Hydration-induced climb dissociation of dislocations in naturally deformed mantle olivine

摘要: Widely dissociated dislocations have been observed in mantle olivine from the Erro-Tobbio peridotite N.W. Italy. Analysis of diffraction contrast transmission electron microscopy (TEM) indicates that dissociation reaction involves climb on (001) and {021} planes b=[001] unit into partial with Burgers vectors approximately equal to 1/x 〈011〉. In most extreme case a dislocation dissociates four partials which bound three planar defects. The unusually wide greater extent amphibole-bearing rocks suggests is related hydration. occurrence fluid inclusions along confirms defects are saturated volatiles. possible defect structures Fo90 shows that; (i) likely b=〈0 3/11 1/4〉; (ii) two cation-deficient can be stabilised by segregation H+ produce (Mg, Fe) (OH)2 layers iso-structural OH-rich interlayer humite group minerals; (iii) central formed removing stoichiometric (002) layer so does not any local chemical changes. provides mechanism for transformation mineral. interlayers may nucleate extend crystal resulting gradual increase content. only addition material required hydrogen rapidly diffuse olivine. If stable occurs at high temperatures pressures it significantly influence nature kinetics deformation mechanisms — spinel shear hydrated