Pierre Courjault-Radé

Multi-stage fluid incursion in the Palaeozoic basement-hosted Saint-Salvy ore deposit (NW Montagne Noire, southern France)

Abstract The Saint-Salvy vein-hosted Zn (+Ge) deposit occurs in an E–W fault system which flanks the southern margin of the late Variscan Sidobre granite, and cross-cuts Cambrian black shales of the Palaeozoic basement. Comprehensive mineralogical and geochemical studies of vein samples have revealed four mineralizing events (M1–M4) related to late and post-Variscan tectonic events. A further late-stage event may be related to weathering. M1 (=skarn deposits) and M2 (=patchily mineralized quartz veinlets) are associated with granite emplacement. Quartz contains low salinity, H2O CO2 (NaCl)-dominated fluids(⩽6wt% NaCl equiv.) of relatively high temperature (300–580°C), trapped under moderate to high pressure. Estimated M1 fluid δD and calculated fluidδ18O plot within the metamorphic water field. There appears to be no involvement of magmatic fluids. By contrast, M3 (= barren quartz) and M4 (= zinciferous economic mineralization) stages have H2O CO2 NaCl CaCl2 fluid inclusions with high salinities (23–25 wt% NaCl equiv.) and low temperatures(∼ 80–140°C), which were trapped under low-pressure conditions. The high salinity and NaCl + CaCl2 content of both M3 and M4 indicates that their parent fluids leached evaporitic salts. M3 fluids are meteoric water dominated, falling close to the meteoric water line (δD andδ18O averaging −64 and −8‰, respectively). M4 fluids have highly distinctive δD averaging −101‰, and calculated fluidδ18O varying from−1.2to+7.1‰. The unusually low δD composition of M4 suggests the involvement of “organic” fluids, in which H is derived directly or indirectly from organic matter. The relatively highδ18O of M4 fluids indicates that considerable isotopic exchange with sedimentary material took place, displacing theδ18O from the meteoric water line. The data imply interaction of meteoric waters with evaporite and hydrocarbon-bearing sedimentary sequences, most probably the adjacent Aquitain Basin. The main economic mineralization (M4 stage) took place during a tensional event, probably coincident with the Lias-Dogger transition. Calculatedδ34SH2S of M4 sulphide(+5.4to+8.2‰) is almost identical toδ34S of local Cambrian sulphides(+4.7to+9.4‰) suggesting a genetic link. Abundant siderite associated with M4 sphalerite hasδ13C ranging from−2.6to−4.4‰ indicating that carbon was sourced from sedimentary carbonate mobilized by, or equilibrated with the hydrothermal fluid. Late-stage sulphides exhibit extraordinary and highly distinctiveδ34S. Sphalerite has extremely low δ34S(−42.5to−50.5‰), whereas pyrite has an extraordinary large range from−33.2‰to+74.3‰. Closed system sulphate reduction is held to be responsible for the extremely highδ34S: whereas more open system reduction produces the very low values. The coincidence of isotopically lowδ13C(−7.6to−11.9‰) for co-genetic calcite suggests the involvement of organic matter in the reduction process.

Heavy metal contamination and ecological risk assessment in the surface sediments of the coastal area surrounding the industrial complex of Gabes city, Gulf of Gabes, SE Tunisia.

In the present study, the concentrations of 6 trace metals (Hg, Cd, Cu, Pb, Cr and Zn) were assessed in the surface sediments of the central coastal area of Gabes Gulf to determine their contamination status, source, spatial distribution and ecological risks. The ranking of metal contents was found to be Zn>Cd>Cr>Pb>Cu>Hg. Correlation analysis indicated that Cd and Zn derived mainly from the Tunisian Chemical Group phosphogypsum. The other pollutants may originate from other industrial wastes. Metallic contamination was detected in the south of chemical complex, especially in the inter-harbor zone, where the ecological risk of surface sediments is the highest, implying potential negative impacts of industrial pollutants. The spatial distribution of pollutants seems to be due to the effect of harbor installations and coastal currents. The metallic pollution status of surface sediments of Gabes Gulf is obvious, very worrying and requires rapid intervention.

