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Resume Les etudes gitologiques comparees de deux placers francais a silice ultrapure pour l'electrometallurgie du silicium et du ferro-silicium de classe europeenne, les gisements de Boudeau en Dordogne et de Thedirac dans le Lot, montrent une forte similitude en ce qui concerne les sources potentielles et le mode de transport des galets de quartz, tandis qu'un meme processus de karstification sous couverture comme facteur determinant dans la formation des gisements est observe. La principale difference reside dans le nombre d'etapes necessaires a la constitution du piege. Cette etude comparative a permis la constitution de modeles dynamiques pour la genese de ces concentrations economiques. Pour citer cet article : L. Desindes et al., C. R. Geoscience 337 (2005).

The Sando Alcalde ore deposit (southwestern Peru) has been studied in order to characterize the physicochemical parameters of the ore fluids and to determine the fluid process (mixing or boiling) which involves the precious metal mineralization. Mineralogy, δ18Oquartz isotopic values and fluid inclusion data give arguments in favour of a boiling phenomenon. This conclusion corroborates fluid inclusion studies previously performed in this area on the low-sulphidation epithermal deposits of Arcata, Orcopampa and Apacheta, where boiling has been described as the main factor for ore deposition. To cite this article: A.-S. Andre-Mayer et al., C. R. Geoscience 337 (2005).

We report here the transformation of aldehydes to their (Z)-α-fluoro-α,β-unsaturated aldehyde homologs by condensation with the phosphonium salt of the Meyer’s oxazine obtained from bromofluoroacetonitrile. After methylation with trimethyloxonium tetrafluoroborate the quaternized oxazine is cleanly reduced to mostly Z 2-fluoro-2-alkenals by sodium borohydride at room temperature. This methodology is compatible with usual protecting groups and affords an efficient access to functionalized mostly Z 2-fluoro-2-alkenals derived from natural products and their corresponding (Z)-2-fluoro-2-alkenols.

An efficient synthesis of 2,3,5,6-tetrafluoro-4-iodo-benzaldehyde ( 1 ) is presented. This new compound was readily obtained via iodination at low temperature of the lithio derivative of 2-(2,3,5,6-tetrafluoro-phenyl)-[1,3]dioxolane ( 4 ). The crystal structure of 1 consists of linear polymeric chains, with non-covalent O⋯I bonding as the directing interaction, responsible for the observed assembly. Aldehyde 1 is further employed in the synthesis of 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin ( 6 ), a potential precursor of supramolecular assemblies.

The Bolcana ore deposit (Metaliferi Mountains, western Romania) is a porphyry ore deposit with associated epithermal veins. On the basis of different parageneses, four alteration types were distinguished: potassic, phyllic, argillic and propylitic. The mineralogical and geochemical data and estimated crystallisation temperatures of alteration minerals indicate an evolution of the system from an early period of porphyry type mineralisation (Cu+Au) to a late period of low-sulphidation epithermal mineralisation (Au+base metal). To cite this article: V. Milu et al., C. R. Geoscience 335 (2003).

We chose one silicic center (Danesti dacitic dome) to characterize the magmas associated with hydrothermal ore-formingsystems before fluid extraction from the melt and hydrothermal alteration, in the major gold/polymetallic Baia Mare province (Romania). Interpretation of melt inclusion data indicates that the dacites were derived from potassium-enriched, metaluminous magmas. We suggest that the aluminous character of the residual melt (trapped as melt inclusions) may play a role in the oreforming processes, as the chemistry of these melts controls the composition of evolving magmatic-hydrothermal fluid. The study of the geochemical features of silicate melt inclusions and the determination of their water contents using the recently developed Raman spectroscopy method, also reveals that the decompression was the dominant driving force for the crystallization at this silicic center.

Careful analysis of fully and partially β-fluorinated dicationic porphyrins have been performed suggesting an electronic influence of the β-fluorine atoms on the extent of the macrocycle deformation, in agreement with the crystal structure of β-octafluoro- meso -tetraphenylporphyrin dication.

