Abstract In order to unravel the Mesozoic sedimentation in response to multistage deformation of the western Ordos fold-thrust belt, combined zircon U-Pb and fission track analyses of single zircon grain are conducted for seven sandstone samples in the Helanshan area. Zircon FT ages are calculated using absolute uranium concentration determined by LA-ICP-MS during the procedure of zircon U-Pb dating. The newly-obtained zircon FT data show age features that are comparable with the previous zircon FT ages obtained by conventional FT methods (by which uranium contents are determined through an external detector to map induced fission tracks). The newly-obtained zircon FT ages have four subordinate FT age peaks (i.e., 225 Ma, 165 Ma, 125 Ma and 80 Ma) which are well matched with the regional geodynamic events occurred in the Late Triassic, Late Jurassic, Late Cretaceous and Early Cenozoic, respectively; and the zircon U-Pb ages have two main peaks at the Paleoproterozoic and the Late Paleozoic. The zircon U-Pb ages, integrating with the FT ages and available paleocurrents, suggest that the Paleoproterozoic basement rocks and Late Paleozoic plutonic rocks of the Alxa Block are the source rocks for the Triassic sandstones, and the Jurassic sandstones are associated with a multi-cycling sedimentation. The Jurassic sandstones contain recycled zircons that firstly deposited in the Triassic strata and subsequently exhumed during the Late Triassic-Early Jurassic.

中文翻译：

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鄂尔多斯褶皱冲断带西部贺兰山晚古生代至早中生代砂岩碎屑锆石裂变径迹和U-Pb定年：物源和折断历史的制约

摘要 为揭示鄂尔多斯褶皱冲断带西部多期变形引起的中生代沉积作用，对贺兰山地区7个砂岩样品进行了锆石U-Pb和单颗锆石裂变径迹分析。在锆石 U-Pb 定年过程中，使用 LA-ICP-MS 确定的绝对铀浓度计算锆石 FT 年龄。新获得的锆石 FT 数据显示的年龄特征与通过传统 FT 方法（通过外部探测器确定铀含量以绘制诱发裂变轨迹图）获得的先前锆石 FT 年龄相当。新获得的锆石FT年龄有4个次级FT年龄峰（225 Ma、165 Ma、125 Ma和80 Ma），与晚三叠世发生的区域地球动力学事件相吻合，分别为晚侏罗世、晚白垩世和早新生代；锆石U-Pb年龄在古元古代和晚古生代有两个主峰。锆石U-Pb年龄，结合FT年龄和可用古洋流，表明阿拉善地块的古元古代基底岩和晚古生代深成岩是三叠纪砂岩的烃源岩，侏罗纪砂岩与多循环沉淀。侏罗纪砂岩含有再生锆石，这些锆石首先沉积在三叠纪地层中，随后在晚三叠世-早侏罗世期间出土。表明阿拉善地块的古元古代基底岩和晚古生代深成岩是三叠纪砂岩的烃源岩，侏罗纪砂岩与多旋回沉积有关。侏罗纪砂岩含有再生锆石，这些锆石首先沉积在三叠纪地层中，随后在晚三叠世-早侏罗世期间出土。表明阿拉善地块的古元古代基底岩和晚古生代深成岩是三叠纪砂岩的烃源岩，侏罗纪砂岩与多旋回沉积有关。侏罗纪砂岩含有再生锆石，这些锆石首先沉积在三叠纪地层中，随后在晚三叠世-早侏罗世期间出土。