科研之友
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摘要
The relationship of the Pyongnam basin with other basins in the Eastern North China Craton (Sino-Korean Craton) is in debating; and the deposition age is one key to solve this. The strata in the Pyongnam basin are mainly composed of the Sangwon Supergroup, which comprises the Jikhyon Group, the Sadangu Group, the Muckchon Group, the Myoransan Group and the Yontan Group from bottom to up. The Jikhyon Group is the lowermost formation and comprises of mainly terrestrial clastic sediments. Detrital zircons were separated from the clastic rocks of the Jikhyon Group of both the 'north-type' and 'south-type' strata of the Pyongnam basin, and their LA-ICP-MS U-Pb ages constrain the maximum deposition age to be 1100Ma. It further suggests that there are no differences either in deposition age or provenance between the so-called 'north-type' and 'south-type' strata. As the mafic sills in the Muckchon Group were intruded at similar to 900Ma, we suggest that the majority of the Sangwon Supergroup was deposited at 1000 similar to 900Ma, with the Yontan Group to be slightly younger. This indicates that the Pyongnam basin is contemporary with those in the Xu-Huai and Lv-Da basins. The variation of delta C-13 values of the carbonate samples from the Sangwon Supergroup shows a distinct negative drifting(delta C-13 value as low as -6 parts per thousand similar to -5 parts per thousand) in the Mukchon Group. As the mafic sills in the Mukchon Group were emplaced at similar to 900Ma, we suggest that this negative drifting of delta C-13 values happened slightly older than similar to 900Ma, and is possibly related to a coeval magmatic event.
- 出版日期2016-7
- 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