The synthesis of partially β-fluorinated meso -tetraphenylporphyrins using Lindsey conditions, has been examined, starting either from 3,4-difluoro-1 H -pyrrole or from 3-fluoro-1 H -pyrrole. In the case of the first synthon, condensation with pyrrole and benzaldehyde afforded a mixture of porphyrins of general formula β-F n TPP ( n =0,2,4,6,8) displaying linearly correlated spectroscopic and electrochemical properties. With the second synthon, condensation with benzaldehyde produced an unresolvable mixture of β-tetrafluoroporphyrins presenting spectroscopic and electrochemical properties in coherence with those observed in the first case. Preliminarily, the synthesis and isolation of the hitherto unknown 3-fluoro-1 H -pyrrole has been approached via several methods.

Characterization of the genetic relations between magma suites and associated gold/base metal hydrothermal deposits is imperative to our understanding of the role of magmas in the mineralization process. Melt inclusions trapped in igneous phenocrysts were used to characterize calc–alkaline magmas associated with Valea Morii porphyry–copper deposit, Romania. A comparative study of mineralized intrusion versus barren intrusion reveals parameters that may influence the magmatic–hydrothermal connection. The present results emphasize the importance of the chemistry of residual melts (trapped in magmatic inclusions) rather than bulk magma compositions (derived from whole rock analysis) in determining the metal concentration in released magmatic fluid.

The Valea Morii Cu–Au ore deposit (Apuseni mountains, Romania) is characterised by a spatial association of a porphyry copper (Cu±Au) with a low-sulfidation epithermal deposit (Au). Microthermometric and sulphur isotopic data, obtained on both porphyry and epithermal veins, express a telescoping between these two types of mineralization, which can be explained either by an erosion phenomenon during the hydrothermal activity or by a collapse of the upper part of the hydrothermal system.

The electrochemical synthesis of tetraarylporphyrins has been reinvestigated. Whereas the direct electrolysis of a mixture of benzaldehyde and pyrrole gave only a 1% yield of tetraphenylporphyrin (A. Stanienda, Z. Naturforschg. 22b (1967) 1107), the electrochemical oxidation for 2 h of preformed porphyrinogens, obtained under the Lindsey conditions, can be successfully performed using catalytic amount of quinone as mediator. Furthermore, when condensation involves 3,4-difluoropyrrole, the electrolysis, at 1.2–1.45 V versus ECS, can be realized without any mediator, owing to the good electrochemical stability of the compound. The porphyrins yields (21–41%) depend on the nature of the aldehyde (benzaldehyde, pentafluorobenzaldehyde) and of the pyrrole (pyrrole, 3-fluoropyrrole, 3,4-difluoropyrrole). They are slightly smaller in the case of a redox catalysis and a little larger for the direct electrolysis. An improvement of the purification step was obtained by decreasing the quantity of quinone and performing the chromatography of the dication porphyrins.

The different fluid percolations in the granitic complex of Saint-Sylvestre (Northwest French Massif Central) at the end of the Hercynian orogeny is relatively well described in the mining area, but their extension is unknown at the scale of the whole massif. Microthermometric and microstructural studies, outside any mineralized zone, show that different fluids circulated among three sets of microfissures: i) aqueous-carbonic fluids (N40 °E and N150 °E), ii) aqueous vapours and liquids (east-west) similar to those considered as linked to the granite episyenitisation, and iii) low temperature aqueous fluids (east-west). The first event is characterized by high temperatures at rather low pressures, indicating a high geothermal gradient (80–90 °C·km−1) similar to those observed in the proximity of intrusions in the present-day geothermal field. It confirms the close space-time relationships between the migration of these aqueous-carbonic fluids and the Late Hercynian granites intruding the Saint-Sylvestre massif some kilometers southwards. Other fluid events, attesting a cooling of more than 200 °C after the previous fluid stages, seem to be related to the incoming of meteoric fluids in the system, followed by local fluid immiscibility and cooling. These processes are common features of geothermal areas.

