The mechanism of veining and retrograde alteration of Alpine eclogites

摘要: The introduction of externally derived fluids into rocks the Zermatt–Saas zone Swiss Alps gave rise to simultaneous formation shear and hydraulic fractures. These fractures are now filled with albite-rich assemblages surrounded by alteration halos up c. 2 m wide. zoned an examination reactions in P–T–aH2O space implies that parageneses developed hydration fluid-absent eclogites. A mechanical analysis veins (after Sibson, 1981) shows Pfluid/Pload must have been at least 0.96. Fluid migration country driven excess head either from vertical extent or due their connection a deeper, external reservoir, possibly tapped along thrust surface(s). Diffusive capillary transport were insignificant. may underlying metasediments dehydrating during quasi-isothermal uplift this part Alps, they originated prograde mesoalpine metamorphism documented area.