The celestite ore of Jebel Doghra occurs as stratabound deposits within the cap-rock of a diapiri... more The celestite ore of Jebel Doghra occurs as stratabound deposits within the cap-rock of a diapiric structure of Triassic salt-rocks. The celestite deposits result mainly from the late diagenetic to epigenetic replacement of the carbonated host-rocks giving rise to a dolomite-celestite " ...
Travaux et Documents des Laboratoires de Géologie de Lyon, 2002
Abdallah Hassen, Sassi Sassi, Souissi Fouad, Meister Christian. Sequence stratigraphy, palaeoenvi... more Abdallah Hassen, Sassi Sassi, Souissi Fouad, Meister Christian. Sequence stratigraphy, palaeoenvironments and tectonics at the Cenomanian-Turonian boundary : tilted bloc of Jabal Chemsi, northern part of southern Tunisia. In: Documents des Laboratoires de Géologie, Lyon, n°156, 2002. STRATI 2002. 3ème congrès français de stratigraphie. Lyon, 8-10 juillet 2002. p. 15
The Pb–Zn deposit at Jebel Ghozlane, in the Nappe zone (northern Tunisia), is hosted by Triassic ... more The Pb–Zn deposit at Jebel Ghozlane, in the Nappe zone (northern Tunisia), is hosted by Triassic dolostones and Eocene limestones and is located along faults and a thrust‐sheet boundary. The sulfide mineralization of the deposit consists mainly of galena and sphalerite and occurs as vein, stockwork, breccia, dissemination and replacement ores. Three hydrothermal stages are involved in the formation of the ores: stage I is dominated by celestite‐barite, hydrothermal dolomite DII, colloform sphalerite, and galena I; stage II consist of galena II; and stage III contains calcite. Galena in the deposit yielded average 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios of 18.705, 15.667 and 38.734, respectively, suggesting a single upper crustal source reservoir for metals. Trace element data indicate the presence of Zn‐ and As‐free galena and As‐rich galena (with 0.2–0.5% As). Sphalerite contains 0.4% As, 0.7–0.9% Cd and 0.1–1.5% Fe. Microthermometric analysis of fluid inclusions in celestite shows that the deposit formed from fluids composed of heterogeneous mixtures of saline (19.5 ± 1 wt% NaCl eq.) aqueous solutions sourced from basinal brines, and gaseous CO2‐rich phases bearing low amounts of CH4, N2 and/or H2S, at temperatures of 172 ± 5°C.
The mineralization of Jebel Stah consists almost exclusively of fluorite. It is associated to the... more The mineralization of Jebel Stah consists almost exclusively of fluorite. It is associated to the unconformity surface which separates the palaeorelief of the Lower Liassic limestones (Oust Formation) from the condensed layers of the Carixian phosphatic limestones and the Middle-Upper Domerian marls-limestones alternance. Evidences of emergence are visible at the top of the infra-Liassic and the Carixian carbonates. These two formations have, furthermore undergone a strong epigenetic dolomitization. The mineralization is hosted in the Carixian layers essentially. We observed that the mineralization has been deposited during an epigenetic stage both replacing the dolomitic rocks and within veins and geodes. The microthermometric study of fluid inclusions in fluorite and quartz (two phase aqueous inclusions, aqueous inclusions enclosing a fine liquid hydrocarbon drop, and gazeous CO 2 -rich inclusions) shows that the mineralizing fluids are hydrothermal brines. Two stages of cristalli...
