Chronology and geological implication of the Palco-Mesoproterozoic alkaline-rich intrusions belt from the northern part in the North China Craton.

U-Pb age data on zircons is reported for the Paleo-Mesoproterozoic alkaline-rich intrusions respectively in the Yan-Liao triple-junction aulacogen system and in the Liao-Ji aulacogen of the North China Craton (NCC). These intrusives, which are approximately distributed along east-west direction, together with other anorogenic rocks in the same period, such as rapakivi granites, anorthosite and the Dahongyu formation volcanic rocks, are formed in the extensional tectonic settings. These alkaline-rich intrusions are distributed near 1000km in length and form an oldest alkaline-rich intrusion belt so far reported in the world. The belt is characteristed by older rocks (> 1.8Ga) in east end of the belt than those in west end (about 1.7Ga). The Paleo-Mesoproterozoic alkaline-rich intrusion belt is an excellent example to indicate that the Northern part of the NCC was under extending rift system during 1.85 similar to 1.70Ga, and also provide a new information for study on Precambrian supercontinent breakup.