Geochemical characteristics and tectonic significances of volcanic rocks in Haizhou Group, Northern Jiangsu Basin

In the Northern Jiangsu Basin,large amounts of volcanic rocks generated in the Haizhou Group during the late Proterozoic Era.Quartz keratophyre accounts for the largest proportion,spilite the second,and keratophyre the least.The volcanic rocks in the Haizhou Formation are rich in alkali and Na,and are characterized by bimodal distribution.The geochemical features of major,trace and rare elements indicate that the volcanic rocks formed in tensional environment,i.e.taphrogenic trough.They were related to the Rodinia Supercontinent during the late Proterozoic Era.