The Jebel El Akhouat Zn-Pb-(Ba-Sr) ore deposit, located in the Tunisian Dome zone, is hosted main... more The Jebel El Akhouat Zn-Pb-(Ba-Sr) ore deposit, located in the Tunisian Dome zone, is hosted mainly in the organic matter-rich Albian and Cenomanian–Turonian rocks. The orebodies occur mainly as open-space fillings and are structurally-controlled. The paragenetic sequence consists of three stages, which reflect three ore events. Three discrete stages of Zn-Pb sulfide and/or Zn-Pb-Ba-Sr sulfide-sulfate ores are identified. Fluid inclusion study carried out on selected minerals of different stages reveals that sphalerite, galena, marcasite, celestine, barite, and fluorite precipitated as a result of mixing between a hydrothermal, saline, metal-rich basinal fluid and a low-temperature, less saline, metal-depleted, sulfur- or sulfate-rich fluid with the intermittent involvement of hydrocarbons. Based on sulfur isotope data, sulfur of sulfides was derived from the reduction of the dissolved Triassic sulfates primary through thermochemical sulfate reduction with a contribution of bacterial sulfate reduction. The Pb isotopic composition of galena samples and trace elements data of the host carbonate rocks suggest that metals were derived primarily from the Paleozoic siliciclastic rocks with a contribution of the organic matter-rich Albian and Cenomanian–Turonian rocks. The Alpine orogeny triggered the migration of the metalliferous fluids from the deep parts of the basin towards the peridiapiric paleohigh of Ech Chehid diapir through major faults towards the loci of deposition.
Under semi-arid climatic conditions, Pb, Zn and Cd bearing particles are carried by wind and wate... more Under semi-arid climatic conditions, Pb, Zn and Cd bearing particles are carried by wind and water from the flotation tailing heaps of the former Pb-Zn mine of Jebel Ressas towards the surrounding agricultural areas. The risk of ecotoxicity depends on the phytoaccessible fraction of metals which is closely related to their physico-chemical and biological environment. The objective of this study is to assess the contamination of soils surrounding the waste dumps and to estimate the bioaccessible fraction of metals present in these soils. These silty soils are mainly composed of calcite (45 % CaCO3) and clays. Metal bearing minerals are hemimorphite (Zn4Si2O72H2O), cerussite (PbCO3), and smithsonite (ZnCO3). The flotation tailings display high amounts of Zn, Pb and Cd, averaging 7.11%, 2.30% and 290 mg.kg-1, respectively. The concentrations found in soils reach 6.3% Zn, 2.3% Pb and 290 mg.kg-1 Cd. Such results show that the soils in the mining area are highly contaminated by heavy met...
The Pb–Zn ore deposits in the Guern Halfaya and Bou Grine areas (northern Tunisia) are hosted mai... more The Pb–Zn ore deposits in the Guern Halfaya and Bou Grine areas (northern Tunisia) are hosted mainly by dolostones in the contact zone between Triassic and Upper Cretaceous strata and by Upper Cretaceous limestones. The deposits occur as lenticular, stratiform, vein, disseminations and stockwork ore bodies consisting of sphalerite, galena, pyrite, chalcopyrite and sulfosalt (gray copper). Barite and celestite dominate the gangue, with lesser calcite. The δ34S values of barite and celestite (12.7–15.0‰) at the Oum Edeboua mine are consistent with the reduction of sulfates in Triassic evaporites within the study area (12.8 b δ34S b 14.0‰). The δ34S values in base-metal sulfides from both study areas (2.6–9.5‰) and the presence of bacterial relics suggest involvement of bacterially-mediated sulfate reduction in the mineralization. The present Pb isotope data are homogeneous with 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios of 18.723–18.783, 15.667–15.685 and 38.806–38.889, respectively, which suggest a single source reservoir of Pb at depth in the upper crust. The syn-diagenetic mineralization in the Bahloul Formation and the calculated age from the Pb isotopic data suggest an Upper Cretaceous age for the Pb–Zn deposits in the Guern Halfaya and Bou Grine areas. During this period, NE–SW to ENE–WSW trending regional extensional tectonic structures likely favored migration of mineralizing fluids and eventual deposition at Guern Halfaya and Bou Grine.
