| South China is the core part of Rodinia supercontinent rebuilt, while Yangtze block is a major part of the South China plate, and the Neoproterozoic episodic volcanic activity of Yangtze block periphery edge serves many information of the tectonic-volcanic history of Yangtze block. With the developing of the situ U-Pb dating technology, the study of Pre-Cambrian period Yangtze block opened a new chapter. In recent years, magmatic zircon U-Pb dating technology has obtained lots of achievements. It provides trustworthy basis for the restoration of stratigraphic framework and the recovery of tectonic-magmatic evolution. The detrital zircons contain comprehensive age record. And the detrital zircons' age spectrum can effectively reflect the composition of rock and their relative proportions, and show the tectonic-magmatic evolution of the source area. While the usage of detrital zircons are not as common as magmatic zircons nowadays.Recently, the tectonic attribute of South China is still in datate. So the research gathers three samples namely GLK-28 from Kaijianqiao formation and JNC-N1 from Chengjiang formation of Kangdian rift basin in western margin of the Yangtze block, 13LSQ-N1 from Qingshuijiang formation of Nanhua rift basin in southeastern margin of the Yangtze block. By dating the U-Pb isotopic age of the detrital samples, counting the data of age, making the age spectrum and other procedures, comparing with the Cathysian block, North China block and Tarim block, the researcher went deep into the tectonic-magmatic history of the detrital samples' source area.The result shows that Kaijianqiao Formation sample GLK-28 obtains 61 effective Neoproterozoic magmatic zircons. The ages distribute uniform, and the peak value is 798 Ma, second peaks are 849 Ma, 819 Ma, 779 Ma, 750 Ma and 720 Ma. Chengjiang Formation sample JNC-N1 received 69 valid data, including 56 data located in the Neoproterozoic 878Ma~795Ma, the main peak is 820 Ma, the second peak are 844 Ma and 802 Ma. In addition, there are 13 old age-records, a large age span, from Archaean to Mesoproterozoic(2844Ma ~ 1122Ma). Qingshuijiang Formation sample 13LSQ-N1 has 56 valid age data, the number mainly concentrates in 934Ma~763Ma, the peak value is 781 Ma, and the second peak are 932 Ma, 850 Ma, 826 Ma, 800 Ma and 766 Ma. Besides, there are 8 Archean-Proterozoic(2619Ma~1980Ma) old ages.From the gathered data aforementioned above, three groups of detrital zircon age spectrum showed similar values, showing the consistency of the tectonic-magmatic activities, reflecting the connection with Rodinia supercontinent's converge and diverge. Combining the studies of Neoproterozoic sedimentary sequences and chronology, and comparing the ages from the edge of Yangtze block, the detrital zircon age data in this research paper verifies that, under the background of Rodinia supercontinent converge and diverge, the Yangtze block develops rifting by the influence of the mantle column, with active volcanic and the evolution from the opening and developing of the rift basin to the rapid filling.In addition, I make an age spectrum which represent the properties of Yangtze block by three groups of age-data from the samples acquired in this research, compared with Cathysian block, North China block and Tarim block. Analysis of U-Pb age spectrum similarity indicates that the close affinity between the Yangtze block and Cathysian block only occurred when they collided since 1000 Ma. The difference of the age spectrum between the Yangtze block and North China is huge, shows that there's a poor relationship between them. While the Yangtze block and Tarim block have a close affinity for their age spectrum, and are similar to that in Neoproterozoic, Paleoproterozoic and Archean which indicates the synchronous of tectonic-magmatic history. So the former placed Tarim block on the eastern side of Australia still should under rethinking. |
PDF Full Text Request