Human mercury exposure associated with small-scale gold mining in Burkina Faso.

PURPOSE: In Burkina Faso, gold ore is one of the main sources of income for an important part of the active population. Artisan gold miners use mercury in the extraction, a toxic metal whose human health risks are well known. The aim of the present study was to assess mercury exposure as well as to understand the exposure determinants of gold miners in Burkinabe small-scale mines.METHODS: The examined gold miners' population on the different selected gold mining sites was composed by persons who were directly and indirectly related to gold mining activities. But measurement of urinary mercury was performed on workers most susceptible to be exposed to mercury. Thus, occupational exposure to mercury was evaluated among ninety-three workers belonging to eight different gold mining sites spread in six regions of Burkina Faso. Among others, work-related exposure determinants were taken into account for each person during urine sampling as for example amalgamating or heating mercury. All participants were medically examined by a local medical team in order to identify possible symptoms related to the toxic effect of mercury.RESULTS: Mercury levels were high, showing that 69% of the measurements exceeded the ACGIH (American Conference of Industrial Hygienists) biological exposure indice (BEI) of 35 µg per g of creatinine (µg/g-Cr) (prior to shift) while 16% even exceeded 350 µg/g-Cr. Basically, unspecific but also specific symptoms related to mercury toxicity could be underlined among the persons who were directly related to gold mining activities. Only one-third among the studied subpopulation reported about less than three symptoms possibly associated to mercury exposure and nearly half of them suffered from at least five of these symptoms. Ore washers were more involved in the direct handling of mercury while gold dealers in the final gold recovery activities. These differences may explain the overexposure observed in gold dealers and indicate that the refining process is the major source of exposure.CONCLUSIONS: This study attests that mercury exposure still is an issue of concern. North-South collaborations should encourage knowledge exchange between developing and developed countries, for a cleaner artisanal gold mining process and thus for reducing human health and environmental hazards due to mercury use.

Ecologie industrielle de l'aluminium, flux de matières et d'énergie : réalités et enjeux du recyclage

