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新元古代康滇裂谷盆地是位于华南扬子古大陆西缘的一个大陆裂谷盆地,其开启时间与充填样式研究是华南扬子古大陆形成演化研究的重要方面.陆良组是该裂谷盆地东部的早期充填物,其沉积时代和充填序列研究对于区域地层对比、盆地开启时间及其充填样式研究具有重要意义.自陆良组建立以来,人们对它的时代归属和区域地层对比关系存在着不同的认识:或将其与中元古代昆阳群上部进行对比,或将其与新元古代澄江组进行对比,其原因是缺少绝对年龄的制约.本文报道了滇东陆良组下段底部和上段底部的凝灰岩夹层锆石SHRIMP U-Pb年代学研究新成果,其高精度同位素年龄值分别为(818.6±9.2)和(805±14)Ma.考虑误差因素,陆良组下段的底界年龄可解释为820 Ma,与华南扬子古大陆新元古代裂谷典型盆地——湘桂裂谷盆地早期充填物板溪群下部底界年龄相当;陆良组上段的底界年龄可解释为(800±5)Ma,与盆地西部澄江组底界年龄相当,也与湘桂裂谷盆地早期充填物板溪群上部底界年龄相当.上述年龄还表明,康滇裂谷盆地的开启时间与华南新元古代裂谷盆地的开启时间~820 Ma一致,具有相同的充填序列.盆地分析结果表明,康滇裂谷盆地属于典型的半地堑盆地,主边界断裂位于盆地西部,盆地中心位于盆地东部.该盆地幼年期由分布局限的小型同向半地堑盆地群组成,成熟期则简化为统一的大型半地堑盆地,属上叠滑脱盆地.
The Neoproterozoic Kangdian rift basin is a continental rift basin located at the western margin of the Yangtze ancient continent in South China. The study on the opening time and filling pattern of the Neoproterozoic Kangdian rift basin is an important aspect of the study on the formation and evolution of the ancient continent in the Yangtze River in South China. The study on the sedimentary age and filling sequence in eastern China is of great significance for the study of regional stratigraphic correlation, basin opening time and filling pattern. Since the establishment of Luliang Formation, there is a relationship between its age attribution and regional stratigraphic correlation Different understandings: It is compared with the upper part of the Mesoproterozoic Kunyang Group, or compared with the Neoproterozoic Chengjiang Formation because of the lack of absolute age constraints.This paper reports that the lower part of the Luliang Formation in eastern Yunnan and The new results of the SHRIMP U-Pb dating of tuff intercalated in the bottom of the upper segment show that the high-precision isotopic age values are (818.6 ± 9.2) and (805 ± 14) Ma, respectively. Considering the error factors, the lower boundary ages Which can be interpreted as 820 Ma, which is similar to the lower boundary of the lower part of Banxi Group, an early filling of the Xianggui rift basin, a typical basin of the Neoproterozoic rift in the Yangtze Triassic, The age of the bottom boundary can be interpreted as (800 ± 5) Ma, which is similar to the age of the bottom boundary of the Chengjiang Formation in the western part of the basin and to the upper boundary of the upper part of the Banxi Group in the early filling of the Xiang-GUI rift basin. The basin opening time coincides with the opening time of the Neoproterozoic rift basin in South China ~ 820 Ma and has the same filling sequence.The basin analysis shows that the Kangdian rift basin belongs to a typical semi-graben basin with the main boundary faults located in the basin In the west, the center of the basin is located in the eastern part of the basin, where the juvenile period consisted of small-scale co-directional semi-graben basins with limited distribution, and matured into simple large semi-graben basins, belonging to the super-slip basin.