朝鲜平南盆地古元古界-下古生界沉积岩碎屑锆石年龄谱对比及意义

发布时间：2018-03-06 16:03

本文选题：朝鲜半岛　切入点：中朝古陆(华北古陆)　出处：《岩石学报》2016年10期 　论文类型：期刊论文

【摘要】：中朝古陆(华北古陆)平南盆地面积~25000km~2,位于朝鲜半岛中部,发育从中元古界到下古生界地层,但经历了低级变质作用(绿片岩相及以下)。变质基底岩石中有一套角闪岩相-麻粒岩相的变质的古元古界地层。本文根据盆地不同时代沉积岩碎屑锆石/变质锆石U-Pb LA-ICP MS年龄数据讨论沉积源区的变化,并对区域演化进行制约。甑山群/杂岩为盆地基底岩系,变质砂岩样品中碎屑锆石出现ca.2500~2100Ma的年龄峰值。另外,36.5亿年的碎屑锆石是朝鲜迄今发现的最古老碎屑锆石;夕线榴片麻岩样品记录了~1850Ma(1859±9Ma)的变质年龄;推测甑山群沉积于ca.2100~1900Ma,变质于1850 Ma。黄海群局限分布于朝鲜半岛中部,碎屑锆石年龄谱显示~1850 Ma的峰值,可见~1250 Ma的年龄,推测对应物源为古元古代基底岩浆岩和变质岩系;结合其上覆直岘群的沉积时代,推测地层沉积于ca.1250~1000Ma。直岘群是平南盆地分布最广的地层之一,底部长峰组样品显示明显的~1850Ma的峰值,而其上第二个和第三个组则显示明显的ca.1400~1600Ma和ca.1000~1200 Ma年龄峰值,~1850 Ma年龄很少;推测直岘群开始沉积时,物源主体是盆地基底岩系,但之后出现大量中元古代物质;推测其沉积时代为ca.1000~900Ma。黄州群有~1850Ma和~2500Ma的峰值,另外,还有较少的ca.1000~1200Ma及1400~1600 Ma年龄,表明沉积物源主体仍是基底岩系,可能有中新元古代沉积岩(黄州群-直岘群)的再沉积。这些沉积岩碎屑锆石年龄峰值与辽东和山东半岛沉积地层相似,并且中新元古代地层中均有大量1000~1200Ma及1400~1600Ma的物质,推测可能来自华北古陆之外,如圣弗朗西斯科克拉通。
[Abstract]:China continent (North China paleocontinent) Pingnan basin area of ~25000km~2, located in the middle of the Korean Peninsula, developed from Middle Proterozoic to Paleozoic strata, but experienced low-grade metamorphism (greenschist and below). Ancient Proterozoic strata have a amphibolite facies granulite facies metamorphic metamorphic basement rocks in the basin. According to the different the age of sedimentary rock detrital zircon / metamorphic zircon U-Pb LA-ICP age MS data to discuss changes of sedimentary source area, and the evolution of regional constraints. Jeungsan group / complex basin basement rocks, metamorphic sandstone detrital zircon age peak appeared in the sample of ca.2500~2100Ma. In addition, 3 billion 650 million years of detrital zircon is the oldest detrital zircon North Korea so far found; sillimanite garnet gneiss samples recorded ~1850Ma (1859 + 9Ma) metamorphic age; that the mountains are deposited on ca.2100~1900Ma, Ma. in the 1850 metamorphic limit distribution in North Korea Huang Hai Qun In the middle of the Korean Peninsula, detrital zircon age spectrum shows that the peak of ~1850 Ma, ~1250 Ma visible age, deduced the provenance of Paleoproterozoic basement magmatite and metamorphic rocks; with the overlying straight Xian group sedimentary strata deposited in that era, ca.1250~1000Ma. direct Xian group is one of the most widely distributed stratigraphic Pingnan basin. At the bottom of long peak group samples showed obvious peak of ~1850Ma, while the second and third group showed significant ca.1400~1600Ma and ca.1000~1200 Ma ~1850 Ma peak age, the age is very few; that straight Xian group the beginning of deposition, the source is the main body of the basin basement rocks, but after the emergence of a large number of Mesoproterozoic that matter; the deposition time for the peak, Huangzhou ca.1000~900Ma. group ~1850Ma and ~2500Ma in addition, there are fewer ca.1000~1200Ma and 1400~1600 Ma showed that the age, is still the main source of sediment in the basement, there may be new The ancient sedimentary rock (Huangzhou group - direct Xian group) and deposition. These sedimentary detrital zircon age peak with Liaodong and Shandong Peninsula, sedimentary strata are similar, and in the Neoproterozoic strata have a large number of 1000~1200Ma and 1400~1600Ma material, presumably from the North China block, such as San Francisco craton.

【作者单位】：朝鲜国家科学院地质学研究所;中国科学院地质与地球物理研究所岩石圈演化国家重点实验室;
【基金】：国家自然科学基金项目(41210003)资助
【分类号】：P597.3;P534

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