Age and tectonic setting of Triassic basic volcanic rocks in southern Da Hinggan Range

作者：Zhang LianChang^*; Ying JiFeng; Chen ZhiGuang; Wu HuaYing; Wang Fei; Zhou XinHua

来源：Acta Petrologica Sinica, 2008, 24(4): 911-920.

• tholeiite
• triassic volcanics
• lithogeochemistry
• extension of post-orogeny
• southern Da Hinggan Range

Using zircon U-Pb LA-ICPMS and matrix Ar-Ar dating for volcanies, it is indicated that some Triassic (214 similar to 250 Ma) basic volcanics were distributed in southern Da Hinggan Range. The analysis of major and trace elements show that the volcanics are characterized by low K. 0 contents (0.16% similar to 1.70%), low MgO contents (2.89% similar to 10.30%), enrichment of LREE, no pronounced Eu anomaly (delta Eu = 0.73-1.09) and weak negative Nb and Ta anomalies. These geochemical characteristics are similar to those of continental tholeiite. Discrimination diagrams of various trace elements indicate that these volcanic rocks were formed in post-orogen stage. Isotopic geochemistries show that values of epsilon(Nd)(t) and (Sr-87/Sr-86)(i) of the volcanic range from 0.4 to 6.9 and from 0.7032 to 0.7049, respectively. The ratios of Pb-206/Pb-204, Pb-207/Pb-204 and Pb-208/Pb-204 vary from 18.22 to 18.59, 15.55 to 15.61 and 38.18 to 38.52, respectively. These geochemistries show that the basaltic magam was formed in partial melting of lithoshperic mantle. Based on above mentioned characteristics, combined with the regional researching results, we suggest that the southern Da Hinggan Range was very likely to an extensional environment of post-orogen during the Triassic.

• 出版日期2008-4
• 单位中国科学院地质与地球物理研究所; 中国科学院地质与地球物理研究所兰州油气资源研究中心