Évolution pression–température des amphibolites de la zone axiale au cours du métamorphisme hercynien des Pyrénées orientales

Thin levels of amphibolites from the Canigou, Albères and Cap de Creus massifs have been studied in order to investigate their pressure and temperature evolution during time. P and T values have been calculated using the amphibole–plagioclase–quartz thermo-barometer. Si, Al, Mg and Fe of zoned amphiboles have been analysed from core to rim by microprobe. By combining the results obtained from several (or different) crystals, P–T–t paths have been determined using the amphibole-plagioclase-quartz equilibriums. In the Canigou Massif, the amphibolites have recorded anti-clockwise P–T–t paths around a peak of metamorphism located at about 650?°C–6.1 kbar, whereas in the Albères Massif, the calculated P–T–t paths of amphibolites near the paragneisses are retrograde only, from 600?°C–5 kbar to 450?°C–2.5 kbar, but one cummingtonite-bearing amphibolite has also recorded an anti-clockwise evolution around 650?°C–4.5 kbar. The retrograde P–T–t paths recorded for amphibolites from the ‘Cap de Creus’ Massif are retrograde only, from 650?°C–6 kbar and 400?°C–1 kbar. To cite this article: C. Triboulet et al., C. R. Geoscience 337 (2005).     

Impacts « multi-échelle » d'un échange (Mg,Ca)–Pb et ses conséquences sur l'augmentation de la perméabilité d'une bentonite

The article addresses the structural effects of solutions of lead nitrate on a suspended or compacted bentonite. A permeability increase is observed on compacted clay. Investigating the composition of output solution, using X-Rays Diffusion at Small Angles and Scanning Electron Microscopy, this permeability increase is explained from structural variations at nanometric (reduction of particle size) and micrometric scales (microfissuration of aggregates). To cite this article: N. Jozja et al., C. R. Geoscience 335 (2003).     

Nouvelles données structurales et datations 40K–40Ar sur les roches métamorphiques de la région de Neyriz (zone de Sanandaj–Sirjan,Iran méridional). Leur intérêt dans le cadre du domaine néo-téthysien du Moyen-Orient

The metamorphic rocks of the Neyriz area (Sanandaj–Sirjan zone) represent a Palaeozoic sequence, the upper part of which being palaeontologically dated from the Carboniferous and the Permian. Field structural analysis of the whole sequence, detailed in laboratory by microstructural one and ⁴⁰K–⁴⁰Ar dating carried on separated minerals, lead to establish that the whole sequence, from gneisses to Permian rocks, has suffered a unique synmetamorphic deformation, of variable intensity, marked by a foliation. Isotopic ages measured on extracted amphiboles and micas, clustered in four groups between 300 and 60 Ma, show the successive stages of their slow exhumation, which ended by the end of the Cretaceous. To cite this article: R. Sheikholeslami et al., C. R. Geoscience 335 (2003).