Dans les dernières années du 20ème siècle, l'aluminium a fait l'objet de beaucoup de communications outrancières et divergentes cautionnées par des scientifiques et des organismes faisant autorité. En 1986, la société PECHINEY le décrète perpétuel tel le mouvement « L'aluminium est éternel. Il est recyclable indéfiniment sans que ses propriétés soient altérées », ce qui nous avait alors irrité. Peu de temps après, en 1990, une communication tout aussi outrancière et irritante d'une grande organisation environnementale, le World Wild Fund, décrète que « le recyclage de l'aluminium est la pire menace pour l'environnement. Il doit être abandonné ». C'est ensuite à partir de la fin des années 1990, l'explosion des publications relatives au développement durable, le bien mal nommé. Au développement, synonyme de croissance obligatoire, nous préférons société ou organisation humaine et à durable, mauvaise traduction de l'anglais « sustainable », nous préférons supportable : idéalement, nous aurions souhaité parler de société durable, mais, pour être compris de tous, nous nous sommes limités à parler dorénavant de développement supportable. Pour l'essentiel, ces publications reconnaissent les très graves défauts de la métallurgie extractive de l'aluminium à partir du minerai et aussi les mérites extraordinaires du recyclage de l'aluminium puisqu'il représente moins de 10% de la consommation d'énergie de la métallurgie extractive à partir du minerai (on verra que c'est aussi moins de 10% de la pollution et du capital). C'est précisément sur le recyclage que se fondent les campagnes de promotion de l'emballage boisson, en Suisse en particulier. Cependant, les données concernant le recyclage de l'aluminium publiées par l'industrie de l'aluminium reflètent seulement en partie ces mérites. Dans les années 1970, les taux de croissance de la production recyclée sont devenus plus élevés que ceux de la production électrolytique. Par contre, les taux de recyclage, établis à indicateur identique, sont unanimement tous médiocres comparativement à d'autres matériaux tels le cuivre et le fer. Composante de l'industrie de l'aluminium, le recyclage bénéficie d'une image favorable auprès du grand public, démontrant le succès des campagnes de communication. A l'inverse, à l'intérieur de l'industrie de l'aluminium, c'est une image dévalorisée. Les opinions émises par tous les acteurs, commerçants, techniciens, dirigeants, encore recueillies pendant ce travail, sont les suivantes : métier de chiffonnier, métier misérable, métier peu technique mais très difficile (un recycleur 15 d'aluminium n'a-t-il pas dit que son métier était un métier d'homme alors que celui du recycleur de cuivre était un jeu d'enfant). A notre avis ces opinions appartiennent à un passé révolu qu'elles retraduisent cependant fidèlement car le recyclage est aujourd'hui reconnu comme une contribution majeure au développement supportable de l'aluminium. C'est bien pour cette raison que, en 2000, l'industrie de l'aluminium mondiale a décidé d'abandonner le qualificatif « secondaire » jusque là utilisé pour désigner le métal recyclé. C'est en raison de toutes ces données discordantes et parfois contradictoires qu'a débuté ce travail encouragé par de nombreuses personnalités. Notre engagement a été incontestablement facilité par notre connaissance des savoirs indispensables (métallurgie, économie, statistiques) et surtout notre expérience acquise au cours d'une vie professionnelle menée à l'échelle mondiale dans (recherche et développement, production), pour (recherche, développement, marketing, stratégie) et autour (marketing, stratégie de produits connexes, les ferro-alliages, et concurrents, le fer) de l'industrie de l'aluminium. Notre objectif est de faire la vérité sur le recyclage de l'aluminium, un matériau qui a très largement contribué à faire le 20ème siècle, grâce à une revue critique embrassant tous les aspects de cette activité méconnue ; ainsi il n'y a pas d'histoire du recyclage de l'aluminium alors qu'il est plus que centenaire. Plus qu'une simple compilation, cette revue critique a été conduite comme une enquête scientifique, technique, économique, historique, socio-écologique faisant ressortir les faits principaux ayant marqué l'évolution du recyclage de l'aluminium. Elle conclut sur l'état réel du recyclage, qui se révèle globalement satisfaisant avec ses forces et ses faiblesses, et au-delà du recyclage sur l'adéquation de l'aluminium au développement supportable, adéquation largement insuffisante. C'est pourquoi, elle suggère les thèmes d'études intéressant tous ceux scientifiques, techniciens, historiens, économistes, juristes concernés par une industrie très représentative de notre monde en devenir, un monde où la place de l'aluminium dépendra de son aptitude à satisfaire les critères du développement supportable. ABSTRACT Owing to recycling, the aluminium industry's global energetic and environmental prints are much lower than its ore extractive metallurgy's ones. Likewise, recycling will allow the complete use of the expected avalanche of old scraps, consequently to the dramatic explosion of aluminium consumption since the 50's. The recycling state is characterized by: i) raw materials split in two groups :one, the new scrap, internal and prompt, proportional to semi-finished and finished products quantities, exhibits a fairly good and regular quality. The other, the old scrap, proportional to the finished products arrivïng at their end-of--life, about 22 years later on an average, exhibits a variable quality depending on the collect mode. ii) a poor recycling rate, near by that of steel. The aluminium industry generates too much new internal scrap and doesn't collect all the availa~e old scrap. About 50% of it is not recycled (when steel is recycling about 70% of the old scrap flow). iii) recycling techniques, all based on melting, are well handled in spite of aluminium atiiníty to oxygen and the practical impossibility to purify aluminium from any impurity. Sorting and first collect are critical issues before melting. iv) products and markets of recycled aluminium :New scraps have still been recycled in the production lines from where there are coming (closed loop). Old scraps, mainly those mixed, have been first recycled in different production lines (open loop) :steel deoxidation products followed during the 30's, with the development of the foundry alloys, by foundry pieces of which the main market is the automotive industry. During the 80's, the commercial development of the beverage can in North America has permitted the first old scrap recycling closed loop which is developing. v) an economy with low and erratic margins because the electrolytic aluminium quotation fixes scrap purchasing price and recycled aluminium selling price. vi) an industrial organisation historically based on the scrap group and the loop mode. New scrap is recycled either by the transformation industry itself or by the recycling industry, the remelter, old scrap by the refiner, the other component of the recycling industry. The big companies, the "majors" are often involved in the closed loop recycling and very seldom in the open loop one. To-day, aluminium industry's global energetic and environmental prints are too unbeara~ e and the sustainaЫe development criteria are not fully met. Critical issues for the aluminium industry are to better produce, to better consume and to better recycle in order to become a real sustainaЫe development industry. Specific issues to recycling are a very efficient recycling industry, a "sustainaЫe development" economy, a complete old scrap collect favouring the closed loop. Also, indirectly connected to the recycling, are a very efficient transformation industry generating much less new scrap and a finished products industry delivering only products fulfilling sustainaЫe development criteria.

Reliability of stable carbon and oxygen isotope compositions of pedogenic needle fibre calcite as environmental indicators: examples from Western Europe.

Stable carbon and oxygen isotope analyses were conducted on pedogenic needle fibre calcite (NFC) from seven sites in areas with roughly similar temperate climates in Western Europe, including the Swiss Jura Mountains, eastern and southern France, northern Wales, and north-eastern Spain. The δ(13)C values (-12.5 to-6.8 0/00 Vienna Pee Dee Belemnite (VPDB)) record the predominant C(3) vegetation cover at the sites. A good correlation was found between mean monthly climatic parameters (air temperature, number of frost days, humidity, and precipitation) and δ(18)O values (-7.8 to-3.40/00 VPDB) of all the NFC. Similar seasonal variations of δ(18)O values for monthly NFC samples from the Swiss sites and those of mean monthly δ(18)O values of local precipitation and meteorological data point out precipitation and preferential growth/or recrystallisation of the pedogenic needle calcite during dry seasons. These covariations indicate the potential of stable isotope compositions of preserved NFC in fossil soil horizons as a promising tool for palaeoenvironmental reconstructions.

