Emplacement P-T conditions of granitoids from the NW-part of the Malayer-Boroujerd plutonic complex, W Iran

The application of different geothermometer and geobarometer for selected granitoids from the NW-part of the Malayer-Boroujerd plutonic complex (NW MBPC) indicates they were sourced at pressures below 14 kb and emplaced at 8 to 4 kb. The results show relatively three areas of P-T condition for emplacement of NW MBPC granitoids: (1) Low- P and T (P< 5kb and T < 680°C) for Garnet-bearing monzogranite (Grt- MG) and quartz sample diorite, (2) High- P and T (~ 8 kb and T = 721°C) for garnet-bearing alkali granite (Grt- Alk Gr), and (3) Low- P and high T (P< 5kb and T > 750°C) for hornblende-bearing I-type granite (Hbl-granite) and hornblende-free S-type granite. The P–T estimation suggests that the hydrous felsic magma with S-type affinity were formed either by melting of deep crustal components followed by extensive assimilation of muscovite-bearing sediments or direct melting of muscovite-bearing metapelitic rocks at low pressure, both emplaced within muscovite-free domain of granitic system. The hydrous I-type felsic magmas which were mainly formed by melting of lower crustal materials cut the granite solidus at low pressure and show little evidence for assimilation of crustal components at emplacement level. The calibrations applied for NW MBPC granitoids indicates an important role for muscovite as H2O-supplier for felsic parent magma. The temperature increasing gradient against pressure for this region is greater than standard gradient for subduction zone indicating the intrusion of mantle-derived mafic magma into the crust or local thickening of continental crust.