Experimental Evidence for a Weak Calcic‐Amphibole‐Rich Deep Crust in Orogens

Abstract Amphibole‐rich rocks constitute significant components of the mid‐ to lower continental crust, particularly in active orogens characterized with thick and hot crusts. Nevertheless, experimental data on their viscosity remain scarce. We conducted axial compression deformation experiments synthetic amphibolites under temperature pressure conditions resembling deep sections overthickened crust. A novel flow law for a calcic‐amphibole‐rich rock (80% amphibole +20% garnet) dislocation creep regime is derived from these experiments. Contrary common assumptions, our results reveal that calcic‐amphibolite 1‐2 orders magnitude weaker than plagioclase‐rich amphibolite, granulite, or gabbro. calcic‐amphibole‐rich, low crust may not only support “channel flow” model proposed Tibetan Plateau but also explain observed high crustal seismic anisotropy region.