Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The subcontinental lithospheric mantle evolves through time due to tectonic events and processes as static recrystallization and melt percolation. To constrain the extent of these processes in the South Patagonian subcontinental mantle lithosphere we performed a microstructural and Electron Backscattered Diffraction (EBSD) study of a suite of 35 peridotite xenoliths brought to the surface by Plio-Pleistocene alkaline volcanic rocks from Gobernador Gregores and Pali Aike. All samples show a well-developed olivine and pyroxene crystallographic preferred orientation (CPO), consistent with deformation by dislocation creep with dominant activation of [100]{0kl} in olivine. The coarse granular or tabular textures and the low density of intracrystalline deformation features indicate that deformation was followed by annealing under static conditions. The xenoliths also show microstructural evidence of multiple episodes of reactive melt percolation. Neither annealing nor melt percolation erased the olivine CPO, which has [010]-fiber, [100]-fiber and orthorhombic patterns in Pali Aike xenoliths and essentially [010]-fiber and orthorhombic patterns in Gobernador Gregores xenoliths. Seismic properties calculated based on the CPO and modal compositions are, however, rather homogeneous, with fast S-wave polarization and P-wave propagation parallel to the [100] olivine axis. The variation in the olivine CPO solely changes the minimum S-wave birefringence direction, which is normal to the foliation for axial-[010] olivine CPO. Average samples for the two localities, obtained by adding up the individual samples CPO data in a common reference frame, show, however, a 'normal' upper mantle anisotropy with a maximum S-wave birrenfringence of ca. 5% at high angle to the both the maximum [010] and [100] axes concentrations, that is in the foliation, but normal to the lineation, and a minimum birefringence at low angle to the [100] maximum, that is parallel to the lineation.
ISSN: 0040-1951

hal-01053500
https://hal.archives-ouvertes.fr/hal-01053500
DOI : 10.1016/j.tecto.2014.02.017

Éditeur(s) : HAL CCSD CRC Press
Résumé : Among the ecosystem services provided by forests, wood provisioning takes a central position. Wood and derived products have played a critical role in the evolution of human kind and demand for raw material is increasing in a foreseeable future. Wood is used for energy production, construction and a wide variety of products for which different properties are required. Anatomical, chemical and physical properties of wood are determined through a complex process called xylogenesis controlled by internal and external signals and occurring during the life of the tree. In this chapter we describe i/how wood is formed and ii/the different factors controlling this developmental process with emphasis on the molecular machinery involved, iii/the functions of wood and iv/the biotechnology approaches developed to improve wood biomass production and properties genetically.
Tree Biotechnology

ISBN : 9781466597143
hal-01204210
https://hal.archives-ouvertes.fr/hal-01204210
PRODINRA : 257126