The Au-Cu-Zn-Sb epithermal mineralisations of the Baia Mare district (north Romania) and their Mio-Pliocene calc-alkaline volcanic host rocks are linked to the presence, at depth, of the Baia Mare batholith, recognised by geophysical and field studies. The salinity and temperature evolution of fluid inclusions from Baia Sprie and Sasar deposits are interpreted as being linked to the thermal evolution of the underlying laccolith. The global evolution, however, shows many irregularities related to brittle tectonic activity and phreatomagmatism during mineral deposition.

N-Unsubstituted 3,4-difluoropyrrole is synthesized via a thermal [2+3] cycloaddition reaction of a N-tert-butyl 2-alkoxycarbonyl aziridine and chlorotrifluoroethylene. Dealkylation of an intermediate N-tert-butylpyrrole is obtained with trifluoromethanesulfonic acid.

The aim of SETH is to give end-users specific advice concerning treatment and monitoring of adult drug poisoning. SETH is developed with an off of the shelf expert system shell (KBMS) and runs on a microcomputer. Technical choices were done according to this analysis, financial considerations and portability. Currently, the database contains 1000 French drugs from 75 different toxicological classes. The SETH expert system simulates the expert reasoning, taking into account for each toxicological class delay, signs and dose. Two phases of evaluation were performed. The experimental implementation of SETH began in April 1992 in our Poison Control Centre. Since then, 1100 cases inputted by residents were analysed by SETH. The extension of the knowledge base to child poisoning began in March 1993.

The two epimers of methyl 3-oxo-7-oxabicyclo[2.2.1]hept-5-en-2-carboxylate have been prepared from furan and methyl 3-bromopropiolate as a methoxycarbonylketene equivalent. The final step required hydrolysis of acetals by Nafion-H.

Comparative mineralogical, petrographical and geochemical studies were undertaken in several places in the world, Sierra Pena Blanca (Mexico), Macusani field (Peru), Meseta Los Frailes (Bolivia) and Puna (Argentina), in order to understand the behaviour of uranium in volcanic environment and to define the characteristics of a volcanic source rock and the main concentration mechanisms. Our results indicate: 1. (1) A fertile volcanic rock is alumina- and alkali-rich (alumino-potassic in the granite terminology). Alkaline, subalkaline and calc-alkaline volcanics are much less favorable. 2. (2) Because of the stability of the accessory minerals during all the events which occur during and/or after the cooling of the volcanic formations, uranium is only leached from the matrix. Thus the leachable metal stock is directly related to the proportionate volume of the matrix and to its U content. 3. (3) The early post-magmatic stages, such as the high-temperature devitrification and the vapor phase crystallization, concentrate the previously disseminated uranium at the mineral scale and increase the efficiency of the subsequent leaching stages. The glass hydration does not mobilize uranium. 4. (4) The uranium deposits spatially related to volcanism may result from different processes, either hydrothermal and related to the volcanic activity, or supergene. The host rocks may be the volcanic rocks themselves or the surrounding country rocks.

This paper describes a synthesis of 3-(trifluoromethyl)pyrrole from t -butyl ( E )-4,4,4-trifluorobutenoate and tosylmethylisocyanide via decarboxylation in 45% yield of 4-(lrifluoromethyl) pyrrole-3-carboxylic acid over barium-promoted copper chromite in quinoline.

The Hercynian (325 Ma) granitic complex of Saint-Sylvestre experienced two hydrothermal episodes: the first one leading to the formation of a typical alteration facies called “episyenite”, mainly characterized by the dissolution of granitic quartz; the second one leading to the deposition (at ∼280 Ma) of a major U deposit. The present study documents the isotopic characteristics of these hydrothermal events. 18 O 16 O , D/H and 13 C 12 C systematics demonstrate that barren episyenites were generated during hydrothermal interaction of large amounts of mainly meteoric water with the granite; the ore-depositing fluid equilibrated in a sedimentary formation before entering the granite. Episyenitization was dated at 301 ± 2 Ma, which is 25 Ma later than the granite emplacement. The Rb-Sr isochron relationship implies isotopic equilibrium within the fluid phase and between the fluid and the host rocks, which confirms the high water/rock ratio inferred from O-H isotope systematics. A coupled Nd and Sr isotope investigation demonstrates that at least Nd was reworked from the granite in the episyenite genesis, but Sr and possibly Nd had an exotic origin consistent with the inferred sedimentary origin during the ore-forming stage. The present study emphasizes the fact that spatially superimposed hydrothermal events in a granitic environment can be: (1) disconnected from the magmatic history of the granite itself; and (2) mutually disconnected from chronological and chemical points of view.

