Amphibole-bearing migmatite in North Dabie, eastern China: Water-fluxed melting of the orogenic crust

Amphibole-bearing migmatites from the North Dabie Zone in the Dabie Mountains were investigated in order to constrain the partial melting process. These migmatites are characterized by large euhedral poi lcilitic amphiboles with abundant inclusions of plagioclase, biotite, and quartz in leucosome and melanosome. The amphiboles show large variations in REE compositions, which is interpreted as the result of equilibration with different melts during melting and crystallization. Hornblende-plagiocase thermobarometry indicates that the migmatites formed at P-T conditions of similar to 700-750 degrees C and 5 kbar, suggesting partial melting of a biotite + plagioclase + quartz-bearing protolith under water-fluxed conditions. The leucosomes range from tonalitic to granitic in composition having higher SiO2, Na2O, Sr, and Ba contents than the mesosome, but lower contents of CaO, FeO, MgO, TiO2, and MnO2. The granitic leucosomes are enriched in Ba, Rb, and K2O compared to the tonalitic leucosomes. The leucosomes have variable rare earth element patterns, which is attributed to different degrees of amphibole entrainment into the leucosome and feldspar fractionation during partial melting. (C) 2016 Elsevier Ltd. All rights reserved.