Health risk assessment for human exposure by direct ingestion of Pb, Cd, Zn bearing dust in the former miners’ village of Jebel Ressas (NE Tunisia)

Mining activity in Jebel Ressas (1880–1956) generated important quantities of wastes. The former miners’ village is expanding very close to the waste dumps which are highly concentrated in Pb, Zn and Cd. Under the semi-arid Mediterranean climate, wind erosion triggers the transport of contaminated dust towards the village. A health risk may exist for inhabitants related to their exposure to contaminated dust via ingestion, inhalation and dermal contact. This study is dedicated to the evaluation of the health risk after direct ingestion of dusts. Seven samples of dusts were collected in living places over the village. Anomalous metal concentrations in dusts range respectively from 0.16 wt% to 1.14 wt% of Pb, 0.35 wt% to 2.49 wt% of Zn and 14 to 109 mg/kg of Cd. SEM-EDS analysis of the dust particles shows that calcite is dominant and that metalliferous minerals are mainly Pb and Zn carbonates and Zn silicates. Iron oxy-hydroxides exist in small proportions and Pb and Zn sulfides are scarce. Modeling the quantity of dissolved metals in a simulated gastric fluid was performed taking into account the dust mineralogy and the daily ingested quantities of dust, ranging from 100 mg for adults to 200 mg for children. The ratio of dissolved metals to initially ingested ones defines the bioaccessibility factor. It gives the fraction of metals able to reach the blood through the intestinal wall. Modeling the dissolution of two dust samples, the most and the less concentrated ones in metals, was performed considering a gastric fluid with two extreme pH values (0.93 and 5.0). All dust minerals totally dissolve except cerussite for the most concentrated sample in a gastric fluid of pH 5. Therefore, the bioaccessibility factor of Zn and Cd is equal to 1, that of Pb ranges between 0.27 and 1. Then, an estimation of the occurrence of risk was calculated from the ratio of the daily exposure dose by direct ingestion and the reference dose. The risk occurs with a ratio above 1. The global risk of ingestion of three metals is high for the children, especially for Pb with a ratio reaching 39. The risk for adults appears for Pb with a ratio of 4.6 in the case of ingestion of most concentrated dusts. However, the integration of the other routes of exposure in the calculation of the risk must be taken into account for a thorough estimation.

Continental basinal origin of ore fluids from southwestern Massif central fluorite veins (Albigeois, France): evidence from fluid inclusion and stable isotope analyses

The most important fluorspar mining district in France is located in the Palaeozoic basement of the Albigeois in southwestern French Massif Central. The massive fluorite is hosted within large E–W striking fractures, crosscutting Cambro–Ordovician clastics, associated with large zones of hypersilicified tectonic breccia which form the wall of the mined deposits. Fluid inclusion data for pre-fluorite and fluorite stage fluids have salinities between 20–26 wt% NaCl equiv., with homogenisation temperatures between 85–170°C. Furthermore, low first ice melting temperatures (around −50°C) indicates the presence of significant CaCl2 and possibly MgCl2 together with NaCl. Calculated fluid δ18O for pre-fluorite quartz ranges from −9.1‰ to −5.2‰, with δD between −55‰ to −64‰, placing the data directly on the present day meteoric water line. Fluorite stage fluids have δ18O between +0.1‰ to +3.2‰, and δD ranging from −53‰ to −75‰, indicating an interacted meteoric fluid origin. Combining the fluid inclusion and stable isotope data illustrates that the main fluorite depositing fluid has characteristics typical of a basinal brine. The authors have no evidence that a magmatic system was involved in the deposit genesis. The proposed model highlights that mineralisation was related to major Mesozoic extensional events coinciding with the gradual opening of the Atlantic and Tethys oceans. In order to account for the chemistry of the fluids, and the siting of the deposits, the authors postulate a genetic relationship with local, continental, evaporite-bearing basins coincident with, and controlled by the E–W fractures.

Shelf to basin transition in the Cambrian-Lower Ordovician of Sardinia (Italy) reply

In southern and central Sardinia two different Cambrian-Lower Ordovician sedimentary belts occur. The former is exposed in southwestern Sardinia (Iglesiente and Sulcis), and is characterized by shallow-marine siliciclastic and carbonate sediments settled on a continental shelf with lowangle morphology. The latter, exposed in the Nappe Zone (central and southeastern Sardinia), consists of a thick monotonous sequence of siliciclastic deposits settled in a deeper-water basin.

