, G.2; Arfe, G.2; Mondillo, N.2; Joachimski, M.3; Bouhlel, S.1; Balassone, G.2

 
1University of Tunis El Manar, Faculty of Sciences of Tunis, Mineral Resources and Environment Lab (LR01ES06),
   Mineralogy and Geochemistry Research Group, 2092 Tunis, Tunisia
2  Dipartimento di Scienze della Terra, dell’Ambiente e delle Risorse, Università degli Studi di Napoli Federico II, Complesso Universitario di Monte S. Angelo, Via Cintia 21, 80126, Napoli (Italy)
3GeoZentrum Nordbayern, University of Erlangen-Nuremberg, Schlossgarten 5, 91054, Erlangen  (Germany)



MINERALSvol. 8 (1)

January 2018; Article Number: 13

DOI: 10.3390/min8010013


Abstract
A preliminary C-O stable isotopes geochemical characterization of several nonsulfide Zn-Pb Tunisian deposits has been carried out, in order to evidence the possible differences in their genesis. Nonsulfide ores were sampled from the following deposits: Ain Allegua, Jebel Ben Amara, Jebel Hallouf (Nappe Zone), Djebba, Bou Grine, Bou Jaber, Fedj el Adoum, Slata Fer (Diapir Zone), Jebel Ressas, Jebel Azreg, Mecella (North South Axis Zone), Jebel Trozza, Sekarna (Graben Zone). After mineralogical investigation of selected specimens, the C-O stable isotopic study was carried out on smithsonite, hydrozincite, cerussite and calcite. The data have shown that all the carbonate generations in the oxidized zones of Ain Allegua and Jebel Ben Amara (Nappe Zone), Bou Jaber, Bou Grine and Fedj el Adoum (Diapir Zone), Mecella and Jebel Azreg (North South Zone) have a supergene origin, whereas the carbonates sampled at Sekarna (Graben Zone) (and in limited part also at Bou Jaber) precipitated from thermal waters at moderately high temperature. Most weathering processes that controlled the supergene alteration of the Zn-Pb sulfide deposits in Tunisia had probably started in the middle to late Miocene interval and at the beginning of the Pliocene, both periods corresponding to two distinct tectonic pulses that produced the exhumation of sulfide ores, but the alteration and formation of oxidized minerals could have also continued through the Quaternary. The isotopic characteristics associated with the weathering processes in the sampled localities were controlled by the different locations of the sulfide protores within the tectonic and climatic zones of Tunisia during the late Tertiary and Quaternary.
 
Figure 1: Metallogenic map of central and northern Tunisia showing the distribution of the Pb-Zn-Fe-Ba-Sr-F deposit groups (modified from Bouhlel, 2005). The underlined and large character names on the map are the studied deposits.