Search Results (5)

The Hammam–Zriba F–Ba (Zn–Pb) stratabound deposit is located within the Zaghouan Fluorite Province (ZFP), which is the most important mineral sub-province in NE Tunisia, with several CaF₂ deposits occurring mainly along the Zaghouan Fault and corresponding to an F-rich MVT mineral system developed along the unconformity surface between the uppermost Jurassic limestones and the late Cretaceous layers. Petrographic analysis, microthermometry, and Raman spectroscopy applied to fluid inclusions in fluorite revealed various types of inclusions containing brines, oil, CO₂, and CH₄ along with solid phases such as evenkite, graphite, kerogen and bitumen. Microthermometric data indicate homogenization temperatures ranging from 85 °C to 145 ± 5 °C and salinities of 13–22 wt.% NaCl equivalent. This study supports a model of heterogeneous trapping, where saline basinal brines, oil, and gases were simultaneously trapped within fluorite, which indicates fluid immiscibility. The Raman analysis identified previously undetected organic compounds, including the first documented occurrence of evenkite, a mineral hydrocarbon, co-genetically trapped with graphite. The identification of evenkite and graphite in fluid inclusions offers new insights into the composition of hydrocarbon-bearing fluids within the MVT deposits in Tunisia, contributing to an understanding of the mineralogical characteristics of these deposits. The identified hydrocarbons correspond to three oil families. Family I (aliphatic compounds) is attributed to the lower-Eocene Bou-Dabbous Formation, family II (aromatic compounds) is attributed to the Albian Fahdene Formation and the Cenomanian–Turonian Bahloul Formation, and family III is considered as a mixture of aliphatic and aromatic compounds generated by the three sources. The presence of graphite in fluid inclusions could suggest the involvement of a thermal effect from deep-seated sources through the reservoir to the site of fluorite precipitation. These findings suggest that the fluorite mineral system might have been linked with the interaction of multi-reservoir fluids, potentially linked to the neighboring petroleum system in northeastern Tunisia during the Miocene. This study aims to investigate the composition of fluid inclusions in fluorite from the Hammam–Zriba F–Ba (Zn–Pb) deposit, with a particular focus on the plausible sources of hydrocarbons and their implications for the genetic relationship between the mineralizing system and petroleum reservoirs. Full article

The Zaghouan Fluorite Province (ZFP) encloses F-Ba(Pb-Zn) ores hosted within Jurassic carbonate series, in northeastern Tunisia. Critical breakthroughs on the Jebel Stah fluorite deposits, an MVT-style F-mineralization, have been made within the Lower Jurassic limestones along the Zaghouan Fault, which is a major target for mineralization. This study presents the first REE-Y analyses conducted by LA-ICP-MS on fluorites in Tunisia, and specifically on the fluorites of Jebel Stah deposit. This analytical technique provides highly accurate insights into the geochemical regime of mineralizing fluids and the related scavenging sources. Distinct geochemical characteristics between two fluorite generations (G1 and G2) were revealed. Fluorites (Fl2) from the early generation (G1) showed low ΣREE + Y (36.3 and 39.73 ppm, respectively). When normalized to chondrites, early fluorite G1 displayed a bell-shaped REE + Y pattern with a depletion in LREE relative to HREE and a slight MREE hump. Late fluorite (Fl3) generation (G2) displayed higher ΣREE + Y concentrations (77.43 ppm), but an almost similar REE pattern. Ce/Ce* ratios demonstrated strong negative Ce anomalies in all fluorites, while Eu/Eu* ratios indicated weak negative Eu anomalies. The positive Y anomaly observed in the REE + Y patterns of fluorites G1 and G2 suggests Y-Ho fractionation in the fluid system. Moreover, significant degrees of differentiation between terbium (Tb) and lanthanum (La) have been observed in all fluorite samples. The plot of fluorites from both fluorite generations on the Tb/La–Tb/Ca diagram gives evidence of the sedimentary hydrothermal origin of the ore-forming fluids in the Jebel Stah F-deposit. Sr isotopes show that the mineralizing fluids are radiogenic and deeply sourced basinal brines, whereas the small variation in ⁸⁷Sr/⁸⁶Sr ratios suggests a similar source for Sr in fluorites G1 and G2. These results allow us to conclude that the economic fluorite (G1) ore of Jebel Stah was deposited due to the interaction of the deeply sourced hydrothermal fluid with the carbonated host rocks (dolomitization, an increase in pH, and Ca activity), whereas the late fluorite (G2) is an accessory and could have resulted from the mixing of the hydrothermal fluid with shallow meteoric waters. Full article

