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RESEARCH PRODUCT

Dilatant plasticity applied to Alpine collision: ductile void growth in the intraplate area beneath the Eifel volcanic field

subject

description

The Eifel is located in the middle of the European plate far away from any active plate boundary, yet it appears to be a maximum of intraplate tectonic activity. A map of intraplate seismic energy flow shows that the Eifel is linked to the Alpine collisional belt via a narrow seismoactive shear zone. Two parallel Quaternary volcanic zones (the East Eifel Volcanic Zone EEVZ and the West Eifel Volcanic Zone WEVZ) line up with the seismogenic shear zone. Xenoliths ejected from these volcanic lineaments indicate upper mantle shearing by dynamic recrystallization textures and metasomatized chemistry. Important CO2-dominated mantle degassing observed in mineral springs, lakes or dry degassing suggests a presently ongoing flushing of brines. Here, the hypothesis of intraplate ductile void growth as a consequence of the Alpine collision is tested by finite element models. It is shown that in the tensile domain of Alpine collision, a small amount of dilatancy along shear bands in the upper mantle and lower crust can open pathways for fluids, thus transfer of melts and gases through the lithosphere and thereby controls mantle metasomatism along highly oriented mantle shear zones.