Fluid channelling during ductile shearing: transformation of granodiorite into aluminous schist in the Tauern Window, Eastern Alps

Publisher Website
Google Scholar
Abstract
Ductile shearing in the core of the Tauern Window, Austria, transformed metagranodiorite into Si‐undersaturated garnet‐chlorite‐staurolite schist at a depth of c. 35–40 km during the Alpine orogeny. Four distinct zones have been recognized extending from the wallrock into the centre of the shear zone: Zone I—unaltered metagranodiorite with subordinate amphibolite; Zone II—biotite‐white mica‐garnet schist; Zone III—biotite‐phengite schist; Zone IV—quartz‐absent, garnet‐chlorite‐staurolite schist with garnets up to 10 cm across. Whole‐rock analyses show a dramatic decrease in SiO2 from >65 wt% in Zone I to 8 cm3 cm−2 in Zone IV. This large volume of fluid may have originated, in part, from dehydration of flysch carried beneath the metagranodiorites during Eocene movement on the North Penninic subduction zone. Development of an inverted thermal gradient during subduction would have allowed the fluid to scavenge large amounts of silica from the shear zone during ascent and heating.

This publication has 21 references indexed in Scilit: