The genesis of LCT-type granitic pegmatites, as illustrated by lithium isotopes in micas

International audienceIsotopic compositions in the Monts d’Ambazac Pegmatite Field (French Massif Central) exhibit a narrow range of mica δ7Li values, ranging from -3.6 to + 3.4‰. The value obtained in biotite from the host Saint Sylvestre granite falls within this range (δ7Li = -1.5‰). Lithium concentrations are consistent with the degree of magmatic evolution of each pegmatite type: from 630 ppm in Type II up to 13,500 ppm in the more evolved Type VI pegmatite. Although the rare-element contents e.g., Li, Cs, Ta of the micas are consistent with pegmatite differentiation, δ7Li (‰) are firstly, independent of the degree of magmatic differentiation (independent of pegmatite type) and secondly, independent of the content of Li and other flux-elements such as Be and Cs. Muscovite sampled in pegmatite V from the Chabannes locality is the only pegmatite to exhibit a δ7Li variation from intermediate unit (-1.7‰) to internal pegmatitic unit (+ 3.4‰). The nature of this δ7Li variation suggests that there was extensive fractional crystallisation during the pegmatite’s consolidation. The independence of δ7Li (‰) evolution from the degree of magmatic evolution and the presence of distinct major rare-element bearing phases throughout the pegmatite field tend to confirm that the δ7Li (‰) values recorded in mica are inherited from crustal source rocks common to the granite and pegmatite-forming melts. We propose that the distinct pegmatite subtypes (beryl columbite vs lepidolite-petalite subtypes) observed throughout the Monts d’Ambazac Pegmatite Field reflect the diverse contributions of crustal protoliths. The lack of evidence of surrounding alteration combined with the absence of increasing Li-content within the host granite tend to confirm that the δ7Li values obtained within this pegmatite field are primary, and that no Li-diffusional process and/or mixing-driven Li-isotope fractionation has overprinted these isotopic compositions. In light of these results, the process of partial melting of protoliths enriched in rare-element bearing phases, e.g., mica, garnet, seems to be more responsible for Li-isotope fractionation than Li-diffusion or fractional crystallisation at the temperature of pegmatite consolidation. Finally, we discuss the use of Li isotopic compositions to identify the most highly evolved pegmatitic systems

Oral Kaposi Sarcoma in two patients living with HIV despite sustained viral suppression : new clues

Kaposi sarcoma (KS) etiologically linked to Kaposi sarcoma-associated herpesvirus (KSHV) is the most common HIV associated cancer despite the generalization of antiretroviral therapy. Head, neck, and especially oral cavity are common and specific sites f

Characteristics of sound production and associated pharyngeal jaws in the tomtate grunt Haemulon aurolineatum (Cuvier, 1830) in Caribbean reefs

International audienceThe ability to produce sounds for acoustic communication is well known in different grunt species (Haemulidae). However, most of the sounds have not been described and the sound-producing mechanism of very few grunt species has been deeply studied. Additional data is needed to search for synapomorphy in the sonic mechanism. This study describes acoustic features and branchial anatomy in Haemulon aurolineatum. Correlations were found between some acoustic features and standard length, showing the largest specimens produced shorter, lower-pitched grunts of higher intensity. Examinations of acoustic features and branchial anatomy show that H. aurolineatum uses the same stridulatory mechanism described previously in H. flavolineatum. The unusual feature of Haemulon species concerns the fourth ceratobranchials. These appear to be part of the lower pharyngeal jaws since they possess firmly attached teeth that face the upper pharyngeal jaws. The stridulation results from the rubbing of both pharyngeal and fourth ceratobranchial teeth. This mechanism is probably common to the 23 Haemulon species, but additional information is needed regarding the mechanism of other Haemulinae species to produce stridulatory sounds. Fourth ceratobranchials could constitute a key element of Haemulinae ability to produce sounds providing an eventual synapomorphic aspect of the mechanism in the family

When worlds collide: Invader-driven benthic habitat complexity alters predatory impacts of invasive and native predatory fishes