The stability and catalytic activity of the β-octafluoro-meso-tetraarylporphyrin iron complexes for cyclooctene epoxidation, cyclohexane and benzene hydroxylation by hydrogen peroxide and iodosylbenzene are studied. The results are compared to those obtained for the β-hydrogenated analogues.

Although variously fluorinated esters of acrylic acid have received important applications as monomers in the polymer field, the chemistry of genuine fluoroacrylic acids and esters, i.e. bearing fluorine atoms at the α and/or β positions, has received scarce attention, except for the promising α-fluoroacrylates. This is mainly owing to synthesis problems. Two routes to some (previously unknown) β-fluoroacrylic esters have already been reported [H. Molines and C. Wakselman, J. Fluorine Chem., 25 (1984) 447. idem., J. Fluorine Chem. 45 (1989) 155; IXth European Symposium on Fluorine Chemistry, Leicester (UK), September 4–8, 1989]. We propose here a new, short sequence affording the β-fluoroacrylic acid 1 directly as a single E isomer in a reasonable yield (25% overall), starting from vinyl fluoride and carbon tetrabromide. The same sequence was applied to 1,1-dipfluoroethylene (vinylidene fluoride) as a possible route to 3,3-difluoroacrylic acid 2 . The dehydrobromination step proved to be delicate due to halogen interchange [J. Leroy, H. Molines and C. Wakselman, J. Org. Chem., 52 (1987) 290] and subsequent easy formation of 3,3,3-trifluoropropanoic acid 3 in basic medium.

Resume Durant sa condensation avec les cetones α-halogenees, le complexe hexafluoroacetone-fluorure de potassium se comporte comme un faible nucleophile et une base forte. La substitution nucleophile produit des cetones α-perfluoroalcoxylees. L'abstraction d'un proton en α de la fonction carbonyle conduit a la formation d'ether-cetones substituees par le groupe C(CF 3 ) 2 . Dans certains cas, l'elimination d'hydracide peut se produire.

Resume Les monofluorophosphoranes R3MePF sont utilises dans des reactions d'echange, pour la preparation de composes organiques monofluores. Le tri-(n-butyl) methylfluorophosphorane (n-Bu3MePF), facilement accessible, est le plus reactif. Dans des solvants faiblement polaires ou meˆme apolaires, il reagit des −70° avec les sulfonates d'alkyle et les halogenures actives par les fonctions ester, cetone,ether. Desepoxydes fluores ont pueˆtre ainsi obtenus directement parechangeapartir de leurs homologues chlores ou bromes.

Mineralogical and chemical studies of pitchblendes, pyrites and coffinites from the Margnac and Fanay mines (Limousin, France) indicate that chemical exchanges between uraniferous solutions and vein wall-rocks are reflected in the chemical compositions of pitchblendes. An age of 276 Ma is given for the primary pitchblende—pyrite association by the U-Pb method. Isotopic analysis of Pb in galena, crystallized during coffinitization of pitchblende, gives an interval of 6 Ma between pitchblende precipitation and its remobilization as coffinite. Analyses by electron microprobe indicate that this hydrothermal transformation affects more or less all the pitchblende spherulites, even if the volume of coffinite is low. This leads to Si-enriched pitchblende and explains the systematic age of 270 Ma obtained by Pb-Pb and concordia diagrams. A mineralogically undetected remobilization stage is also found in some samples at 170–175 Ma. Finally, this work specifies the life time (20–30 Ma) of the geothermal system which is considered to be responsible for the episyenitization of the two-mica granite, the precipitation of pitchblende and its remobilization as coffinite.

