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

Giuseppina Balassone,Giuliana Buongiovanni,Giuseppe Arfè,Hechmi Garnit,Salah Bouhlel,Michael Joachimski,Nicola Mondillo,Maria Boni

doi:10.3390/min8010013

Giuseppina Balassone, Giuliana Buongiovanni + Show 6 more

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https://doi.org/10.3390/min8010013

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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.

Highlights

North-Central Tunisia is part of the Alpine Atlas mountain ranges, extending toward the west through Algeria and Morocco along the Mediterranean coast
We present the results of a preliminary C–O stable isotopes’ geochemical study on carbonate minerals occurring in several nonsulfide Zn-Pb Tunisian deposits, in order to evidence possible differences in their genesis
Alteration and supergene oxidized minerals formation likely continued during the Pliocene and between the late Pleistocene and Holocene, during the onset of some relatively wet climatic periods, creating a favorable environment for weathering of sulfides

Summary

Introduction

North-Central Tunisia is part of the Alpine Atlas mountain ranges, extending toward the west through Algeria and Morocco along the Mediterranean coast In this mountain belt, Triassic to upper. The nonsulfide Zn-Pb deposits of Tunisia have not been investigated since the pioneering works of [6,7,8,9] These authors reported that Pb-Zn sulfide ores overlain by oxidized gossans and caps were widely distributed throughout the Tunisian belts [6,7,8,9]. Minerals 2018, 8, 13 replacing the hypogene sulfide bodies in oxidation zones For this reason, these authors proposed that all of the Tunisian nonsulfide ores were formed through supergene processes associated with weathering. Even though recent papers (e.g., [10]) have shown that C–O stable isotopes can be useful to better identify the nature of the fluids precipitating nonsulfide mineralizations, stable isotopes data on Zn and Pb carbonates from Tunisian nonsulfide deposits have been lacking so far [4,5]

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