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扬子陆块出露了较多前南华纪地层和岩浆岩,碎屑沉积岩中保存的碎屑锆石对限定地层沉积时代、示踪沉积物源和反演早期大陆构造演化具有重要意义.通过对扬子北缘大洪山地区中元古代打鼓石群碎屑锆石年代学的研究,结果显示李家咀组最年轻的锆石年龄为1 250±64Ma,主要峰值为2 078Ma、2 437Ma、2 659Ma和3 084Ma附近;罗汉岭组最年轻锆石年龄为1 077±51Ma,主要峰值为1 126Ma、2 044Ma、2 458Ma和2 635Ma附近.根据结果认为:李家咀组的沉积时代在1 250±64Ma与1 126Ma之间,罗汉岭组沉积时代晚于1 077±51Ma,可以确定打鼓石群的沉积时代为中元古代.另外,通过对打鼓石群、神农架群、会理群和东川群的碎屑锆石统计频谱特征的对比分析,发现在扬子陆块不同地区出露的中元古代地层,具有明显不同的锆石年谱特征,反映了各地层单元的物源差异很大,在中元古时期应分属不同的地块,经历了中-新元古代构造演化,才逐渐拼合成统一的扬子陆块基底.
The Yangtze block reveals more Pre-South Chinaian strata and magmatic rocks, and the detrital zircons preserved in the clastic sedimentary rocks are of great significance for defining the sedimentary age of the strata, tracing sedimentary source and inverting the tectonic evolution of the early continental continent. The results show that the youngest zircon age of the Lijiazui Formation is 1 250 ± 64Ma and the main peaks are 2 078Ma, 2 437Ma and 2 659Ma And the vicinity of 3 084M. The youngest zircon age of the Luohanling Formation is 1 077 ± 51Ma and the main peaks are 1 126Ma, 2 044Ma, 2 458Ma and 2 635Ma.According to the results, the depositional age of the Lijiazui Formation is in the range of 1 250 ± 64Ma and 1 126Ma, the depositional age of Luohanling Formation is later than 1 077 ± 51Ma, it can be determined that the age of Taigu rock group was Mesoproterozoic.In addition, by analyzing the characteristics of Taigu rock group, Shennongjia group, Huili group and Dongchuan group The results show that the Mesoproterozoic strata exposed in different areas of the Yangtze block have significantly different zircon age spectrum characteristics and reflect the great difference in provenance between the stratigraphic units. Proterozoic should belong to different plots, after After the Sino-Neoproterozoic tectonic evolution, it gradually assembled into a unified base of the Yangtze block.