Interactions between multiple invasive alien species (IAS) might increase their ecological impacts, yet relatively few studies have attempted to quantify the effects of facilitative interactions on the success and impact of aquatic IAS. Further, the effect of abiotic factors, such as habitat structure, have lacked consideration in ecological impact prediction for many high-profile IAS, with most data acquired through simplified assessments that do not account for real environmental complexities. In the present study, we assessed a potential facilitative interaction between a predatory invasive fish, the Ponto-Caspian round goby (Neogobius melanostomus), and an invasive bivalve, the Asian clam (Corbicula fluminea). We compared N. melanostomus functional responses (feeding-rates under different prey densities) to a co-occurring endangered European native analogue fish, the bullhead (Cottus gobio), in the presence of increased levels of habitat complexity driven by the accumulation of dead C. fluminea biomass that persists within the environment (i.e. 0, 10, 20 empty bivalve shells). Habitat complexity significantly influenced predation, with consumption in the absence of shells being greater than where 10 or 20 shells were present. However, at the highest shell density, invasive N. melanostomus maximum feeding-rates and functional response ratios were substantially higher than those of native C. gobio. Further, the Relative Impact Potential metric, by combining per capita effects and population abundances, indicated that higher shell densities exacerbate the relative impact of the invader. It therefore appears that N. melanostomus can better tolerate higher IAS shell abundances when foraging at high prey densities, suggesting the occurrence of an important facilitative interaction. Our data are thus fully congruent with field data that link establishment success of N. melanostomus with the presence of C. fluminea. Overall, we show that invader-driven benthic habitat complexity can alter the feeding-rates and thus impacts of predatory fishes, and highlight the importance of inclusion of abiotic factors in impact prediction assessments for IAS

Osteomyelitis of the Mandible after Dental Implants in an Immunocompetent Patient

Dental implants are now broadly used to replace missing teeth, and the presence of infectious complications is rising. Dental implant therapy as a local risk factor for the onset of osteomyelitis and its management have not been widely explored. Here, we report an unusual case of mandibular suppurative osteomyelitis caused by Streptococcus intermedius in a healthy and immunocompetent patient secondary to mandibular implants. We describe how surgery combined with systemic application of antibiotics allowed conservation of the dental implants in the mandibular bone, discuss the probable source of contamination, and present the follow-up of the osteomyelitis

Mise au point en 2014 sur la prise en charge du patient atteint de fibromyalgie

REIMS-BU Santé (514542104) / SudocSudocFranceF

Etude de l'erythropoïèse dans un modéle murin d'anémie chronique (Réponse à l'injection d'Erythropoïètine)

PARIS5-BU Cordeliers (751062101) / SudocSudocFranceF

Rare-element pegmatite-forming melt during Variscan orogeny: genesis, propagation and consolidation

International audienceThe Variscan rare-element pegmatite fields mainly enriched in Li, Nb and Ta are subject to increasing mining exploration in the last few years. Indeed, Li from pegmatite deposits is recognised to be less sensitive to supply disruptions than Li from brine deposits. Thus, new metallogenic guides need to be defined in order to meet the growing demand for Li, Nb and Ta metals, and to ensure supply of strategic metals at the European scale. Three Variscan rare-element pegmatite fields have been selected to apply a multi-approach study in order to understand the genesis of pegmatite-forming melt, their propagation and their clustered consolidation at the crustal scale. The Monts d'Ambazac (French Massif Central), Barroso-Alvão (Portugal) and Forcarei-Lalin (Galicia, Spain) pegmatite fields present a similar age (∼305-315 Ma), a similar geodynamical context (syn-to post-collisional) and same kind of mineralisations (LiCsTa type) but show distinct intensity of deformation affecting various country-rocks. Firstly, spatial statistical analyses have been developed to constrain the spatial distribution of the Monts d'Ambazac and the Barroso-Alvão pegmatite fields. Secondly, Li-isotopic analyses in micas have been used to investigate the role of δ7Li as geochemical tracer of LCT-pegmatites (from the less to the more evolved and lithium-rich pegmatite type). Finally, spatial and temporal relationships between pegmatites and hosting-rocks have been discriminated with structural field data mainly obtained on the Monts d'Ambazac and Forcarei-Lalin pegmatite fields. In addition, Li-isotopes results corroborate that Li-fractionation is neither affected by fractional crystallisation nor by crustal anatexis processes in a significant way. These δ7Li values () being independent from the degree of magmatic fractionation (K/Rb ratio) and ranging from-3.5 to +3.5 tend to confirm that these pegmatite-forming melts evolve independently of each other. Our results demonstrate the main role of tectonic context during pegmatite-forming melt genesis and their propagation through activated shear-bands, opening of tensions gashes, magma pumping and space filling by pegmatite-melt crystallisation. Based on field observation such as mineralised ptygmatic veins, the role of chemistry and rheology of hosting-rocks on pegmatite differentiation type and on their morphology can be constrained. In particular, high permeability shear zones could play a crucial role in the ascent of low viscosity pegmatite-forming melts. To refine our results, preliminary numerical models have been developed to constrain the ascent of a pegmatitic melt from a deep crustal source. The " exotic " physico-chemical properties (large viscosity contrasts due to temperature-and water content-dependence) have been accounted for, and the experiments with large Peclet numbers reproduce individual patches of low viscosity melts disconnected from the parental source