| 扬子北缘大洪山地区中元古代打鼓石群碎屑锆石年代学及其地质意义 |
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| 引用本文： | 孔令耀,毛新武,陈超,邓乾忠,张汉金,杨青雄,李琳静,李启文.扬子北缘大洪山地区中元古代打鼓石群碎屑锆石年代学及其地质意义[J].地球科学,2017,42(4):485-501. |
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| 作者姓名： | 孔令耀 毛新武 陈超 邓乾忠 张汉金 杨青雄 李琳静 李启文 |
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| 作者单位： | 湖北省地质调查院，湖北武汉430034 |
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| 基金项目： | 中国地质调查局项目12120113012800湖北省地质局项目KJ2015-1中国地质调查局项目ZYTZ20168001 |
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| 摘 要： | 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±64 Ma，主要峰值为2 078 Ma、2 437 Ma、2 659 Ma和3 084 Ma附近；罗汉岭组最年轻锆石年龄为1 077±51 Ma，主要峰值为1 126 Ma、2 044 Ma、2 458 Ma和2 635 Ma附近.根据结果认为:李家咀组的沉积时代在1 250±64 Ma与1 126 Ma之间，罗汉岭组沉积时代晚于1 077±51 Ma，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.
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| 关 键 词： | 扬子陆块 中元古界 打鼓石群 碎屑锆石 年代学 |
| 收稿时间： | 2016-09-18 |
Chronological Study on Detrital Zircons and Its Geological Significance from Mesoproterozoic Dagushi Group in the Dahongshan Area,North Margin of the Yangtze Block |
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| Abstract: | There are many Pre-Nanhua strata and magmatic rocks in Yangtze Block, the detrital zircon preserved in sedimentary clastic rocks have great significances for limiting rock's age, tracing the source of sediments and revealing early evolution of the continent. This study is the first research of detrital zircon geochronology in both Lijiazui Formation and Luohanling Formation of Dagushi Group in the Dahongshan area, northern margin of the Yangtze block. The detrital zircons from Lijiazui Formation are dated a youngest age of 1 250±64 Ma, and several main age peaks of about 2 078 Ma, 2 437 Ma, 2 659 Ma and 3 084 Ma; the youngest age of Lijiazui Formation is 1 077±51 Ma, and it's ages peaks are about 1 126 Ma, 2 044 Ma, 2 458 Ma and 2 635 Ma. It is inferred that the sedimentary age of Lijiazui Formation is between 1 250±64 Ma and 1 126 Ma, and of Luohanling Formation is later than 1 077±51 Ma, indicating that Dagushi Group belongs to Mesoproterozoic. In addition, the age-histogram comparison of Dagushi Group and Shennongjia Goup, Kunyang Group, Dongchuan Group from different areas of Yangtze block, show that the source of these stratigraphic units are different from each other, which means the magmatic events and tectonic evolutions of each stratigraphic unit are different. Combined with previous research data of Yangtze block, we conclude that the blocks represented by each stratigraphic units are independent continent fragments in Mesoproterozoic, and amalgamated into the crystalline basement of the Yangtze block gradually in Mesoproterozoic to Neoproterozoic. |
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