鸭绿江盆地鹰嘴砬子组和馒头组的沉积时限及物源:碎屑锆石U-Pb年代学证据

Depositional age and provenances of Yingzuilazi Formation and Mantou Formation in Yalu River Basin:evidence from U-Pb ages of detrital zircons

鸭绿江盆地中生界鹰嘴砬子组与古生界馒头组河口段碎屑锆石LA-ICP-MS U-Pb的年代学研究结果表明,采自鹰嘴砬子组的凝灰质粉砂岩(样品HD1-3),其碎屑锆石年龄分布区间为3 259~123Ma。主要年龄峰为2 500 Ma(33%)、1 807 Ma(11%)、282 Ma(11%)、235 Ma(5%)、150 Ma(7%)和126 Ma(5%),最年轻的一组锆石加权平均年龄(126 Ma)限定地层的沉积下限为早白垩世,其沉积物源来自于盆地内部及其邻区古元古代、古生代和中生代岩浆作用的产物。采自馒头组河口段的岩屑长石砂岩(样品SD2-1),其碎屑锆石年龄分布区间为2 350~503 Ma。形成的年龄峰值主要为1 553 Ma(13%)、1 396 Ma(13%)、1 086 Ma(17%)和787 Ma(30%)。最小的锆石年龄(503 Ma)限定地层沉积下限为晚寒武世,其沉积物源主要来自鸭绿江盆地内部及其邻区的中元古代和新元古代岩浆作用的产物。

The studies on LA-ICP-MS U-Pb geochronology of detrital zircons from sedimentary rocks within the Yingzuilazi Formation and Hekou member of Mantou Formation in the Yalu River Basin indicate that tuffaceous siltstone（sample HD1-3） collected from the Yingzuilazi Formatioin yielded ages ranging from 3 259 to 123 Ma,which can be subdivided into six age populations with peaks at 2 500（33%）,1 807（11%）,282（11%）,235（5%）,150（7%） and 126 Ma（5%）.The group of youngest weighted mean age of 126 Ma indicates that the lower limit of the deposition age of Yingzuilazi Formation is Early Cretaceous.Its sedimentary provenances mainly source from the detrital material produced by Paleoproterozoic,Paleozoic and Mesozoic magmatism exposed in the sedimentary basin and adjacent area.Lithic feldspar sandstone（sample SD2-1） collected from the Hekou member of the Mantou Formation yielded ages ranging from 2 350 to 503 Ma,which can be subdivided into four agepopulations with peaks at 1 553（13%）,1 396（13%）,1 086（17%） and 787 Ma（30%）.The youngest zircon age of 503 Ma indicates that the lower limit of the deposition age of Mantou Formation is Late Cambrain.Its sedimentary provenances mainly source from the detrital material produced by Mesoproterozoic and Neoproterozoic magmatism exposed in the sedimentary basin and adjacent area.