Pb–Zn mineralization in a Miocene regional extensional context: The case of the Sidi Driss and the Douahria ore deposits (Nefza mining district, northern Tunisia)

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.

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“…Most of these deposits are located in the Nappe Zone of the Tellian Atlas (e.g., Jebel Hallouf, Sidi Bouaouane, Sidi Driss, Djebba) [1,40].…”

Section: Distribution and General Characteristics Of Zn-pb Ore Depositsmentioning

confidence: 99%

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

et al. 2018

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“…The ore is now exhausted. Studies devoted to the geology and origin of the deposit have been conducted by Sainfeld (1952), Gottis and Sainfeld (1952), Stefanov and Ouchev (1972) (exploiting new exploratory drillings performed by the Tunisian National Mine Office (ONM) in the 1970s), Negra (1987), Dermech (1990), and Decrée et al (2008a). The small Sidi Driss-Tamra and Douahria basins unconformably overlie the eroded nappe pile.…”

Section: The Messinian Sedimentary Basinsmentioning

confidence: 99%

“…However, this zone is better known for containing a large variety of polymetallic deposits, among which several are present in the Nefza district. This district is characterized by the occurrence of late Tertiary mineral deposits, including the Tortonian Oued Belif iron oxide uranium (IOU) showing (Decrée et al 2013), the Messinian Sidi Driss and Douahria Ba-Zn-Pb Sedex deposits (Decrée et al 2008a), and the Pliocene iron deposit of Tamera (Decrée et al 2008b). The two Sedex deposits are attributed to formation by thermally-driven circulating fluids related to Late Miocene magmatism and reactivation of shear zones during Messinian extension.…”

Section: Introductionmentioning

confidence: 99%

“…The two Sedex deposits are attributed to formation by thermally-driven circulating fluids related to Late Miocene magmatism and reactivation of shear zones during Messinian extension. These events (magmatism and reactivation of shear zones) are particularly well expressed in northern Tunisia (Decrée et al 2008a). The Jebel el Hamra (Jb el Hamra hereafter) encompasses the Ba-Sr-Zn-Pb-Hg deposits of Aïn Allega, El Aguiba, and El Arja (Sainfeld 1952;Gharbi 1977;Abidi et al 2010).…”

Section: Introductionmentioning

confidence: 99%

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Tectonomagmatic Context of Sedex Pb–Zn and Polymetallic Ore Deposits of the Nappe Zone Northern Tunisia, and Comparisons with MVT Deposits in the Region

Decrée

Marignac

Abidi

et al. 2016

Mineral Deposits of North Africa

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The Nefza region (Nappe Zone, northern Tunisia) is known both as a Late Miocene magmatic province and a base-metal district. In this region, small, post-nappe, continental extensional basins (Sidi Driss and (Sedex). In addition to this mineralization, the Nappe zone contains other Pb-Zn and polymetallic deposits that show similarities both to the SHMS-Sedex and MVT deposits of the Dome and Graben zones, namely the "peri-diapiric" deposits of Jebel (Jb) el Hamra, Jalta, and Jebel Ghozlane. All of the Nappe Zone deposits share common characteristics, including: (1) age-the deposits formed between late collisional events (Late Tortonian) and inception of the Early Messinian extensional regime, in the context of the Alpine Maghrebide belt formation; (2) presence of pre-existing sulphates-these were likely the main source of sulphur for the sulphides; and (3) hydrothermal systems leading to their genesisthese testify to alternating influx of cold and warm fluids. The involvement of high temperature fluids are deduced from fluid inclusion studies (Th values of 140-240°C), whereas the presence of distinctive sphalerite textures (microspherules and colloform textures) and sulphur isotopic compositions demonstrate in situ bacterial sulphate reduction, and consequently deposition at temperatures below 80°C. These data constitute unifying characteristics for these mineralizations that are in contrast to the features of Pb-Zn(-fluorite) MVT deposits occurring in the Dome and Graben zones of Tunisia. The geodynamic context prevailing during the Late Miocene in the Nappe Zone is the underlying common factor that explains the diversity of ore deposits formed at that time in this region. Most deposits are located in the vicinity of shear zones and associated lineaments inherited from the Variscan orogeny. These deep structures were reactivated by transtensional processes during the Alpine orogeny and controlled post-collisional magmatism, circulation of hydrothermal fluids, and locations of related ore deposits and showings in the Nappe Zone.

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“…Thus, the Tertiary orogeny in this case, as mentioned before, is represented by the Maghrebides fold-thrust belt, which was formed during the Alpine orogeny. Similarly, a genetic link between the Messinian mafic magmatism and Sidi Driss Pb-Zn deposit has been proposed by Decrée et al [40]. In the Oued Maden deposit, the Pb-isotopic data give negative model ages.…”

Section: Age Of Mineralizationmentioning

confidence: 61%

Lead Isotopes as Tracers of Metal Sources and Timing of the Carbonate-Hosted Pb-Zn Deposits in the Nappes Zone, Northern Tunisia

Jemmali¹,

Souissi²

2018

Contributions to Mineralization

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The polymetallic deposits in the Nappes zone, Northern Tunisia occur in the contact between Triassic-Miocene/Eocene carbonate rocks and in the Upper Cretaceous limestones. They can be divided into two groups: one is Pb-Zn mineralization with Hg and As in fractures with local intrusions of Neogene volcanics (e.g., Fej Hassene, Oued Maden), and the second is stratabound and karst Pb-Zn mineralization with arsenic and antimony hosted in the continental Neogene strata or situated immediately below them (Aïn Allega, Sidi Embarek, Jebel Hallouf-Sidi Bou Aouane, Bazina, Jalta and Jebel Ghozlane). Pb-isotopic compositions of galenas display a homogeneous Pb isotope signature. Generally, Pb isotope ratios on ores from the Jalta, Jebel Ghozlane, Jebel Hallouf, Oued Maden and Fedj Hassene plot between samples of the Late Miocene igneous rocks and the sedimentary country rocks of the Nefza area and between the upper crust and orogen curves. This intermediate position may imply potential mixing between end-member sources. Because the Pb-Zn mineralization is fault-controlled and spatially associated with the post-nappe Miocene series and the calculated model age is about 10.86 Ma, one is led to argue that the mineralization in the Nappes zone deposits occurred during the last paroxysmal phase of the Alpine folding (i.e., Miocene age).

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Pb–Zn mineralization in a Miocene regional extensional context: The case of the Sidi Driss and the Douahria ore deposits (Nefza mining district, northern Tunisia)

Cited by 59 publications

References 24 publications

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

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

Tectonomagmatic Context of Sedex Pb–Zn and Polymetallic Ore Deposits of the Nappe Zone Northern Tunisia, and Comparisons with MVT Deposits in the Region

Lead Isotopes as Tracers of Metal Sources and Timing of the Carbonate-Hosted Pb-Zn Deposits in the Nappes Zone, Northern Tunisia

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