Éditeur(s) : HAL CCSD Société géologique de France
Résumé : International audience
Age constraints on the protoliths, deformation, metamorphism and melting events are key parameters when correlating different continental lithospheric remnants among each other and disentangling their evolution within large-scale orogens. In situ U-Th-Pb chemical dating on monazites using Electron Probe Micro-Analyser (EPMA) has been performed on eight samples throughout the Variscan Maures-Tanneron massif (SE France) in order to date the medium to high-tectonothermal events related to the Variscan orogeny.Results indicate a polyphased crustal evolution : (i) U-Th-Pb ages obtained in polygenetic monazite grain cores gave inherited Upper Ordovician (456 ± 11 Ma) age, highlighting the large scale occurrence of the Ordovician magmatic activity in the North Gondwanian margin. An Early Devonian (404 ± 10 Ma) age may date a protolith emplacement related to calc-alkaline supra-subduction magmatism or could be associated to an early medium-grade metamorphism, prior to collisional stage. (ii) The crustal thickening stage has been further recorded in prograde metamorphic monazites formed during the underthrusting and subsequent nappe stacking events, under amphibolite facies conditions. This stage is dated between 382 ± 11 (Middle Devonian) and 331 ± 5 Ma (Late Visean). (iii) An orogenic partial melting event took place during Middle Carboniferous and is accompanied by the crystallization of crustal peraluminous magmas (Plan-de-la-Tour granite, 329 ± 3 Ma).This contribution demonstrates the capacity of monazite to record the prograde path of rocks during increasing metamorphic conditions related to stages of crustal thickening, and the robustness of the U-Th-Pb chronometer in monazite despite the overprinting of high-grade thermal events, including partial melting. The age ranges of the different orogenic stages reported in this study are in good agreement with those reported in adjacent Variscan Corsica and Sardinia; while correlations with other nearest Variscan massifs like the Argentera massif in the southwestern Alps or the French Massif Central remain more hypothetic. The Internal Zone of the Maures-Tanneron massif, and more widely the Internal Zone of the Maures-Tanneron-Corsica-Sardinia segment, is part of the southern orogenic root system of the Variscan belt.
EISSN: 1777-5817

insu-01140973
https://hal-insu.archives-ouvertes.fr/insu-01140973
DOI : 10.2113/gssgfbull.186.2-3.145

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
This study aimed to identify factors associated with virological response (VR) to raltegravir (RAL)-containing regimens in 468 treatment-experienced but integrase inhibitor-naive HIV-1 patients receiving a RAL-containing regimen. VR was defined at Month 6 (M6) as HIV-1 RNA viral load (VL) <50 copies/mL. The impacts on VR of baseline integrase mutations, VL, CD4 count, genotypic sensitivity score for nucleoside reverse transcriptase inhibitors, non-nucleoside reverse transcriptase inhibitors and protease inhibitors, and the number of new antiretrovirals used for the first time associated with RAL were investigated. For patients with VL >50 copies/mL at M6, integrase mutations selected were characterised. Median baseline VL was 4.2 log(10)copies/mL (IQR 3.3-4.9 log(10) copies/mL) and CD4 count was 219 cells/mm(3) (IQR 96-368 cells/mm(3)). At M6, 71% of patients were responders. In multivariate analysis, baseline VL and CD4 count and ≥ 2 new antiretrovirals among darunavir, etravirine, maraviroc and enfuvirtide were associated with VR to RAL. Neither HIV-1 subtype nor baseline integrase polymorphisms were associated with VR to RAL. Among 63 failing patients at M6, selection of ≥ 1 change in the integrase gene was observed in 49 (77.8%), and 27/63 (42.9%) were considered as RAL-associated resistance mutations. Factors independently associated with the occurrence of ≥ 1 RAL-associated resistance mutation were VL at failure >3 log(10) and having no new drugs associated with RAL. RAL showed great potency in treatment-experienced patients. The number of new drugs associated with RAL was an important factor associated with VR. HIV-1 subtype and baseline integrase polymorphisms do not influence the RAL VR.
ISSN: 0924-8579

hal-00875083
https://hal.archives-ouvertes.fr/hal-00875083
DOI : 10.1016/j.ijantimicag.2013.02.016
PUBMED : 23562640