The celestite ore of Jebel Doghra occurs as stratabound deposits within the cap-rock of a diapiri... more The celestite ore of Jebel Doghra occurs as stratabound deposits within the cap-rock of a diapiric structure of Triassic salt-rocks. The celestite deposits result mainly from the late diagenetic to epigenetic replacement of the carbonated host-rocks giving rise to a dolomite-celestite “banded ore”. Celestite is locally observed within fractures. This study proposes a new genetic model based on fluid inclusion (FI) microthermometry and REE geochemistry. FI show that celestite, occurring either as stratabound bodies or lodes, was deposited from a highly saline (20.7 ± 1.3 wt%NaCl equivalents) and warm (174 ± 3oC) basinal fluid, which contains hydrocarbon droplets and CO2. The geochemistry of the REE shows that the deposition of celestite is due to the mixing between a deep-sourced fluid which has acquired high Sr concentrations by leaching feldspar-rich series in depth and a sulfate-rich solution associated with the Triassic evaporites.
Transfer and accumulation of lead, zinc, cadmium and copper in plants growing in abandoned mining... more Transfer and accumulation of lead, zinc, cadmium and copper in plants growing in abandoned mining-district area
La region d’etude situee a une quarantaine de kilometres au sud de Tunis, est un ancien golfe lar... more La region d’etude situee a une quarantaine de kilometres au sud de Tunis, est un ancien golfe largement ouvert vers le nord‐ouest et en communication avec le golfe de Tunis. Il s’agit d’une plaine qui fait partie d’un systeme multicouche a trois niveaux aquiferes : une nappe phreatique, une nappe semi‐profonde et une nappe profonde. L’ensemble de ces trois niveaux aquiferes couvre une superficie de 719 km 2 dont 407 km 2 de recouvrement quaternaire. L’etude geochimique des eaux de la nappe phreatique effectuee durant deux campagnes (mai 2000 et avril 2001), a ete abordee par les mesures in situ des parametres physico‐chimiques, l’analyse au laboratoire des elements majeurs (anions et cations) ainsi que les elements nutritifs. Cette etude nous a permis de montrer que : les eaux souterraines sont caracterisees par une salinite comprise entre 0,7 g\L et 4,7 g\L ; les concentrations des ions majeurs, qui depassent generalement les normes nationales et internationales, montrent un gradie...
The celestite ore of Jebel Doghra occurs as stratabound deposits within the cap-rock of a diapiri... more The celestite ore of Jebel Doghra occurs as stratabound deposits within the cap-rock of a diapiric structure of Triassic salt-rocks. The celestite deposits result mainly from the late diagenetic to epigenetic replacement of the carbonated host-rocks giving rise to a dolomite-celestite " ...
Travaux et Documents des Laboratoires de Géologie de Lyon, 2002
Abdallah Hassen, Sassi Sassi, Souissi Fouad, Meister Christian. Sequence stratigraphy, palaeoenvi... more Abdallah Hassen, Sassi Sassi, Souissi Fouad, Meister Christian. Sequence stratigraphy, palaeoenvironments and tectonics at the Cenomanian-Turonian boundary : tilted bloc of Jabal Chemsi, northern part of southern Tunisia. In: Documents des Laboratoires de Géologie, Lyon, n°156, 2002. STRATI 2002. 3ème congrès français de stratigraphie. Lyon, 8-10 juillet 2002. p. 15
The Pb–Zn deposit at Jebel Ghozlane, in the Nappe zone (northern Tunisia), is hosted by Triassic ... more The Pb–Zn deposit at Jebel Ghozlane, in the Nappe zone (northern Tunisia), is hosted by Triassic dolostones and Eocene limestones and is located along faults and a thrust‐sheet boundary. The sulfide mineralization of the deposit consists mainly of galena and sphalerite and occurs as vein, stockwork, breccia, dissemination and replacement ores. Three hydrothermal stages are involved in the formation of the ores: stage I is dominated by celestite‐barite, hydrothermal dolomite DII, colloform sphalerite, and galena I; stage II consist of galena II; and stage III contains calcite. Galena in the deposit yielded average 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios of 18.705, 15.667 and 38.734, respectively, suggesting a single upper crustal source reservoir for metals. Trace element data indicate the presence of Zn‐ and As‐free galena and As‐rich galena (with 0.2–0.5% As). Sphalerite contains 0.4% As, 0.7–0.9% Cd and 0.1–1.5% Fe. Microthermometric analysis of fluid inclusions in celestite shows that the deposit formed from fluids composed of heterogeneous mixtures of saline (19.5 ± 1 wt% NaCl eq.) aqueous solutions sourced from basinal brines, and gaseous CO2‐rich phases bearing low amounts of CH4, N2 and/or H2S, at temperatures of 172 ± 5°C.
