Mineralogical and Hf isotope study of the Dorolj granite in Hinggan League, Inner Mongolia

The Doroji granite is located in the southern part of the Da Hinggan Mountains, lying in a polymetallic ore-forming zone (Au-Ag-Cu-Zn-Sn-Fe) of the Da Hinggan Mountains. There are various kinds of magmatic rocks in this area, with multiple metallogenic elements, and Doroji granite is one of the biggest plutons, with an exposed area of about 190 km². To clarify the source of the Doroji granite and the relationship with the mineralization, the authors conducted a systematic study of the mineralogy and Hfisotopic compositions. Doroji granite is dominated by monzonitic granite and syenogranite. The monzonitic granite is composed of plagioclase (32%), K-feldspar (45%), quartz (20%), with miner biotite, muscovite, amphibole and pyroxene (3%). The syenogranite consists of quartz (10%-15%), K-feldspar (60%-70%), plagioclase (30%) with minor biotite (about 5%). Perthites is well developed in the monzonitic granite and syenogranite. Biotites are mainly ferribiotite and siderophyllite. Amphiboles are mainly kaersutite and hornblende. Pyroxenes are augites. The mineralogy indicates that the Doroji granite belongs to I-type. The ε_Hf values of monzonitic granite range from-1.6 to 17.6, and the ε_Hf values of syenogranite range from-3.3 to 12.2. Hf isotopic compositions of the Doroji granite indicates that the source was the juvenile crust, resulting from the remelting of the depleted basaltic rocks.