Mining waste is an obvious source of environmental pollution due to the presence of heavy metals, which can contaminate soils, water resources, sediments, air, and people living nearby. The F-(Ba-Pb-Zn) deposit of Hammam Zriba located in northeast Tunisia, 8 km southeast of Zaghouan was intensively exploited from 1970 to 1992. More than 250,000 m³ of flotation tailings were produced and stored in the open air in three dumps without any measure of environmental protection. Thus, in this paper, mineralogical and chemical characterization, especially the sulfide and carbonate phases, were carried out to evaluate the potential for acid mining drainage (AMD) and metal leaching (ML). Conventional analytical methods (XRD, XRF, SEM) have revealed that this mining waste contains on average 34.8% barite–celestine series, 26.6% calcite, 23% quartz, 6.3% anglesite, 4.8% fluorite, 2.1% pyrite, and 0.4% sphalerite. The content of sulfides is less important. The tailing leaching tests (AFNOR NFX 31-210 standard) did not generate acidic leachate (pH: 8.3). The acidity produced by sulfide oxidation was neutralized by calcite present in abundance. Furthermore, the leaching tests yielded leachates with high concentrations of heavy metals, above the authorized thresholds. This high mobilization rate in potential toxic elements (PTE) represents a contamination risk for the environment. Full article

The Mediterranean coastal aquifer system of the Grombalia basin (NE Tunisia) offers immense potential as a source of fresh water for agriculture, industry, and drinking water supply. Nonetheless, due to its intricate hydrogeological characteristics and the prevailing issue of groundwater salinity, comprehending its groundwater system behavior becomes crucial for the effective and sustainable management of this aquifer system. Based on the hydrogeological characterization of the Grombalia basin, a novel 3D hydrogeological conceptual model was developed to enhance the understanding of its complex aquifer system. The integration of insights from geological, hydrogeological, hydrodynamic, and hydrochemical components facilitated the construction of the hydrogeological conceptual model. Although the model’s validity faced initial uncertainties due to spatial interpolation of lithological sequences, this study’s thorough and encompassing hydrogeological investigation overcame these limitations. As a result, a more informed comprehension of the aquifer system complexities was achieved. This study reveals that the basin is underlain by an extensive, cohesive Mio–Plio–Quaternary aquifer system. The model demonstrates vertical and lateral hydrogeological continuity between the Quaternary and underlying Mio–Pliocene deposits, enabling groundwater flow and exchange between these layers. Over-abstraction of the Mio–Plio–Quaternary aquifer system has led to a significant drop in piezometric levels and raised the risk of seawater intrusion. These findings emphasize the critical necessity of taking into account the interconnections among hydrogeological units to ensure sustainable groundwater management. The developed conceptual model offers a key tool for understanding the hydrodynamic functioning of the Grombalia aquifer system with a view toward guiding future groundwater management strategies. The application of this approach in the Grombalia basin suggests its potential applicability to other regional aquifers facing comparable challenges. Full article

Electric resistivity sounding and tomography, as well as electromagnetic sounding, are the classical methods frequently used for hydrogeological studies. In this work, we propose the development and implementation of an original integrated approach using the unconventional hydro–geophysical methods of gravity and seismic reflection for the fast, large–scale characterization of hydrogeological potential using the Ain El Beidha plain (central Tunisia) as an analogue. Extending the values of vintage petroleum seismic reflection profiles and gravity data, in conjunction with available geological and hydrogeological information, we performed an advanced analysis to characterize the geometry of deep tertiary (Oligocene and Eocene) aquifers in this arid area. Residual and tilt angle gravity maps revealed that most gravity anomalies have a short wavelength. The study area was mainly composed of three major areas: the Oued Ben Zitoun and Ain El Beidha basins, which are both related to negative gravity trends corresponding to low–density subsiding depocenters. These basins are separated by an important NE–SW trend called “El Gonna–J. El Mguataa–Kroumet Zemla” gravity high. Evaluation of the superposition of detected lineaments and Euler deconvolution solutions’ maps showed several NE–SW and N–S relay system faults. The 3D density inversion model using a lateral and vertical cutting plane suggested the presence of two different tectonic styles (thin VS thick). Results from the gravity analysis were in concordance with the seismic analysis. The deep Oligocene and Eocene seismic horizons were calibrated to the hydraulic wells and surrounding outcrops. Oligocene and Eocene geological reservoirs appear very fractured and compartmented. The faulting network also plays an important role in enhancing groundwater recharge process of the Oligocene and Eocene aquifers. Finally, generated isochron maps provided an excellent opportunity to develop future comprehensive exploration surveys over smaller and more favorable areas’ sub–basins. Full article