Metal bioaccumulation in two edible cephalopods in the Gulf of Gabes, South-Eastern Tunisia: environmental and human health risk assessment

Samples of Octopus vulgaris and Sepia officinalis were collected from four areas in the Gulf of Gabes, south-eastern Tunisia, and their edible tissues (mantle and arms) were analyzed for cadmium, copper, mercury, and zinc. While the concentrations of metals showed significant differences between the sampling sites, no differences were revealed between the tissues of the two species. The spatial distribution of metals analyzed showed similar pattern for both tissues of the two species, with the highest concentrations found in the central area of Gabes Gulf, and the lowest in the northern and/or southern areas. From a human health risk point of view, the highest values of estimated daily intake, target hazard quotient, and hazard index were found in the central area of Gabes Gulf. Although the results of these indices were, in general, not alarming, the health risks posed by the consumption of cephalopods on local consumers cannot be excluded.

2D propogation of a sequence of aftershocks combining anisotropic wavelet transform and GIS

Abstract This study is based on a data set of aftershocks (location, fault-plane solutions) following the M=5.1 Arudy earthquake (02/29/80, French Western Pyrenees), and complementary geomorphological data (virtual geology using DEM and aerial photography). Data processing using Geophysical Information System are combined with identification of multi-structures based on the anisotropic wavelet formalism (NOAWC method). A local tectonic model and images of 2D propagation of the post-mainshock rupture are presented.

Le filon (Zn, F) de Peyrebrune (SW Massif central, France): caractérisation géochimique des fluides au cours du Mésozoïque à la bordure orientale du bassin d'Aquitaine

Fluid inclusion and stable isotope data on the Palaeozoic basement-hosted Peyrebrune (Zn, F) Iodedeposit (Albigeois region), indicate that mineralization originated from circulation of basinal-derived brines during distinct successive Mesozoic extensional events. These new data, set in a regional context, suggest the occurrence of two distinct evaporite-bearing sedimentary basins, now concealed by the Tertiary cover: to the south, an organic matter-rich basin leading to economic Zn-sulfide deposition, and to the north an organic matter-free basin, leading to a small Cu-sulfide deposition. During the fluorite episode, the two basins differentiate by the development of the E-W fracturation: minor in the southern basin, major in the northern one.

Characterization of phosphate rock and phosphogypsum from Gabes phosphate fertilizer factories (SE Tunisia): high mining potential and implications for environmental protection

Since the establishment of the coastal industrial complex in Gabes city (Gulf of Gabes, SE Tunisia), hundred million tons of untreated phosphogypsum have been discharged in the open sea causing serious environmental problems. To better understand the dynamic and behavior of phosphate/phosphogypsum contaminants from raw ores to marine environment, a chemical, organic, mineralogical, and morphological characterization of phosphate rock and phosphogypsum was conducted using several sophisticated techniques. The chemical analysis showed that phosphate and phosphogypsum contain high loads of trace elements and that the transfer factors of pollutants varied from 5.83% (U) to 140% (Hg). Estimated annual flows of phosphogypsum contaminants into the marine environment ranged between 0.05 (Re) and 87,249.60 (F) tons. The phosphate rock was found to be formed by carbonate fluorapatite, calcite, dolomite, natural gypsum, quartz, calcite-Mg, apatite, pyrite, fluorite, and sphalerite-Cd and phosphogypsum by synthetic gypsum and sphalerite-Cd. The phosphate was found to be richer in organic compounds compared to phosphogypsum. Based on this work, the Tunisian phosphogypsum has a high mining potential and encourages the development of an economically beneficial and environmentally friendly phosphogypsum-treating industry.

The Economic Gold Deposits of Southeast Asia, the Caraibes and the Alpine-Himalayan Fold Belts

This report surveys Tethyan gold metallogeny by reviewing the principal deposits of the Caraibes, Alps—Himalaya, and southeastern Asia segments. The objective was not to draw up an exhaustive inventory of the gold deposits during the long-lived (≈250 million years) evolution of the Tethys; only those in which gold is, or has been, industrially extracted have been considered. In these cases, the tonnage is usually greater than 5 tons, inclusive of estimated reserves when concentration still is being mined. The resulting inventory is composed of about 150 deposits belonging to the four main Tethyan segments and represents (reserves + input) about 15% (e.g., ≈13,000 tons) of world production (Bache, 1982).