The mineralization of Jebel Stah consists almost exclusively of fluorite. It is associated to the... more The mineralization of Jebel Stah consists almost exclusively of fluorite. It is associated to the unconformity surface which separates the palaeorelief of the Lower Liassic limestones (Oust Formation) from the condensed layers of the Carixian phosphatic limestones and the Middle-Upper Domerian marls-limestones alternance. Evidences of emergence are visible at the top of the infra-Liassic and the Carixian carbonates. These two formations have, furthermore undergone a strong epigenetic dolomitization. The mineralization is hosted in the Carixian layers essentially. We observed that the mineralization has been deposited during an epigenetic stage both replacing the dolomitic rocks and within veins and geodes. The microthermometric study of fluid inclusions in fluorite and quartz (two phase aqueous inclusions, aqueous inclusions enclosing a fine liquid hydrocarbon drop, and gazeous CO 2 -rich inclusions) shows that the mineralizing fluids are hydrothermal brines. Two stages of cristalli...
The Jebel El Akhouat Zn-Pb-(Ba-Sr) ore deposit, located in the Tunisian Dome zone, is hosted main... more The Jebel El Akhouat Zn-Pb-(Ba-Sr) ore deposit, located in the Tunisian Dome zone, is hosted mainly in the organic matter-rich Albian and Cenomanian–Turonian rocks. The orebodies occur mainly as open-space fillings and are structurally-controlled. The paragenetic sequence consists of three stages, which reflect three ore events. Three discrete stages of Zn-Pb sulfide and/or Zn-Pb-Ba-Sr sulfide-sulfate ores are identified. Fluid inclusion study carried out on selected minerals of different stages reveals that sphalerite, galena, marcasite, celestine, barite, and fluorite precipitated as a result of mixing between a hydrothermal, saline, metal-rich basinal fluid and a low-temperature, less saline, metal-depleted, sulfur- or sulfate-rich fluid with the intermittent involvement of hydrocarbons. Based on sulfur isotope data, sulfur of sulfides was derived from the reduction of the dissolved Triassic sulfates primary through thermochemical sulfate reduction with a contribution of bacterial sulfate reduction. The Pb isotopic composition of galena samples and trace elements data of the host carbonate rocks suggest that metals were derived primarily from the Paleozoic siliciclastic rocks with a contribution of the organic matter-rich Albian and Cenomanian–Turonian rocks. The Alpine orogeny triggered the migration of the metalliferous fluids from the deep parts of the basin towards the peridiapiric paleohigh of Ech Chehid diapir through major faults towards the loci of deposition.
Under semi-arid climatic conditions, Pb, Zn and Cd bearing particles are carried by wind and wate... more Under semi-arid climatic conditions, Pb, Zn and Cd bearing particles are carried by wind and water from the flotation tailing heaps of the former Pb-Zn mine of Jebel Ressas towards the surrounding agricultural areas. The risk of ecotoxicity depends on the phytoaccessible fraction of metals which is closely related to their physico-chemical and biological environment. The objective of this study is to assess the contamination of soils surrounding the waste dumps and to estimate the bioaccessible fraction of metals present in these soils. These silty soils are mainly composed of calcite (45 % CaCO3) and clays. Metal bearing minerals are hemimorphite (Zn4Si2O72H2O), cerussite (PbCO3), and smithsonite (ZnCO3). The flotation tailings display high amounts of Zn, Pb and Cd, averaging 7.11%, 2.30% and 290 mg.kg-1, respectively. The concentrations found in soils reach 6.3% Zn, 2.3% Pb and 290 mg.kg-1 Cd. Such results show that the soils in the mining area are highly contaminated by heavy met...
