Zircon SHRIMP U-Pb age of Jinkouhe diabase dykes in Ebian area of western Sichuan Province and its implications for the breakup of Rodinia

There are abundant mafic dykes that intruded the Mesoproterozoic Ebian Group in Jinkouhe area of western Sichuan Province. Their precise emplacement time is significant for revising the time of the Ebian Group and studying the Precambrian tectonic setting of the western margin of Yangtze Craton. One of the diabase dykes from Jiadanqiao Formation of Ebian Group was dated by SHRIMP zircon U-Pb dating. The result shows that the zircons are of typical mafic magmatic origin with clear and wide internal growth zoning and high Th/U ratios, and the weighted mean 206Pb/238U age is (813.4±8.2) Ma (MSWD=0.56). This result represents the emplacement time of the diabase dykes, and also constrains the minimum age of Jiadanqiao Formation in Ebian Group. Based on synthesizing the latest isotopic ages of the Mid-Neoproterozoic mafic magmatic activities along the western margin of Yangtze Craton, the authors confirmed that there were two major active phases: 830~800Ma and 780~745 Ma, and the peak age of the mafic magmatic activities during 830~800Ma was (821±2)Ma. This is perfectly consistent with the previously-reported age distribution characteristics of mafic magmatic activities in South China and Australia, implying that the diabase dykes in Jinkouhe area were probably related to the episodic activities of the mantle plume which led to the breakup of Rodinia supercontinent.