PETROGRAPHIE DU GISEMENT D’OR DE BONIKRO, SILLON BIRIMIEN D’OUME - FETTEKRO, COTE D’IVOIRE

The Bonikro gold deposit is located in the southern part of the Oumé- Fettèkro birimian furrow. Its lithology is made of two primary rocks units; a mafic volcanic sequence in the East and a unit of volcano-sedimentary rocks in the western part. The interface of these two units is occupied by the Bonikro Shear Zone and the granodiorit. This intrusive is associated with the dykes of pegmatite and aplite, but also with volcanic giving the group of felsic rocks in the deposit. The minerals of sericite, chlorite, epidote observed in these rocks are consistent with the impacts of the greenschist facies metamorphism. Also, these lithologies are affected by a strong hydrothermal alteration due to the abundant veins of quartz, carbonate, albite, sulphide, scheelite and gold. The distribution of these aforenamed two units in the east and in the west supports the fact that the birimian has inherited the ancient valley. The various volcanic rocks are linked to the birimian volcanism, when the pyroclastites imply that this volcanism has undergone a possible period of explosive character

PETROGRAPHIE DU GISEMENT D’OR DE BONIKRO, SILLON BIRIMIEN D’OUME - FETTEKRO, COTE D’IVOIRE

The Bonikro gold deposit is located in the southern part of the Oumé- Fettèkro birimian furrow. Its lithology is made of two primary rocks units; a mafic volcanic sequence in the East and a unit of volcano-sedimentary rocks in the western part. The interface of these two units is occupied by the Bonikro Shear Zone and the granodiorit. This intrusive is associated with the dykes of pegmatite and aplite, but also with volcanic giving the group of felsic rocks in the deposit. The minerals of sericite, chlorite, epidote observed in these rocks are consistent with the impacts of the greenschist facies metamorphism. Also, these lithologies are affected by a strong hydrothermal alteration due to the abundant veins of quartz, carbonate, albite, sulphide, scheelite and gold. The distribution of these aforenamed two units in the east and in the west supports the fact that the birimian has inherited the ancient valley. The various volcanic rocks are linked to the birimian volcanism, when the pyroclastites imply that this volcanism has undergone a possible period of explosive character

Carbonate-hosted Pb-Zn±Ag and Ba deposits in the Chañarcillo group, northern Chile : multiple fluid types and genetic processes

D'anciens gisements et indices de Pb-Zn±Ag et Ba dans le Groupe de Chañarcillo, dans le nord du Chili, témoignent de fluides hydrothermaux ayant circulé dans ces formations carbonatées et volcanoclastiques d'arrière-arc depuis le Crétacé inférieur. Une description détaillée et la paragenèse de plusieurs gisements sont présentées, et les fluides minéralisateurs sont étudiés par le biais des inclusions fluides et de la composition isotopique (Sr, S, Pb) des minéraux de gangue et d'altération. L'étude paragénétique met en évidence une diversité de processus minéralisateurs, en partie liés à un contexte tectonique transpressif et la mise en place d'intrusions dioritiques au Crétacé supérieur. Les caractéristiques des fluides indiquent une origine épigénétique des gisements par le mélange de fluides métallifères salins de température modérée issus des roches de l'arc magmatique avec du soufre marin dérivé des roches carbonatées

Stratabound and vein-type Pb-Zn mineralization at Las Canas, Chanarcillo Group, northern Chile; fluid inclusion microthermometry, and sulfur and lead isotope constraints

The Las Canas stratabound Pb-Zn deposit, in northern Chile, is hosted by the Lower Cretaceous back-arc marine carbonate and subordinate andesitic volcanic and volcaniclastic rocks of the Chanarcillo Group, one hundred meters above a thick pile of magmatic arc-related basaltic to andesitic lavas of the Bandurrias Formation. The deposit is not obviously related to local intrusive rocks, which include an Upper Cretaceous granodiorite batholith and dacite dikes emplaced along normal faults. Stratabound Pb-Zn-Ba mineralization is constrained within several porous stratigraphic units, including a 50 cm thick lapilli-tuff and less well mineralized algal-laminated limestone. Veins that locally carry some Pb-Zn occur along normal faults that displace the stratabound orebodies, and this study shows that they represent a different type of mineralization. Fluid inclusion microthermometric data for ore-stage quartz and barite indicate saline fluids (6 to 30 wt% NaCl eq ) and a formation temperature in the range of 80 degrees C to 160 degrees C for the stratabound mineralization. Two types of fluid inclusions occur in the veins. The type I vein fluid inclusions indicate less saline (average 7 wt% NaCl eq ) and slightly higher temperature fluids, in the range of 110 degrees C to 220 degrees C. The type II vein fluid inclusions indicate highly saline fluids (25 to 40 wt% NaCl eq ) which might be related to minor copper mineralization. 206 Pb/ 204 Pb, 207 Pb/ 204 Pb and 208 Pb/ 204 Pb ratios for galenas from the stratabound mineralization, with mean values of 18.42, 15.59, and 38.25, respectively, fall within the range of stratabound polymetallic deposits of northern and central Chile, and indicate a Lower Cretaceous magmatic rock source. Galenas from veins have slightly more radiogenic 206 Pb/ 204 Pb, 207 Pb/ 204 Pb and 208 Pb/ 204 Pb ratios, with mean values of 18.47, 15.61, and 38.34, suggesting two distinct episodes of mineralization. delta 34 S values for galena and barite range from negative values (-31.2 per mil to -12.5 per mil and -7.7 per mil to +12 per mil, respectively) in the mineralized tuff to higher values in the algal-laminated limestone (-2.5 per mil to +1.2 per mil and +13.2 per mil to +17.4 per mil, respectively), close to Lower Cretaceous marine sulfate values for barite, and homogeneous values for the galena from veins (-12.0 per mil+ or -1 per mil). Changing redox conditions can partly account for delta 34 S variations in the tuff. Sulfur sources include magmatic rock sulfur (-1.5 per mil to +9.7 per mil) as well as sedimentary sulfides and marine sulfate