The hypogene iron oxide copper-gold mineralization in the Mantoverde District, Northern Chile

The Mantoverde iron oxide copper-gold (IOCC) district, northern Chile, is known for its Cu production from supergene ores. Recently, exploration outlined an additional hypogene ore resource of 440 Mt with 0.56 percent Cu, and 0.12 g/t An. The hypogene sulfide mineralization occurs mainly as chalcopyrite and pyrite, typically in specularite or magnetite-cemented breccias and associated stockworks. The host rocks underwent variably intense K feldspar alteration, chloritization, sericitization, silicification, and/or carbonatization. A district scale Na(-Ca) alteration is absent. The IOCC mineralization in the district shows a strong tectonic control by northwest- to north-northwest-trending brittle structures. Large Cu sulfide-rich veins or Cu sulfide-cemented breccias are absent. Therefore, head grades of 4 percent Cu are an exception. There is a positive correlation between Cu and An grades. Gold is probably contained mostly in chalcopyrite and pyrite. Elevated concentrations of light rare-earth elements (LREE) occur locally but are attributed to redistribution of LREE within the deposits rather than to derivation from external sources. The Cu-Au ores in the Mantoverde district are low in and have relatively low contents in heavy metals that are potentially hazardous to the environment, such as As (avg 14 ppm), Hg (<5 ppm), or Cd (<0.2 ppm). The sulfur isotope ratios of chalcopyrite from the IOCC deposits lie between -5.6 and 8.9 per mil delta(34)S(VCDT). They show systematic variations within the district, which are interpreted to reflect relative distance to inferred fluid conduits and the level of deposition within the hydrothermal system. Most initial (87)Sr/(86)Sr values of altered volcanic rocks and hydrothermal calcite from the Mantoverde district are between 0.7031 and 0.7060 and are similar to those of the igneous rocks of the region. Lead isotope ratios of chalcopyrite are consistent with Pb (and by inference Cu) derived from Early Cretaceous magmatism. The sulfur, strontium, and lead isotope data of chalcopyrite, calcite gangue, or altered host rocks, respectively, are compatible with a genetic model that involves cooling of metal and sulfur-bearing magmatic-hydrothermal fluids that mix with meteoric waters or seawater at relatively shallow crustal levels. An additional exotic sulfur input is likely, though not required, for the copper mineralization. Apart from the IOCC. deposits, there are a number of smaller magnetite(-apatite) bodies in the district. These are geologically similar to the Cu-Au-bearing magnetite bodies, but are related to splays of the north-south-trending Atacama fault zone and differ in alteration and texture.

Sr, C and O isotope systematics in the Pucara Basin, central Peru - Comparison between Mississippi Valley-type deposits and barren areas

A combined Sr, O and C isotope study has been carried out in the Pucara basin, central Peru, to compare local isotopic trends of the San Vicente and Shalipayco Zn-Pb Mississippi Valley-type (MVT) deposits with regional geochemical patterns of the sedimentary host basin. Gypsum, limestone and regional replacement dolomite yield Sr-87/Sr-86 ratios that fall within or slightly below the published range of seawater Sr-87/Sr-86 values for the Lower Jurassic and the Upper Triassic. Our data indicate that the Sr isotopic composition of seawater between the Hettangian and the Toarcian may extend to lower Sr-87/Sr-86 ratios than previously published values. An Sr-87-enrichment is noted in (1) carbonate rocks from the lowermost part of the Pucara basin, and (2) different carbonate generations at the MVT deposits. This indicates that host rocks at MVT deposits and in the lowermost part of the carbonate sequence interacted with Sr-87-enriched fluids. The fluids acquired their radiogenic nature by interaction with lithologies underlying the carbonate rocks of the Pucara basin. The San Ramon granite, similar Permo-Triassic intrusions and their elastic derivatives in the Mitu Group are likely sources of radiogenic Sr-87. The Brazilian shield and its erosion products are an additional potential source of radiogenic Sr-87. Volcanic rocks of the Mitu Group are not a significant source for radiogenic Sr-87; however, molasse-type sedimentary rocks and volcaniclastic rocks cannot be ruled out as a possible source of radiogenic Sr-87. The marked enrichment in Sr-87 of carbonates toward the lower part of the Pucara Group is accompanied by only a slight decrease in delta(18)O values and essentially no change in delta(13)C values, whereas replacement dolomite and sparry carbonates at the MVT deposits display a coherent trend of progressive Sr-87-enrichment, and O-18- and C-13-depletion. The depletion in O-18 in carbonates from the MVT deposits are likely related to a temperature increase, possibly coupled with a O-18-enrichment of the ore-forming fluids. Progressively lower delta(13)C values throughout the paragenetic sequence at the MVT deposits are interpreted as a gradually more important contribution from organically derived carbon. Quantitative calculations show that a single fluid-rock interaction model satisfactorily reproduces the marked Sr-87-enrichment and the slight decrease in delta(18)O values in carbonate rocks from the lower part of the Pucara Group. By contrast, the isotopic covariation trends of the MVT deposits are better reproduced by a model combining fluid mixing and fluid-rock interaction. The modelled ore-bearing fluids have a range of compositions between a hot, saline, radiogenic brine that had interacted with lithologies underlying the Pucara sequence and cooler, dilute brines possibly representing local fluids within the Pucara sequence. The composition of the local fluids varies according to the nature of the lithologies present in the neighborhood of the different MVT deposits. The proportion of the radiogenic fluid in the modelled fluid mixtures interacting with the carbonate host rocks at the MVT deposits decreases as one moves up in the stratigraphic sequence of the Pucara Group.

