| 其他摘要 | The study areas are located in the Hebei Province, eastern North China Craton (NCC), and Shanxi Province, western NCC. To the east, there is the Yanshan tectonic belt, and to the west, is the Datong coalfield in Datong Basin. Based on the invistigation (e.g., LA-ICP MS zircon U-Pb ages, Major element and trace element, and Sr-Nd isotopes) on the mafic dykes from Sanchakou, Xiabao and Nanweizigou in Hebei Province, and the Tashan-Tongxin carbonatite dykes in Shanxi Province. We have provided the ages, sources and tectonic features of these dykes. Furthermore, we also discuss the NCC destruction; this study will give much important information for the controversy of NCC destruction (e.g., time, mechanism). The zirconLA-ICP-MS U-Pb analysis of Sanchakou mafic dykes shows an age of 222.1 ± 1.6 Ma, implying these dykes were formed in late indosinian. In addition, this age is consisent with that of Xiaobao mafic dykes. Moreover, the ages of the Tashan and tongxin carbonatite dykes are 239.8 Ma and 238.3 Ma. In contrast, the Nanweizigou mafic dykes were formed in 142.1 Ma. The Sanchagou, Xiabao, Nanweizigou mafic dykes, and Tashan-tongxin carbonatite dykes are characterized by enrichment in LREE and LILE, depletion in HSFE (e.g., Nb, Ta and Ti) and HREE. In addition, the sanchakou and nanweizigou mafic dykes, Tashan and Tongxin carbonatite dykes have high intial Sr isotopic compositions and negative εNd (t) values, suggesting that these rocks were derived from enriched lithospheric mantle. During late Triassic, the northern margin of NCC experienced the post-collisional/ post-orogenic lithospheric extension. There are visible different of mamatism between eastern and western NCC, i.e., the magmatic activitiy is intensive in eastern NCC. During late Jurasic and early Cretaceous, another magmatic activity due to extension appeared in northern NCC. Based on the systematical researches on the maifc dykes and carbonatite dykes，the magmatic activity in late Triassic indicated the beginning of the NCC destruciton, and the peak period of the NCC destruction was the late Jurasic and early Cretaceous. In addition, the destruction not only occurred in eastern NCC, but also in western NCC. However, the destruction was stronger in eastern NCC. In summary, the post-collisional/ post-orogenic lithospheric extension after the closing of Paleo-Asian Ocean, and the post-collisional/ post-orogenic lithospheric extension of Mongolia-Okhotsk sea may have provided important contributions to the NCC destruction. |
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