 In the arc-continent collision model, the Eastern Block was not assembled as one block until the Paleoproterozoic.It was formed when the volcanic island arc of Langrim block and the Archean Longgang block collided, resulting in the Jiao-Liao-Ji Belt.The ultramafic to mafic rocks in the North Liaohe group in eastern Liaoning were formed behind the arc where the crust spread (back-arc basin).