Abstract: Plagiogranite was discovered in the Jiaonan area, Shandong province. It occurs in association with Middle Proterozoic metagabbro. The rock consists of 60% plagioclase and 40% quartz and has high Si, low to moderate Al and low K₂O, being similar in chemical composition to oceanic plagiogranite. Its Pb Pb age of single grain zircon is （1 370.6±14.3） Ma.