Sulfur speciation and stable isotope trends of water-soluble sulfates in mine tailings profiles

Sulfur speciation and the sources of water-soluble sulfate in three oxidizing sulfidic mine tailings impoundments were investigated by selective dissolution and stable isotopes. The studied tailings impoundments-Piuquenes, Cauquenes, and Salvador No. 1-formed from the exploitation of the Rio Blanco/La Andina, El Teniente, and El Salvador Chilean porphyry copper deposits, which are located in Alpine, Mediterranean, and hyperarid climates, respectively. The water-soluble sulfate may originate from dissolution of primary ore sulfates (e.g., gypsum, anhydrite, jarosite) or from oxidation of sulfide minerals exposed to aerobic conditions during mining activity. With increasing aridity and decreasing pyrite content of the tailings, the sulfur speciation in the unsaturated oxidation zones showed a trend from dominantly Fe(Ill) oxyhydroxide fixed sulfate (e.g., jarosite and schwertmannite) in Piuquenes toward increasing presence of water-soluble sulfate at Cauquenes and Salvador No. 1. In the saturated primary zones, sulfate is predominantly present in water-soluble form (mainly as anhydrite and/or gypsum). In the unsaturated zone at Piuquenes and Cauquenes,the delta(34)S(S04) values ranged from +0.5 parts per thousand to +2.0 parts per thousand and from -0.4 parts per thousand to +1.4 parts per thousand Vienna Canyon Diablo Troilite (V-CDT), respectively, indicating a major sulfate source from pyrite oxidation (delta(34)S(pyrite) -1.1 parts per thousand and -0.9 parts per thousand). In the saturated zone at Piuquenes and Cauquenes, the values ranged from -0.8%. to +0.3 parts per thousand and from +2.2 parts per thousand to +3.9 parts per thousand, respectively. At Cauquenes the 34 S enrichment in the saturated zone toward depth indicates the increasing contribution of isotopically heavy dissolved sulfate from primary anhydrite (similar to+10.9%o). At El Salvador No. 1, the delta(34)S(SO4) average value is -0.9 parts per thousand, suggesting dissolution of supergene sulfate minerals (jarosite, alunite, gypsum) with a delta(34)S similar to -0.7 parts per thousand as the most probable sulfate source. The gradual decrease Of delta(18)O(S04) values from the surface to the oxidation front in the tailings impoundments at Piuquenes (from -4.5 parts per thousand to -8.6 parts per thousand Vienna Standard Mean Ocean Water, V-SMOW) and at Cauquenes (from -1.3 parts per thousand to -3.5 parts per thousand) indicates the increasing importance of ferric iron as the main electron acceptor in the oxidation of pyrite. The different delta(18)O(SO4) values between the tailings impoundments studied here reflect the local climates.

Better 6 months outcome for steroid refractory ulcerative colitis with infliximab rescue therapy compared to tacrolimus or cyclosporine: a Swiss IBD cohort retrospective analysis