Impact of microbial activities on the mineralogy and performance of column-scale permeable reactive iron barriers operated under two different redox conditions

The present study focuses on the impact of microbial activities on the performance of various long-term operated laboratory-scale permeable reactive barriers. The barriers contained both aquifer and Fe-0 compartments and had received either sulfate or iron(Ill)-EDTAto promote sulfatereducing and iron(Ill)-reducing bacteria, respectively. After dismantlement of the compartments after almost 3 years of operation, DNA-based PCR-DGGE analysis revealed the presence of methanogenic, sulfate-reducing, metalreducing, and denitrifying bacteria within as well as up- and downgradient of the Fe-0 matrix. Under all imposed conditions, the main secondary phases were vivianite, siderite, ferrous hydroxy carbonate, and carbonate green rust as found by scanning electron microscopy (SEM) combined with energy dispersive X-ray analysis (EDX), and X-ray diffraction (XRD). Under sulfate-reduction promoting conditions, iron sulfides were formed in addition, resulting in 7 and 10 times higher degradation rates for PCE and TICE, respectively, compared to unreacted iron. These results indicate that the presence of sulfate-reducing bacteria in or around iron barriers and the subsequent formation of iron sulfides might increase the barrier reactivity

Sr and S isotopic composition of barites from Ba±Pb±Zn occurrences in the Chañarcillo Group, northern Chile

The strontium and sulfur isotopic composition of barites has been analyzed to constrain the genesis of Ba and Ba-Pb-Zn ore occurrences in the Lower Cretaceous back-arc basin of the Atacama Region, northern Chile. The data support an origin by interaction of metal-bearing fluids having leached underlying volcanic rocks with the host carbonate (and evaporitic) rocks. A broad correlation between the strontium and sulfur isotopic composition and the typology of the barites suggest different degrees of interaction between the metal-bearing fluids and the host rocks

5-HT6 receptor blockade differentially affects scopolamine-induced deficits of working memory, recognition memory and aversive learning in mice

International audienceRATIONALE: Blockade of 5-HT6 receptors (5-HT6R) is known to improve cognitive performances in the rodent. This improvement has been hypothesized to be the result, at least in part, of a modulation of the cholinergic neurotransmission. OBJECTIVE: We assessed the effects of 5-HT6R blockade on selected types of memory relevant to functional deficits of ageing and neurodegenerative diseases, in mice that present a scopolamine-induced cholinergic disruption of memory. METHOD: Following the selection of an adequate dose of scopolamine to induce cognitive deficits, we have studied the effects of the selective 5-HT6R antagonist SB-271046, alone or in combination with scopolamine, on working memory (spontaneous alternation task in the T-maze), recognition memory (place recognition) and aversive learning (passive avoidance). RESULTS: SB-271046 alone failed to affect working memory, recognition memory and aversive learning performances. In contrast, SB-271046 was able to reverse the scopolamine-induced deficits in working memory (only at 30 mg kg⁻¹) and those of acquisition and retrieval of aversive learning (dose-dependent effect); scopolamine-induced deficits in episodic-like memory (acquisition and retrieval) were partially counteracted by 5-HT6R blockade. CONCLUSION: The modulation between 5-HT6R and the cholinergic system appears to be predominant for working memory and aversive learning, but not for other types of memory (i.e. episodic-like memory). Interactions between 5-HT6R and alternative neurotransmission systems (i.e. glutamatergic system) should be further studied. The respective involvement of these interactions in the memory disorders related to ageing and neurodegenerative diseases is of pivotal importance regarding the possible use of 5-HT6R antagonists in the treatment of memory disorders in humans