摘要
The Xiong’er Volcanic Province is the most important volcanism event occurring in the North China craton in the Late Paleo-proterozoic. The timing of the volcanism is crucial to understand the tectonic regime and evolutionary history of the North China craton in the Proterozoic. Precise U-Pb ages of zircon/baddeleyite from the quartz diorite and granite-porphyry which intruded the Majiahe Formation of the upper part of the Xiong’er Group were determined by multi-collector SIMS.58 testing points have been obtained from the three samples. The mean 207Pb/206Pb ages from the quartz diorite are 1 789 ± 3.5 Ma for baddeleyite and 1 778 ± 12 Ma for zircon, respectively, while the corresponding mean 207Pb/206Pb age is 1 786 ± 7.7 Ma for zircon from the granite-porphyry. The data implies that it’s a transient and continuous process occurred between the generation and emplacement of the quartz diorite, and the quartz diorite and the granite-porphyry were formed almost contemporaneously. Because the two stocks intruded the Majiahe Formation of the upper part of the Xiong’er Group, the data could constrain the upper age limit of the Xiong’er Volcanic Province. It should be proposed that the volcanism age of the Xiong’er Volcanic Province is between 1 770 Ma and 1 800 Ma combining with previous chronological data. The peak period is 1 780 Ma. This result supports that the Xiong’er volcanic rocks should be formed under a rapidly extensional rift environment.