BACKGROUND: C iclosporine ( CsA), Tacrolimus (Tcl) and Infliximab (IFX) are effective rescue therapies in steroidrefractory ulcerative colitis (UC). Comparative studies are however m issing. M ETHOD: T his i s the retrospective analysis of treatment outcome for oral Tcl (n=27, initially 0.05mg/Kg twice daily, aiming for serum trough levels of 5-10 n g/mL), i ntravenous C sA ( n=23, 2 mg/kg/daily a nd then o ral CsA 5mg/kg/daily) and IFX ( n=43, 5 mg/kg intravenously at week 0, 2, 6 and then every 8 weeks) in patients with s teroid r efractory moderate to s evere UC enrolled i n the SWISS IBD cohort s tudy. After successful rescue therapy with Tcl o r C sA, t hiopurine m aintenance therapy or maintenance therapy with Tcl (in Tcl pretreated patients) was introduced. The endpoints analyzed steroid free r emission r ate (on the basis of m odified Truelove- Witts severity index (MTWSI)) and number of colectomies after 6 m onths. R ESULTS: A t 6 months, 26% ( 7/27) o f patients treated with T cl r emained i n steroid free remission (MTWSI score ≤4) compared to 30 % (7/23) on 18 droplets to the same extend under the linoleic acid treat, whereas lipid hydrolysis or loss was significantly increased in Huh-7 WT cells after 24h. Conclusions: Chronic alcohol feeding in obese, insulin-resistant rats exerts significant and synergistic effects on PNPLA3 mRNA expression, which correlated with triglyceride content. In v itro experiments suggest that PNPLA3 expression depends on the t ypes of d ietary f atty acids with polyunsaturated fatty a cids i nducing a nd monounsaturated fatty a cids inhibiting PNPLA3 mRNA. I148M polymorphism of PNPLA3 l eads to attenuation o f lipolytic processes resulting in fat accumulation in the cell. 20 CsA and 58% ( 27/41) o f patients t reated w ith IFX ( Tcl & CsA vs I FX p = 0 .018). S ignificant m ore patients had primary non response, loss of response or severe adverse events i n the CsA cohort ( 61%, 1 4/23) c ompared to Tcl cohort (33.3 % , 9/27), and IFX cohort (30%, 1 3/43) (p= 0.037). Colectomy rate was significantly higher after CsA (17.4 %, 4/23) compared to Tcl (3.7 %, 1/27) or IFX (2.3 %, 1/43) (p= 0.047).CONCLUSION: After s ix m onth, rescue therapy with I FX h ad t he l owest c olectomy r ate, significantly h igher steroid free r emission rate, a nd t he lowest rate of non-response, loss of response and severe adverse events compared to CsA or Tcl rescue treatment.

Geological setting of the Guelb Moghrein Fe oxide-Cu-Au-Co mineralization, Akjoujt area, Mauritania

The Guelb Moghrein Fe oxide-Cu-Au-Co deposit is located at the western boundary of the West African craton in NW Mauritania. The wall rocks to the mineralization represent a meta-volcanosedimentary succession typical of Archaean greenstone belts. Two types of meta-volcanic rocks are distinguished: (1) volcanoclastic rocks of rhyodacite-dacite composition (Sainte Barbe volcanic unit), which form the stratigraphic base; (2) tholeiitic andesites-basalts (Akjoujt meta-basalt unit). The trace element signature of both types is characteristic of a volcanic arc setting. A small meta-pelitic division belongs to the Sainte Barbe volcanic unit. A meta-carbonate body, which contains the mineralization, forms a tectonic lens in the Akjoujt meta-basalt unit. It can be defined by the high X(mg) (=36) of Fe-Mg carbonate, the REE pattern and the delta(13)C values of -18 to -17 parts per thousand as a marine precipitate similar to Archaean banded iron formation (BIF). Additionally, small slices of Fe-Mg clinoamphibole-chlorite schist in the meta-carbonate show characteristics of marine shale. This assemblage, therefore, does not represent an alteration product, but represents an iron formation unit deposited on a continental shelf, which probably belongs to the Lembeitih Formation. The hydrothermal mineralization at 2492 Ma was contemporaneous with regional D(2) thrusting of the Sainte Barbe volcanic unit and imbrications of the meta-carbonate in the upper greenschist facies. This resulted in the formation of an ore breccia in the meta-carbonate, which is enriched in Fe, Ni, Co, Cu, Bi, Mo, As and Au. Massive sulphide ore breccia contains up to 20 wt% Cu. The ore fluid was aqueous-carbonic in nature and either changed its composition from a Mg-rich oxidizing to an Fe-rich reducing fluid or the two fluid types mixed at the trap site. All lithologies at Guelb Moghrein were deformed by D(3) thrusting to the east in the lower greenschist facies. The mobility of REE in the retrogressed rocks explains the formation of a second generation of hydrothermal monazite, which was dated at c. 1742 Ma. Archaean rocks of the West African craton extend to the west to Guelb Moghrein. The active continental margin was deformed and mineralized in the Late Archaean-Early Proterozoic and again reactivated in the Mid-Proterozoic and Westphalian, showing that the western boundary of the craton was reactivated several times.

