Genesis of trondhjemite by low-pressure low-melt fraction anatexis of hornblende-gabbro at Alvand Plutonic Complex (Hamedan, NW Iran): insights from geochemical modelling

Abstract Amphibole-dominated dehydration melting of gabbro is the primary process responsible for genesis adakites, low-K tonalites, modern trondhjemites, and plagiogranites as well Archean tonalite-trondhjemite-granodiorite suites that represent earliest examples continental crust. Previous literature has mostly focused on role Al-rich amphibole during anatexis a mafic source many these studies have investigated this through experimental runs. However, due to boundary conditions, little known about partial amphibole-bearing rock at temperatures < 800°C upper crustal conditions (pressure 500 MPa). Classic forward thermobarometric modelling suggests in situ trondhjemite leucosomes, hosted by Cheshmeh-Ghasaban metatexites (Alvand Plutonic Complex, Hamedan, NW Iran), rare natural case study low-temperature incipient amphibole-dominated anatectic event with assemblage (Pl+Hbl+Cpx+Bt+Opx) typical hornblende-bearing gabbroic rock.