From the recently described 2,6-diformyl-4-trifluoromethylphenol, we have synthesized the compounds [Cu2(L1,2 CF3)] (ClO4)2·xH2O. L1CF3 and L2CF3 are the 4-trifluoromethyl substituted Robson-type binucleating ligands with propylene and butylene lateral chains, respectively. The crystal structure of [Cu2(L1CF3)](ClO4)2 has been solved. The compound crystallizes in the orthorhombic system, space group Pbca: a = 9.537(4), b = 18.072(10), c = 34.340(11) A, Z = 8. The structure consists of the expected copper(II) dinuclear entities, with the perchlorate groups making additional bridges of either side of the macrocycle. The molecular skeleton is significantly bent in a boat fashion. The electrochemical properties of those two 4-tri- fluoromethyl substituted compounds have been investigated and compared to those of the 4-methyl substituted compounds [Cu2(L1CH3)](ClO4)2·2H2O and [Cu2(L2CH3)](ClO4)2. The replacement of CH3 by CF3 shifts the first reduction wave by ca. 0.15 V and the second one by ca. 0.18 V. The magnetic properties of [Cu2(L1CF3)](ClO4)2 and [Cu2(L1CH3)](ClO4)2·2H2O have been compared. Inspite of the modification of the redox properties, the singlet-triplet energy gaps J have been found equal within the experimental uncertainties (J = −710(10) cm−1).

Episyenites within the uranium ore-bearing Le Bernardan granite (northwest French Massif Central) were formed through the dissolution of quartz by hydrothermal solutions. These solutions may now be found fossilized as fluid inclusions (F.I.). The F.I. form rectilinear trails along microcracks which trapped the percolating fluids. Simultaneous study of the orientations of the trails and the chemistry of the inclusions shows that: 1. (1) the trails may be grouped according to direction, each related to successive regional stress fields 2. (2) the fluids of each group are compositionally distinct, marking different stages of the hydrothermal event. This example shows that the geometric relations between secondary F.I. trails and regional stress fields may be used to establish the chronology of both during a region's geological evolution.

A convenient method for the synthesis of the previously unknown 2, 6-diformyl-4-trifluoromethylphenol is reported by a seven-stage synthesis. A methyl ether is used to protect the phenol moiety and the key-step involves a copper-mediated trifluoromethylation of a bromoanisole prepared from 4-bromophenol.

The two-mica granites which host the two main uranium deposits from the northwestern Massif Central, France (Margnac-Fanay and Le Bernardan deposits), were hydrothermally altered both before and during the deposition of the primary U mineralization. Both altered rocks and mineralizations were then subjected to supergene processes. We have analyzed the rare-earth elements (REE), Th and U in fresh and altered, mineralized and barren whole rocks and in the pitchblendes to study the behaviour of these elements during hydrothermal and supergene processes in a granitic environment. When fluids are aqueous, with a low salt content (mainly chloride), then irrespective of temperature (400–450°C for feldspar episyenitization, 350°C for mica episyenitization, and 100–150°C for the quartz-coffinite-montmorillonite-adularia stage), the REE patterns and parameters, the HREE-LREE fractionation, the Th concentration and the Th/Ce ratio are not modified. This indicates that monazite, which controls these elements in the two-mica granites, remains stable under such conditions. In contrast, when ligands are present in the solutions (CO2−3 or HCO−3 with the pitchblende stage at 350°C; HPO2−4 or other phosphorous anions during supergene events at low temperatures) REE are either leached or concentrated depending on the prevailing redox conditions, and there is HREE-LREE fractionation. The REE content of the newly formed minerals (pitchblende) appears to be mainly controlled in such deposits by the fluid composition.

So far, no general and simple synthetic method was available to prepare 1,2-difluoroethylenes 1 bearing only one hydrocarbon substituent. We developed such a method, using the steps outlined in the following sequence : The alkenes 1 , whose configuration was always found to be Z could be epoxidized into cis 1,2-difluoroepoxydes. The different steps will be detailed and discussed.