Bitumens in the late Variscan hydrothermal vein-type uranium deposit of Pribram, Czech Republic: Sources, radiation-induced alteration, and relation to mineralization

The late Variscan (275-278 Ma) Pribram uranium deposit is one of the largest known accumulations of uraniferous bitumens in hydrothermal veins. The deposit extends along the northwestern boundary of the Central Bohemian pluton (345-335 Ma) with low-grade metamorphosed Late Proterozoic and unmetamorphosed Cambrian rocks. From a net uranium production of 41,742 metric tons (t), more than 6,000 t were extracted from bitumen-uraninite ores during 43 years of exploration and mining. Three morphological varieties of solid bitumen are recognized: globular, asphaltlike, and cokelike. While the globular bitumen is uranium free, the other two types are uraniferous. The amount of bitumen in ore veins gradually decreases toward the contact with the plutonic body and increases with depth. Two types of bitumen microtextures are recognized using high-resolution transmission electron microscopy: amorphous and microporous, the former being less common in uraniferous samples. A lower Raman peak area ratio (1,360/1,575 cm(-1)) in mineralized bitumens (0.9) compared with uranium-free samples (2.0) indicates a lower degree of microtextural organization in the latter The H/C and O/C atomic ratios in uranium-free bitumens (0.9-1.1 and 0.09, respectively) are higher than those in mineralized samples (H/C = 0.3-0.8, O/C = 0.03-0.09). The chloroform extractable matter yield is Very low in uranium-free bitumens (0.30-0.35% of the total organic carbon,TOC) and decreases with uranium content increase. The extracted solid uraniferous bitumen infrared spectra show depletion in aliphatic CH2 and CH3 groups compared to uranium-free samples. The concentration of oxygen-bearing functional groups relative to aromatic bonds in the IR spectra of uranium-free and mineralized bitumen, however, do not differ significantly. C-13 NMR confirmed than the aromaticity of a uraniferous sample is higher (F-ar = 0.61) than in the uranium-free bitumen (F-ar = 0.51). Pyrolysates from uraniferous and nonuraniferous bitumens do not differ significantly, being predominantly cresol, alkylphenols, alkylbenzenes, and alkylnaphthalenes. The liquid pyrolysate yield decreases significantly with increasing uranium content. The delta(13)C Values of bulk uranium-free bitumens and low-grade uraniferous, asphaltlike bitumens range from -43.6 to 52.3 per mil. High-grade, cokelike, uraniferous bitumens are more C-13 depleted (54.5 to -58.4 parts per thousand). In contrast to the very light isotopic ratios of the high-grade uraniferous cokelike bitumen bulk carbon, the individual n-alkanes and isoprenoids (pristane and phytane) extracted from the same sample are significantly C-13 enriched. The isotopic composition of the C13-24 n-alkanes extracted from the high-grade uraniferous sample (delta(13)C = -28.0 to 32.6 parts per thousand) are heavier compared with the same compounds in a uranium-free sample (delta(13)C = 31.9 to 33.8 parts per thousand). It is proposed that the bitumen source was the isotopically light (delta(13)C = 35.8 to 30.2 parts per thousand) organic matter of the Upper Proterozoic host rocks that were pyrolyzed during intrusion of the Central Bohemian pluton. The C-13- depleted pyrolysates were mobilized from the innermost part of the contact-metamorphic aureole, accumulated in structural traps in less thermally influenced parts of the sedimentary complex and were later extracted by hydrothermal fluids. Bitumens at the Pribram deposit are younger than the main part of the uranium mineralization and were formed through water-washing and radiation-induced polymerization of both the gaseous and liquid pyrolysates. Direct evidence for pyrolysate reduction of uranium in the hydrothermal system is difficult to obtain as the chemical composition of the original organic fluid phase was modified during water-washing and radiolytic alteration. However, indirect evidence-e.g., higher O/C atomic ratios in uranium-free bitumens (0.1) relative to the Upper Proterozoic source rocks (0.02-0.05), isotopically very light carbon in associated whewellite (delta(13)C = 31.7 to -28.4 parts per thousand), and the striking absence of bitumens in the pre-uranium, hematite stage of the mineralization-indicates that oxidation of organic fluids may have contributed to lowering of aO(2) and uraninite precipitation.

Organic and inorganic geochemistry of Ljubija siderite deposits, NW Bosnia and Herzegovina