The Pb–Zn ore deposits in the Guern Halfaya and Bou Grine areas (northern Tunisia) are hosted mai... more The Pb–Zn ore deposits in the Guern Halfaya and Bou Grine areas (northern Tunisia) are hosted mainly by dolostones in the contact zone between Triassic and Upper Cretaceous strata and by Upper Cretaceous limestones. The deposits occur as lenticular, stratiform, vein, disseminations and stockwork ore bodies consisting of sphalerite, galena, pyrite, chalcopyrite and sulfosalt (gray copper). Barite and celestite dominate the gangue, with lesser calcite. The δ34S values of barite and celestite (12.7–15.0‰) at the Oum Edeboua mine are consistent with the reduction of sulfates in Triassic evaporites within the study area (12.8 b δ34S b 14.0‰). The δ34S values in base-metal sulfides from both study areas (2.6–9.5‰) and the presence of bacterial relics suggest involvement of bacterially-mediated sulfate reduction in the mineralization. The present Pb isotope data are homogeneous with 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios of 18.723–18.783, 15.667–15.685 and 38.806–38.889, respectively, which suggest a single source reservoir of Pb at depth in the upper crust. The syn-diagenetic mineralization in the Bahloul Formation and the calculated age from the Pb isotopic data suggest an Upper Cretaceous age for the Pb–Zn deposits in the Guern Halfaya and Bou Grine areas. During this period, NE–SW to ENE–WSW trending regional extensional tectonic structures likely favored migration of mineralizing fluids and eventual deposition at Guern Halfaya and Bou Grine.
The celestite ore of Jebel Doghra occurs as stratabound deposits within the cap-rock of a diapiri... more The celestite ore of Jebel Doghra occurs as stratabound deposits within the cap-rock of a diapiric structure of Triassic salt-rocks. The celestite deposits result mainly from the late diagenetic to epigenetic replacement of the carbonated host-rocks giving rise to a dolomite-celestite “banded ore”. Celestite is locally observed within fractures. This study proposes a new genetic model based on fluid inclusion (FI) microthermometry and REE geochemistry. FI show that celestite, occurring either as stratabound bodies or lodes, was deposited from a highly saline (20.7 ± 1.3 wt%NaCl equivalents) and warm (174 ± 3oC) basinal fluid, which contains hydrocarbon droplets and CO2. The geochemistry of the REE shows that the deposition of celestite is due to the mixing between a deep-sourced fluid which has acquired high Sr concentrations by leaching feldspar-rich series in depth and a sulfate-rich solution associated with the Triassic evaporites.
Transfer and accumulation of lead, zinc, cadmium and copper in plants growing in abandoned mining... more Transfer and accumulation of lead, zinc, cadmium and copper in plants growing in abandoned mining-district area
La region d’etude situee a une quarantaine de kilometres au sud de Tunis, est un ancien golfe lar... more La region d’etude situee a une quarantaine de kilometres au sud de Tunis, est un ancien golfe largement ouvert vers le nord‐ouest et en communication avec le golfe de Tunis. Il s’agit d’une plaine qui fait partie d’un systeme multicouche a trois niveaux aquiferes : une nappe phreatique, une nappe semi‐profonde et une nappe profonde. L’ensemble de ces trois niveaux aquiferes couvre une superficie de 719 km 2 dont 407 km 2 de recouvrement quaternaire. L’etude geochimique des eaux de la nappe phreatique effectuee durant deux campagnes (mai 2000 et avril 2001), a ete abordee par les mesures in situ des parametres physico‐chimiques, l’analyse au laboratoire des elements majeurs (anions et cations) ainsi que les elements nutritifs. Cette etude nous a permis de montrer que : les eaux souterraines sont caracterisees par une salinite comprise entre 0,7 g\L et 4,7 g\L ; les concentrations des ions majeurs, qui depassent generalement les normes nationales et internationales, montrent un gradie...
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