The Ljubija siderite deposits, hosted by a Carboniferous sedimentary complex within the Inner Dinarides, occur as stratabound replacement-type ore bodies in limestone blocks and as siderite-sulfides veins in shale. Three principal types of ore textures have been recognized including massive dark siderite and ankerite, siderite with zebra texture, and siderite veins. The ore and host rocks have been investigated by a combination of inorganic (major, trace, and rare earth element concentrations), organic (characterization of hydrocarbons including biomarkers), and stable isotope geochemical methods (isotope ratios of carbonates, sulfides, sulfates, kerogen, and individual hydrocarbons). New results indicate a marine origin of the host carbonates and a hydrothermal-metasomatic origin of the Fe mineralization. The differences in ore textures (e.g., massive siderite, zebra siderite) are attributed to physicochemical variations (e.g., changes in acidity, temperature, and/or salinity) of the mineralizing fluids and to the succession and intensity of replacement of host limestone. Vein siderite was formed by precipitation from hydrothermal fluids in the late stage of mineralization. The equilibrium fractionation of stable isotopes reveals higher formation temperatures for zebra siderites (around 245A degrees C) then for siderite vein (around 185A degrees C). Sulfur isotope ratios suggest Permian seawater or Permian evaporites as the main sulfur source. Fluid inclusion composition confirms a contribution of the Permian seawater to the mineralizing fluids and accord with a Permian mineralization age. Organic geochemistry data reflect mixing of hydrocarbons at the ore site and support the hydrothermal-metasomatic origin of the Ljubija iron deposits.

Origin of mineralizing fluids of the sediment-hosted Navachab gold mine, Namibia: Constraints from stable (O, H, C, S) isotopes

The Navachab gold mine in the Damara belt of central Namibia is characterized by a polymetallic Au-Bi-As-Cu-Ag ore assemblage, including pyrrhotite, chalcopyrite, sphalerite, arsenopyrite, bismuth, gold, bismuthinite, and bismuth tellurides. Gold is hosted by quartz sulfide veins and semimassive sulfide lenses that are developed in a near-vertical sequence of shelf-type metasedimentary rocks, including marble, calcsilicate rock, and biotite schist. The sequence has been intruded by abundant syntectonic lamprophyre, aplite, and pegmatite dikes, documenting widespread igneous activity coeval with mineralization. The majority of quartz from the veins has delta(18)O values of 14 to 15 per mil (V-SMOW). The total variations in delta(18)O values of the biotite schist and calcsilicate rock are relatively small (12-14 parts per thousand), whereas the marble records steep gradients in delta(18)O values (17-21 parts per thousand), the lowest values being recorded at the vein margins. Despite this, there is no correlation between delta(18)O and delta(13)C values and the carbonate content of the rocks, indicating that fluid-rock interaction alone cannot explain the isotopic gradients. In addition, the marble records increased delta(13)C values at the contact to the veins, possibly related to a change in the physicochemical conditions during fluid-rock interaction. Gold is interpreted to have precipitated in equilibrium with metamorphic find (delta(18)O 12-14 parts per thousand; delta D = -40 to -60 parts per thousand) at peak metamorphic conditions of ca. 550 degrees C and 2 kbars, consistent with isotopic fractionations between coexisting calcite, garnet, and clinopyroxene in the alteration halos. The most likely source of the mineralizing fluid was a midcrustal fluid in equilibrium with the Damaran metapelites that underwent prograde metamorphism at amphibolite- to granulite-facies grades. Although there is no isotopic evidence for the contribution of magmatic fluids, they may have been important in contributing to the overall hydraulic regime and high apparent geothermal gradients (ca. 80 degrees C/km(-1)) in the mine area.

"La vie et l'oeuvre"? : Recherches sur le biographique : Actes du colloque de relève organisé à l'Université de Lausanne les 8-9 novembre 2007

La réflexion sur la biographie a connu un renouvellement important ces vingt dernières années dans plusieurs disciplines. Florissant sur le marché ditorial, ce genre ancien trouve aujourd'hui des formes nouvelles, nourries de la galaxie des sciences humaines contemporaines, comme en témoigne l'ouvrage de François Dosse, Le Pari biographique (La Découverte, 2005). Genre fondateur en histoire de l'art, la biographie est pratiquée peu ou prou dans la plupart des disciplines des lettres. Bonne raison pour se pencher de manière interdisciplinaire sur le genre et sa pratique. La vogue des éloges académiques au XVIIIe siècle, et la profusion du discours biographique sur les artistes à l'orée du Romantisme ont ouvert la voie à la fameuse «méthode biographique» de Sainte-Beuve, et à sa reconversion dans les programmes d'enseignement, par le biais de Gustave Lanson et de ses émules. Inculqué à des générations d'élèves, devenu une structure invisible de l'entendement universitaire dans les disciplines littéraires, le couple « la vie et l'oeuvre » a été sévèrement reconsidéré, au XXe siècle, par les approches formalistes, structuralistes ou sociologiques. Qu'en est-il de ce genre actuellement? Comment les travaux de littéraires, d'historiens, d'historiens de l'art, de philosophes envisagent-ils les données biographiques?

Unravelling the enigmatic origin of calcitic nanofibres in soils and caves: purely physicochemical or biogenic processes?

Calcitic nanofibres are ubiquitous habits of sec- ondary calcium carbonate (CaCO3 ) accumulations observed in calcareous vadose environments. Despite their widespread occurrence, the origin of these nanofeatures remains enig- matic. Three possible mechanisms fuel the debate: (i) purely physicochemical processes, (ii) mineralization of rod-shaped bacteria, and (iii) crystal precipitation on organic templates. Nanofibres can be either mineral (calcitic) or organic in na- ture. They are very often observed in association with needle fibre calcite (NFC), another typical secondary CaCO3 habit in terrestrial environments. This association has contributed to some confusion between both habits, however they are truly two distinct calcitic features and their recurrent asso- ciation is likely to be an important fact to help understanding the origin of nanofibres. In this paper the different hypotheses that currently exist to explain the origin of calcitic nanofibres are critically reviewed. In addition to this, a new hypothe- sis for the origin of nanofibres is proposed based on the fact that current knowledge attributes a fungal origin to NFC. As this feature and nanofibres are recurrently observed together, a possible fungal origin for nanofibres which are associated with NFC is investigated. Sequential enzymatic digestion of the fungal cell wall of selected fungal species demonstrates that the fungal cell wall can be a source of organic nanofibres. The obtained organic nanofibres show a striking morpho- logical resemblance when compared to their natural coun- terparts, emphasizing a fungal origin for part of the organic nanofibres observed in association with NFC. It is further hy- pothesized that these organic nanofibres may act as templates for calcite nucleation in a biologically influenced mineraliza- tion process, generating calcitic nanofibres. This highlights the possible involvement of fungi in CaCO3 biomineraliza- tion processes, a role still poorly documented. Moreover, on a global scale, the organomineralization of organic nanofi- bres into calcitic nanofibres might be an overlooked process deserving more attention to specify its impact on the biogeo- chemical cycles of both Ca and C.

Two-stage, extreme albitization of A-type granites from Rajasthan, NW India

Albitization is a common process during which hydrothermal fluids convert plagioclase and/or K-feldspar into nearly pure albite; however, its specific mechanism in granitoids is not well understood. The c. 1700 Ma A-type metaluminous ferroan granites in the Khetri complex of Rajasthan, NW India, have been albitized to a large extent by two metasomatic fronts, an initial transformation of oligoclase to nearly pure albite and a subsequent replacement of microcline by albite, with sharp contacts between the microcline-bearing and microcline-free zones. Albitization has bleached the original pinkish grey granite and turned it white. The mineralogical changes include transformation of oligoclase (similar to An(12)) and microcline (similar to Or(95)) to almost pure albite (similar to An(0 center dot 5-2)), amphibole from potassian ferropargasite (X-Fe 0 center dot 84-0 center dot 86) to potassic hastingsite (X-Fe 0 center dot 88-0 center dot 97) and actinolite (X-Fe 0 center dot 32-0 center dot 67), and biotite from annite (X-Fe 0 center dot 71-0 center dot 74) to annite (X-Fe 0 center dot 90-0 center dot 91). Whole-rock isocon diagrams show that, during albitization, the granites experienced major hydration, slight gain in Si and major gain in Na, whereas K, Mg, Fe and Ca were lost along with Rb, Ba, Sr, Zn, light rare earth elements and U. Whole-rock Sm-Nd isotope data plot on an apparent isochron of 1419 +/- 98 Ma and reveal significant disturbance and at least partial resetting of the intrusion age. Severe scatter in the whole-rock Rb-Sr isochron plot reflects the extreme Rb loss in the completely albitized samples, effectively freezing Sr-87/Sr-86 ratios in the albite granites at very high values (0 center dot 725-0 center dot 735). This indicates either infiltration of highly radiogenic Sr from the country rock or, more likely, radiogenic ingrowth during a considerable time lag (estimated to be at least 300 Myr) between original intrusion and albitization. The albitization took place at similar to 350-400 degrees C. It was caused by the infiltration of an ascending hydrothermal fluid that had acquired high Na/K and Na/Ca ratios during migration through metamorphic rocks at even lower temperatures in the periphery of the plutons. Oxygen isotope ratios increase from delta O-18 = 7 parts per thousand in the original granite to values of 9-10 parts per thousand in completely albitized samples, suggesting that the fluid had equilibrated with surrounding metamorphosed crust. A metasomatic model, using chromatographic theory of fluid infiltration, explains the process for generating the observed zonation in terms of a leading metasomatic front where oligoclase of the original granite is converted to albite, and a second, trailing front where microcline is also converted to albite. The temperature gradients driving the fluid infiltration may have been produced by the high heat production of the granites themselves. The confinement of the albitized granites along the NE-SW-trending Khetri lineament and the pervasive nature of the albitization suggest that the albitizing fluids possibly originated during reactivation of the lineament. More generally, steady-state temperature gradients induced by the high internal heat production of A-type granites may provide the driving force for similar metasomatic and ore-forming processes in other highly enriched granitoid bodies.